Add tests for IfcGridAxis fixes

- Add test_create_axis_curve.py with three unit tests: basic
  polyline creation, safe removal of an unshared existing curve,
  and preservation of a shared curve when only one referencing
  axis is updated (regression for the shallow-copy duplication bug)
- Add feature scenario "Export IFC - with duplicate-of-duplicate
  grid axis locations preserved" to project.feature, reproducing
  the case where duplicates of duplicates lost their positions on
  save/reload

.github/workflows/ci-ifcwrap-standalone.yml

@@ -0,0 +1,155 @@
+# This file was generated with the assistance of an AI coding tool.
+name: ci-ifcwrap-standalone
+
+on:
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - ".github/workflows/ci-ifcwrap-standalone.yml"
+      - "cmake/**"
+      - "src/ifcwrap/**"
+      - "src/ifcparse/**"
+      - "src/ifcgeom/**"
+      - "src/serializers/**"
+      - "src/ifcconvert/**"
+      - "src/ifcopenshell-python/**"
+      - "src/svgfill/**"
+  push:
+    paths:
+      - ".github/workflows/ci-ifcwrap-standalone.yml"
+      - "cmake/**"
+      - "src/ifcwrap/**"
+      - "src/ifcparse/**"
+      - "src/ifcgeom/**"
+      - "src/serializers/**"
+      - "src/ifcconvert/**"
+      - "src/ifcopenshell-python/**"
+      - "src/svgfill/**"
+
+env:
+  IFCOPENSHELL_PREFIX: ${{ github.workspace }}/ifcopenshell-install
+
+jobs:
+  build-ifcopenshell:
+    runs-on: ubuntu-22.04
+
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          submodules: recursive
+
+      - name: Install C++ dependencies
+        run: |
+          sudo apt update
+          sudo apt-get install --no-install-recommends -y \
+            cmake \
+            gcc \
+            g++ \
+            libboost-date-time-dev \
+            libboost-filesystem-dev \
+            libboost-iostreams-dev \
+            libboost-program-options-dev \
+            libboost-regex-dev \
+            libboost-system-dev \
+            libboost-thread-dev \
+            libeigen3-dev \
+            libocct-data-exchange-dev \
+            libocct-draw-dev \
+            libocct-foundation-dev \
+            libocct-modeling-algorithms-dev \
+            libocct-modeling-data-dev \
+            libocct-ocaf-dev \
+            libocct-visualization-dev \
+            libpcre3-dev \
+            libtbb-dev \
+            libxml2-dev \
+            libxi-dev \
+            occt-misc \
+            tcl-dev \
+            tk-dev \
+            swig
+
+      - name: Configure minimal IfcOpenShell
+        run: |
+          cmake -S cmake -B build-ifcopenshell \
+            -DCMAKE_BUILD_TYPE=Release \
+            -DCMAKE_INSTALL_PREFIX="${IFCOPENSHELL_PREFIX}" \
+            -DCMAKE_PREFIX_PATH=/usr \
+            -DCMAKE_SYSTEM_PREFIX_PATH=/usr \
+            -DMINIMAL_BUILD=ON \
+            -DBUILD_IFCPYTHON=OFF \
+            "-DSCHEMA_VERSIONS=4x3_add2"
+
+      - name: Build and install minimal IfcOpenShell
+        run: |
+          cmake --build build-ifcopenshell --target install -j "$(nproc)"
+
+      - name: Set up Python 3.11
+        uses: actions/setup-python@v6
+        with:
+          python-version: 3.11
+
+      - name: Install Python import dependencies
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install numpy typing_extensions
+
+      - name: Configure standalone IfcPython
+        run: |
+          PYTHON_EXECUTABLE="$(python -c 'import sys; print(sys.executable)')"
+          PYTHON_INCLUDE_DIR="$(python -c 'import sysconfig; print(sysconfig.get_path("include"))')"
+
+          cmake -S src/ifcwrap -B "build-ifcwrap-311" \
+            -DCMAKE_BUILD_TYPE=Release \
+            -DCMAKE_PREFIX_PATH="${IFCOPENSHELL_PREFIX};/usr" \
+            -DPython_EXECUTABLE:FILEPATH="${PYTHON_EXECUTABLE}" \
+            -DPython_INCLUDE_DIR:PATH="${PYTHON_INCLUDE_DIR}" \
+            -DPYTHON_EXECUTABLE:FILEPATH="${PYTHON_EXECUTABLE}" \
+            -DPYTHON_INCLUDE_DIR:PATH="${PYTHON_INCLUDE_DIR}"
+
+      - name: Build and install standalone IfcPython
+        run: |
+          cmake --build "build-ifcwrap-311" --target install -j "$(nproc)"
+
+      - name: Import installed IfcPython
+        run: |
+          PYTHONPATH="${RUNNER_TEMP}/ifcopenshell-python" python - <<'PY'
+          import ifcopenshell
+
+          print("IfcOpenShell import ok:", ifcopenshell.version)
+          PY
+
+      - name: Set up Python 3.12
+        uses: actions/setup-python@v6
+        with:
+          python-version: 3.12
+
+      - name: Install Python import dependencies
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install numpy typing_extensions
+
+      - name: Configure standalone IfcPython
+        run: |
+          PYTHON_EXECUTABLE="$(python -c 'import sys; print(sys.executable)')"
+          PYTHON_INCLUDE_DIR="$(python -c 'import sysconfig; print(sysconfig.get_path("include"))')"
+
+          cmake -S src/ifcwrap -B "build-ifcwrap-312" \
+            -DCMAKE_BUILD_TYPE=Release \
+            -DCMAKE_PREFIX_PATH="${IFCOPENSHELL_PREFIX};/usr" \
+            -DPython_EXECUTABLE:FILEPATH="${PYTHON_EXECUTABLE}" \
+            -DPython_INCLUDE_DIR:PATH="${PYTHON_INCLUDE_DIR}" \
+            -DPYTHON_EXECUTABLE:FILEPATH="${PYTHON_EXECUTABLE}" \
+            -DPYTHON_INCLUDE_DIR:PATH="${PYTHON_INCLUDE_DIR}"
+
+      - name: Build and install standalone IfcPython
+        run: |
+          cmake --build "build-ifcwrap-312" --target install -j "$(nproc)"
+
+      - name: Import installed IfcPython
+        run: |
+          PYTHONPATH="${RUNNER_TEMP}/ifcopenshell-python" python - <<'PY'
+          import ifcopenshell
+
+          print("IfcOpenShell import ok:", ifcopenshell.version)
+          PY

.github/workflows/ci-lint.yaml

@@ -30,7 +30,7 @@ jobs:
           uv tool install ruff
           uv tool install black
           uv tool install poethepoet
-          uv tool install ty
+          uv tool install ty==0.0.34
 
       # black doesn't catch all syntax errors, so we check them explicitly.
       - name: Check syntax errors

.github/workflows/ci.yml

@@ -10,9 +10,13 @@ on:
       - 'src/ifcgeomserver/**'
       - 'src/ifcjni/**'
       - 'src/ifcmax/**'
+      - 'src/ifc5d/**'
+      - 'src/ifcedit/**'
+      - 'src/ifcmcp/**'
       - 'src/ifcopenshell-python/**'
       - '!src/ifcopenshell-python/docs/**'
       - 'src/ifcparse/**'
+      - 'src/ifcquery/**'
       - 'src/ifcwrap/**'
       - 'src/qtviewer/**'
       - 'src/svgfill/**'
@@ -51,7 +55,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install xmlschema xsdata numpy lxml pytest isodate lark networkx tabulate python-dateutil shapely
+          pip install xmlschema xsdata numpy lxml pytest isodate lark networkx tabulate python-dateutil shapely pyparsing psutil
           pip install src/bcf --no-deps
           pip install pytest-xdist==3.8.0
 
@@ -252,13 +256,26 @@ jobs:
           pip install deepdiff
           cd ../ifcdiff && make test || ERROR=1
           cd ../ifcpatch && make test || ERROR=1
+          pip install -e ../ifc5d --no-deps
+          pip install odfpy xlsxwriter
+          cd ../ifc5d && make test || ERROR=1
+          pip install -e ../ifcquery --no-deps
+          cd ../ifcquery && make test || ERROR=1
+          pip install -e ../ifcedit --no-deps
+          cd ../ifcedit && make test || ERROR=1
+          pip install mcp
+          pip install -e ../ifcmcp --no-deps
+          cd ../ifcmcp && make test || ERROR=1
           pip install -e ../ifctester --no-deps
           cd ../ifctester && make test || ERROR=1
           make build-ids-docs || ERROR=1
           # Run mathutils related tests at the end to ensure no other code is relying on mathutils.
+          # mathutils only has pre-built wheels for Python 3.13+; skip on older versions.
           cd ../ifcopenshell-python
-          pip install mathutils
-          make test-mathutils || ERROR=1
+          if python -c "import sys; sys.exit(0 if sys.version_info >= (3, 13) else 1)"; then
+            pip install mathutils
+            make test-mathutils || ERROR=1
+          fi
           if [ $ERROR -ne 0 ]; then
             echo "One or more tests failed";
             exit 1;

.gitignore

@@ -28,6 +28,7 @@ venv
 !.vscode/launch.json
 !.vscode/tasks.json
 .vs
+/*.code-workspace
 
 # PyCharm files
 .idea
@@ -128,3 +129,4 @@ src/ifcopenshell-python/ifcopenshell/express/*.exp.cache.dat
 *.claude
 *.py.tmp*
 *.json.tmp*
+

cmake/CMakeLists.txt

@@ -27,13 +27,14 @@ endif()
 set(CMAKE_CXX_STANDARD_REQUIRED ON) # not necessary, but encouraged
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
-if(VERSION_OVERRIDE)
-    file(READ "../VERSION" "RELEASE_VERSION_")
-    string(STRIP "${RELEASE_VERSION_}" RELEASE_VERSION)
-    message(STATUS "Detected version '${RELEASE_VERSION}'")
-else()
-    set(RELEASE_VERSION "0.8.0")
-endif()
+# The VERSION file in the repository root is the single source of truth for the
+# release version. Read it unconditionally so a plain source build reports the
+# real version through buildinfo.cpp instead of the stale hardcoded 0.8.0
+# fallback (see #8164). VERSION_OVERRIDE still controls the branch name used
+# when ADD_COMMIT_SHA embeds a commit sha.
+file(READ "../VERSION" "RELEASE_VERSION_")
+string(STRIP "${RELEASE_VERSION_}" RELEASE_VERSION)
+message(STATUS "Detected version '${RELEASE_VERSION}'")
 
 add_definitions(-D_DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR)
 
@@ -258,10 +259,14 @@ if(WITH_ROCKSDB)
     set(ROCKSDB_LIBRARIES "IFCOPENSHELL_RocksDB")
     target_compile_definitions(IFCOPENSHELL_RocksDB INTERFACE IFOPSH_WITH_ROCKSDB)
     set(SWIG_DEFINES ${SWIG_DEFINES} -DIFOPSH_WITH_ROCKSDB)
-    # Shared binaries for `rocksdb` only support limited API (only `c.h`), but we use `db.h` API.
-    # So rocksdb supported only as a static library.
     # See https://github.com/facebook/rocksdb/issues/981.
-    target_link_libraries(IFCOPENSHELL_RocksDB INTERFACE RocksDB::rocksdb)
+    if(TARGET RocksDB::rocksdb)
+        target_link_libraries(IFCOPENSHELL_RocksDB INTERFACE RocksDB::rocksdb)
+    elseif(TARGET RocksDB::rocksdb-shared)
+        target_link_libraries(IFCOPENSHELL_RocksDB INTERFACE RocksDB::rocksdb-shared)
+    else()
+        message(FATAL_ERROR "RocksDB found but neither RocksDB::rocksdb nor RocksDB::rocksdb-shared target exists")
+    endif()
 
     if(WITH_ZSTD)
         # @todo do we actually need the zstd include dir or rather just pass
@@ -656,6 +661,11 @@ if(ADD_COMMIT_SHA)
     endif()
 endif(ADD_COMMIT_SHA)
 
+# Always expose the release version (from the VERSION file) to buildinfo.cpp so
+# that a build without commit-sha info reports the correct version instead of a
+# stale hardcoded fallback. See #8164.
+target_compile_definitions(IfcParse PRIVATE IFCOPENSHELL_VERSION_STRING=${RELEASE_VERSION})
+
 if(MSVC)
     # @todo still needs to be understood better, but the cgal and cgal-simple kernel cause multiply defined boost lambda placeholders _1 ... _3
     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} /FORCE:MULTIPLE")

cmake/FindHDF5.cmake

@@ -88,7 +88,15 @@ if(NOT HDF5_INCLUDE_DIR OR NOT HDF5_LIBRARY_DIR)
     mark_as_advanced(HDF5_DIR)
     if(HDF5_DIR)
         message(STATUS "HDF5: found config at '${HDF5_DIR}'.")
-        set(HDF5_LIBRARIES hdf5_cpp-static)
+        if(TARGET hdf5_cpp-static)
+            set(HDF5_LIBRARIES hdf5_cpp-static)
+        elseif(TARGET hdf5_cpp-shared)
+            set(HDF5_LIBRARIES hdf5_cpp-shared)
+        elseif(TARGET hdf5::hdf5_cpp-shared)
+            set(HDF5_LIBRARIES hdf5::hdf5_cpp-shared)
+        else()
+            find_package(HDF5 REQUIRED COMPONENTS CXX)
+        endif()
     else()
         # If it failed, still try to find as a module.
         # E.g. on Ubuntu `libhdf5-dev` doesn't provie hdf5-config.cmake.

cmake/FindIfcOpenShell.cmake

@@ -0,0 +1,131 @@
+# This file was generated with the assistance of an AI coding tool.
+################################################################################
+#                                                                              #
+# This file is part of IfcOpenShell.                                           #
+#                                                                              #
+# IfcOpenShell is free software: you can redistribute it and/or modify         #
+# it under the terms of the Lesser GNU General Public License as published by  #
+# the Free Software Foundation, either version 3.0 of the License, or          #
+# (at your option) any later version.                                          #
+#                                                                              #
+# IfcOpenShell is distributed in the hope that it will be useful,              #
+# but WITHOUT ANY WARRANTY; without even the implied warranty of               #
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                 #
+# Lesser GNU General Public License for more details.                          #
+#                                                                              #
+# You should have received a copy of the Lesser GNU General Public License     #
+# along with this program. If not, see <http://www.gnu.org/licenses/>.         #
+#                                                                              #
+################################################################################
+
+include("${CMAKE_CURRENT_LIST_DIR}/utilities.cmake" OPTIONAL)
+
+set(_IfcOpenShell_find_args)
+if(IfcOpenShell_FIND_VERSION)
+    list(APPEND _IfcOpenShell_find_args "${IfcOpenShell_FIND_VERSION}")
+    if(IfcOpenShell_FIND_VERSION_EXACT)
+        list(APPEND _IfcOpenShell_find_args EXACT)
+    endif()
+endif()
+list(APPEND _IfcOpenShell_find_args CONFIG QUIET)
+if(IfcOpenShell_FIND_COMPONENTS)
+    list(APPEND _IfcOpenShell_find_args COMPONENTS ${IfcOpenShell_FIND_COMPONENTS})
+endif()
+
+set(_IfcOpenShell_saved_module_path "${CMAKE_MODULE_PATH}")
+list(REMOVE_ITEM CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")
+find_package(IfcOpenShell ${_IfcOpenShell_find_args})
+set(CMAKE_MODULE_PATH "${_IfcOpenShell_saved_module_path}")
+
+if(NOT IfcOpenShell_FOUND)
+    set(_IfcOpenShell_error "Could not find an IfcOpenShell CMake config package. Set IfcOpenShell_DIR or CMAKE_PREFIX_PATH.")
+    if(IfcOpenShell_FIND_REQUIRED)
+        message(FATAL_ERROR "${_IfcOpenShell_error}")
+    elseif(NOT IfcOpenShell_FIND_QUIETLY)
+        message(STATUS "${_IfcOpenShell_error}")
+    endif()
+    return()
+endif()
+
+set(_IfcOpenShell_required_targets IfcOpenShell::IfcParse IfcOpenShell::IfcGeom)
+set(_IfcOpenShell_missing_targets "")
+foreach(_IfcOpenShell_target IN LISTS _IfcOpenShell_required_targets)
+    if(NOT TARGET ${_IfcOpenShell_target})
+        list(APPEND _IfcOpenShell_missing_targets ${_IfcOpenShell_target})
+    endif()
+endforeach()
+
+if(_IfcOpenShell_missing_targets)
+    set(IfcOpenShell_FOUND FALSE)
+    string(REPLACE ";" ", " _IfcOpenShell_missing_targets_text "${_IfcOpenShell_missing_targets}")
+    set(_IfcOpenShell_error "IfcOpenShell config was found, but required targets are missing: ${_IfcOpenShell_missing_targets_text}.")
+    if(IfcOpenShell_FIND_REQUIRED)
+        message(FATAL_ERROR "${_IfcOpenShell_error}")
+    elseif(NOT IfcOpenShell_FIND_QUIETLY)
+        message(STATUS "${_IfcOpenShell_error}")
+    endif()
+    return()
+endif()
+
+if(NOT DEFINED IFCOPENSHELL_WITH_OPENCASCADE)
+    set(IFCOPENSHELL_WITH_OPENCASCADE OFF)
+    if(TARGET IfcOpenShell::geometry_kernel_opencascade)
+        set(IFCOPENSHELL_WITH_OPENCASCADE ON)
+    endif()
+endif()
+
+if(NOT DEFINED IFCOPENSHELL_WITH_CGAL)
+    set(IFCOPENSHELL_WITH_CGAL OFF)
+    if(TARGET IfcOpenShell::IFCOPENSHELL_CGAL)
+        set(IFCOPENSHELL_WITH_CGAL ON)
+    endif()
+endif()
+
+if(NOT DEFINED IFCOPENSHELL_IFCXML)
+    set(IFCOPENSHELL_IFCXML OFF)
+endif()
+
+if(NOT DEFINED IFCOPENSHELL_WITH_ROCKSDB)
+    set(IFCOPENSHELL_WITH_ROCKSDB OFF)
+endif()
+
+set(IFCOPENSHELL_LIBRARIES IfcOpenShell::IfcParse)
+foreach(_IfcOpenShell_target IN ITEMS IfcOpenShell::geometry_serializer IfcOpenShell::Serializers)
+    if(TARGET ${_IfcOpenShell_target})
+        list(APPEND IFCOPENSHELL_LIBRARIES ${_IfcOpenShell_target})
+    endif()
+endforeach()
+
+set(IFCOPENSHELL_KERNEL_LIBRARIES "")
+foreach(_IfcOpenShell_target IN ITEMS
+    IfcOpenShell::geometry_kernel_opencascade
+    IfcOpenShell::geometry_kernel_cgal
+    IfcOpenShell::geometry_kernel_cgal_simple
+)
+    if(TARGET ${_IfcOpenShell_target})
+        list(APPEND IFCOPENSHELL_KERNEL_LIBRARIES ${_IfcOpenShell_target})
+    endif()
+endforeach()
+
+set(IFCOPENSHELL_GEOMETRY_LIBRARIES IfcOpenShell::IfcGeom ${IFCOPENSHELL_KERNEL_LIBRARIES})
+
+if(TARGET IfcOpenShell::OpenCASCADE_INTERFACE)
+    set(OpenCASCADE_LIBRARIES IfcOpenShell::OpenCASCADE_INTERFACE)
+endif()
+
+if(TARGET IfcOpenShell::IFCOPENSHELL_CGAL)
+    set(CGAL_LIBRARIES IfcOpenShell::IFCOPENSHELL_CGAL)
+endif()
+
+if(TARGET IfcOpenShell::svgfill)
+    set(IFCOPENSHELL_SVGFILL_LIBRARY IfcOpenShell::svgfill)
+endif()
+
+mark_as_advanced(IfcOpenShell_DIR)
+
+unset(_IfcOpenShell_error)
+unset(_IfcOpenShell_find_args)
+unset(_IfcOpenShell_missing_targets)
+unset(_IfcOpenShell_missing_targets_text)
+unset(_IfcOpenShell_required_targets)
+unset(_IfcOpenShell_target)

cmake/IfcOpenShellConfig.cmake.in

@@ -7,12 +7,26 @@ set(IFCOPENSHELL_WITH_OPENCASCADE @WITH_OPENCASCADE@)
 set(IFCOPENSHELL_WITH_CGAL @WITH_CGAL@)
 set(IFCOPENSHELL_IFCXML @IFCXML_SUPPORT@)
 set(IFCOPENSHELL_WITH_ROCKSDB @WITH_ROCKSDB@)
+set(IFCOPENSHELL_COLLADA_SUPPORT @COLLADA_SUPPORT@)
+set(IFCOPENSHELL_GLTF_SUPPORT @GLTF_SUPPORT@)
+set(IFCOPENSHELL_HDF5_SUPPORT @HDF5_SUPPORT@)
+set(IFCOPENSHELL_WITH_PROJ @WITH_PROJ@)
+set(IFCOPENSHELL_USD_SUPPORT @USD_SUPPORT@)
 
 include(CMakeFindDependencyMacro)
 
-set(Boost_USE_STATIC_LIBS ON)
-set(Boost_USE_STATIC_RUNTIME OFF)
-set(Boost_USE_MULTITHREADED ON)
+set(IFCOPENSHELL_BOOST_USE_STATIC_LIBS "@Boost_USE_STATIC_LIBS@")
+set(IFCOPENSHELL_BOOST_USE_STATIC_RUNTIME "@Boost_USE_STATIC_RUNTIME@")
+set(IFCOPENSHELL_BOOST_USE_MULTITHREADED "@Boost_USE_MULTITHREADED@")
+if(NOT "${IFCOPENSHELL_BOOST_USE_STATIC_LIBS}" STREQUAL "")
+    set(Boost_USE_STATIC_LIBS ${IFCOPENSHELL_BOOST_USE_STATIC_LIBS})
+endif()
+if(NOT "${IFCOPENSHELL_BOOST_USE_STATIC_RUNTIME}" STREQUAL "")
+    set(Boost_USE_STATIC_RUNTIME ${IFCOPENSHELL_BOOST_USE_STATIC_RUNTIME})
+endif()
+if(NOT "${IFCOPENSHELL_BOOST_USE_MULTITHREADED}" STREQUAL "")
+    set(Boost_USE_MULTITHREADED ${IFCOPENSHELL_BOOST_USE_MULTITHREADED})
+endif()
 set(Boost_COMPONENTS
     system
     program_options
@@ -43,13 +57,33 @@ if(IFCOPENSHELL_WITH_ROCKSDB)
 endif()
 
 if(IFCOPENSHELL_IFCXML)
-    find_dependency(LibXml2 CONFIG)
+    find_dependency(LibXml2)
 endif()
 
 if(IFCOPENSHELL_WITH_CGAL)
     find_dependency(CGAL CONFIG)
 endif()
 
+if(IFCOPENSHELL_COLLADA_SUPPORT)
+    find_dependency(OpenCOLLADA)
+endif()
+
+if(IFCOPENSHELL_GLTF_SUPPORT)
+    find_dependency(nlohmann_json CONFIG)
+endif()
+
+if(IFCOPENSHELL_HDF5_SUPPORT)
+    find_dependency(HDF5 COMPONENTS C CXX)
+endif()
+
+if(IFCOPENSHELL_WITH_PROJ)
+    find_dependency(PROJ)
+endif()
+
+if(IFCOPENSHELL_USD_SUPPORT)
+    find_dependency(USD)
+endif()
+
 if(IFCOPENSHELL_WITH_OPENCASCADE)
     find_dependency(OpenCASCADE CONFIG)
     if(OpenCASCADE_VERSION VERSION_LESS "7.7.0")

nix/build-all.py

@@ -126,9 +126,8 @@ ssl._create_default_https_context = ssl._create_unverified_context
 import time
 from collections.abc import Generator, Sequence
 from pathlib import Path
-from urllib.request import urlretrieve
-
 from typing import Literal, Union
+from urllib.request import urlretrieve
 
 logger = logging.getLogger(__name__)
 logger.setLevel(logging.INFO)

src/bonsai/Makefile

@@ -106,7 +106,7 @@ endif
 endif # def PLATFORM
 
 # Current build commit hash.
-OLD:=1c5b825
+OLD:=3e7b739
 .PHONY: bump
 bump:
 ifndef NEW
@@ -192,7 +192,11 @@ endif
 	# Provides networkx graph analysis for project dependency calculations
 	cd build && . env/$(VENV_ACTIVATE) && $(PIP) download networkx --dest=./wheels
 	# Required by IFCDiff
-	cd build && . env/$(VENV_ACTIVATE) && $(PIP) download deepdiff --dest=./wheels
+	# Pinned <9.1: deepdiff 9.1.0 adds cachebox<6,>=5.2 which only ships macOS x86_64
+	# wheels for macosx_10_12+ and is incompatible with our macos py311 --platform
+	# macosx_10_10_x86_64 target. Revisit once the macos py311 platform tag is bumped
+	# to 10_13 (matching py312/py313).
+	cd build && . env/$(VENV_ACTIVATE) && $(PIP) download "deepdiff<9.1" --dest=./wheels
 	# Required by IFCCSV and ifcopenshell.util.selector
 	cd build && . env/$(VENV_ACTIVATE) && $(PIP) download lark --dest=./wheels
 	# Required by IFC4D
@@ -356,6 +360,10 @@ else
 	pytest test/tool/test_$(MODULE).py --maxfail=1
 endif
 
+.PHONY: test-modal
+test-modal:
+	blender --enable-event-simulate --python test/modal/test_modal.py --window-maximized
+
 # Reregistering test is not added to the standard test suite because during unregister
 # Blender removes all Bonsai dependencies breaking dev-environment symlinks.
 .PHONY: test-reregister

src/bonsai/bonsai/bim/__init__.py

@@ -15,6 +15,8 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 import importlib
 import os
@@ -25,7 +27,7 @@ import bpy
 import bpy.utils.previews
 from bpy_extras.io_utils import ExportHelper, ImportHelper
 
-from . import handler, operator, prop, ui
+from . import handler, operator, parametric_lifecycle, prop, ui
 
 try:
     from bonsai.translations import translations_dict
@@ -88,6 +90,7 @@ modules = {
     "web": None,
     "light": None,
     "alignment": None,
+    "clip_box": None,
     # Uncomment this line to enable loading of the demo module. Happy hacking!
     # The name "demo" must correlate to a folder name in `bim/module/`.
     # "demo": None,
@@ -157,9 +160,6 @@ classes = [
     ui.BIM_UL_tab_visibilities,
     ui.BIM_UL_panel_visibilities,
     ui.DocPreferences,
-    ui.GizmoPreferencesDoor,  # Register before GizmoPreferences
-    ui.GizmoPreferencesWindow,  # Register before GizmoPreferences
-    ui.GizmoPreferencesStair,  # Register before GizmoPreferences
     ui.GizmoPreferences,
     # ui.DefaultParameters and ui.BIM_ADDON_preferences are registered separately after modules (see late_classes below)
     # Tabs panel
@@ -268,6 +268,8 @@ def register():
     bpy.app.handlers.depsgraph_update_post.append(on_register)
     bpy.app.handlers.undo_post.append(handler.undo_post)
     bpy.app.handlers.redo_post.append(handler.redo_post)
+    # Must follow the two appends above so regenerators see restored IFC state.
+    parametric_lifecycle.install_parametric_lifecycle_handlers()
     bpy.app.handlers.load_post.append(handler.load_post)
     bpy.app.handlers.load_post.append(handler.loadIfcStore)
     bpy.types.Scene.BIMProperties = bpy.props.PointerProperty(type=prop.BIMProperties)
@@ -325,6 +327,7 @@ def unregister():
 
     unregister_classes(classes)
 
+    parametric_lifecycle.uninstall_parametric_lifecycle_handlers()
     bpy.app.handlers.load_post.remove(handler.load_post)
     bpy.app.handlers.load_post.remove(handler.loadIfcStore)
     del bpy.types.Scene.BIMProperties

src/bonsai/bonsai/bim/data/pset/EPset_Drawing.ifc

@@ -5,7 +5,7 @@ FILE_NAME('EPset_Drawing.ifc','2020-01-01T00:00:00',$,$,'EPset_Drawing','EPset_D
 FILE_SCHEMA(('IFC4'));
 ENDSEC;
 DATA;
-#1=IFCPROPERTYSETTEMPLATE('2JhNIvqZrFnAgxfhK0XVQX',$,'EPset_Drawing','',.PSET_OCCURRENCEDRIVEN.,'IfcAnnotation/DRAWING',(#23,#22,#27,#24,#19,#12,#26,#9,#8,#7,#6,#4,#18,#11,#5,#20,#25,#14,#10,#17,#28,#16,#3,#21,#13,#15,#2));
+#1=IFCPROPERTYSETTEMPLATE('2JhNIvqZrFnAgxfhK0XVQX',$,'EPset_Drawing','',.PSET_OCCURRENCEDRIVEN.,'IfcAnnotation/DRAWING',(#23,#22,#27,#24,#29,#30,#19,#12,#26,#9,#8,#7,#6,#4,#18,#11,#5,#20,#25,#14,#10,#17,#28,#16,#3,#21,#13,#15,#2));
 #2=IFCSIMPLEPROPERTYTEMPLATE('23JavTMk98ZxXhrUEnjAcf',$,'TargetView','',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #3=IFCSIMPLEPROPERTYTEMPLATE('1yVWUt5H9DAOuu0OaMMLpe',$,'Scale','The scale of this drawing represented as a numerator and denominator, such as 1/100',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #4=IFCSIMPLEPROPERTYTEMPLATE('3gsuPBtU93b8f0gg1pjkq6',$,'HumanScale','The scale of this drawing in human readable format, such as 1:100',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
@@ -33,5 +33,7 @@ DATA;
 #26=IFCSIMPLEPROPERTYTEMPLATE('2iwERDOW55Pf4hCbuFRe1Q',$,'FillMode','Method to fill areas seen in projection',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #27=IFCSIMPLEPROPERTYTEMPLATE('1YF$qLzBzF19Io8aB2N8cE',$,'CutMode','Method for cutting geometry',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #28=IFCSIMPLEPROPERTYTEMPLATE('1YSnFzurrEyRNtoLdmmddP',$,'BringToFront','The objects with these SVG classes will render in front of all other objects.Ex: IfcBeam, IfcColumn',.P_SINGLEVALUE.,'IfcText',$,$,$,$,$,.READWRITE.);
+#29=IFCSIMPLEPROPERTYTEMPLATE('0lP6Y8q9v2QhDnR4sT7uVx',$,'PerspectiveShiftX','Horizontal perspective camera shift stored as drawing metadata using Blender camera shift units.',.P_SINGLEVALUE.,'IfcReal',$,$,$,$,$,.READWRITE.);
+#30=IFCSIMPLEPROPERTYTEMPLATE('2mR8b1NcW5EoFyG7hJ9kLp',$,'PerspectiveShiftY','Vertical perspective camera shift stored as drawing metadata using Blender camera shift units.',.P_SINGLEVALUE.,'IfcReal',$,$,$,$,$,.READWRITE.);
 ENDSEC;
 END-ISO-10303-21;

src/bonsai/bonsai/bim/decorator_cache.py

@@ -0,0 +1,119 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""Shared structural-change cache token for POST_VIEW decorators.
+
+Decorators include the token in their cache key and rebuild on bump."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from typing import Any, Generic, TypeVar
+
+import bpy
+
+T = TypeVar("T")
+
+_DECORATOR_CACHE_TOKEN = 0
+
+
+def get_decorator_cache_token() -> int:
+    return _DECORATOR_CACHE_TOKEN
+
+
+def reset_for_test() -> None:
+    """Test-only: reset the cache token to 0 so bump-count assertions are stable."""
+    global _DECORATOR_CACHE_TOKEN
+    _DECORATOR_CACHE_TOKEN = 0
+
+
+@bpy.app.handlers.persistent
+def _bump_decorator_cache_token(*args: Any) -> None:
+    """depsgraph_update_post fires every animation frame and every driver
+    evaluation, even when no IFC-relevant ID block changed. Unconditional
+    bumping defeats the cache: an animated scene rebuilds every decorator
+    every viewport tick. Gate the depsgraph path on Object geometry or
+    transform updates; undo / redo / load have no depsgraph and always
+    invalidate.
+
+    Coverage assumption: ``TokenCache`` consumers key on Object identity
+    (depsgraph updates whose ``id`` is a ``bpy.types.Object``). Mesh /
+    Material / NodeTree updates that don't surface as an Object change
+    do NOT invalidate the token — a decorator that caches material- or
+    mesh-data-derived state must gate on a separate signal."""
+    global _DECORATOR_CACHE_TOKEN
+    if len(args) >= 2:
+        depsgraph = args[1]
+        if depsgraph is not None and hasattr(depsgraph, "updates"):
+            if not any(
+                (getattr(u, "is_updated_geometry", False) or getattr(u, "is_updated_transform", False))
+                and hasattr(u, "id")
+                and isinstance(u.id, bpy.types.Object)
+                for u in depsgraph.updates
+            ):
+                return
+    _DECORATOR_CACHE_TOKEN += 1
+
+
+def _hooks() -> tuple[Any, ...]:
+    return (
+        bpy.app.handlers.depsgraph_update_post,
+        bpy.app.handlers.undo_post,
+        bpy.app.handlers.redo_post,
+        bpy.app.handlers.load_post,
+    )
+
+
+def install_decorator_cache_handlers() -> None:
+    """Append the bump handler to each hook; idempotent."""
+    for hook in _hooks():
+        if _bump_decorator_cache_token not in hook:
+            hook.append(_bump_decorator_cache_token)
+
+
+def uninstall_decorator_cache_handlers() -> None:
+    for hook in _hooks():
+        try:
+            hook.remove(_bump_decorator_cache_token)
+        except ValueError:
+            pass
+
+
+class TokenCache(Generic[T]):
+    """Memoise a single value keyed on ``(caller_key, get_decorator_cache_token())``.
+
+    The token component invalidates the cache on depsgraph / undo / redo / load,
+    so cached ``bpy.types.Object`` references can't outlive the underlying ID
+    blocks. Holds exactly one entry — last key wins."""
+
+    __slots__ = ("_key", "_value")
+
+    def __init__(self) -> None:
+        self._key: tuple[Any, int] | None = None
+        self._value: T | None = None
+
+    def get_or_compute(self, key: Any, compute: Callable[[], T]) -> T:
+        token_key = (key, _DECORATOR_CACHE_TOKEN)
+        if token_key == self._key:
+            return self._value  # type: ignore[return-value]
+        value = compute()
+        self._key = token_key
+        self._value = value
+        return value

src/bonsai/bonsai/bim/export_ifc.py

@@ -120,10 +120,10 @@ class IfcExporter:
                 # updata_representation will run edit_object_placement if object is scaled
                 # and had no openings.
                 return element
-        if not tool.Ifc.is_moved(obj):
-            return
         if element.is_a("IfcGridAxis"):
             return self.sync_grid_axis_object_placement(obj, element)
+        if not tool.Ifc.is_moved(obj):
+            return
         if not hasattr(element, "ObjectPlacement"):
             return
         bonsai.core.geometry.edit_object_placement(tool.Ifc, tool.Geometry, tool.Surveyor, obj=obj)
@@ -134,7 +134,8 @@ class IfcExporter:
         grid_obj = tool.Ifc.get_object(grid)
         if grid_obj:
             self.sync_object_placement(grid_obj)
-            if grid_obj.matrix_world != obj.matrix_world:
+            matrices_differ = grid_obj.matrix_world != obj.matrix_world
+            if matrices_differ:
                 bpy.ops.bim.update_representation(obj=obj.name)
         tool.Geometry.record_object_position(obj)
 

src/bonsai/bonsai/bim/handler.py

@@ -15,11 +15,12 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 import os
 import weakref
 from collections.abc import Callable
-from math import cos
 from typing import Union
 
 import bpy
@@ -31,16 +32,32 @@ from bpy.app.handlers import persistent
 from mathutils import Vector
 
 import bonsai.bim
+import bonsai.core.model as core_model
 import bonsai.tool as tool
-from bonsai.bim.ifc import IfcStore
+from bonsai.bim.decorator_cache import (
+    install_decorator_cache_handlers,
+    uninstall_decorator_cache_handlers,
+)
+from bonsai.bim.ifc import IfcStore, get_cache_or_detect_lock
 from bonsai.bim.module.aggregate.decorator import AggregateDecorator
 from bonsai.bim.module.georeference.decorator import GeoreferenceDecorator
+from bonsai.bim.module.model.array import (
+    ArrayPreviewDecorator,
+    ArraySelectionHighlightDecorator,
+)
 from bonsai.bim.module.model.data import AuthoringData
 from bonsai.bim.module.model.decorator import (
+    BendPreviewDecorator,
     BoundingBoxDecorator,
+    DoorSwingReadonlyDecorator,
+    MEPSegmentExtendPreviewDecorator,
+    MEPSystemPathDecorator,
     SlabDirectionDecorator,
     WallAxisDecorator,
+    WallFilletPreviewDecorator,
+    WallSystemPathDecorator,
 )
+from bonsai.bim.module.model.wall import WallGizmoPreviewDecorator
 from bonsai.bim.module.nest.decorator import NestDecorator
 
 cwd = os.path.dirname(os.path.realpath(__file__))
@@ -108,19 +125,13 @@ def active_object_callback():
 
 
 def update_bim_tool_props():
-    """update BIM Tools props (such as extrusion_depth, length and x_angle) when active object changes"""
-    obj = bpy.context.active_object
-
-    # bunch of checks to see if we're in a valid state
-    if not obj:
-        return
-    mode = bpy.context.mode
-    current_tool = bpy.context.workspace.tools.from_space_view3d_mode(mode)
-    if not current_tool or current_tool.idname not in tool.Blender.get_list_of_tools():
-        return
-    element = tool.Ifc.get_entity(obj)
-    if not element:
+    """Selection-driven BIM Tool sync: re-target user-intent enums
+    (ifc_class, relating_type_id) AND refresh header values
+    (extrusion_depth, length, x_angle) for the new active object."""
+    ctx = _resolve_bim_tool_context()
+    if ctx is None:
         return
+    obj, current_tool, element = ctx
 
     props = tool.Model.get_model_props()
     aprops = tool.Drawing.get_annotation_props()
@@ -133,18 +144,85 @@ def update_bim_tool_props():
 
             if is_annotation_tool and (object_type := tool.Drawing.get_annotation_type_object_type(element_type)):
                 aprops.object_type = object_type
-                aprops.relating_type_id = str(element_type.id())
+                try:
+                    aprops.relating_type_id = str(element_type.id())
+                except TypeError:
+                    # EnumProperty items are rebuilt asynchronously when ifc_class changes;
+                    # this assignment can race a stale item list. Skipping is harmless —
+                    # the UI will resync on the next active_object_callback.
+                    pass
                 return
 
             if is_bim_tool:
-                props.ifc_class = element_type.is_a()
+                try:
+                    props.ifc_class = element_type.is_a()
+                except TypeError:
+                    # ifc_class only lists element/space types present in the model, so an
+                    # unsupported type (e.g. a raw IfcTypeProduct) or a stale item list mid-
+                    # rebuild raises `enum "<class>" not found`. Skip rather than crash the
+                    # handler — it re-fires on the next selection and the panel resyncs.
+                    pass
 
-            if is_bim_tool or TOOLS_TO_CLASSES_MAP.get(current_tool.idname) == element_type.is_a():
-                props.relating_type_id = str(element_type.id())
+            # Only assign when the target enum is the one that lists this type — otherwise
+            # we hit `enum "<id>" not found in (...)` if the user selects an element of a
+            # different class than the workspace tool was built for (e.g. selecting a wall
+            # while the door tool is active).
+            tool_class_match = TOOLS_TO_CLASSES_MAP.get(current_tool.idname) == element_type.is_a()
+            bim_tool_class_match = is_bim_tool and props.ifc_class == element_type.is_a()
+            if bim_tool_class_match or tool_class_match:
+                try:
+                    props.relating_type_id = str(element_type.id())
+                except TypeError:
+                    # Defensive: the enum item list can lag behind ifc_class assignment
+                    # above. Skipping leaves the panel briefly out of sync rather than
+                    # crashing the handler (which Blender re-fires on every selection).
+                    pass
 
     if is_annotation_tool:
         return
 
+    _read_headers_into_props(obj, element)
+
+
+def refresh_bim_tool_headers():
+    """Push the active IFC entity's current header float values
+    (extrusion_depth, length, x_angle) into ``BIMModelProperties``.
+    Enum-safe: never writes user-intent enum slots, which are owned by
+    the selection callback."""
+    ctx = _resolve_bim_tool_context()
+    if ctx is None:
+        return
+    obj, current_tool, element = ctx
+    if current_tool.idname not in tool.Blender.get_property_header_tools():
+        return
+    _read_headers_into_props(obj, element)
+
+
+def _resolve_bim_tool_context():
+    """Return ``(obj, current_tool, element)`` when an active BIM workspace
+    tool sees a resolvable IFC element; ``None`` otherwise. Defensive
+    against stripped operator contexts — a missing ``active_object`` /
+    ``mode`` / ``workspace`` short-circuits to ``None`` instead of raising."""
+    obj = tool.Blender.get_active_object()
+    if not obj:
+        return None
+    mode = getattr(bpy.context, "mode", None)
+    workspace = getattr(bpy.context, "workspace", None)
+    if mode is None or workspace is None:
+        return None
+    current_tool = workspace.tools.from_space_view3d_mode(mode)
+    if not current_tool or current_tool.idname not in tool.Blender.get_list_of_tools():
+        return None
+    element = tool.Ifc.get_entity(obj)
+    if not element:
+        return None
+    return obj, current_tool, element
+
+
+def _read_headers_into_props(obj, element):
+    """Populate ``BIMModelProperties`` header values from the active
+    object's IFC extrusion. Enum-safe: writes only header floats, never
+    user-intent enum slots, so it is safe to call on the post-commit hook."""
     representation = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
     if not representation:
         return
@@ -162,10 +240,13 @@ def update_bim_tool_props():
     if not AuthoringData.is_loaded:
         AuthoringData.load()
 
+    props = tool.Model.get_model_props()
     if AuthoringData.data["active_material_usage"] == "LAYER2":
         x_angle = get_x_angle(extrusion)
         axis = tool.Model.get_wall_axis(obj)["reference"]
-        props.extrusion_depth = abs(extrusion.Depth * si_conversion * cos(x_angle))
+        props.extrusion_depth = core_model.vertical_height_from_extrusion_depth(
+            extrusion.Depth * si_conversion, x_angle
+        )
         props.length = (axis[1] - axis[0]).length
         props.x_angle = x_angle
 
@@ -356,8 +437,10 @@ def subscribe_to_viewport_shading_changes():
             )
 
 
-@persistent
-def load_post(scene):
+def _apply_save_file_invariants(scene: bpy.types.Scene) -> None:
+    """Invariants enforced on every load_post: msgbus subscription, IFC owner
+    settings, scene-bound caches, load-transient parametric state, and the
+    multi-instance lock probe."""
     global global_subscription_owner
     active_object_key = bpy.types.LayerObjects, "active"
     bpy.msgbus.subscribe_rna(
@@ -368,6 +451,23 @@ def load_post(scene):
     ifcopenshell.api.owner.settings.get_application = get_application
     AuthoringData.type_thumbnails = {}
 
+    tool.Parametric.on_load_post(scene)
+
+    if tool.Ifc.get() and bpy.data.is_saved:
+        props = tool.Blender.get_bim_props()
+        props.has_blend_warning = True
+
+    # Probe the H5 cooked-geometry cache so the multi-instance warning surfaces
+    # right after .blend load. Without this, the lock is only detected when a
+    # mutation triggers ``clear_cache`` — by which time the user has already
+    # made changes that may now conflict with the other Blender instance.
+    if tool.Ifc.get():
+        get_cache_or_detect_lock()
+
+
+def _apply_user_preferences() -> None:
+    """User-preference-driven UI setup: toolbar, BIM workspace, viewport shading
+    subscription, scene-panel hijack, tab layout, snap defaults."""
     preferences = tool.Blender.get_addon_preferences()
     if not preferences.should_setup_toolbar:
         tool.Blender.unregister_toolbar()
@@ -391,11 +491,21 @@ def load_post(scene):
         tool.Blender.override_scene_panel(panel)
     tool.Blender.setup_tabs()
 
-    if tool.Ifc.get() and bpy.data.is_saved:
-        props = tool.Blender.get_bim_props()
-        props.has_blend_warning = True
+    if preferences.should_use_snap and (scene := bpy.context.scene):
+        # Snapping is off by default in Blender, but in BIM, it's more useful to be on
+        scene.tool_settings.use_snap = True
+        # Match default Bonsai snaps
+        scene.tool_settings.snap_elements_base = {"EDGE", "EDGE_PERPENDICULAR", "VERTEX", "EDGE_MIDPOINT", "FACE"}
 
-    # Bonsai overlays
+    tool.Blender.sync_old_preferences()
+
+
+def _install_viewport_overlays() -> None:
+    """Sync every Bonsai viewport decorator to its enabled state.
+
+    Wrapped in uninstall/install of the decorator-cache bump handlers so a
+    decorator's own install path doesn't double-bind to depsgraph_update_post
+    via ``TokenCache`` instances created during their own ``install()``."""
     georeference_props = tool.Georeference.get_georeference_props()
     aggregate_props = tool.Aggregate.get_aggregate_props()
     nest_props = tool.Nest.get_nest_props()
@@ -405,23 +515,62 @@ def load_post(scene):
     NestDecorator.uninstall()
     WallAxisDecorator.uninstall()
     SlabDirectionDecorator.uninstall()
-    if georeference_props.should_visualise:
-        GeoreferenceDecorator.install(bpy.context)
-    if aggregate_props.aggregate_decorator:
-        AggregateDecorator.install(bpy.context)
-    if nest_props.nest_decorator:
-        NestDecorator.install(bpy.context)
-    if model_props.show_wall_axis:
-        WallAxisDecorator.install(bpy.context)
-    if model_props.show_slab_direction:
-        SlabDirectionDecorator.install(bpy.context)
-    if model_props.show_bounding_box:
-        BoundingBoxDecorator.install(bpy.context)
+    MEPSystemPathDecorator.uninstall()
+    WallSystemPathDecorator.uninstall()
+    WallFilletPreviewDecorator.uninstall()
+    BendPreviewDecorator.uninstall()
+    MEPSegmentExtendPreviewDecorator.uninstall()
+    WallGizmoPreviewDecorator.uninstall()
+    DoorSwingReadonlyDecorator.uninstall()
+    ArrayPreviewDecorator.uninstall()
+    ArraySelectionHighlightDecorator.uninstall()
+    uninstall_decorator_cache_handlers()
+    try:
+        if georeference_props.should_visualise:
+            GeoreferenceDecorator.install(bpy.context)
+        if aggregate_props.aggregate_decorator:
+            AggregateDecorator.install(bpy.context)
+        if nest_props.nest_decorator:
+            NestDecorator.install(bpy.context)
+        if model_props.show_wall_axis:
+            WallAxisDecorator.install(bpy.context)
+        if model_props.show_slab_direction:
+            SlabDirectionDecorator.install(bpy.context)
+        if model_props.show_paths:
+            MEPSystemPathDecorator.install(bpy.context)
+            WallSystemPathDecorator.install(bpy.context)
+        if model_props.show_bounding_box:
+            BoundingBoxDecorator.install(bpy.context)
+        # Always-installed: draw() self-polls on Scene.BIMPreviewProperties.
+        # wall_fillet.is_active, so installation has no cost when no preview
+        # is open. No corresponding addon-preference toggle.
+        WallFilletPreviewDecorator.install(bpy.context)
+        # Always-installed siblings of WallFilletPreviewDecorator: each
+        # self-polls on its own scene.BIMPreviewProperties subgroup or on
+        # selection + hover gizmo state — zero cost when nothing is active.
+        BendPreviewDecorator.install(bpy.context)
+        MEPSegmentExtendPreviewDecorator.install(bpy.context)
+        # Always-installed: draw_lines() self-polls on selection + hover state
+        # for join / extend-to-wall / cursor-extend / cursor-split previews.
+        # Free when no preview-eligible state is active.
+        WallGizmoPreviewDecorator.install(bpy.context)
+        # Always-installed: draw() self-polls on active object + IfcDoor +
+        # parametric pset, so the cost is one bpy/IFC lookup per redraw when
+        # nothing eligible is selected.
+        DoorSwingReadonlyDecorator.install(bpy.context)
+        # Always-installed: draw() self-polls on the active object's array
+        # family membership, so installation has no cost when no array
+        # element is selected.
+        ArraySelectionHighlightDecorator.install(bpy.context)
+        # Always-installed: draw() self-polls on props.is_editing — only
+        # paints during an active array edit lifecycle.
+        ArrayPreviewDecorator.install(bpy.context)
+    finally:
+        install_decorator_cache_handlers()
 
-    if preferences.should_use_snap and (scene := bpy.context.scene):
-        # Snapping is off by default in Blender, but in BIM, it's more useful to be on
-        scene.tool_settings.use_snap = True
-        # Match default Bonsai snaps
-        scene.tool_settings.snap_elements_base = {"EDGE", "EDGE_PERPENDICULAR", "VERTEX", "EDGE_MIDPOINT", "FACE"}
 
-    tool.Blender.sync_old_preferences()
+@persistent
+def load_post(scene):
+    _apply_save_file_invariants(scene)
+    _apply_user_preferences()
+    _install_viewport_overlays()

src/bonsai/bonsai/bim/ifc.py

@@ -64,6 +64,44 @@ class TransactionStep(TypedDict):
     operations: list[Operation]
 
 
+# Set when ``IfcStore.get_cache`` observes an external lock on the HDF5 cache —
+# signal that another Blender process has the same IFC file open. Project panel
+# polls ``is_cache_locked_by_other_process`` to warn the user. The dismissed
+# flag is sticky per-session so the warning doesn't re-nag once the user has
+# acknowledged it.
+_cache_locked_by_other_process: bool = False
+_multi_instance_warning_dismissed: bool = False
+
+
+def is_cache_locked_by_other_process() -> bool:
+    return _cache_locked_by_other_process and not _multi_instance_warning_dismissed
+
+
+def dismiss_multi_instance_warning() -> None:
+    global _multi_instance_warning_dismissed
+    _multi_instance_warning_dismissed = True
+
+
+def get_cache_or_detect_lock() -> ifcopenshell.geom.serializers.hdf5 | None:
+    """Like ``IfcStore.get_cache`` but tracks the multi-instance lock flag — sets
+    it on ``PermissionError``, clears it (along with the dismiss flag) when a
+    subsequent call succeeds. Returns ``None`` on lock; other exceptions
+    propagate. Callers that don't need the warning side effect can use
+    ``IfcStore.get_cache`` directly."""
+    global _cache_locked_by_other_process, _multi_instance_warning_dismissed
+    try:
+        cache = IfcStore.get_cache()
+    except PermissionError:
+        _cache_locked_by_other_process = True
+        return None
+    if _cache_locked_by_other_process:
+        # Lock released — clear both flags so a future re-locking re-surfaces
+        # the warning rather than staying suppressed by the previous dismiss.
+        _cache_locked_by_other_process = False
+        _multi_instance_warning_dismissed = False
+    return cache
+
+
 class IfcStore:
     path: str = ""
     """Should be set only using ``tool.Ifc.set_path``."""
@@ -196,7 +234,7 @@ class IfcStore:
                 shutil.copy2(IfcStore.cache_path, new_cache_path)
             except PermissionError:
                 pass  # Well we tried. No cache for you!
-        IfcStore.get_cache()
+        get_cache_or_detect_lock()
 
     @staticmethod
     def load_file(path: str) -> None:
@@ -514,6 +552,7 @@ class IfcStore:
                     BrickStore.end_transaction()
                 IfcStore.end_transaction(operator)
                 bonsai.bim.handler.refresh_ui_data()
+                tool.Parametric.refresh_post_commit(operator)
 
                 if method == "MODAL":
                     cls.modal_in_progress = False
@@ -527,6 +566,19 @@ class IfcStore:
                 result = getattr(operator, "_modal")(context, event)
         except:
             bonsai.last_error = traceback.format_exc()
+            # An operator that mutated IFC then raised leaves the IFC graph captured
+            # by the transaction but the Blender side stale. Blender does not push an
+            # undo step for a raised operator (mirror of the CANCELLED-modal gap
+            # handled below), so we push one here so Ctrl+Z actually rewinds the
+            # partial mutation, then surface the recovery path to the user.
+            ifc_file = tool.Ifc.get()
+            if ifc_file and ifc_file.transaction and ifc_file.transaction.operations:
+                bpy.ops.ed.undo_push(message=f"Recover {operator.bl_idname}")
+                operator.report(
+                    {"WARNING"},
+                    "Operation partially completed (IFC changed, Blender state may be stale). "
+                    "Press Ctrl+Z to restore the previous state.",
+                )
             # Try to ensure undo will work since Blender undo does work in case of errors.
             # As error come unexpectedly, it's important that user might have a chance to save the file
             # before they got the error and not to lose the work they've done.

src/bonsai/bonsai/bim/import_ifc.py

@@ -223,6 +223,7 @@ class IfcImporter:
         self.elements: set[ifcopenshell.entity_instance] = set()
         self.annotations: set[ifcopenshell.entity_instance] = set()
         self.gross_elements: set[ifcopenshell.entity_instance] = set()
+        self.broken_arrays: set[ifcopenshell.entity_instance] = set()
         self.element_types: set[ifcopenshell.entity_instance] = set()
         self.spatial_elements: set[ifcopenshell.entity_instance] = set()
         self.meshes: dict[str, OBJECT_DATA_TYPE] = {}
@@ -1219,8 +1220,18 @@ class IfcImporter:
                         if element not in elements_to_import:
                             continue
                     for i in range(len(data)):
-                        tool.Blender.Modifier.Array.set_children_lock_state(element, i, True)
-                        tool.Blender.Modifier.Array.constrain_children_to_parent(element)
+                        tool.Array.set_children_lock_state(element, i, True)
+                    tool.Array.constrain_children_to_parent(element)
+                    for layer in data:
+                        for child_guid in layer.get("children", ()):
+                            try:
+                                self.file.by_guid(child_guid)
+                            except RuntimeError:
+                                print(
+                                    f"setup_arrays: array parent {element.GlobalId} references missing "
+                                    f"child GUID {child_guid!r}."
+                                )
+                                self.broken_arrays.add(element)
 
     def update_linked_aggregates(self):
         # TODO Remove this after a while. See commit 17d6b8a

src/bonsai/bonsai/bim/module/aggregate/decorator.py

@@ -20,7 +20,6 @@ import blf
 import bpy
 import gpu
 import ifcopenshell.util.element
-from bpy.types import SpaceView3D
 from bpy_extras import view3d_utils
 from gpu_extras.batch import batch_for_shader
 from mathutils import Vector
@@ -28,12 +27,6 @@ from mathutils import Vector
 import bonsai.tool as tool
 
 
-def transparent_color(color, alpha=0.1):
-    color = [i for i in color]
-    color[3] = alpha
-    return color
-
-
 def create_bounding_box(objs):
     # Initialize the bounding box coordinates
     min_x, min_y, min_z = float("inf"), float("inf"), float("inf")
@@ -79,26 +72,8 @@ def create_bounding_box(objs):
     return indices, edges
 
 
-class AggregateDecorator:
-    is_installed = False
-    handlers = []
-
-    @classmethod
-    def install(cls, context):
-        if cls.is_installed:
-            cls.uninstall()
-        handler = cls()
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_aggregate, (context,), "WINDOW", "POST_VIEW"))
-        cls.is_installed = True
-
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
+class AggregateDecorator(tool.Blender.ViewportDecorator):
+    draw_method = "draw_aggregate"
 
     def dotted_line_shader(self):
         vert_out = gpu.types.GPUStageInterfaceInfo("my_interface")
@@ -153,14 +128,6 @@ class AggregateDecorator:
         shader.uniform_float("u_Scale", 25)
         batch.draw(shader)
 
-    def draw_batch(self, shader_type, content_pos, color, indices=None):
-        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
-            return
-        shader = self.line_shader if shader_type == "LINES" else self.shader
-        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
-        shader.uniform_float("color", color)
-        batch.draw(shader)
-
     def draw_aggregate(self, context):
         props = tool.Aggregate.get_aggregate_props()
         self.addon_prefs = tool.Blender.get_addon_preferences()
@@ -191,12 +158,13 @@ class AggregateDecorator:
                 aggregates.append(obj)
                 continue
 
+            aggregate = None
             aggregates_list = tool.Aggregate.get_aggregates_recursively(element)
             if props.in_aggregate_mode and props.editing_aggregate:
                 index = aggregates_list.index(tool.Ifc.get_entity(props.editing_aggregate))
                 if index > 0:
                     aggregate = aggregates_list[index - 1]
-            else:
+            elif aggregates_list:
                 aggregate = aggregates_list[-1]
             if aggregate:
                 aggregates.append(tool.Ifc.get_object(aggregate))
@@ -225,39 +193,11 @@ class AggregateDecorator:
             self.draw_custom_batch(line, decorator_color_unselected)
 
 
-class AggregateModeDecorator:
-    is_installed = False
-    handlers = []
-
-    @classmethod
-    def install(cls, context):
-        if cls.is_installed:
-            cls.uninstall()
-        handler = cls()
-        cls.handlers.append(
-            SpaceView3D.draw_handler_add(handler.draw_aggregate_name, (context,), "WINDOW", "POST_PIXEL")
-        )
-        cls.handlers.append(
-            SpaceView3D.draw_handler_add(handler.draw_aggregate_empty, (context,), "WINDOW", "POST_VIEW")
-        )
-        cls.is_installed = True
-
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
-
-    def draw_batch(self, shader_type, content_pos, color, indices=None):
-        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
-            return
-        shader = self.line_shader if shader_type == "LINES" else self.shader
-        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
-        shader.uniform_float("color", color)
-        batch.draw(shader)
+class AggregateModeDecorator(tool.Blender.ViewportDecorator):
+    draw_methods = (
+        ("draw_aggregate_name", "POST_PIXEL"),
+        ("draw_aggregate_empty", "POST_VIEW"),
+    )
 
     def draw_aggregate_name(self, context):
         if context.mode == "EDIT_MESH":

src/bonsai/bonsai/bim/module/aggregate/prop.py

@@ -139,6 +139,7 @@ class BIMAggregateProperties(PropertyGroup):
     previous_editing_aggregate: PointerProperty(name="Editing Aggregate", type=bpy.types.Object)
     editing_objects: CollectionProperty(type=Objects)
     not_editing_objects: CollectionProperty(type=Objects)
+    previously_selected_objects: CollectionProperty(type=Objects)
     aggregate_decorator: BoolProperty(
         name="Display Aggregate",
         default=False,
@@ -155,5 +156,6 @@ class BIMAggregateProperties(PropertyGroup):
         previous_editing_aggregate: Union[bpy.types.Object, None]
         editing_objects: bpy.types.bpy_prop_collection_idprop[Objects]
         not_editing_objects: bpy.types.bpy_prop_collection_idprop[Objects]
+        previously_selected_objects: bpy.types.bpy_prop_collection_idprop[Objects]
         aggregate_decorator: bool
         previous_state: bool

src/bonsai/bonsai/bim/module/attribute/ui.py

@@ -48,12 +48,14 @@ def draw_ui(context: bpy.types.Context, layout: bpy.types.UILayout, attributes)
         row = layout.row()
         op = row.operator("bim.enable_editing_attributes", icon="GREASEPENCIL", text="Edit")
 
+        element = tool.Ifc.get_entity(obj)
+        key_prefix = "type." if (element and element.is_a("IfcTypeObject")) else ""
         for attribute in attributes:
             row = layout.row(align=True)
             row.label(text=attribute["name"])
             value = bonsai.bim.helper.get_display_value(attribute["value"])
             op = row.operator("bim.select_similar", text=value, icon="NONE", emboss=False)
-            op.key = attribute["name"]
+            op.key = key_prefix + attribute["name"]
 
     # TODO: reimplement, see #1222
     # if "IfcSite/" in context.active_object.name or "IfcBuilding/" in context.active_object.name:

src/bonsai/bonsai/bim/module/boundary/decorator.py

@@ -56,11 +56,6 @@ class BoundaryDecorator:
         unselected_elements_color = self.addon_prefs.decorator_color_unselected
         special_elements_color = self.addon_prefs.decorator_color_special
 
-        def transparent_color(color, alpha=0.1):
-            color = [i for i in color]
-            color[3] = alpha
-            return color
-
         gpu.state.point_size_set(6)
         gpu.state.blend_set("ALPHA")
 
@@ -109,7 +104,11 @@ class BoundaryDecorator:
 
         if unselected_edges:
             self.draw_batch("LINES", unselected_vertices, special_elements_color, unselected_edges)
-            self.draw_batch("TRIS", unselected_vertices, transparent_color(special_elements_color), unselected_tris)
+            self.draw_batch(
+                "TRIS", unselected_vertices, tool.Blender.transparent_color(special_elements_color), unselected_tris
+            )
         if selected_edges:
             self.draw_batch("LINES", selected_vertices, selected_elements_color, selected_edges)
-            self.draw_batch("TRIS", selected_vertices, transparent_color(selected_elements_color), selected_tris)
+            self.draw_batch(
+                "TRIS", selected_vertices, tool.Blender.transparent_color(selected_elements_color), selected_tris
+            )

src/bonsai/bonsai/bim/module/cad/operator.py

@@ -345,9 +345,17 @@ class CadArcFrom3Points(bpy.types.Operator):
 class CadOffset(bpy.types.Operator):
     bl_idname = "bim.cad_offset"
     bl_label = "CAD Offset"
-    bl_description = "Copy selected mesh geometry at provided offset. Mesh copied based on the current viewport angle."
+    bl_description = (
+        "Offset selected mesh geometry at provided distance, based on the current viewport angle. "
+        "Creates a copy by default, or moves the existing edges if Copy is disabled."
+    )
     bl_options = {"REGISTER", "UNDO"}
     distance: bpy.props.FloatProperty(name="Distance", default=0.1, subtype="DISTANCE")
+    copy: bpy.props.BoolProperty(
+        name="Copy",
+        description="Create a new offset copy of the geometry. If disabled, move the existing edges to the offset location",
+        default=True,
+    )
 
     @classmethod
     def poll(cls, context):
@@ -405,6 +413,11 @@ class CadOffset(bpy.types.Operator):
         rotation = Matrix.Rotation(pi / 2, 2, "Z")
         rotation_i = Matrix.Rotation(-pi / 2, 2, "Z")
 
+        # When not copying, the offset positions are gathered here and applied to
+        # the existing verts only after all loops are processed, so that the
+        # original coordinates are still available while computing offsets.
+        moved_verts = []
+
         # Create loops from edges
         loop_edges = set(edges)
         loops = []
@@ -517,12 +530,15 @@ class CadOffset(bpy.types.Operator):
                     offset_length = self.distance / sqrt((1 + normals[0].dot(normals[1])) / 2)
                     offset = mw.inverted().to_quaternion() @ (wp.to_quaternion() @ (new_normal * offset_length).to_3d())
                     new_vert = v1.co + offset
-                    new_verts.append(bm.verts.new(new_vert))
                 else:
                     normal = (normals[0] * self.distance).to_3d()
                     offset = mw.inverted().to_quaternion() @ (wp.to_quaternion() @ normal)
                     new_vert = v1.co + offset
+
+                if self.copy:
                     new_verts.append(bm.verts.new(new_vert))
+                else:
+                    moved_verts.append((v1, new_vert))
 
                 processed_verts.add(v1.index)
 
@@ -531,9 +547,14 @@ class CadOffset(bpy.types.Operator):
 
                 v1 = v2
 
-            [bm.edges.new((new_verts[i], new_verts[i + 1])) for i in range(len(new_verts) - 1)]
-            if is_closed:
-                bm.edges.new((new_verts[len(new_verts) - 1], new_verts[0]))
+            if self.copy:
+                [bm.edges.new((new_verts[i], new_verts[i + 1])) for i in range(len(new_verts) - 1)]
+                if is_closed:
+                    bm.edges.new((new_verts[len(new_verts) - 1], new_verts[0]))
+
+        # Move the existing edges to the offset location.
+        for vert, new_co in moved_verts:
+            vert.co = new_co
 
         bm.verts.index_update()
         bm.edges.index_update()

src/bonsai/bonsai/bim/module/cad/prop.py

@@ -27,6 +27,11 @@ class BIMCadProperties(PropertyGroup):
     resolution: bpy.props.IntProperty(name="Arc Resolution", min=1, default=1)
     radius: bpy.props.FloatProperty(name="Radius", default=0.1, subtype="DISTANCE")
     distance: bpy.props.FloatProperty(name="Distance", default=0.1, subtype="DISTANCE")
+    copy: bpy.props.BoolProperty(
+        name="Copy",
+        description="Create a new offset copy of the geometry. If disabled, move the existing edges to the offset location",
+        default=True,
+    )
     x: bpy.props.FloatProperty(name="X", default=0.2, subtype="DISTANCE")
     y: bpy.props.FloatProperty(name="Y", default=0.1, subtype="DISTANCE")
     gable_roof_edge_angle: bpy.props.FloatProperty(
@@ -37,6 +42,7 @@ class BIMCadProperties(PropertyGroup):
         resolution: int
         radius: float
         distance: float
+        copy: bool
         x: float
         y: float
         gable_roof_edge_angle: float

src/bonsai/bonsai/bim/module/cad/workspace.py

@@ -256,6 +256,8 @@ class CadHotkey(bpy.types.Operator):
         elif self.hotkey == "S_O":
             row = self.layout.row()
             row.prop(props, "distance")
+            row = self.layout.row()
+            row.prop(props, "copy")
 
         elif self.hotkey == "S_R":
             if tool.Geometry.is_profile_object_active():
@@ -291,7 +293,7 @@ class CadHotkey(bpy.types.Operator):
             bpy.ops.bim.cad_fillet(resolution=self.props.resolution, radius=self.props.radius)
 
     def hotkey_S_O(self):
-        bpy.ops.bim.cad_offset(distance=self.props.distance)
+        bpy.ops.bim.cad_offset(distance=self.props.distance, copy=self.props.copy)
 
     def hotkey_S_Q(self):
         obj = bpy.context.active_object

src/bonsai/bonsai/bim/module/clash/decorator.py

@@ -18,43 +18,17 @@
 
 import blf
 import gpu
-from bpy.types import SpaceView3D
 from bpy_extras.view3d_utils import location_3d_to_region_2d
-from gpu_extras.batch import batch_for_shader
 from mathutils import Vector
 
 import bonsai.tool as tool
 
 
-class ClashDecorator:
-    is_installed = False
-    handlers = []
-
-    @classmethod
-    def install(cls, context):
-        if cls.is_installed:
-            cls.uninstall()
-        handler = cls()
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_text, (context,), "WINDOW", "POST_PIXEL"))
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_geometry, (context,), "WINDOW", "POST_VIEW"))
-        cls.is_installed = True
-
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
-
-    def draw_batch(self, shader_type, content_pos, color, indices=None):
-        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
-            return
-        shader = self.line_shader if shader_type == "LINES" else self.shader
-        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
-        shader.uniform_float("color", color)
-        batch.draw(shader)
+class ClashDecorator(tool.Blender.ViewportDecorator):
+    draw_methods = (
+        ("draw_text", "POST_PIXEL"),
+        ("draw_geometry", "POST_VIEW"),
+    )
 
     def draw_text(self, context):
         self.addon_prefs = tool.Blender.get_addon_preferences()

src/bonsai/bonsai/bim/module/clip_box/__init__.py

@@ -0,0 +1,130 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+import bpy
+from bpy.app.handlers import persistent
+
+import bonsai.tool as tool
+
+from . import face_quad, gizmos, operator, prop, ui
+
+classes = (
+    operator.BIM_OT_add_clip_box,
+    operator.BIM_OT_add_clip_box_for_source,
+    operator.BIM_OT_align_view_to_clip_face,
+    operator.BIM_OT_duplicate_clip_box,
+    operator.BIM_OT_remove_clip_box,
+    operator.BIM_OT_set_active_clip_box,
+    operator.BIM_OT_toggle_clip_box_enabled,
+    prop.BIMClipBoxProperties,
+    prop.BIMSceneClipBoxProperties,
+    face_quad.BIM_GT_box_face_quad,
+    face_quad.BIM_GT_box_face_outline,
+    gizmos.OBJECT_GGT_bim_clip_box,
+    ui.BIM_MT_clip_box_add_for_source,
+    ui.BIM_MT_clip_box_info,
+    ui.BIM_MT_clip_box_settings,
+    ui.BIM_UL_clip_box,
+    ui.BIM_PT_clip_box,
+)
+
+
+@persistent
+def _on_depsgraph_update(scene, depsgraph):
+    tool.ClipBox.on_depsgraph_update(scene, depsgraph)
+    tool.ClipBox.on_depsgraph_update_caps(scene, depsgraph)
+
+
+@persistent
+def _on_load_pre(filepath):
+    # Tear down any in-flight clip-box timers before Blender frees the
+    # WM / screens / areas / regions for the loading file. A refresh timer
+    # that survives the teardown fires against the new file's freshly-
+    # allocated regions before their GPU state is wired, CTD-ing inside
+    # GPU_matrix_ortho_set. The gate also blocks the depsgraph IFC-reload
+    # branch and is held closed until on_pre_view fires for the first time
+    # on the new file (first paint = GPU contexts wired).
+    tool.ClipBox._file_loading = True
+    tool.ClipBox._post_load_paint_pending = True
+    tool.ClipBox._cancel_pending_refresh()
+    tool.ClipBox._cancel_pending_cap_rebuild()
+
+
+@persistent
+def _on_load_post(filepath):
+    # The _file_loading gate is NOT cleared here: load_post fires before
+    # the new file's first paint, so GPU contexts may still be uninitialised.
+    # on_pre_view consumes _post_load_paint_pending to open the gate at the
+    # safe moment and kick the post-load re-arm.
+    # Restore the per-scene clip-box list from the project's BBIM_ClipBoxes
+    # pset. Runs after the standard load_post that creates Blender objects.
+    tool.ClipBox._last_seen_object_matrices.clear()
+    tool.ClipBox.load_from_project_pset()
+
+
+_draw_handler_pre = None
+_draw_handler_post = None
+
+
+def register():
+    global _draw_handler_pre, _draw_handler_post
+    bpy.types.Object.BIMClipBoxProperties = bpy.props.PointerProperty(type=prop.BIMClipBoxProperties)
+    bpy.types.Scene.BIMSceneClipBoxProperties = bpy.props.PointerProperty(type=prop.BIMSceneClipBoxProperties)
+    tool.ClipBox.reset_ownership()
+    if _on_depsgraph_update not in bpy.app.handlers.depsgraph_update_post:
+        bpy.app.handlers.depsgraph_update_post.append(_on_depsgraph_update)
+    if _on_load_pre not in bpy.app.handlers.load_pre:
+        bpy.app.handlers.load_pre.append(_on_load_pre)
+    if _on_load_post not in bpy.app.handlers.load_post:
+        bpy.app.handlers.load_post.append(_on_load_post)
+    if _draw_handler_pre is None:
+        _draw_handler_pre = bpy.types.SpaceView3D.draw_handler_add(tool.ClipBox.on_pre_view, (), "WINDOW", "PRE_VIEW")
+    if _draw_handler_post is None:
+        _draw_handler_post = bpy.types.SpaceView3D.draw_handler_add(
+            tool.ClipBox.on_post_view_caps, (), "WINDOW", "POST_VIEW"
+        )
+
+
+def unregister():
+    global _draw_handler_pre, _draw_handler_post
+    if _draw_handler_post is not None:
+        try:
+            bpy.types.SpaceView3D.draw_handler_remove(_draw_handler_post, "WINDOW")
+        except ValueError:
+            pass
+        _draw_handler_post = None
+    if _draw_handler_pre is not None:
+        try:
+            bpy.types.SpaceView3D.draw_handler_remove(_draw_handler_pre, "WINDOW")
+        except ValueError:
+            pass
+        _draw_handler_pre = None
+    if _on_load_post in bpy.app.handlers.load_post:
+        bpy.app.handlers.load_post.remove(_on_load_post)
+    if _on_load_pre in bpy.app.handlers.load_pre:
+        bpy.app.handlers.load_pre.remove(_on_load_pre)
+    if _on_depsgraph_update in bpy.app.handlers.depsgraph_update_post:
+        bpy.app.handlers.depsgraph_update_post.remove(_on_depsgraph_update)
+    tool.ClipBox._cancel_pending_refresh()
+    tool.ClipBox._cancel_pending_cap_rebuild()
+    tool.ClipBox._last_seen_object_matrices.clear()
+    tool.ClipBox.clear_clip_planes()
+    del bpy.types.Object.BIMClipBoxProperties
+    del bpy.types.Scene.BIMSceneClipBoxProperties

src/bonsai/bonsai/bim/module/clip_box/data.py

@@ -0,0 +1,212 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""EnumProperty ``items=`` callbacks for the source-based clip-box picker.
+
+Each callback returns ``[(id_str, label, description)]`` where ``id_str`` is
+an IFC entity id stringified for entity-driven kinds, an IFC class name for
+``CLASS``, or a fixed status name for ``STATUS``. The clip-box operator
+turns the picked id into a ``matrix_world`` via the source-preset helper.
+"""
+
+from __future__ import annotations
+
+import bonsai.tool as tool
+
+EnumItems = list[tuple[str, str, str]]
+
+# Module-level cache. Blender's EnumProperty stores raw char pointers from the
+# tuples a callback returns, so the Python strings must outlive the draw call.
+# Stashing the latest result per kind keeps them alive across callback firings.
+_items_cache: dict[str, EnumItems] = {}
+
+# Sentinel id used for the "no options available" placeholder. The operator
+# treats this as an invalid pick and surfaces an ERROR.
+NO_OPTIONS_ID = "__none__"
+
+
+def _cache(kind: str, items: EnumItems) -> EnumItems:
+    _items_cache[kind] = items
+    return items
+
+
+def _no_options(label: str) -> EnumItems:
+    # Blender refuses to draw an EnumProperty with zero entries — show a
+    # placeholder so the dialog renders and the user sees the empty state.
+    return [(NO_OPTIONS_ID, label, "")]
+
+
+def _label(entity, ifc_class: str | None = None) -> str:
+    name = (getattr(entity, "Name", None) or "Unnamed").strip() or "Unnamed"
+    return f"{ifc_class}: {name}" if ifc_class else name
+
+
+def _build_items(kind: str, empty_label: str, build_fn) -> EnumItems:
+    """Shared shape for the IFC-driven enum callbacks.
+
+    Returns the no-IFC placeholder if no file is loaded, then runs
+    ``build_fn(ifc_file)``, sorts the result alphabetically by label, and
+    returns the empty-result placeholder if nothing matched. The output is
+    always routed through the module cache.
+    """
+    ifc = tool.Ifc.get()
+    if ifc is None:
+        return _cache(kind, _no_options("No IFC loaded"))
+    items = build_fn(ifc)
+    items.sort(key=lambda t: t[1].lower())
+    if not items:
+        return _cache(kind, _no_options(empty_label))
+    return _cache(kind, items)
+
+
+# Top-down spatial hierarchy so the picker reads in the order an architect
+# already thinks in, rather than a flat alphabetical mix. IfcSpace is excluded
+# — spaces are typically empty volumes used for room metadata, so clipping to
+# one rarely matches the user intent of "show me what's in this container".
+SPATIAL_CLASSES: tuple[str, ...] = (
+    "IfcProject",
+    "IfcSite",
+    "IfcBuilding",
+    "IfcBuildingStorey",
+)
+
+
+def spatial_items(self, context) -> EnumItems:
+    # Special-case: per-class sort within the hierarchy order rather than a
+    # flat alphabetical sort, so the dropdown reads project → site → building.
+    ifc = tool.Ifc.get()
+    if ifc is None:
+        return _cache("SPATIAL", _no_options("No IFC loaded"))
+    items: EnumItems = []
+    for ifc_class in SPATIAL_CLASSES:
+        try:
+            entities = ifc.by_type(ifc_class, include_subtypes=False)
+        except RuntimeError:
+            continue
+        for entity in sorted(entities, key=lambda e: (e.Name or "").lower()):
+            items.append((str(entity.id()), _label(entity, ifc_class), ""))
+    if not items:
+        return _cache("SPATIAL", _no_options("No spatial containers"))
+    return _cache("SPATIAL", items)
+
+
+def class_items(self, context) -> EnumItems:
+    # Special-case: the picker value IS the IFC class name, not an entity id,
+    # so the build shape differs from the other entity-driven callbacks.
+    ifc = tool.Ifc.get()
+    if ifc is None:
+        return _cache("CLASS", _no_options("No IFC loaded"))
+    # List only IFC classes ACTUALLY present in the file (not the whole
+    # schema), so the user picks from classes that can produce a non-empty
+    # clip volume. ``e.is_a()`` returns the most specific class per element.
+    present = sorted({e.is_a() for e in ifc.by_type("IfcProduct")})
+    if not present:
+        return _cache("CLASS", _no_options("No products"))
+    return _cache("CLASS", [(cls, cls, "") for cls in present])
+
+
+def type_items(self, context) -> EnumItems:
+    return _build_items(
+        "TYPE",
+        "No types defined",
+        lambda ifc: [(str(e.id()), _label(e, e.is_a()), "") for e in ifc.by_type("IfcTypeProduct")],
+    )
+
+
+def material_items(self, context) -> EnumItems:
+    return _build_items(
+        "MATERIAL",
+        "No materials defined",
+        lambda ifc: [(str(e.id()), _label(e), "") for e in ifc.by_type("IfcMaterial")],
+    )
+
+
+def profile_items(self, context) -> EnumItems:
+    # ProfileName is optional. Skip unnamed profiles — they can't be
+    # meaningfully picked from a flat list.
+    return _build_items(
+        "PROFILE",
+        "No named profiles",
+        lambda ifc: [
+            (str(e.id()), f"{e.is_a()}: {e.ProfileName}", "")
+            for e in ifc.by_type("IfcProfileDef")
+            if getattr(e, "ProfileName", None)
+        ],
+    )
+
+
+def drawing_items(self, context) -> EnumItems:
+    return _build_items(
+        "DRAWING",
+        "No drawings defined",
+        lambda ifc: [(str(e.id()), _label(e), "") for e in ifc.by_type("IfcAnnotation") if e.ObjectType == "DRAWING"],
+    )
+
+
+# Display labels for each status value. The id strings on the left are the
+# canonical Pset_*Common.Status enum values accepted by Bonsai's status query.
+STATUS_LABELS: tuple[tuple[str, str], ...] = (
+    ("No Status", "No Status"),
+    ("NEW", "New"),
+    ("EXISTING", "Existing"),
+    ("DEMOLISH", "Demolish"),
+    ("TEMPORARY", "Temporary"),
+    ("OTHER", "Other"),
+    ("NOTKNOWN", "Not Known"),
+    ("UNSET", "Unset"),
+)
+
+
+def status_items(self, context) -> EnumItems:
+    # Fixed enum; no IFC needed. Still routed through the cache to share the
+    # same string-lifetime guarantee as the other callbacks.
+    return _cache("STATUS", [(value, label, "") for value, label in STATUS_LABELS])
+
+
+def system_items(self, context) -> EnumItems:
+    # IfcStructuralAnalysisModel is a structural-grouping container, not a
+    # distribution system — excluded to match Bonsai's other system pickers.
+    return _build_items(
+        "SYSTEM",
+        "No systems defined",
+        lambda ifc: [
+            (str(e.id()), _label(e, e.is_a()), "")
+            for e in ifc.by_type("IfcSystem")
+            if not e.is_a("IfcStructuralAnalysisModel")
+        ],
+    )
+
+
+def group_items(self, context) -> EnumItems:
+    # include_subtypes=False so IfcSystem and IfcZone instances don't appear
+    # under Group as well — those get their own picker entries.
+    return _build_items(
+        "GROUP",
+        "No groups defined",
+        lambda ifc: [(str(e.id()), _label(e), "") for e in ifc.by_type("IfcGroup", include_subtypes=False)],
+    )
+
+
+def zone_items(self, context) -> EnumItems:
+    return _build_items(
+        "ZONE",
+        "No zones defined",
+        lambda ifc: [(str(e.id()), _label(e), "") for e in ifc.by_type("IfcZone")],
+    )

src/bonsai/bonsai/bim/module/clip_box/face_quad.py

@@ -0,0 +1,879 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""Generic face-quad resize gizmos for any axis-aligned local box.
+
+This module contains the box-agnostic core of the interactive
+face-resize gizmos: two Gizmo classes (a near-invisible click target
+welded to each face, and a thin colored edge outline), a per-redraw
+orchestrator that places six of each on a box, and the pure one-sided
+resize arithmetic. None of it knows about IFC, clip boxes, or
+``BIMSceneClipBoxProperties`` — a future camera-view-box adapter can
+reuse the same classes and helpers.
+
+Consumer contract — the adapter group must:
+
+1. Create six ``BIM_GT_box_face_quad`` and six ``BIM_GT_box_face_outline``
+   instances at ``setup()`` time, in :data:`FACE_ROUTES` order, and bind
+   each quad's ``move_get_cb`` / ``move_set_cb`` to closures that read
+   and mutate the box's host (e.g. an Empty's ``location`` / ``scale``).
+2. Call :func:`apply_face_quad_layout` from ``refresh()`` /
+   ``draw_prepare()`` with the box's local-frame ``bmin`` / ``bmax``,
+   the host's ``matrix_world``, the OBB rotation as a 4x4
+   (``Matrix.Identity(4)`` when the rotation rides in ``matrix_world``),
+   and the current ``region`` / ``rv3d``.
+3. Implement ``_lock_for(active_gz)`` / ``_unlock_all()`` on the group
+   for drag mutual exclusion; the quad's ``invoke`` / ``exit`` call them.
+
+The resize arithmetic in :func:`compute_face_resize` is pure: feed it
+the modal scalar plus drag-start snapshots and it returns the host's
+new scale-on-axis and new origin location.
+"""
+
+from __future__ import annotations
+
+import math
+from collections.abc import Sequence
+from typing import Any
+
+import bpy
+from bpy_extras.view3d_utils import location_3d_to_region_2d, region_2d_to_location_3d
+from mathutils import Matrix, Vector
+
+# ---------------------------------------------------------------------------
+# Public iteration order
+# ---------------------------------------------------------------------------
+
+# (axis, is_max) pairs. The adapter group's ``setup()`` MUST create its
+# six face-quad gizmos in this order so positional indexing into the
+# layout helper stays correct.
+FACE_ROUTES: tuple[tuple[int, bool], ...] = (
+    (0, False),
+    (0, True),
+    (1, False),
+    (1, True),
+    (2, False),
+    (2, True),
+)
+
+
+# ---------------------------------------------------------------------------
+# Public visual constants (adapter reads these in setup())
+# ---------------------------------------------------------------------------
+
+# Standard XYZ axis colors (Blender convention).
+AXIS_COLOR: dict[int, tuple[float, float, float]] = {
+    0: (1.0, 0.2, 0.2),
+    1: (0.2, 1.0, 0.2),
+    2: (0.2, 0.4, 1.0),
+}
+
+# Documented "selectable but unpainted" trick: the GPU still writes the
+# selection buffer at this alpha so clicks register, but no visible
+# pixels are produced.
+FACE_QUAD_ALPHA: float = 0.001
+
+# Very faint hover tint — just enough to confirm "you're aiming at this
+# face" without painting visibly over geometry behind it.
+FACE_QUAD_ALPHA_HIGHLIGHT: float = 0.04
+
+# Setup-time default for ``select_bias``; the layout helper overwrites
+# it per frame to the front-facing or halo value below. Kept below the
+# canonical arrow bias so a bailed frame can't let a front quad steal
+# clicks meant for a hidden control.
+FACE_QUAD_SELECT_BIAS: float = 0.5
+
+
+# ---------------------------------------------------------------------------
+# Internal constants
+# ---------------------------------------------------------------------------
+
+# Unit quad in the local XY plane spanning [-0.5, 0.5]^2 at z=0. Two
+# CCW triangles viewed from +Z. matrix_basis stretches it onto the
+# face's perpendicular extents.
+_QUAD_TRIS: list[tuple[float, float, float]] = [
+    (-0.5, -0.5, 0.0),
+    (0.5, -0.5, 0.0),
+    (0.5, 0.5, 0.0),
+    (-0.5, -0.5, 0.0),
+    (0.5, 0.5, 0.0),
+    (-0.5, 0.5, 0.0),
+]
+
+# Unit-quad outline as 4 line segments in the local XY plane at z=0.
+_QUAD_OUTLINE_LINES: list[tuple[float, float, float]] = [
+    (-0.5, -0.5, 0.0),
+    (0.5, -0.5, 0.0),
+    (0.5, -0.5, 0.0),
+    (0.5, 0.5, 0.0),
+    (0.5, 0.5, 0.0),
+    (-0.5, 0.5, 0.0),
+    (-0.5, 0.5, 0.0),
+    (-0.5, -0.5, 0.0),
+]
+
+# Degenerate zero-area triangle for hidden back-facing quads with no
+# visible-adjacent neighbours (rare orientation). Blender tolerates
+# this; the gizmo is hidden anyway so nothing renders.
+_EMPTY_TRIS: list[tuple[float, float, float]] = [
+    (0.0, 0.0, 0.0),
+    (0.0, 0.0, 0.0),
+    (0.0, 0.0, 0.0),
+]
+
+# Rotates the gizmo's local +Z onto the outward face normal in the
+# box's local frame. Right-hand rotation around the named axis.
+_AXIS_ORIENT: dict[tuple[int, bool], Matrix] = {
+    (0, False): Matrix.Rotation(-math.pi / 2, 4, "Y"),
+    (0, True): Matrix.Rotation(math.pi / 2, 4, "Y"),
+    (1, False): Matrix.Rotation(math.pi / 2, 4, "X"),
+    (1, True): Matrix.Rotation(-math.pi / 2, 4, "X"),
+    (2, False): Matrix.Rotation(math.pi, 4, "X"),
+    (2, True): Matrix.Identity(4),
+}
+
+# Per-face mapping from face-quad local axes to local box axes for the
+# perpendicular-extent scale. ``(w_axis, h_axis)`` — the box-local axis
+# indices the quad's local X and Y span after the orientation rotation.
+_QUAD_PERP_AXES: dict[tuple[int, bool], tuple[int, int]] = {
+    (0, False): (2, 1),
+    (0, True): (2, 1),
+    (1, False): (0, 2),
+    (1, True): (0, 2),
+    (2, False): (0, 1),
+    (2, True): (0, 1),
+}
+
+# Front-facing quad sits ABOVE the halo strips so the cursor on the
+# visible face area always grabs the visible face, never accidentally
+# routes to a back-face halo strip in an adjacent screen region.
+_FACE_QUAD_FRONT_FACING_SELECT_BIAS: float = 1.5
+_FACE_QUAD_HALO_FRAME_SELECT_BIAS: float = 1.0
+
+# Target halo-strip thickness in screen pixels. The world-space margin
+# is recomputed per frame so the rim stays a roughly constant on-screen
+# size regardless of viewport zoom.
+_FACE_QUAD_HALO_TARGET_PIXELS: float = 20.0
+
+# Minimum world half-extent a face resize may shrink to. Stops a drag
+# from collapsing the host to zero or negative scale.
+_MIN_HALF_EXTENT: float = 1e-4
+
+
+# ---------------------------------------------------------------------------
+# Pure predicates (testable without Blender)
+# ---------------------------------------------------------------------------
+
+Vec3 = tuple[float, float, float]
+
+
+def face_outward_axis_local(axis: int, is_max: bool) -> Vec3:
+    """Un-rotated outward face normal in the box's local AABB coords.
+
+    For ``(axis=0, is_max=True)`` returns ``(+1, 0, 0)``; for the −X
+    face ``(-1, 0, 0)``; etc. The rotated world normal is obtained by
+    applying the host's rotation and the OBB rotation:
+    ``mw_rot @ cage_rotation @ this``.
+    """
+    sign = 1.0 if is_max else -1.0
+    out = [0.0, 0.0, 0.0]
+    out[axis] = sign
+    return (out[0], out[1], out[2])
+
+
+def front_facing_face_mask(
+    face_normals_world: Sequence[Vec3],
+    view_dir_world: Vec3,
+    eps: float = 1e-6,
+) -> tuple[bool, ...]:
+    """Which of the 6 box faces point toward the camera.
+
+    A face is front-facing iff its outward normal points AGAINST the
+    view direction (``dot(normal, view_dir) < -eps``). The ``-eps``
+    margin prevents flicker at grazing angles.
+
+    ``face_normals_world`` must be in :data:`FACE_ROUTES` order; returns
+    a 6-tuple of bool parallel to that order.
+    """
+    if len(face_normals_world) != 6:
+        msg = f"expected 6 face normals, got {len(face_normals_world)}"
+        raise ValueError(msg)
+    vx, vy, vz = view_dir_world
+    return tuple((n[0] * vx + n[1] * vy + n[2] * vz) < -eps for n in face_normals_world)
+
+
+def view_axis_parallel_face_mask(
+    face_normals_world: Sequence[Vec3],
+    view_dir_world: Vec3,
+    threshold: float = 0.95,
+) -> tuple[bool, ...]:
+    """Which faces have normals (anti-)parallel to the view direction.
+
+    True iff ``abs(dot(normal, view_dir)) >= threshold`` — i.e. the
+    face is nearly perpendicular to the screen plane. Provided as a
+    pure predicate for callers that want to detect degenerate-drag
+    conditions; the layout helper itself no longer gates on it.
+    """
+    if len(face_normals_world) != 6:
+        msg = f"expected 6 face normals, got {len(face_normals_world)}"
+        raise ValueError(msg)
+    vx, vy, vz = view_dir_world
+    return tuple(abs(n[0] * vx + n[1] * vy + n[2] * vz) >= threshold for n in face_normals_world)
+
+
+# ---------------------------------------------------------------------------
+# Pure resize arithmetic
+# ---------------------------------------------------------------------------
+
+
+def compute_face_resize(
+    *,
+    value: float,
+    init_world_half: float,
+    init_location: tuple[float, float, float],
+    world_axis: tuple[float, float, float],
+    display_size: float,
+) -> tuple[float, tuple[float, float, float]]:
+    """Pure one-sided face-resize arithmetic.
+
+    Returns ``(new_scale_axis, new_location)`` — the host's new scale
+    on the dragged axis and its new world origin — such that the
+    dragged face moves by the modal's outward delta while the OPPOSITE
+    face stays put.
+
+    ``value`` is ``init + delta``, where ``init`` is the unsigned
+    drag-start world half-extent and ``delta`` is the cursor projection
+    onto the face's OUTWARD world normal. Realized half-extent is
+    clamped to a small floor; the location shift uses the realized
+    (post-clamp) delta so the opposite face stays fixed even at the
+    clamp.
+    """
+    face_delta = value - init_world_half
+    new_world_half = init_world_half + 0.5 * face_delta
+    if new_world_half < _MIN_HALF_EXTENT:
+        new_world_half = _MIN_HALF_EXTENT
+    realized_delta = 2.0 * (new_world_half - init_world_half)
+
+    ds = display_size if display_size != 0.0 else 1.0
+    new_scale_axis = new_world_half / ds
+    shift = 0.5 * realized_delta
+    new_location = (
+        init_location[0] + shift * world_axis[0],
+        init_location[1] + shift * world_axis[1],
+        init_location[2] + shift * world_axis[2],
+    )
+    return new_scale_axis, new_location
+
+
+# ---------------------------------------------------------------------------
+# Internal geometry helpers
+# ---------------------------------------------------------------------------
+
+
+def _compute_face_quad_scale(bmin: Any, bmax: Any, axis: int, is_max: bool) -> tuple[float, float]:
+    """Return ``(w, h)`` for the face quad's scale matrix."""
+    w_axis, h_axis = _QUAD_PERP_AXES[(axis, is_max)]
+    w = float(bmax[w_axis] - bmin[w_axis])
+    h = float(bmax[h_axis] - bmin[h_axis])
+    return w, h
+
+
+def _shared_edge_corner_keys(
+    axis_a: int, is_max_a: bool, axis_b: int, is_max_b: bool
+) -> tuple[tuple[int, int, int], tuple[int, int, int]] | None:
+    """Return the 2 corner-bit triples shared by two adjacent faces.
+
+    Corner keys are 3-tuples of bits (0 = bmin, 1 = bmax). The two
+    returned corners are ordered with the free-axis bit ascending.
+    """
+    if axis_a == axis_b:
+        return None
+    free_axis = 3 - axis_a - axis_b
+    bit_a = 1 if is_max_a else 0
+    bit_b = 1 if is_max_b else 0
+    corner_lo = [0, 0, 0]
+    corner_hi = [0, 0, 0]
+    corner_lo[axis_a] = bit_a
+    corner_hi[axis_a] = bit_a
+    corner_lo[axis_b] = bit_b
+    corner_hi[axis_b] = bit_b
+    corner_lo[free_axis] = 0
+    corner_hi[free_axis] = 1
+    return (
+        (corner_lo[0], corner_lo[1], corner_lo[2]),
+        (corner_hi[0], corner_hi[1], corner_hi[2]),
+    )
+
+
+def _face_corner_keys(axis: int, is_max: bool) -> tuple[
+    tuple[int, int, int],
+    tuple[int, int, int],
+    tuple[int, int, int],
+    tuple[int, int, int],
+]:
+    """Return the 4 corner-bit triples of a face in CCW order.
+
+    Triangulation as ``[(0,1,2), (0,2,3)]`` covers the whole face with
+    two non-overlapping triangles.
+    """
+    fixed_bit = 1 if is_max else 0
+    free_axes = [a for a in (0, 1, 2) if a != axis]
+    fa0, fa1 = free_axes
+    corners = []
+    for ka, kb in ((0, 0), (1, 0), (1, 1), (0, 1)):
+        key = [0, 0, 0]
+        key[axis] = fixed_bit
+        key[fa0] = ka
+        key[fa1] = kb
+        corners.append((key[0], key[1], key[2]))
+    return (corners[0], corners[1], corners[2], corners[3])
+
+
+def _build_strip_tris_relative(
+    edge_p0_local: tuple[float, float, float],
+    edge_p1_local: tuple[float, float, float],
+    extrusion_local: tuple[float, float, float],
+) -> list[tuple[float, float, float]]:
+    """Build two CCW triangles (6 vertices) for a thin halo strip.
+
+    All inputs are in coords relative to the gizmo's ``matrix_basis``
+    anchor. The strip runs along ``[edge_p0_local, edge_p1_local]`` and
+    extrudes by ``extrusion_local`` perpendicular to the edge.
+    """
+    p0x, p0y, p0z = edge_p0_local
+    p1x, p1y, p1z = edge_p1_local
+    ex, ey, ez = extrusion_local
+    p0e = (p0x + ex, p0y + ey, p0z + ez)
+    p1e = (p1x + ex, p1y + ey, p1z + ez)
+    return [
+        (p0x, p0y, p0z),
+        p0e,
+        p1e,
+        (p0x, p0y, p0z),
+        p1e,
+        (p1x, p1y, p1z),
+    ]
+
+
+def _strips_geometry_changed(quad_gz, face_quad_local, all_tris) -> bool:
+    """True if the back-face quad's geometry differs from the cached upload.
+
+    Pure orbit/pan doesn't change either the box pose or the cage
+    rotation, so the computed strip vertices are byte-identical to the
+    previous frame's. Hitting the cache lets the back-facing branch
+    skip ``new_custom_shape`` and the GPU upload.
+    """
+    cached = getattr(quad_gz, "_strips_cache_key", None)
+    last_state = getattr(quad_gz, "_last_geometry_state", None)
+    key = (face_quad_local, all_tris)
+    if cached is None or last_state != "strips" or cached != key:
+        quad_gz._strips_cache_key = key
+        quad_gz._last_geometry_state = "strips"
+        return True
+    return False
+
+
+def _compute_face_basis(
+    mw: Any,
+    mw_rot: Any,
+    cage_rotation: Any,
+    pivot_local: Any,
+    face_local: Any,
+    orient: Any,
+) -> tuple[Any, Any]:
+    """World-space (translation, outward-normal-direction) for one face."""
+    rotated_face_local = cage_rotation.to_3x3() @ (face_local - pivot_local) + pivot_local
+    face_world = mw @ rotated_face_local
+    world_axis = (mw_rot @ cage_rotation.to_3x3() @ (orient.to_3x3() @ Vector((0.0, 0.0, 1.0)))).normalized()
+    return face_world, world_axis
+
+
+def _compose_face_matrix_basis(
+    face_world: Any,
+    mw_rot_scale: Any,
+    cage_rotation: Any,
+    orient: Any,
+    w: float,
+    h: float,
+) -> Any:
+    """Compose the 5-term ``matrix_basis`` for a face-plane gizmo.
+
+    Returns ``Translation @ mw_rot_scale @ cage_rotation @ orient @
+    Diagonal((w, h, 1, 1))`` — maps a unit-square local quad onto the
+    world-space face rectangle, including the host's scale.
+    """
+    quad_scale = Matrix.Diagonal((w, h, 1.0, 1.0))
+    return Matrix.Translation(face_world) @ mw_rot_scale.to_4x4() @ cage_rotation @ orient @ quad_scale
+
+
+def _compute_box_corners_world(
+    bmin: Any,
+    bmax: Any,
+    pivot_local: Any,
+    cage_rotation_3x3: Any,
+    mw: Any,
+) -> dict[tuple[int, int, int], Any]:
+    """Return the 8 OBB corners in world space, keyed by bit-triple."""
+    corners: dict[tuple[int, int, int], Any] = {}
+    for ix in (0, 1):
+        for iy in (0, 1):
+            for iz in (0, 1):
+                local = Vector(
+                    (
+                        float(bmax.x if ix else bmin.x),
+                        float(bmax.y if iy else bmin.y),
+                        float(bmax.z if iz else bmin.z),
+                    )
+                )
+                rotated = cage_rotation_3x3 @ (local - pivot_local) + pivot_local
+                corners[(ix, iy, iz)] = mw @ rotated
+    return corners
+
+
+def _abs_scale_matrix(mw: Any) -> Any:
+    """Return a copy of ``mw`` with all scale components ``abs()``-ed.
+
+    Without this, a negative-scale host produces a visible/clickable
+    face inversion: ``mw @ local_vec`` flips the +axis face onto the
+    -axis world side, while the rotation-only normal stays pointing
+    in the +axis direction — so the gizmo for "the +X face" sits at
+    world -X but reports its outward normal as +X.
+    """
+    loc, rot, scale = mw.decompose()
+    abs_scale = Vector((abs(scale.x), abs(scale.y), abs(scale.z)))
+    return Matrix.LocRotScale(loc, rot, abs_scale)
+
+
+def _world_radius_to_screen_pixels(
+    region: Any,
+    rv3d: Any,
+    center_world: Vector,
+    world_radius: float,
+    *,
+    min_pixels: float = 0.0,
+) -> float:
+    """Return the on-screen pixel radius of a world-space circle.
+
+    Projects ``center_world`` and a sample point offset by
+    ``world_radius`` along the camera's view-aligned right axis to
+    region pixels, and returns the screen-pixel distance between them.
+    Falls back to ``min_pixels`` if either projection fails.
+    """
+    try:
+        view_inv = rv3d.view_matrix.inverted()
+        right = Vector((view_inv[0][0], view_inv[0][1], view_inv[0][2])).normalized()
+    except (AttributeError, ValueError):
+        right = Vector((1.0, 0.0, 0.0))
+    sample_world = center_world + right * world_radius
+    return _world_segment_to_screen_pixels(region, rv3d, center_world, sample_world, min_pixels=min_pixels)
+
+
+def _world_segment_to_screen_pixels(
+    region: Any,
+    rv3d: Any,
+    p0_world: Vector,
+    p1_world: Vector,
+    *,
+    min_pixels: float = 0.0,
+) -> float:
+    """Return the on-screen pixel length of an arbitrary world segment.
+
+    Unlike :func:`_world_radius_to_screen_pixels`, this measures the
+    ACTUAL projected length of the segment — foreshortening included.
+    Use this when the segment direction is known to be oblique to the
+    screen plane (e.g. a back face's outward normal): a perpendicular
+    radius measurement overestimates the on-screen length, leaving
+    halo strips visually narrower than the requested pixel target.
+    """
+    p0 = location_3d_to_region_2d(region, rv3d, p0_world)
+    p1 = location_3d_to_region_2d(region, rv3d, p1_world)
+    if not p0 or not p1:
+        return min_pixels
+    dx = float(p1[0]) - float(p0[0])
+    dy = float(p1[1]) - float(p0[1])
+    return max(min_pixels, (dx * dx + dy * dy) ** 0.5)
+
+
+# ---------------------------------------------------------------------------
+# Gizmo classes
+# ---------------------------------------------------------------------------
+
+
+class BIM_GT_box_face_quad(bpy.types.Gizmo):  # noqa: N801 — Blender bl_idname convention
+    """Near-invisible face-quad click target with drag-to-resize modal.
+
+    Geometry: a unit quad in the local XY plane at z=0. The adapter
+    group's layout helper rotates and scales it onto the face plane;
+    the quad is welded to the world face (``use_draw_scale = False``).
+    """
+
+    bl_idname = "BIM_GT_box_face_quad"
+    bl_target_properties = ({"id": "offset", "type": "FLOAT", "array_length": 1},)
+
+    __slots__ = (
+        "custom_shape",
+        "custom_shape_select",
+        "init_value",
+        "move_get_cb",
+        "move_set_cb",
+        "axis",
+        "start_location",
+        "depth_point",
+        "callback",
+        "ctrl_click_cb",
+        "_group",
+        "_face_axis",
+        "is_max",
+        "_drag_snapshot",
+        "_last_geometry_state",
+        "_strips_cache_key",
+    )
+
+    def draw(self, context: Any) -> None:
+        self.draw_custom_shape(self.custom_shape)
+
+    def draw_select(self, context: Any, select_id: int) -> None:
+        # Back-facing quads bind ``custom_shape_select`` to the halo-strip
+        # TRIS so clicks OUTSIDE the box silhouette catch the back face.
+        # Front-facing quads leave it None and reuse ``custom_shape``.
+        shape = getattr(self, "custom_shape_select", None) or self.custom_shape
+        self.draw_custom_shape(shape, select_id=select_id)
+
+    def setup(self) -> None:
+        if not hasattr(self, "custom_shape_"):
+            self.custom_shape = self.new_custom_shape("TRIS", _QUAD_TRIS)
+        self.custom_shape_select = None
+        # Quad welded to world geometry — clicks must align with the
+        # visible face, not a screen-size widget. Disables Blender's
+        # per-frame pixel-constant autoscale.
+        self.use_draw_scale = False
+
+    # ---- modal -------------------------------------------------------------
+
+    def invoke(self, context: Any, event: Any) -> set[str]:
+        # CTRL+click handoff: dispatch a host-defined callback (e.g.
+        # align-view) instead of starting a drag.
+        if event.ctrl and getattr(self, "ctrl_click_cb", None) is not None:
+            self.ctrl_click_cb(context, event)
+            return {"FINISHED"}
+
+        region = context.region
+        rv3d = context.region_data
+        if region is None or rv3d is None:
+            return {"CANCELLED"}
+        self.init_value = self.move_get_cb()
+        # Freeze the projection plane at invoke — projection-plane
+        # drift on tilted axes causes exponential delta runaway.
+        self.depth_point = self.matrix_basis.translation.copy()
+        self.start_location = region_2d_to_location_3d(region, rv3d, (event.mouse_x, event.mouse_y), self.depth_point)
+
+        if getattr(self, "_group", None) is not None:
+            self._group._lock_for(self)
+        return {"RUNNING_MODAL"}
+
+    def exit(self, context: Any, cancel: bool) -> None:
+        try:
+            if context.area:
+                context.area.header_text_set(None)
+            if cancel:
+                self.move_set_cb(self.init_value)
+            if hasattr(self, "callback"):
+                self.callback(self.move_get_cb())
+        finally:
+            self._drag_snapshot = None
+            if getattr(self, "_group", None) is not None:
+                self._group._unlock_all()
+
+    def modal(self, context: Any, event: Any, tweak: set[str]) -> set[str]:
+        if event.type == "ESC":
+            return {"CANCELLED"}
+        region = context.region
+        rv3d = context.region_data
+        if region is None or rv3d is None:
+            return {"CANCELLED"}
+        end_location = region_2d_to_location_3d(region, rv3d, (event.mouse_x, event.mouse_y), self.depth_point)
+        delta = (end_location - self.start_location).dot(self.axis)
+        if "SNAP" in tweak:
+            delta = round(delta, 1)
+        if "PRECISE" in tweak:
+            delta /= 10.0
+        self.move_set_cb(self.init_value + delta)
+        if context.area:
+            context.area.header_text_set(f"Value: {self.move_get_cb():.3f} ({delta:.3f})")
+        return {"RUNNING_MODAL"}
+
+
+class BIM_GT_box_face_outline(bpy.types.Gizmo):  # noqa: N801 — Blender bl_idname convention
+    """Thin non-interactive colored edge outline for one face.
+
+    Drawn as 4 line segments in the face plane. The layout helper
+    toggles its ``alpha`` between near-zero and ``1.0`` based on the
+    sibling face-quad's ``is_highlight`` state — so hovering the quad
+    lights up the matching outline. ``hide_select = True`` keeps the
+    outline out of the GPU selection buffer.
+    """
+
+    bl_idname = "BIM_GT_box_face_outline"
+    bl_target_properties = ()
+
+    __slots__ = (
+        "custom_shape",
+        "_face_axis",
+        "is_max",
+        "_last_outline_state",
+    )
+
+    def draw(self, context: Any) -> None:
+        self.draw_custom_shape(self.custom_shape)
+
+    def draw_select(self, context: Any, select_id: int) -> None:
+        return None
+
+    def setup(self) -> None:
+        if not hasattr(self, "custom_shape_"):
+            self.custom_shape = self.new_custom_shape("LINES", _QUAD_OUTLINE_LINES)
+        self.use_draw_scale = False
+        self.hide_select = True
+        self._last_outline_state = "unit"
+
+
+# ---------------------------------------------------------------------------
+# Per-redraw orchestrator
+# ---------------------------------------------------------------------------
+
+
+def apply_face_quad_layout(
+    *,
+    quad_gizmos,
+    outline_gizmos,
+    bmin: Any,
+    bmax: Any,
+    matrix_world: Any,
+    cage_rotation: Any,
+    region: Any,
+    rv3d: Any,
+    locked: bool,
+) -> None:
+    """Lay out 6 face quads + 6 outlines on the box for this redraw.
+
+    ``quad_gizmos`` / ``outline_gizmos`` are length-6 sequences in
+    :data:`FACE_ROUTES` order. ``bmin`` / ``bmax`` are the box corners
+    in the host's local frame; ``matrix_world`` is the host's world
+    matrix; ``cage_rotation`` is the OBB rotation as a 4x4 (use
+    ``Matrix.Identity(4)`` when rotation rides in ``matrix_world``).
+    ``region`` / ``rv3d`` drive the view-dependent front/back split and
+    the screen-constant halo margin; passing ``rv3d = None`` bails.
+
+    Negative scale on the host is normalized to positive internally so
+    the visible cube and the clickable face gizmos stay aligned —
+    callers don't need to pre-process ``matrix_world``.
+
+    When ``locked`` (a drag is active), ``hide`` / ``select_bias``
+    writes are skipped — the active quad's geometry is still refreshed
+    so it tracks the moving box.
+    """
+    if rv3d is None or getattr(rv3d, "view_rotation", None) is None:
+        return
+    if len(quad_gizmos) != 6 or len(outline_gizmos) != 6:
+        return
+
+    mw = _abs_scale_matrix(matrix_world)
+    mw_rot = mw.to_quaternion().to_matrix()
+    mw_rot_scale = mw.to_3x3()
+    cage_rotation_3x3 = cage_rotation.to_3x3()
+    pivot_local = (bmin + bmax) * 0.5
+    box_center_local = pivot_local
+    face_midpoints_local = {
+        (0, False): Vector((float(bmin.x), box_center_local.y, box_center_local.z)),
+        (0, True): Vector((float(bmax.x), box_center_local.y, box_center_local.z)),
+        (1, False): Vector((box_center_local.x, float(bmin.y), box_center_local.z)),
+        (1, True): Vector((box_center_local.x, float(bmax.y), box_center_local.z)),
+        (2, False): Vector((box_center_local.x, box_center_local.y, float(bmin.z))),
+        (2, True): Vector((box_center_local.x, box_center_local.y, float(bmax.z))),
+    }
+
+    view_dir = (rv3d.view_rotation @ Vector((0.0, 0.0, -1.0))).normalized()
+    view_dir_tuple = (float(view_dir.x), float(view_dir.y), float(view_dir.z))
+    face_normals_world = []
+    for route_axis, route_is_max in FACE_ROUTES:
+        axis_local = Vector(face_outward_axis_local(route_axis, route_is_max))
+        n_world = (mw_rot @ cage_rotation_3x3 @ axis_local).normalized()
+        face_normals_world.append((float(n_world.x), float(n_world.y), float(n_world.z)))
+    front = front_facing_face_mask(tuple(face_normals_world), view_dir_tuple)
+
+    box_center_world = mw @ pivot_local
+    corners_world = _compute_box_corners_world(bmin, bmax, pivot_local, cage_rotation_3x3, mw)
+    route_to_index = {route: i for i, route in enumerate(FACE_ROUTES)}
+
+    for i, route in enumerate(FACE_ROUTES):
+        quad_gz = quad_gizmos[i]
+        is_front = front[i]
+        axis_b, is_max_b = route
+
+        # Place the colored OUTLINE on every face using the same composed
+        # face matrix the front-facing solid quad uses. Hidden/shown via
+        # alpha at the end of the pass.
+        outline_orient = _AXIS_ORIENT[route]
+        outline_face_world, _outline_axis = _compute_face_basis(
+            mw,
+            mw_rot,
+            cage_rotation,
+            pivot_local,
+            face_midpoints_local[route],
+            outline_orient,
+        )
+        ow, oh = _compute_face_quad_scale(bmin, bmax, axis_b, is_max_b)
+        outline_gizmos[i].matrix_basis = _compose_face_matrix_basis(
+            outline_face_world, mw_rot_scale, cage_rotation, outline_orient, ow, oh
+        )
+
+        if is_front:
+            if not locked:
+                quad_gz.hide = False
+                quad_gz.select_bias = _FACE_QUAD_FRONT_FACING_SELECT_BIAS
+            orient = _AXIS_ORIENT[route]
+            face_world, world_axis = _compute_face_basis(
+                mw,
+                mw_rot,
+                cage_rotation,
+                pivot_local,
+                face_midpoints_local[route],
+                orient,
+            )
+            w, h = _compute_face_quad_scale(bmin, bmax, axis_b, is_max_b)
+            quad_gz.matrix_basis = _compose_face_matrix_basis(face_world, mw_rot_scale, cage_rotation, orient, w, h)
+            quad_gz.axis = world_axis
+            if getattr(quad_gz, "_last_geometry_state", None) != "solid":
+                quad_gz.custom_shape = quad_gz.new_custom_shape("TRIS", _QUAD_TRIS)
+                quad_gz.custom_shape_select = None
+                quad_gz._last_geometry_state = "solid"
+            continue
+
+        # Back-facing: anchor at the back face centre; build halo strips
+        # in the planes of the adjacent FRONT faces, extruded outside
+        # the silhouette toward this face's outward normal.
+        face_world = mw @ (cage_rotation_3x3 @ (face_midpoints_local[route] - pivot_local) + pivot_local)
+        quad_gz.matrix_basis = Matrix.Translation(face_world)
+        quad_gz.axis = (mw_rot @ cage_rotation_3x3 @ Vector(face_outward_axis_local(axis_b, is_max_b))).normalized()
+
+        adjacent_front_routes = [
+            (axis_a, is_max_a)
+            for axis_a in range(3)
+            if axis_a != axis_b
+            for is_max_a in (False, True)
+            if front[route_to_index[(axis_a, is_max_a)]]
+        ]
+        # Per-face world margin: measure the screen-projected length of
+        # ONE world unit along THIS face's outward normal. The world
+        # margin that yields ~N pixels on screen is then ``N / length``.
+        # Foreshortening on oblique faces shortens the projected step,
+        # so the world step must grow to keep the strip the same width
+        # on screen.
+        face_world_margin = 0.0
+        if region is not None:
+            sample_end = box_center_world + quad_gz.axis * 1.0
+            screen_step = _world_segment_to_screen_pixels(region, rv3d, box_center_world, sample_end, min_pixels=0.0)
+            if screen_step > 0.0:
+                face_world_margin = _FACE_QUAD_HALO_TARGET_PIXELS / screen_step
+        if face_world_margin <= 0.0 or not adjacent_front_routes:
+            if not locked:
+                quad_gz.hide = True
+                quad_gz.select_bias = _FACE_QUAD_HALO_FRAME_SELECT_BIAS
+            if getattr(quad_gz, "_last_geometry_state", None) != "empty":
+                quad_gz.custom_shape = quad_gz.new_custom_shape("TRIS", _EMPTY_TRIS)
+                quad_gz.custom_shape_select = None
+                quad_gz._last_geometry_state = "empty"
+            continue
+
+        extrusion_world = quad_gz.axis * face_world_margin
+        extrusion_local = (
+            float(extrusion_world.x),
+            float(extrusion_world.y),
+            float(extrusion_world.z),
+        )
+        all_tris: list[tuple[float, float, float]] = []
+        for axis_a, is_max_a in adjacent_front_routes:
+            edge_keys = _shared_edge_corner_keys(axis_a, is_max_a, axis_b, is_max_b)
+            if edge_keys is None:
+                continue
+            key0, key1 = edge_keys
+            wp0 = corners_world[key0]
+            wp1 = corners_world[key1]
+            local_p0 = (
+                float(wp0.x - face_world.x),
+                float(wp0.y - face_world.y),
+                float(wp0.z - face_world.z),
+            )
+            local_p1 = (
+                float(wp1.x - face_world.x),
+                float(wp1.y - face_world.y),
+                float(wp1.z - face_world.z),
+            )
+            all_tris.extend(_build_strip_tris_relative(local_p0, local_p1, extrusion_local))
+
+        if not locked:
+            quad_gz.hide = False
+            quad_gz.select_bias = _FACE_QUAD_HALO_FRAME_SELECT_BIAS
+
+        corner_keys = _face_corner_keys(axis_b, is_max_b)
+        wc_local = [
+            (
+                float(corners_world[k].x - face_world.x),
+                float(corners_world[k].y - face_world.y),
+                float(corners_world[k].z - face_world.z),
+            )
+            for k in corner_keys
+        ]
+        face_quad_local = [
+            wc_local[0],
+            wc_local[1],
+            wc_local[2],
+            wc_local[0],
+            wc_local[2],
+            wc_local[3],
+        ]
+        if _strips_geometry_changed(quad_gz, tuple(face_quad_local), tuple(all_tris)):
+            quad_gz.custom_shape = quad_gz.new_custom_shape("TRIS", face_quad_local)
+            quad_gz.custom_shape_select = quad_gz.new_custom_shape("TRIS", all_tris)
+        quad_gz._last_geometry_state = "strips"
+
+    # Outline alpha follows ONLY the hovered quad's own state — light
+    # the outline of the face under the cursor, nothing else.
+    if not locked:
+        for outline_gz, quad_gz in zip(outline_gizmos, quad_gizmos, strict=True):
+            lit = bool(getattr(quad_gz, "is_highlight", False))
+            outline_gz.alpha = 1.0 if lit else 0.0
+            outline_gz.alpha_highlight = 1.0 if lit else 0.0
+
+
+__all__ = [
+    "AXIS_COLOR",
+    "FACE_QUAD_ALPHA",
+    "FACE_QUAD_ALPHA_HIGHLIGHT",
+    "FACE_QUAD_SELECT_BIAS",
+    "FACE_ROUTES",
+    "BIM_GT_box_face_outline",
+    "BIM_GT_box_face_quad",
+    "apply_face_quad_layout",
+    "compute_face_resize",
+    "face_outward_axis_local",
+    "front_facing_face_mask",
+    "view_axis_parallel_face_mask",
+]

src/bonsai/bonsai/bim/module/clip_box/gizmos.py

@@ -0,0 +1,312 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""Interactive face-quad resize gizmos for the active clip box.
+
+Adapter group that binds the generic :mod:`face_quad` core to a Bonsai
+clip-box Empty: six near-invisible click quads + six edge outlines on
+the cube's faces. Dragging a face does a ONE-SIDED resize — the dragged
+face moves along its outward world normal while the opposite face stays
+put — by writing the empty's ``location`` and ``scale``. Bonsai's
+depsgraph handler then re-arms the clip planes from the new matrix.
+"""
+
+from __future__ import annotations
+
+import contextlib
+from typing import Any
+
+import bpy
+from mathutils import Matrix, Vector
+
+import bonsai.tool as tool
+
+from . import face_quad
+
+# Local-frame bounds of the empty's CUBE display. The display spans
+# ``[-empty_display_size, +empty_display_size]^3``; Bonsai always sets
+# ``empty_display_size = 1.0`` on clip-box hosts, so the local box is
+# the unit cube. The empty's per-axis scale + rotation + translation
+# ride in ``matrix_world``, which the layout helper applies.
+_LOCAL_BMIN = Vector((-1.0, -1.0, -1.0))
+_LOCAL_BMAX = Vector((1.0, 1.0, 1.0))
+
+
+def _world_axis(empty: bpy.types.Object, axis: int, is_max: bool) -> Vector:
+    """Outward world-space unit normal of the ``(axis, is_max)`` face.
+
+    Uses the rotation-only matrix so a negative-scale empty doesn't
+    flip the resulting direction — the visible "+X face" then stays
+    associated with world +X (transformed through rotation).
+    """
+    rot_mat = empty.matrix_world.to_quaternion().to_matrix()
+    n = Vector(rot_mat.col[axis])
+    if n.length <= 0.0:
+        return Vector((0.0, 0.0, 0.0))
+    n.normalize()
+    return n if is_max else -n
+
+
+def _world_half_extent(empty: bpy.types.Object, axis: int) -> float:
+    """The empty's box half-extent along local ``axis`` in WORLD units.
+
+    A CUBE empty's local cube is ``±empty_display_size``; ``matrix_world``
+    stretches it by the column length on ``axis``. So the world
+    half-extent is ``|column[axis]| * empty_display_size``.
+    """
+    col_len = empty.matrix_world.to_3x3().col[axis].length
+    display_size = abs(float(getattr(empty, "empty_display_size", 1.0) or 1.0))
+    return float(col_len) * display_size
+
+
+def _make_face_get_cb(gz: Any, group: Any, axis: int, is_max: bool):
+    """Closure returning the world half-extent at drag start and
+    snapshotting the empty's full transform on the gizmo instance.
+
+    The snapshot lives on the gizmo (not the group) so a PERSISTENT
+    group servicing multiple clip boxes can't bleed one drag's state
+    onto another. Cleared on ``exit`` by the shared face-quad hook.
+    """
+
+    def getter() -> float:
+        empty = group._empty
+        if empty is None:
+            return 0.0
+        existing = getattr(gz, "_drag_snapshot", None)
+        if existing is not None and existing.get("empty_name") == getattr(empty, "name", None):
+            return float(existing["world_half"])
+
+        world_half = _world_half_extent(empty, axis)
+        display_size = abs(float(getattr(empty, "empty_display_size", 1.0) or 1.0))
+        gz._drag_snapshot = {
+            "empty_name": getattr(empty, "name", None),
+            "world_half": world_half,
+            "location": tuple(float(v) for v in empty.location),
+            "scale": tuple(float(v) for v in empty.scale),
+            "display_size": display_size if display_size != 0.0 else 1.0,
+            "world_axis": tuple(_world_axis(empty, axis, is_max)),
+        }
+        return float(world_half)
+
+    return getter
+
+
+def _make_ctrl_click_cb(axis: int, is_max: bool):
+    """Closure that dispatches CTRL+click on a face to the align-view operator.
+
+    Routing through an operator (rather than mutating ``rv3d`` here)
+    keeps the action F3-searchable and undoable.
+    """
+
+    def _callback(_context: Any, _event: Any) -> None:
+        bpy.ops.bim.align_view_to_clip_face("INVOKE_DEFAULT", axis=axis, is_max=is_max)
+
+    return _callback
+
+
+def _make_face_set_cb(gz: Any, group: Any, axis: int, is_max: bool):
+    """Closure that applies a one-sided face resize by writing the
+    empty's ``location`` + ``scale``.
+
+    The modal calls this with ``value = init + delta`` where ``delta``
+    is the cursor's projection onto the face's OUTWARD world normal.
+    Both reads come from ``gz._drag_snapshot`` so every frame is
+    relative to drag start, never compounding.
+    """
+    del is_max  # snapshot's world_axis carries the direction
+
+    def setter(value: float) -> None:
+        empty = group._empty
+        if empty is None:
+            return
+        snap = getattr(gz, "_drag_snapshot", None)
+        if snap is None or snap.get("empty_name") != getattr(empty, "name", None):
+            return
+
+        new_scale_axis, new_location = face_quad.compute_face_resize(
+            value=value,
+            init_world_half=snap["world_half"],
+            init_location=snap["location"],
+            world_axis=snap["world_axis"],
+            display_size=snap["display_size"],
+        )
+        new_scale = list(snap["scale"])
+        # Preserve the sign of the original scale so a user-flipped empty
+        # stays flipped after the resize — compute_face_resize returns a
+        # positive magnitude, the sign is the user's intent to keep.
+        sign = -1.0 if snap["scale"][axis] < 0.0 else 1.0
+        new_scale[axis] = sign * new_scale_axis
+
+        empty.scale = new_scale
+        empty.location = Vector(new_location)
+
+    return setter
+
+
+class OBJECT_GGT_bim_clip_box(bpy.types.GizmoGroup):  # noqa: N801 — Blender bl_idname convention
+    """Face-quad resize handles on the active clip box.
+
+    Renders six near-invisible click-target quads and six colored edge
+    outlines on the active clip-box empty whenever clipping is enabled.
+    Click-and-drag a face to resize one-sided; the opposite face stays
+    put. CTRL+click and plain click fall through to selection.
+    """
+
+    bl_idname = "OBJECT_GGT_bim_clip_box"
+    bl_label = "Bonsai Clip Box Faces"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options = {"3D", "PERSISTENT", "SHOW_MODAL_ALL"}
+
+    @classmethod
+    def poll(cls, context: Any) -> bool:
+        scene = getattr(context, "scene", None)
+        if scene is None:
+            return False
+        scene_props = tool.ClipBox.get_scene_props(scene)
+        if not scene_props.enabled or not scene_props.enable_gizmos:
+            return False
+        active_clip_box = tool.ClipBox.get_active_clip_box(scene)
+        if active_clip_box is None:
+            return False
+        # Only render when the user has the active clip box itself
+        # selected — otherwise the face handles would intercept clicks
+        # meant for the geometry behind them.
+        return getattr(context, "active_object", None) is active_clip_box
+
+    @classmethod
+    def setup_keymap(cls, keyconfig):
+        # Bind CLICK_DRAG so plain LEFTMOUSE PRESS passes through to
+        # selection — the user can still click through a near-invisible
+        # face quad to pick a mesh behind it.
+        km = keyconfig.keymaps.new(
+            name=cls.bl_idname,
+            space_type=cls.bl_space_type,
+            region_type=cls.bl_region_type,
+        )
+        km.keymap_items.new("gizmogroup.gizmo_tweak", type="LEFTMOUSE", value="CLICK_DRAG")
+        km.keymap_items.new("gizmogroup.gizmo_tweak", type="LEFTMOUSE", value="PRESS", ctrl=True)
+        return km
+
+    def setup(self, context: Any) -> None:
+        # ``_empty`` is resolved each refresh so the PERSISTENT group
+        # follows whichever clip box is active in the scene PG.
+        self._empty: bpy.types.Object | None = None
+        self._locked = False
+        self._face_routes: list[tuple[int, bool]] = []
+
+        for axis, is_max in face_quad.FACE_ROUTES:
+            gz = self.gizmos.new(face_quad.BIM_GT_box_face_quad.bl_idname)
+            gz._group = self
+            gz._face_axis = axis
+            gz.is_max = is_max
+            gz._drag_snapshot = None
+            gz._last_geometry_state = "solid"
+            gz._strips_cache_key = None
+            gz.color = face_quad.AXIS_COLOR[axis]
+            gz.color_highlight = tuple(min(1.0, c + 0.3) for c in face_quad.AXIS_COLOR[axis])
+            gz.alpha = face_quad.FACE_QUAD_ALPHA
+            gz.alpha_highlight = face_quad.FACE_QUAD_ALPHA_HIGHLIGHT
+            gz.use_draw_modal = True
+            gz.scale_basis = 1.0
+            gz.select_bias = face_quad.FACE_QUAD_SELECT_BIAS
+            gz.move_get_cb = _make_face_get_cb(gz, self, axis, is_max)
+            gz.move_set_cb = _make_face_set_cb(gz, self, axis, is_max)
+            # CTRL+click on a face aligns the viewport to look at it.
+            gz.ctrl_click_cb = _make_ctrl_click_cb(axis, is_max)
+            self._face_routes.append((axis, is_max))
+
+        # Outlines added last so they composite on top of the quad
+        # fills (Blender draws gizmos in creation order).
+        for axis, is_max in face_quad.FACE_ROUTES:
+            ol = self.gizmos.new(face_quad.BIM_GT_box_face_outline.bl_idname)
+            ol._face_axis = axis
+            ol.is_max = is_max
+            ol.color = face_quad.AXIS_COLOR[axis]
+            ol.color_highlight = face_quad.AXIS_COLOR[axis]
+            ol.alpha = 0.0
+            ol.alpha_highlight = 0.0
+            ol.line_width = 2.5
+
+    def _quad_gizmos(self):
+        return self.gizmos[: len(self._face_routes)]
+
+    def _outline_gizmos(self):
+        n = len(self._face_routes)
+        return self.gizmos[n : 2 * n]
+
+    def refresh(self, context: Any) -> None:
+        """State-change path: resolve the active empty, then run the
+        shared face-quad layout so the quads aren't stale for a frame
+        after a selection or active-index change."""
+        empty = tool.ClipBox.get_active_clip_box(context.scene)
+        self._empty = empty
+        if empty is None:
+            for gz in self.gizmos:
+                gz.hide = True
+            return
+        self._layout(context, empty)
+
+    def draw_prepare(self, context: Any) -> None:
+        """Per-redraw — fires on orbit — re-run the layout so the
+        front/back split, halo strips, and outline highlights track
+        the camera and any live G/R/S on the empty."""
+        empty = self._empty
+        if empty is None:
+            return
+        self._layout(context, empty)
+
+    def _layout(self, context: Any, empty: bpy.types.Object) -> None:
+        face_quad.apply_face_quad_layout(
+            quad_gizmos=self._quad_gizmos(),
+            outline_gizmos=self._outline_gizmos(),
+            bmin=_LOCAL_BMIN,
+            bmax=_LOCAL_BMAX,
+            matrix_world=empty.matrix_world,
+            # The empty's rotation rides in matrix_world, so the
+            # box-local OBB rotation is identity.
+            cage_rotation=Matrix.Identity(4),
+            region=getattr(context, "region", None),
+            rv3d=getattr(context, "region_data", None),
+            locked=self._locked,
+        )
+
+    # ---- mutual exclusion (lock siblings during a drag) ------------------
+
+    def _lock_for(self, active_gizmo) -> None:
+        self._locked = True
+        for gz in self.gizmos:
+            if gz is not active_gizmo:
+                with contextlib.suppress(ReferenceError, RuntimeError):
+                    gz.hide = True
+
+    def _unlock_all(self) -> None:
+        self._locked = False
+        for gz in self.gizmos:
+            with contextlib.suppress(ReferenceError, RuntimeError):
+                gz.hide = False
+        # Rebuild caps synchronously so the cross-section overlay
+        # re-forms the instant the user releases the handle, rather
+        # than waiting for the depsgraph's debounced rebuild path.
+        with contextlib.suppress(RuntimeError, ReferenceError):
+            tool.ClipBox.rebuild_caps_now()
+        # Push an undo step so the user can revert a face drag with Ctrl+Z.
+        with contextlib.suppress(RuntimeError):
+            bpy.ops.ed.undo_push(message="Resize Clip Box")

src/bonsai/bonsai/bim/module/clip_box/operator.py

@@ -0,0 +1,294 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+import bpy
+from mathutils import Matrix, Vector
+
+import bonsai.tool as tool
+from bonsai.bim.helper import prop_with_search
+
+from . import data
+
+# NOTE: do NOT add ``from __future__ import annotations`` to this module.
+# PEP 563 stringifies the operator's EnumProperty class annotations, which
+# breaks any introspection that reads ``cls.__annotations__[name].keywords``
+# — including the enum-search helper that draws the search-button icon.
+
+CLIP_BOX_NAME = "ClipBox"
+
+# Display labels for the source-based picker, used for the menu entries and
+# the dialog title. The dict keys are the canonical source-kind identifiers.
+SOURCE_KIND_LABELS: dict[str, str] = {
+    "SPATIAL": "Spatial Element",
+    "CLASS": "Class",
+    "TYPE": "Type",
+    "MATERIAL": "Material",
+    "PROFILE": "Profile",
+    "DRAWING": "Drawing",
+    "STATUS": "Status",
+    "SYSTEM": "System",
+    "GROUP": "Group",
+    "ZONE": "Zone",
+}
+
+
+_SOURCE_ID_DISPATCH = {
+    "SPATIAL": data.spatial_items,
+    "CLASS": data.class_items,
+    "TYPE": data.type_items,
+    "MATERIAL": data.material_items,
+    "PROFILE": data.profile_items,
+    "DRAWING": data.drawing_items,
+    "STATUS": data.status_items,
+    "SYSTEM": data.system_items,
+    "GROUP": data.group_items,
+    "ZONE": data.zone_items,
+}
+
+
+def _source_id_items(self, context):
+    """Dispatch the ``source_id`` enum items based on the picked ``source_kind``."""
+    fn = _SOURCE_ID_DISPATCH.get(self.source_kind)
+    if fn is None:
+        return [(data.NO_OPTIONS_ID, "No options", "")]
+    return fn(self, context)
+
+
+def _source_display_name(kind, source_id):
+    """Human-readable name of the picked source, used in the clip-box name."""
+    if kind == "STATUS":
+        return next((label for value, label in data.STATUS_LABELS if value == source_id), source_id)
+    if kind == "CLASS":
+        # source_id IS the human-readable IFC class name.
+        return source_id
+    ifc = tool.Ifc.get()
+    if ifc is None:
+        return source_id
+    try:
+        entity = ifc.by_id(int(source_id))
+    except (TypeError, ValueError, RuntimeError):
+        return source_id
+    return (getattr(entity, "Name", None) or "Unnamed").strip() or "Unnamed"
+
+
+class BIM_OT_align_view_to_clip_face(bpy.types.Operator):
+    bl_idname = "bim.align_view_to_clip_face"
+    bl_label = "Align View to Clip Box Face"
+    bl_description = "Orient the 3D viewport to look directly at the picked clip-box face"
+    bl_options = {"REGISTER"}
+
+    axis: bpy.props.IntProperty(default=0, options={"SKIP_SAVE"})
+    is_max: bpy.props.BoolProperty(default=True, options={"SKIP_SAVE"})
+
+    def execute(self, context):
+        rv3d = getattr(context, "region_data", None)
+        if rv3d is None:
+            return {"CANCELLED"}
+        clip_box = tool.ClipBox.get_active_clip_box(context.scene)
+        if clip_box is None:
+            return {"CANCELLED"}
+        rot_mat = clip_box.matrix_world.to_quaternion().to_matrix()
+        outward_local = Vector((0.0, 0.0, 0.0))
+        outward_local[self.axis] = 1.0 if self.is_max else -1.0
+        outward = (rot_mat @ outward_local).normalized()
+        if outward.length == 0.0:
+            return {"CANCELLED"}
+        up_world = (rot_mat @ _local_up_for_face(self.axis, self.is_max)).normalized()
+        rv3d.view_rotation = _view_rotation_from_forward_and_up(-outward, up_world)
+        return {"FINISHED"}
+
+
+def _local_up_for_face(axis: int, is_max: bool) -> Vector:
+    """Box-local up direction for a face, following Blender numpad conventions.
+
+    Side faces (local ±X / ±Y normal) → local +Z is up. Top face (local +Z
+    normal) → local +Y is up; bottom face (local -Z normal) → local -Y is
+    up. The caller rotates this through the empty's matrix so the
+    resulting world up axis tracks the box's orientation.
+    """
+    if axis == 2:
+        return Vector((0.0, 1.0, 0.0)) if is_max else Vector((0.0, -1.0, 0.0))
+    return Vector((0.0, 0.0, 1.0))
+
+
+def _view_rotation_from_forward_and_up(forward: Vector, up_hint: Vector) -> "bpy.types.Quaternion":
+    """Build a camera ``view_rotation`` that looks along ``forward`` with
+    ``up_hint`` projected to the camera's local +Y."""
+    back = -forward.normalized()
+    right = up_hint.cross(back)
+    if right.length < 1e-6:
+        right = Vector((1.0, 0.0, 0.0))
+    right.normalize()
+    up = back.cross(right).normalized()
+    return Matrix(
+        (
+            (right.x, up.x, back.x),
+            (right.y, up.y, back.y),
+            (right.z, up.z, back.z),
+        )
+    ).to_quaternion()
+
+
+class BIM_OT_add_clip_box(bpy.types.Operator):
+    bl_idname = "bim.add_clip_box"
+    bl_label = "Add Clip Box"
+    bl_description = (
+        "Create a clip box empty at the 3D cursor. The empty's location, rotation, and scale "
+        "drive the viewport clip planes; resize with S, move with G, rotate with R"
+    )
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context):
+        # Default to a 20m cube (scale 10 around [-1, +1] local cube) so
+        # the volume covers a typical building storey or two rather than
+        # the meaningless 2m unit cube. The user resizes with S.
+        matrix = Matrix.Translation(context.scene.cursor.location.copy()) @ Matrix.Diagonal((10.0, 10.0, 10.0, 1.0))
+        tool.ClipBox.create_clip_box_empty(context, matrix, name=CLIP_BOX_NAME)
+        return {"FINISHED"}
+
+
+class BIM_OT_add_clip_box_for_source(bpy.types.Operator):
+    bl_idname = "bim.add_clip_box_for_source"
+    bl_label = "Add Clip Box From Source"
+    bl_description = (
+        "Create a clip box sized to a chosen source: a spatial container, IFC type, material, "
+        "profile, drawing camera frustum, element status, system, group, or zone"
+    )
+    bl_options = {"REGISTER", "UNDO"}
+
+    source_kind: bpy.props.EnumProperty(
+        name="Source Kind",
+        items=[(kind, label, "") for kind, label in SOURCE_KIND_LABELS.items()],
+        default="SPATIAL",
+        options={"SKIP_SAVE"},
+    )
+    source_id: bpy.props.EnumProperty(
+        name="Source",
+        items=_source_id_items,
+        options={"SKIP_SAVE"},
+    )
+
+    def invoke(self, context, event):
+        return context.window_manager.invoke_props_dialog(self)
+
+    def draw(self, context):
+        layout = self.layout
+        label = f"Clip {SOURCE_KIND_LABELS.get(self.source_kind, 'Source')}"
+        # Search button appears once the enum exceeds the helper's threshold,
+        # giving the user a popup picker instead of a plain dropdown.
+        prop_with_search(layout, self, "source_id", text=label)
+
+    def execute(self, context):
+        if not self.source_id or self.source_id == data.NO_OPTIONS_ID:
+            self.report({"ERROR"}, "No source selected.")
+            return {"CANCELLED"}
+        matrix = tool.ClipBox.compute_matrix_for_source(self.source_kind, self.source_id)
+        if matrix is None:
+            kind_label = SOURCE_KIND_LABELS.get(self.source_kind, self.source_kind)
+            self.report(
+                {"ERROR"},
+                f"No elements found for {kind_label} '{_source_display_name(self.source_kind, self.source_id)}'.",
+            )
+            return {"CANCELLED"}
+        name = f"ClipBox.{SOURCE_KIND_LABELS.get(self.source_kind, self.source_kind)}.{_source_display_name(self.source_kind, self.source_id)}"
+        tool.ClipBox.create_clip_box_empty(context, matrix, name=name)
+        return {"FINISHED"}
+
+
+class BIM_OT_remove_clip_box(bpy.types.Operator):
+    bl_idname = "bim.remove_clip_box"
+    bl_label = "Remove Clip Box"
+    bl_description = "Remove this clip box and its host empty"
+    bl_options = {"REGISTER", "UNDO"}
+
+    index: bpy.props.IntProperty(default=-1, options={"SKIP_SAVE"})
+    delete_object: bpy.props.BoolProperty(default=True, name="Delete Host Object")
+
+    def execute(self, context):
+        scene_props = tool.ClipBox.get_scene_props(context.scene)
+        index = self.index if self.index >= 0 else scene_props.active_clip_box_index
+        if index < 0 or index >= len(scene_props.clip_boxes):
+            return {"CANCELLED"}
+
+        entry = scene_props.clip_boxes[index]
+        obj = entry.obj
+        scene_props.clip_boxes.remove(index)
+        if scene_props.active_clip_box_index >= len(scene_props.clip_boxes):
+            scene_props.active_clip_box_index = max(0, len(scene_props.clip_boxes) - 1)
+
+        if self.delete_object and obj is not None:
+            bpy.data.objects.remove(obj, do_unlink=True)
+
+        tool.ClipBox.refresh(context.scene)
+        tool.ClipBox.save_to_project_pset(context.scene)
+        return {"FINISHED"}
+
+
+class BIM_OT_set_active_clip_box(bpy.types.Operator):
+    bl_idname = "bim.set_active_clip_box"
+    bl_label = "Set Active Clip Box"
+    bl_description = "Set this clip box as the active one driving the viewport clip"
+    bl_options = {"REGISTER", "UNDO"}
+
+    index: bpy.props.IntProperty(default=-1, options={"SKIP_SAVE"})
+
+    def execute(self, context):
+        scene_props = tool.ClipBox.get_scene_props(context.scene)
+        if self.index < 0 or self.index >= len(scene_props.clip_boxes):
+            return {"CANCELLED"}
+        scene_props.active_clip_box_index = self.index
+        return {"FINISHED"}
+
+
+class BIM_OT_toggle_clip_box_enabled(bpy.types.Operator):
+    bl_idname = "bim.toggle_clip_box_enabled"
+    bl_label = "Toggle Clip Box"
+    bl_description = "Toggle whether the active clip box is driving the viewport clip planes"
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context):
+        scene_props = tool.ClipBox.get_scene_props(context.scene)
+        scene_props.enabled = not scene_props.enabled
+        return {"FINISHED"}
+
+
+class BIM_OT_duplicate_clip_box(bpy.types.Operator):
+    bl_idname = "bim.duplicate_clip_box"
+    bl_label = "Duplicate Clip Box"
+    bl_description = "Duplicate this clip box: copy its empty + matrix into a new entry"
+    bl_options = {"REGISTER", "UNDO"}
+
+    index: bpy.props.IntProperty(default=-1, options={"SKIP_SAVE"})
+
+    def execute(self, context):
+        scene_props = tool.ClipBox.get_scene_props(context.scene)
+        source_index = self.index if self.index >= 0 else scene_props.active_clip_box_index
+        if source_index < 0 or source_index >= len(scene_props.clip_boxes):
+            return {"CANCELLED"}
+        source = scene_props.clip_boxes[source_index].obj
+        if source is None:
+            return {"CANCELLED"}
+
+        copy = tool.ClipBox.create_clip_box_empty(context, source.matrix_world.copy(), name=source.name)
+        # Preserve the source's display attrs so the duplicate matches.
+        copy.empty_display_type = source.empty_display_type
+        copy.empty_display_size = source.empty_display_size
+        copy.show_in_front = source.show_in_front
+        return {"FINISHED"}

src/bonsai/bonsai/bim/module/clip_box/prop.py

@@ -0,0 +1,165 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import bpy
+from bpy.types import PropertyGroup
+
+import bonsai.tool as tool
+from bonsai.bim.prop import ObjProperty
+
+
+class BIMClipBoxProperties(PropertyGroup):
+    """Per-object marker for a clip-box host empty.
+
+    The host empty's ``matrix_world`` is the single source of truth for
+    the clip box's pose and dimensions: translation = box centre,
+    rotation = box orientation, per-axis scale = world half-extents. The
+    visible cube comes from the empty's CUBE display.
+
+    Only ``is_clip_box`` lives here; visibility (``enabled``) and overlay
+    (``show_caps``) are global per-file and live on the Scene PG.
+    """
+
+    is_clip_box: bpy.props.BoolProperty(
+        default=False,
+        description="True when this empty was created as a clip-box host. Internal flag; not user-edited.",
+    )
+
+    if TYPE_CHECKING:
+        is_clip_box: bool
+
+
+def update_active_clip_box_index(self, context):
+    tool.ClipBox.schedule_refresh()
+    tool.ClipBox.select_active_clip_box(context)
+    # Rebuild caps for the new active box's clip volume.
+    tool.ClipBox.invalidate_cap_cache(immediate=True)
+
+
+def update_show_caps(self, context):
+    tool.ClipBox.schedule_refresh()
+    # Off → on must trigger a rebuild so caps reappear immediately rather
+    # than wait for the next depsgraph tick. The rebuild is a no-op when
+    # show_caps is now False (it clears and returns), so this is safe in
+    # both directions.
+    tool.ClipBox.invalidate_cap_cache()
+
+
+def update_enabled(self, context):
+    tool.ClipBox.schedule_refresh()
+
+
+def update_clip_only_ifc_products(self, context):
+    # The eligibility set for capping changed — drop the cache and let the
+    # debounced rebuild pick up the new objects on the next idle tick.
+    tool.ClipBox.invalidate_cap_cache()
+
+
+def update_include_linked_ifc(self, context):
+    tool.ClipBox.invalidate_cap_cache()
+
+
+class BIMSceneClipBoxProperties(PropertyGroup):
+    """Scene-level registry of clip boxes in this file.
+
+    Multiple boxes may exist; ``active_clip_box_index`` selects which one
+    drives the viewport clip at any time. ``enabled`` and ``show_caps``
+    are global because the user's intent ("hide everything outside the
+    box", "draw cap overlays") applies file-wide, not per box.
+
+    ``enabled`` is intentionally not persisted to the project pset:
+    opening a fresh IFC should never silently hide geometry behind a
+    remembered toggle. Selecting any clip-box empty in the viewport
+    re-arms it (see :meth:`tool.ClipBox._sync_active_to_selection`).
+    """
+
+    clip_boxes: bpy.props.CollectionProperty(type=ObjProperty)
+    active_clip_box_index: bpy.props.IntProperty(
+        default=0,
+        min=0,
+        update=update_active_clip_box_index,
+        description="Index of the clip box currently driving the viewport clip planes",
+    )
+    enabled: bpy.props.BoolProperty(
+        name="Enabled",
+        default=False,
+        update=update_enabled,
+        description="When enabled, the active clip box hides all viewport geometry outside its 6 faces",
+    )
+    show_caps: bpy.props.BoolProperty(
+        name="Show Caps",
+        default=True,
+        update=update_show_caps,
+        description=(
+            "Draw filled cross-section caps where IFC product geometry "
+            "crosses the active clip planes. Disable for performance on "
+            "very heavy scenes"
+        ),
+    )
+    # Stored on the Scene PG so Blender persists it in the .blend; deliberately
+    # NOT written to the project pset so the IFC stays portable across users
+    # who may have different Blender-side reference geometry to clip.
+    clip_only_ifc_products: bpy.props.BoolProperty(
+        name="Only IFC Products",
+        default=True,
+        update=update_clip_only_ifc_products,
+        description=(
+            "When enabled, only IFC element geometry gets cross-section caps. "
+            "Disable to also cap Blender-side reference meshes (sketches, "
+            "imported obj, primitive cubes, …)"
+        ),
+    )
+    # Opt-in inclusion of geometry sitting inside loaded Project › Links
+    # collection-instance empties. Off by default — linked IFCs commonly
+    # carry the entire site / structural / MEP context, and bisecting
+    # them on every clip-box edit can be expensive.
+    include_linked_ifc: bpy.props.BoolProperty(
+        name="Include Linked IFC",
+        default=False,
+        update=update_include_linked_ifc,
+        description=(
+            "Also generate cross-section caps for geometry inside linked "
+            "IFC files (Project ▸ Links). Off by default — linked IFCs may "
+            "carry the entire site / structural backbone, and capping them "
+            "adds per-mesh bisect cost on every clip-box edit"
+        ),
+    )
+    # Also Scene-only — gizmo visibility is a per-user editing preference,
+    # not a portable IFC property.
+    enable_gizmos: bpy.props.BoolProperty(
+        name="Show Face Handles",
+        default=True,
+        description=(
+            "Show interactive face-resize handles on the active clip box. "
+            "Disable to fall back to plain G/R/S transforms on the empty"
+        ),
+    )
+
+    if TYPE_CHECKING:
+        active_clip_box_index: int
+        enabled: bool
+        show_caps: bool
+        clip_only_ifc_products: bool
+        include_linked_ifc: bool
+        enable_gizmos: bool

src/bonsai/bonsai/bim/module/clip_box/ui.py

@@ -0,0 +1,145 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+from __future__ import annotations
+
+from bpy.types import Menu, Panel, UIList
+
+import bonsai.tool as tool
+
+# Per-kind icon for the source-picker menu. Picked from Blender's built-in
+# icon set; semantically close to the kind so users can scan the menu visually.
+_SOURCE_MENU_ENTRIES: tuple[tuple[str, str, str], ...] = (
+    ("SPATIAL", "Clip Spatial Element", "OUTLINER_COLLECTION"),
+    ("CLASS", "Clip by Class", "BLANK1"),
+    ("TYPE", "Clip Type", "FILE_3D"),
+    ("MATERIAL", "Clip Material", "MATERIAL"),
+    ("PROFILE", "Clip Profile", "MESH_CIRCLE"),
+    ("DRAWING", "Clip Drawing Extents", "CAMERA_DATA"),
+    ("STATUS", "Clip by Status", "INFO"),
+    ("SYSTEM", "Clip by System", "MOD_FLUID"),
+    ("GROUP", "Clip by Group", "OUTLINER_OB_GROUP_INSTANCE"),
+    ("ZONE", "Clip by Zone", "MOD_LATTICE"),
+)
+
+
+class BIM_MT_clip_box_add_for_source(Menu):
+    bl_idname = "BIM_MT_clip_box_add_for_source"
+    bl_label = "Add Clip Box From Source"
+
+    def draw(self, context):
+        layout = self.layout
+        for kind, label, icon in _SOURCE_MENU_ENTRIES:
+            op = layout.operator("bim.add_clip_box_for_source", text=label, icon=icon)
+            op.source_kind = kind
+
+
+class BIM_MT_clip_box_settings(Menu):
+    bl_idname = "BIM_MT_clip_box_settings"
+    bl_label = "Clip Box Settings"
+
+    def draw(self, context):
+        scene_props = tool.ClipBox.get_scene_props(context.scene)
+        self.layout.prop(scene_props, "clip_only_ifc_products")
+        self.layout.prop(scene_props, "include_linked_ifc")
+        self.layout.prop(scene_props, "enable_gizmos")
+
+
+class BIM_MT_clip_box_info(Menu):
+    bl_idname = "BIM_MT_clip_box_info"
+    bl_label = "Clip Box Face Handles"
+
+    def draw(self, context):
+        layout = self.layout
+        layout.label(text="Face Handles", icon="INFO")
+        layout.separator()
+        layout.label(text="Drag a face to resize the clip box on that axis.")
+        layout.label(text="The opposite face stays fixed (one-sided resize).")
+        layout.label(text="Ctrl+Click a face to align the viewport to it.")
+        layout.separator()
+        layout.label(text="Toggle handles from the Settings (gear) menu.")
+
+
+class BIM_UL_clip_box(UIList):
+    def draw_item(self, context, layout, data, item, icon, active_data, active_propname, index, flt_flag):
+        obj = item.obj
+        row = layout.row(align=True)
+        if obj is None:
+            # Host empty was deleted from outliner; still expose the
+            # remove button so the orphan entry isn't permanent.
+            row.label(text="(missing)", icon="ERROR")
+            row.operator("bim.remove_clip_box", text="", icon="X", emboss=False).index = index
+            return
+        row.prop(obj, "name", text="", emboss=False, icon="MESH_CUBE")
+        row.operator("bim.duplicate_clip_box", text="", icon="DUPLICATE", emboss=False).index = index
+        row.operator("bim.remove_clip_box", text="", icon="X", emboss=False).index = index
+
+
+class BIM_PT_clip_box(Panel):
+    bl_idname = "BIM_PT_clip_box"
+    bl_label = "Clip Box"
+    bl_space_type = "PROPERTIES"
+    bl_region_type = "WINDOW"
+    bl_context = "scene"
+    bl_options = {"DEFAULT_CLOSED"}
+    bl_parent_id = "BIM_PT_tab_sandbox"
+
+    def draw(self, context):
+        layout = self.layout
+        scene_props = tool.ClipBox.get_scene_props(context.scene)
+
+        toggles = layout.row(align=True)
+        toggles.scale_y = 2.0
+        toggles.prop(
+            scene_props,
+            "enabled",
+            text="Enable Clipping",
+            icon="HIDE_OFF" if scene_props.enabled else "HIDE_ON",
+            toggle=True,
+        )
+        toggles.prop(scene_props, "show_caps", text="Show Caps", icon="MOD_SOLIDIFY", toggle=True)
+        toggles.menu("BIM_MT_clip_box_settings", icon="PREFERENCES", text="")
+        toggles.menu("BIM_MT_clip_box_info", icon="INFO", text="")
+
+        layout.separator()
+        row = layout.row(align=True)
+        row.operator("bim.add_clip_box", icon="ADD", text="Add Clip Box")
+        row.menu("BIM_MT_clip_box_add_for_source", icon="DOWNARROW_HLT", text="")
+
+        layout.template_list(
+            "BIM_UL_clip_box",
+            "",
+            scene_props,
+            "clip_boxes",
+            scene_props,
+            "active_clip_box_index",
+            rows=3,
+        )
+
+        obj = tool.ClipBox.get_active_clip_box(context.scene)
+        if obj is None:
+            layout.label(text="No active clip box", icon="INFO")
+            return
+
+        col = layout.column(align=True)
+        col.label(text="Edit the empty with G / R / S to move / rotate / resize")
+        col.prop(obj, "location")
+        col.prop(obj, "rotation_euler")
+        col.prop(obj, "scale")

src/bonsai/bonsai/bim/module/drawing/__init__.py

@@ -15,6 +15,8 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 import bpy
 
@@ -136,14 +138,34 @@ classes = (
     gizmos.GizmoArrow2D,
     gizmos.GizmoCone,
     gizmos.GizmoDimension,
-    gizmos.GizmoLock,
+    gizmos.GizmoLockOpen,
+    gizmos.GizmoLockClosed,
     gizmos.GizmoArc,
+    gizmos.GizmoLinkToggle,
+    gizmos.GizmoFillet,
+    gizmos.GizmoWallCornerIcon,
+    gizmos.GizmoWallTeeIcon,
     gizmos.GizmoPen,
     gizmos.GizmoValidate,
     gizmos.GizmoCancel,
     gizmos.GizmoPlus,
     gizmos.GizmoMinus,
+    gizmos.GizmoTrash,
+    gizmos.GizmoArrayParent,
+    gizmos.GizmoArrayAll,
+    gizmos.GizmoArrayLayerIndicator,
+    gizmos.GizmoCountLabel,
+    gizmos.GizmoMerge,
+    gizmos.GizmoSplit,
+    gizmos.GizmoUnjoin,
+    gizmos.GizmoExtend,
+    gizmos.GizmoExtendVertical,
+    gizmos.GizmoOffsetExterior,
+    gizmos.GizmoOffsetCenter,
+    gizmos.GizmoOffsetInterior,
+    gizmos.GizmoAddOpening,
     gizmos.GizmoCycle,
+    gizmos.GizmoMenu,
     # Drawing-specific gizmos
     gizmos.UglyDotGizmo,
     gizmos.ExtrusionGuidesGizmo,

src/bonsai/bonsai/bim/module/drawing/handler.py

@@ -50,6 +50,9 @@ def set_active_camera_resolution(scene: bpy.types.Scene) -> None:
     if camera.type != props.camera_type:
         camera.type = props.camera_type
 
+    if props.update_props and (drawing := tool.Ifc.get_entity(camera_obj)):
+        tool.Drawing.sync_perspective_camera_shifts(drawing, camera)
+
     ortho_scale, aspect_ratio = props.get_scale_and_aspect_ratio()
     scene_render = scene.render
     if (camera.ortho_scale != ortho_scale) or not tool.Cad.is_x(

src/bonsai/bonsai/bim/module/drawing/operator.py

@@ -57,7 +57,7 @@ import shapely
 from bpy_extras.image_utils import load_image
 from bpy_extras.io_utils import ImportHelper
 from lxml import etree
-from mathutils import Color, Vector
+from mathutils import Color, Matrix, Vector
 
 import bonsai.bim.export_ifc
 import bonsai.bim.handler
@@ -602,6 +602,7 @@ class CreateDrawing(bpy.types.Operator):
         context_type: Literal["body", "annotation"],
         drawing_elements: set[ifcopenshell.entity_instance],
         target_view: str,
+        link_matrix: Optional[Matrix] = None,
     ) -> None:
         drawing_elements = drawing_elements.copy()
         contexts_: list[list[int]] = getattr(contexts, context_type)
@@ -613,9 +614,19 @@ class CreateDrawing(bpy.types.Operator):
                 geom_settings.set("dimensionality", ifcopenshell.ifcopenshell_wrapper.CURVES_SURFACES_AND_SOLIDS)
                 geom_settings.set("iterator-output", ifcopenshell.ifcopenshell_wrapper.NATIVE)
 
-                if ifc.by_id(context[0]).ContextType == "Plan" and "PLAN_VIEW" in target_view:
+                is_plan = ifc.by_id(context[0]).ContextType == "Plan" and "PLAN_VIEW" in target_view
+                z_offset = (0.002 if target_view == "PLAN_VIEW" else -0.002) if is_plan else 0.0
+
+                if link_matrix is not None:
+                    unit_scale = ifcopenshell.util.unit.calculate_unit_scale(ifc)
+                    t = link_matrix.to_translation()
+                    offset = (t.x / unit_scale, t.y / unit_scale, t.z / unit_scale + z_offset)
+                    geom_settings.set("model-offset", offset)
+                    q = link_matrix.to_quaternion()
+                    geom_settings.set("model-rotation", (q.x, q.y, q.z, q.w))
+                elif z_offset:
                     # A 2mm Z offset to combat Z-fighting in plan or RCPs
-                    geom_settings.set("model-offset", (0.0, 0.0, 0.002 if target_view == "PLAN_VIEW" else -0.002))
+                    geom_settings.set("model-offset", (0.0, 0.0, z_offset))
 
                 geom_settings.set("context-ids", context)
                 it = ifcopenshell.geom.iterator(
@@ -923,11 +934,16 @@ class CreateDrawing(bpy.types.Operator):
 
         bim_props = tool.Blender.get_bim_props()
         prefs = tool.Blender.get_addon_preferences()
-        files = {bim_props.ifc_file: tool.Ifc.get()}
+        # Map ifc_path → (ifc_file, link_matrix); main file has no link_matrix (None)
+        files: dict[str, tuple[ifcopenshell.file, Optional[Matrix]]] = {bim_props.ifc_file: (tool.Ifc.get(), None)}
 
         props = tool.Project.get_project_props()
         for link in props.get_loaded_links_for_drawings():
-            files[link.filepath] = self.get_linked_file(link)
+            try:
+                link_matrix = tool.Project.calculate_link_matrix(link)
+            except Exception:
+                link_matrix = None
+            files[link.filepath] = (self.get_linked_file(link), link_matrix)
 
         target_view = ifcopenshell.util.element.get_psets(self.camera_element)["EPset_Drawing"]["TargetView"]
         self.setup_serialiser(target_view)
@@ -935,7 +951,13 @@ class CreateDrawing(bpy.types.Operator):
         tree = ifcopenshell.geom.tree()
         tree.enable_face_styles(True)
 
-        for ifc_path, ifc in files.items():
+        # Accumulated across every file in the loop below (main model plus any
+        # linked models) so the SHAPELY fill pass after the loop covers all of
+        # them, not just whichever file happened to be processed last.
+        raycast_objs = set()
+        elements_with_faces = set()
+
+        for ifc_path, (ifc, link_matrix) in files.items():
             # Don't use draw.main() just whilst we're prototyping and experimenting
             # TODO: hash paths are never used
             ifc_hash = hashlib.md5(ifc_path.encode("utf-8")).hexdigest()
@@ -944,13 +966,24 @@ class CreateDrawing(bpy.types.Operator):
             self.serialiser.setFile(ifc)
             drawing_elements = tool.Drawing.get_drawing_elements(self.camera_element, ifc_file=ifc)
 
+            if self.cprops.fill_mode == "SHAPELY":
+                for element in drawing_elements.copy():
+                    if element.is_a("IfcAnnotation"):
+                        continue
+                    obj = tool.Ifc.get_object(element)
+                    if obj and obj.type == "MESH" and len(obj.data.polygons):
+                        elements_with_faces.add(element.GlobalId)
+                        raycast_objs.add(obj)
+
             # Get all representation contexts to see what we're dealing with.
             # Drawings only draw bodies and annotations (and facetation, due to a Revit bug).
             # A drawing prioritises a target view context first, followed by a model view context as a fallback.
             # Specifically for PLAN_VIEW and REFLECTED_PLAN_VIEW, any Plan context is also prioritised.
             contexts = self.get_linework_contexts(ifc, target_view)
-            self.serialize_contexts_elements(ifc, tree, contexts, "body", drawing_elements, target_view)
-            self.serialize_contexts_elements(ifc, tree, contexts, "annotation", drawing_elements, target_view)
+            self.serialize_contexts_elements(ifc, tree, contexts, "body", drawing_elements, target_view, link_matrix)
+            self.serialize_contexts_elements(
+                ifc, tree, contexts, "annotation", drawing_elements, target_view, link_matrix
+            )
 
             if tool.Ifc.get() == ifc and self.camera_element not in drawing_elements:
                 with profile("Camera element"):
@@ -1017,16 +1050,6 @@ class CreateDrawing(bpy.types.Operator):
             # shapely variant
             group = root.find("{http://www.w3.org/2000/svg}g")
 
-            raycast_objs = set()
-            elements_with_faces = set()
-            for element in drawing_elements.copy():
-                if element.is_a("IfcAnnotation"):
-                    continue
-                obj = tool.Ifc.get_object(element)
-                if obj and obj.type == "MESH" and len(obj.data.polygons):
-                    elements_with_faces.add(element.GlobalId)
-                    raycast_objs.add(obj)
-
             projections = root.xpath(
                 ".//svg:g[contains(@class, 'projection')]", namespaces={"svg": "http://www.w3.org/2000/svg"}
             )
@@ -2319,7 +2342,8 @@ class ActivateDrawingBase(tool.Ifc.Operator):
     bl_description = (
         "Activates the selected drawing view.\n\n"
         + "ALT+CLICK to keep the viewport position.\n\n"
-        + "SHIFT+CLICK to load a quick preview of the drawing view"
+        + "SHIFT+CLICK to load a quick preview of the drawing view.\n\n"
+        + "SHIFT+CTRL+CLICK to load the annotations of all selected drawings without switching views"
     )
 
     drawing: bpy.props.IntProperty()
@@ -2335,13 +2359,23 @@ class ActivateDrawingBase(tool.Ifc.Operator):
         default=False,
         options={"SKIP_SAVE"},
     )
+    load_selected_annotations: bpy.props.BoolProperty(
+        name="Load Selected Annotations",
+        description="Load the annotations of all selected drawings without switching the active view.",
+        default=False,
+        options={"SKIP_SAVE"},
+    )
 
     if TYPE_CHECKING:
         drawing: int
         should_view_from_camera: bool
         use_quick_preview: bool
+        load_selected_annotations: bool
 
     def invoke(self, context, event) -> set["rna_enums.OperatorReturnItems"]:
+        if event.type == "LEFTMOUSE" and event.shift and event.ctrl:
+            self.load_selected_annotations = True
+            return self.execute(context)
         if event.type == "LEFTMOUSE" and event.alt:
             self.should_view_from_camera = False
         if event.type == "LEFTMOUSE" and event.shift:
@@ -2354,6 +2388,18 @@ class ActivateDrawingBase(tool.Ifc.Operator):
         if props.is_editing_drawings == False:
             bpy.ops.bim.load_drawings()
 
+        if self.load_selected_annotations:
+            for d in props.drawings:
+                if not (d.is_drawing and d.is_selected):
+                    continue
+                selected_drawing = tool.Ifc.get().by_id(d.ifc_definition_id)
+                # Importing the camera (if missing) ensures the drawing's
+                # collection exists so the annotations get collected into it.
+                if not tool.Ifc.get_object(selected_drawing):
+                    tool.Drawing.import_drawing(selected_drawing)
+                tool.Drawing.import_annotations_in_group(tool.Drawing.get_drawing_group(selected_drawing))
+            return {"FINISHED"}
+
         drawing = tool.Ifc.get().by_id(self.drawing)
         dprops = tool.Drawing.get_document_props()
 
@@ -2439,7 +2485,8 @@ class ActivateDrawing(bpy.types.Operator, ActivateDrawingBase):
     bl_description = (
         "Activates the selected drawing view.\n\n"
         + "ALT+CLICK to keep the viewport position.\n\n"
-        + "SHIFT+CLICK to load a quick preview of the drawing view"
+        + "SHIFT+CLICK to load a quick preview of the drawing view.\n\n"
+        + "SHIFT+CTRL+CLICK to load the annotations of all selected drawings without switching views"
     )
 
 

src/bonsai/bonsai/bim/module/drawing/prop.py

@@ -604,6 +604,7 @@ class BIMCameraProperties(PropertyGroup):
         return tool.Blender.get_active_uilist_element(dprops.drawing_styles, self.active_drawing_style_index)
 
     # For now, this JSON dump are all the parameters that determine a camera's "Block representation"
+    # Perspective camera shift is stored in EPset_Drawing and intentionally excluded here.
     # By checking this, you will know whether or not the camera IFC representation needs to be refreshed
     def update_representation(self, matrix_world: Matrix) -> bool:
         """Update ``representation`` based on current camera properties and the provided world matrix.

src/bonsai/bonsai/bim/module/drawing/ui.py

@@ -99,6 +99,10 @@ class BIM_PT_camera(Panel):
         if props.target_view == "MODEL_VIEW":
             row = self.layout.row()
             row.prop(props, "camera_type")
+            if props.camera_type == "PERSP":
+                row = self.layout.row(align=True)
+                row.prop(camera_data, "shift_x", text="Camera Shift X/Y:")
+                row.prop(camera_data, "shift_y", text="")
 
         row = self.layout.row()
         row.prop(props, "linework_mode")

src/bonsai/bonsai/bim/module/geometry/data.py

@@ -44,8 +44,12 @@ class ViewportData:
 
     @classmethod
     def load(cls):
-        cls.is_loaded = True
+        # Populate data BEFORE flipping is_loaded so a raising ``mode()``
+        # call doesn't leave the class half-loaded (flag set, dict empty).
+        # Subsequent items-callback invocations skip load() on a True flag
+        # and would hit ``cls.data["mode"]`` → KeyError.
         cls.data = {"mode": cls.mode()}
+        cls.is_loaded = True
 
     @classmethod
     def mode(cls) -> tool.Blender.BLENDER_ENUM_ITEMS:
@@ -76,9 +80,9 @@ class ViewportData:
                 modes.append(edit_mode)
             elif element.is_a("IfcGridAxis"):
                 modes.append(edit_mode)
-            elif tool.Blender.Modifier.is_roof(element):
+            elif tool.Parametric.is_roof(element):
                 modes.append(edit_mode)
-            elif tool.Blender.Modifier.is_railing(element):
+            elif tool.Parametric.is_railing(element):
                 modes.append(edit_mode)
             elif item_mode not in modes:
                 modes.append(item_mode)

src/bonsai/bonsai/bim/module/geometry/decorator.py

@@ -16,8 +16,6 @@
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
 
-from collections.abc import Sequence
-
 import blf
 import bpy
 import gpu
@@ -25,15 +23,16 @@ import ifcopenshell
 import numpy as np
 from bpy.types import SpaceView3D
 from bpy_extras.view3d_utils import location_3d_to_region_2d
-from gpu_extras.batch import batch_for_shader
 from mathutils import Matrix, Vector
 
 import bonsai.tool as tool
 
 
-class ItemDecorator:
-    is_installed = False
-    handlers = []
+class ItemDecorator(tool.Blender.ViewportDecorator):
+    draw_methods = (
+        ("draw_text", "POST_PIXEL"),
+        ("draw", "POST_VIEW"),
+    )
     objs: dict[str, dict[str, list]]
     obj_is_selected: dict[str, bool]
     obj_is_boolean: dict[str, list[ifcopenshell.entity_instance]]
@@ -119,23 +118,6 @@ class ItemDecorator:
             "special_edges": special_edges,
         }
 
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
-
-    def draw_batch(self, shader_type, content_pos, color, indices=None):
-        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
-            return
-        shader = self.line_shader if shader_type == "LINES" else self.shader
-        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
-        shader.uniform_float("color", color)
-        batch.draw(shader)
-
     def draw_text(self, context):
         self.addon_prefs = tool.Blender.get_addon_preferences()
         selected_elements_color = self.addon_prefs.decorator_color_selected
@@ -163,11 +145,6 @@ class ItemDecorator:
         blf.disable(font_id, blf.SHADOW)
 
     def draw(self, context: bpy.types.Context) -> None:
-        def transparent_color(color: Sequence[float], alpha: float = 0.05) -> list[float]:
-            color = [i for i in color]
-            color[3] = alpha
-            return color
-
         self.addon_prefs = tool.Blender.get_addon_preferences()
         selected_elements_color = self.addon_prefs.decorator_color_selected
         unselected_elements_color = self.addon_prefs.decorator_color_unselected
@@ -197,15 +174,33 @@ class ItemDecorator:
                     if context.mode != "OBJECT":
                         continue
                     self.draw_batch("LINES", data["verts"], selected_elements_color, data["edges"])
-                    self.draw_batch("TRIS", data["verts"], transparent_color(selected_elements_color), data["tris"])
+                    self.draw_batch(
+                        "TRIS",
+                        data["verts"],
+                        tool.Blender.transparent_color(selected_elements_color, alpha=0.05),
+                        data["tris"],
+                    )
                     self.draw_batch("LINES", data["special_verts"], selected_elements_color, data["special_edges"])
                 elif self.obj_is_boolean[obj_name]:
                     self.draw_batch("LINES", data["verts"], special_elements_color, data["edges"])
-                    self.draw_batch("TRIS", data["verts"], transparent_color(special_elements_color), data["tris"])
+                    self.draw_batch(
+                        "TRIS",
+                        data["verts"],
+                        tool.Blender.transparent_color(special_elements_color, alpha=0.05),
+                        data["tris"],
+                    )
                     self.draw_batch("LINES", data["special_verts"], special_elements_color, data["special_edges"])
                 else:
                     self.draw_batch(
-                        "LINES", data["verts"], transparent_color(unselected_elements_color, alpha=0.2), data["edges"]
+                        "LINES",
+                        data["verts"],
+                        tool.Blender.transparent_color(unselected_elements_color, alpha=0.2),
+                        data["edges"],
+                    )
+                    self.draw_batch(
+                        "TRIS",
+                        data["verts"],
+                        tool.Blender.transparent_color(special_elements_color, alpha=0.05),
+                        data["tris"],
                     )
-                    self.draw_batch("TRIS", data["verts"], transparent_color(special_elements_color), data["tris"])
                     self.draw_batch("LINES", data["special_verts"], special_elements_color, data["special_edges"])

src/bonsai/bonsai/bim/module/geometry/operator.py

@@ -60,6 +60,7 @@ import bonsai.core.root
 import bonsai.core.spatial
 import bonsai.tool as tool
 from bonsai.bim.ifc import IfcStore
+from bonsai.bim.module.model import preview_base
 from bonsai.bim.module.model.decorator import ProfileDecorator
 
 if TYPE_CHECKING:
@@ -545,6 +546,13 @@ class UpdateRepresentation(bpy.types.Operator, tool.Ifc.Operator):
         objs = [bpy.data.objects[obj_name]] if obj_name else context.selected_objects
         self.file = tool.Ifc.get()
 
+        # Tessellated face sets (IfcTriangulatedFaceSet/IfcPolygonalFaceSet) were
+        # introduced in IFC4 and do not exist in IFC2X3. Catch this early so we
+        # don't silently fall back to a faceted brep after stripping materials.
+        if self.ifc_representation_class == "IfcTessellatedFaceSet" and self.file.schema == "IFC2X3":
+            self.report({"ERROR"}, "Tessellated face sets are not supported in IFC2X3.")
+            return {"CANCELLED"}
+
         for obj in objs:
             # TODO: write unit tests to see how this bulk operation handles
             # contradictory ifc_representation_class values and when
@@ -882,6 +890,16 @@ class OverrideDelete(bpy.types.Operator):
         # Track aggregates before deleting their parts
         aggregates_to_check = self.track_aggregates(objects_to_remove)
 
+        # Snapshot the set of IFC entity ids being deleted in this batch so the
+        # connection-rel cascade inside `delete_ifc_object` can suppress
+        # partner-side regenerate when the partner is also about to vanish.
+        batch_being_deleted_ids: set[int] = set()
+        for obj in objects_to_remove:
+            if not tool.Blender.is_valid_data_block(obj):
+                continue
+            if (entity := tool.Ifc.get_entity(obj)) is not None:
+                batch_being_deleted_ids.add(entity.id())
+
         clear_active_object = True
 
         for i, obj in enumerate(objects_to_remove, 1):
@@ -923,7 +941,7 @@ class OverrideDelete(bpy.types.Operator):
                 if tool.Drawing.is_auto_annotation(element):
                     self.report({"INFO"}, "References cannot be deleted. Exclude the referenced element instead.")
                     continue
-                tool.Geometry.delete_ifc_object(obj)
+                tool.Geometry.delete_ifc_object(obj, batch_being_deleted_ids=batch_being_deleted_ids)
             elif tool.Geometry.is_representation_item(obj):
                 tool.Geometry.delete_ifc_item(obj)
             else:
@@ -1022,14 +1040,17 @@ class OverrideDelete(bpy.types.Operator):
             pset = ifcopenshell.util.element.get_pset(element, "BBIM_Array")
             if not pset:
                 continue
-            array_parents.add(ifc_file.by_guid(pset["Parent"]))
+            try:
+                array_parents.add(ifc_file.by_guid(pset["Parent"]))
+            except RuntimeError:
+                continue
 
         for array_parent in array_parents:
             array_parent_obj = tool.Ifc.get_object(array_parent)
-            data = [(i, data) for i, data in enumerate(tool.Blender.Modifier.Array.get_modifiers_data(array_parent))]
+            data = [(i, data) for i, data in enumerate(tool.Array.get_modifiers_data(array_parent))]
             # NOTE: there is a way to remove arrays more precisely but it's more complex
             for i, modifier_data in reversed(data):
-                children = set(tool.Blender.Modifier.Array.get_children_objects(modifier_data))
+                children = set(tool.Array.get_children_objects(modifier_data))
                 if children.issubset(selected_objects):
                     with context.temp_override(active_object=array_parent_obj):
                         bpy.ops.bim.remove_array(item=i)
@@ -1183,7 +1204,7 @@ class OverrideDuplicateMove(bpy.types.Operator):
         operator: bpy.types.Operator, context: bpy.types.Context, linked: bool = False
     ) -> set["rna_enums.OperatorReturnItems"]:
         # Deep magick from the dawn of time
-        if tool.Ifc.get():
+        if tool.Ifc.get() and tool.Model.has_selected_ifc_objects(include_active=False):
             IfcStore.execute_ifc_operator(operator, context)
             return {"FINISHED"}
 
@@ -1287,6 +1308,9 @@ class OverrideDuplicateMove(bpy.types.Operator):
                             if part_obj:
                                 all_objects_to_select.add(part_obj)
 
+        # Non-IFC duplicates aren't tracked in old_to_new but are left selected by duplicate_ifc_objects
+        all_objects_to_select.update(obj for obj in context.selected_objects if not tool.Ifc.get_entity(obj))
+
         # Deselect everything first
         bpy.ops.object.select_all(action="DESELECT")
 
@@ -2223,6 +2247,8 @@ class OverrideEscape(bpy.types.Operator):
             bpy.ops.bim.hide_all_openings()
         elif tool.Aggregate.get_aggregate_props().in_aggregate_mode:
             bpy.ops.bim.disable_aggregate_mode()
+        elif preview_base.try_cancel_active_preview(context):
+            pass
         elif active_object := context.active_object:
             if tool.Blender.Modifier.try_canceling_editing_modifier_parameters_or_path(active_object):
                 pass
@@ -2264,6 +2290,8 @@ class OverrideModeSetEdit(bpy.types.Operator, tool.Ifc.Operator):
                 gprops = tool.Geometry.get_geometry_props()
                 if gprops.representation_obj:
                     tool.Geometry.disable_item_mode()
+                    if active_obj := bpy.context.active_object:
+                        active_obj.select_set(False)
                 else:
                     bonsai.core.aggregate.exit_aggregate_mode(tool.Aggregate)
                 return {"FINISHED"}
@@ -2350,6 +2378,7 @@ class OverrideModeSetEdit(bpy.types.Operator, tool.Ifc.Operator):
             and usage in ("LAYER1", "LAYER2")
         ):
             self.report({"INFO"}, f"Parametric {usage} elements cannot be edited directly")
+            obj.select_set(False)
         elif item.is_a("IfcSweptAreaSolid"):
             tool.Geometry.sync_item_positions()
             res = tool.Model.import_profile((profile := item.SweptArea), obj=obj)
@@ -2358,6 +2387,7 @@ class OverrideModeSetEdit(bpy.types.Operator, tool.Ifc.Operator):
                     {"INFO"},
                     f"Couldn't import profile, editing it directly is not yet supported. Failing profile: {profile}.",
                 )
+                obj.select_set(False)
                 return
             tool.Ifc.link(item, obj.data)
             self.enable_edit_mode(context)
@@ -2485,9 +2515,9 @@ class OverrideModeSetObject(bpy.types.Operator, tool.Ifc.Operator):
                     profile = tool.Ifc.get().by_id(profile_id)
                     if tool.Ifc.get_object(profile):  # We are editing an arbitrary profile
                         bpy.ops.bim.edit_arbitrary_profile()
-                elif tool.Blender.Modifier.is_railing(element):
+                elif tool.Parametric.is_railing(element):
                     bpy.ops.bim.finish_editing_railing_path()
-                elif tool.Blender.Modifier.is_roof(element):
+                elif tool.Parametric.is_roof(element):
                     bpy.ops.bim.finish_editing_roof_path()
                 elif tool.Model.get_usage_type(element) == "PROFILE":
                     bpy.ops.bim.edit_extrusion_axis()
@@ -3156,7 +3186,7 @@ class EnableEditingRepresentationItems(bpy.types.Operator, tool.Ifc.Operator):
                 product_reps = element.RepresentationMaps
             item_aspect = {}
             for product_rep in product_reps:
-                for aspect in product_rep.HasShapeAspects:
+                for aspect in getattr(product_rep, "HasShapeAspects", ()):
                     for aspect_rep in aspect.ShapeRepresentations:
                         if aspect_rep.ContextOfItems != representation.ContextOfItems:
                             continue

src/bonsai/bonsai/bim/module/geometry/ui.py

@@ -17,6 +17,7 @@
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
 
 import bpy
+import ifcopenshell.util.unit
 from bpy.types import Menu, Panel, UIList
 
 import bonsai.bim
@@ -483,10 +484,32 @@ class BIM_PT_placement(Panel):
             row.label(text="No Object Placement Found")
             return
 
+        is_imperial = False
+        if tool.Ifc.get():
+            length_unit = ifcopenshell.util.unit.get_project_unit(tool.Ifc.get(), "LENGTHUNIT")
+            if length_unit and length_unit.Name != "METRE":
+                is_imperial = True
+
         row = self.layout.row()
-        row.prop(context.active_object, "location", text="Location")
+        row.label(text="Location:")
+
+        if is_imperial:
+            loc = context.active_object.location
+            for i, (axis, comp) in enumerate(zip("XYZ", (loc.x, loc.y, loc.z))):
+                split = self.layout.split(factor=0.6)
+                split.prop(context.active_object, "location", index=i, text=axis)
+                sub = split.row()
+                sub.enabled = False
+                sub.alignment = "LEFT"
+                sub.label(text=tool.Unit.format_distance(comp))
+        else:
+            for i, axis in enumerate("XYZ"):
+                self.layout.prop(context.active_object, "location", index=i, text=axis)
+
         row = self.layout.row()
-        row.prop(context.active_object, "rotation_euler", text="Rotation")
+        row.label(text="Rotation:")
+        for i, axis in enumerate("XYZ"):
+            self.layout.prop(context.active_object, "rotation_euler", index=i, text=axis)
 
         if props.blender_offset_type != "NONE":
             row = self.layout.row(align=True)

src/bonsai/bonsai/bim/module/georeference/decorator.py

@@ -21,7 +21,6 @@ from math import radians
 import blf
 import gpu
 import ifcopenshell.util.geolocation
-from bpy.types import SpaceView3D
 from bpy_extras.view3d_utils import location_3d_to_region_2d
 from gpu_extras.batch import batch_for_shader
 from mathutils import Matrix, Vector
@@ -30,27 +29,11 @@ import bonsai.tool as tool
 from bonsai.bim.module.georeference.data import GeoreferenceData
 
 
-class GeoreferenceDecorator:
-    is_installed = False
-    handlers = []
-
-    @classmethod
-    def install(cls, context):
-        if cls.is_installed:
-            cls.uninstall()
-        handler = cls()
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_text, (context,), "WINDOW", "POST_PIXEL"))
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_geometry, (context,), "WINDOW", "POST_VIEW"))
-        cls.is_installed = True
-
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
+class GeoreferenceDecorator(tool.Blender.ViewportDecorator):
+    draw_methods = (
+        ("draw_text", "POST_PIXEL"),
+        ("draw_geometry", "POST_VIEW"),
+    )
 
     def draw_batch(self, shader_type, content_pos, color, indices=None, should_scale=True):
         if not tool.Blender.validate_shader_batch_data(content_pos, indices):
@@ -197,6 +180,10 @@ class GeoreferenceDecorator:
         decorator_color_error = self.addon_prefs.decorator_color_error
 
         gpu.state.blend_set("ALPHA")
+        # The georef gizmo is a coordinate-system overlay: it must communicate
+        # orientation regardless of model contents, so depth testing is bypassed.
+        original_depth_test = gpu.state.depth_test_get()
+        gpu.state.depth_test_set("ALWAYS")
 
         self.line_shader = gpu.shader.from_builtin("POLYLINE_UNIFORM_COLOR")
         self.line_shader.bind()  # required to be able to change uniforms of the shader
@@ -335,6 +322,8 @@ class GeoreferenceDecorator:
                 self.draw_batch("LINES", verts, decorator_color_special, edges)
                 self.draw_dashed_line(location * 3, location * 6, decorator_color_error)
 
+        gpu.state.depth_test_set(original_depth_test)
+
     def draw_dashed_line(self, start, end, colour, should_scale=True):
         direction = (end - start).normalized()
         distance = (end - start).length

src/bonsai/bonsai/bim/module/light/decorator.py

@@ -20,44 +20,18 @@
 import blf
 import bpy
 import gpu
-from bpy.types import SpaceView3D
 from bpy_extras.view3d_utils import location_3d_to_region_2d
-from gpu_extras.batch import batch_for_shader
 from mathutils import Matrix, Vector
 
 import bonsai.tool as tool
 from bonsai.bim.module.light.data import SolarData
 
 
-class SolarDecorator:
-    is_installed = False
-    handlers = []
-
-    @classmethod
-    def install(cls, context):
-        if cls.is_installed:
-            cls.uninstall()
-        handler = cls()
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_text, (context,), "WINDOW", "POST_PIXEL"))
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_geometry, (context,), "WINDOW", "POST_VIEW"))
-        cls.is_installed = True
-
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
-
-    def draw_batch(self, shader_type, content_pos, color, indices=None):
-        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
-            return
-        shader = self.line_shader if shader_type == "LINES" else self.shader
-        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
-        shader.uniform_float("color", color)
-        batch.draw(shader)
+class SolarDecorator(tool.Blender.ViewportDecorator):
+    draw_methods = (
+        ("draw_text", "POST_PIXEL"),
+        ("draw_geometry", "POST_VIEW"),
+    )
 
     def draw_text(self, context: bpy.types.Context) -> None:
         self.addon_prefs = tool.Blender.get_addon_preferences()

src/bonsai/bonsai/bim/module/material/operator.py

@@ -637,6 +637,16 @@ class EditAssignedMaterial(bpy.types.Operator, tool.Ifc.Operator):
                     usage=material_set_usage,
                     attributes=attributes,
                 )
+
+                for obj in objects:
+                    obj_element = tool.Ifc.get_entity(obj)
+                    if not obj_element:
+                        continue
+                    obj_material_usage = ifcopenshell.util.element.get_material(obj_element)
+                    if obj_material_usage and obj_material_usage.is_a("IfcMaterialProfileSetUsage"):
+                        obj_material_usage.CardinalPoint = material_set_usage.CardinalPoint
+                        obj_material_usage.ReferenceExtent = material_set_usage.ReferenceExtent
+
                 model_profile.DumbProfileRecalculator().recalculate(objects)
 
         bpy.ops.bim.disable_editing_assigned_material(obj=active_obj.name)

src/bonsai/bonsai/bim/module/model/__init__.py

@@ -15,19 +15,26 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 from typing import NamedTuple
 
 import bpy
 
+import bonsai.tool as tool
+
 from . import (
     array,
     covering,
+    decorator,
     door,
     external,
     grid,
     handler,
+    host_add_opening_gizmo,
     mep,
+    mep_bend_preview,
     opening,
     product,
     profile,
@@ -46,17 +53,28 @@ from . import (
 
 classes = (
     array.AddArray,
-    array.DisableEditingArray,
-    array.EditArray,
+    array.CancelEditingArray,
     array.EnableEditingArray,
+    array.FinishEditingArray,
     array.ApplyArray,
     array.RegenerateArray,
     array.RemoveArray,
     array.SelectAllArrayObjects,
     array.SelectArrayParent,
+    array.ArrayParentGizmoClick,
+    array.EditArrayFromChild,
     array.Input3DCursorXArray,
     array.Input3DCursorYArray,
     array.Input3DCursorZArray,
+    array.EnableEditingParametric,
+    array.AddArrayFromFeatureEdit,
+    array.ArrayGizmoClick,
+    array.ToggleArrayMethod,
+    array.RemoveArrayLayerFromEdit,
+    array.InputArrayCount,
+    array.AdjustArrayCount,
+    array.GizmoArrayEdition,
+    array.GizmoArrayChild,
     product.AddDefaultType,
     product.AddEmptyType,
     product.AddOccurrence,
@@ -68,21 +86,51 @@ classes = (
     product.SetActiveType,
     workspace.Hotkey,
     workspace.BIM_MT_add_representation_item,
+    wall.AddPerpendicularWall,
     wall.AddWallsFromSlab,
     wall.AlignWall,
+    wall.CancelEditingWall,
     wall.ChangeExtrusionDepth,
     wall.ChangeExtrusionXAngle,
     wall.ChangeLayerLength,
+    wall.CycleWallOffset,
     wall.DrawPolylineWall,
+    wall.EnableEditingWall,
+    wall.ExtendWallHeightToCursor,
     wall.ExtendWallsToUnderside,
+    wall.RegenerateWallToUnderside,
     wall.ExtendWallsToWall,
     wall.ExtendWallsToPolylinePoint,
+    wall.ExtendWallToCursor,
+    wall.FinishEditingWall,
     wall.FlipWall,
+    host_add_opening_gizmo.GizmoHostAddOpening,
+    host_add_opening_gizmo.GizmoHostToggleOpenings,
+    wall.GizmoWallEdition,
+    wall.GizmoWallExtendVertically,
+    wall.GizmoWallFilletPreview,
+    wall.GizmoWallFilletReedit,
+    wall.GizmoWallFilletToggleOpenings,
+    wall.GizmoPairDisconnect,
+    wall.GizmoSlabEdition,
+    wall.GizmoSlabUnjoinWalls,
+    wall.GizmoWallJoinIntersection,
+    wall.GizmoWallLinkToggle,
+    wall.GizmoWallUnjoinSingle,
+    wall.JoinWallsIntersection,
     wall.MergeWall,
     wall.OffsetWalls,
     wall.RecalculateWall,
+    wall.RotateWall90,
     wall.SplitWall,
+    wall.SplitWallAtCursor,
+    wall.DisconnectElements,
     wall.UnjoinWalls,
+    wall.EnableWallFilletPreview,
+    wall.FinishWallFilletPreview,
+    wall.CancelWallFilletPreview,
+    wall.EnableWallFilletPreviewFromCorner,
+    wall.CreateWallFillet,
     opening.AddBoolean,
     opening.CloneOpening,
     opening.EditOpenings,
@@ -94,6 +142,7 @@ classes = (
     opening.RemoveBoolean,
     opening.SelectBoolean,
     opening.ShowOpenings,
+    opening.ToggleHostOpenings,
     opening.UpdateOpeningsFocus,
     profile.ChangeCardinalPoint,
     profile.ChangeProfileDepth,
@@ -109,11 +158,14 @@ classes = (
     slab.DisableEditingExtrusionProfile,
     slab.DisableEditingSketchExtrusionProfile,
     slab.AddSlabFromWall,
+    slab.CancelEditingSlab,
     slab.DrawPolylineSlab,
     slab.EditExtrusionProfile,
     slab.EditSketchExtrusionProfile,
     slab.EnableEditingExtrusionProfile,
     slab.EnableEditingSketchExtrusionProfile,
+    slab.EnableEditingSlab,
+    slab.FinishEditingSlab,
     slab.RecalculateSlab,
     slab.ResetVertex,
     slab.SetArcIndex,
@@ -140,10 +192,19 @@ classes = (
     prop.BIMDoorProperties,
     prop.BIMRailingProperties,
     prop.BIMRoofProperties,
+    prop.BIMSlabProperties,
+    prop.BIMWallProperties,
+    prop.BIMPipeSegmentProperties,
+    prop.BIMDuctSegmentProperties,
     prop.BIMPolylineProperties,
     prop.BIMExternalParametricGeometryProperties,
+    prop.BIMBendPreviewProperties,
+    prop.BIMWallFilletPreviewProperties,
+    prop.BIMPreviewProperties,
+    prop.BIMParametricEditDialogPrefs,
     ui.BIM_PT_array,
     ui.BIM_PT_stair,
+    ui.BIM_PT_wall,
     ui.BIM_PT_sverchok,
     ui.BIM_PT_window,
     ui.BIM_PT_door,
@@ -164,7 +225,8 @@ classes = (
     stair.ToggleStairProperty,
     stair.AdjustStairTreads,
     stair.SetStairTreads,
-    stair.CycleStairType,
+    stair.InputStairTreads,
+    stair.PickStairType,
     stair.GizmoStairEdition,
     sverchok_modifier.CreateNewSverchokGraph,
     sverchok_modifier.UpdateDataFromSverchok,
@@ -177,7 +239,7 @@ classes = (
     window.FinishEditingWindow,
     window.EnableEditingWindow,
     window.RemoveWindow,
-    window.CycleWindowType,
+    window.PickWindowType,
     window.GizmoWindowEdition,
     door.BIM_OT_add_door,
     door.AddDoor,
@@ -186,15 +248,19 @@ classes = (
     door.EnableEditingDoor,
     door.RemoveDoor,
     door.ToggleDoorSwing,
-    door.CycleDoorType,
+    door.PickDoorType,
     door.GizmoDoorEdition,
     railing.BIM_OT_add_railing,
     railing.CopyRailingParameters,
     railing.AddRailing,
     railing.CancelEditingRailing,
+    railing.CycleRailingType,
     railing.FinishEditingRailing,
+    railing.PickRailingTerminalType,
     railing.FlipRailingPathOrder,
     railing.EnableEditingRailing,
+    railing.GizmoRailingSchematic,
+    railing.ToggleRailingUseManualSupports,
     railing.CancelEditingRailingPath,
     railing.FinishEditingRailingPath,
     railing.EnableEditingRailingPath,
@@ -203,16 +269,39 @@ classes = (
     roof.AddRoof,
     roof.CancelEditingRoof,
     roof.CopyRoofParameters,
+    roof.CycleRoofGenerationMethod,
     roof.FinishEditingRoof,
     roof.EnableEditingRoof,
     roof.CancelEditingRoofPath,
     roof.FinishEditingRoofPath,
     roof.EnableEditingRoofPath,
+    roof.GizmoRoofEdition,
     roof.RemoveRoof,
     roof.SetGableRoofEdgeAngle,
     mep.MEPAddObstruction,
     mep.MEPAddTransition,
     mep.MEPAddBend,
+    mep.MEPRemoveTerminalFitting,
+    mep.SelectMEPPathMembers,
+    mep.MEPJoinSegments,
+    mep_bend_preview.EnableBendPreview,
+    mep_bend_preview.FinishBendPreview,
+    mep_bend_preview.CancelBendPreview,
+    mep_bend_preview.EnableBendPreviewFromBend,
+    mep_bend_preview.GizmoBendPreview,
+    mep.EnableEditingPipeSegment,
+    mep.FinishEditingPipeSegment,
+    mep.CancelEditingPipeSegment,
+    mep.EnableEditingDuctSegment,
+    mep.FinishEditingDuctSegment,
+    mep.CancelEditingDuctSegment,
+    mep.ExtendPipeSegmentToCursor,
+    mep.ExtendDuctSegmentToCursor,
+    mep.SplitPipeSegmentAtCursor,
+    mep.SplitDuctSegmentAtCursor,
+    mep.GizmoPipeSegmentEdition,
+    mep.GizmoDuctSegmentEdition,
+    mep.GizmoMEPActions,
     external.ApplyExternalParametricGeometry,
 )
 
@@ -264,15 +353,17 @@ def register():
     bpy.types.Scene.BIMModelProperties = bpy.props.PointerProperty(type=prop.BIMModelProperties)
     bpy.types.Scene.BIMPolylineProperties = bpy.props.PointerProperty(type=prop.BIMPolylineProperties)
     bpy.types.Object.BIMArrayProperties = bpy.props.PointerProperty(type=prop.BIMArrayProperties)
-    bpy.types.Object.BIMStairProperties = bpy.props.PointerProperty(type=prop.BIMStairProperties)
     bpy.types.Object.BIMSverchokProperties = bpy.props.PointerProperty(type=prop.BIMSverchokProperties)
-    bpy.types.Object.BIMWindowProperties = bpy.props.PointerProperty(type=prop.BIMWindowProperties)
-    bpy.types.Object.BIMDoorProperties = bpy.props.PointerProperty(type=prop.BIMDoorProperties)
-    bpy.types.Object.BIMRailingProperties = bpy.props.PointerProperty(type=prop.BIMRailingProperties)
-    bpy.types.Object.BIMRoofProperties = bpy.props.PointerProperty(type=prop.BIMRoofProperties)
+    # Per-parametric-type ``BIM<Name>Properties`` PointerProperties — driven by
+    # ``tool.Parametric.EDIT_TYPES``; adding a registry entry is the single touchpoint.
+    tool.Parametric.register_object_properties(prop)
     bpy.types.Object.BIMExternalParametricGeometryProperties = bpy.props.PointerProperty(
         type=prop.BIMExternalParametricGeometryProperties
     )
+    bpy.types.Scene.BIMPreviewProperties = bpy.props.PointerProperty(type=prop.BIMPreviewProperties)
+    bpy.types.WindowManager.BIMParametricEditDialogPrefs = bpy.props.PointerProperty(
+        type=prop.BIMParametricEditDialogPrefs
+    )
 
     bpy.types.VIEW3D_MT_add.prepend(ui.add_menu)
     bpy.app.handlers.load_post.append(handler.load_post)
@@ -281,6 +372,17 @@ def register():
 
 
 def unregister():
+    # DecorationsHandler is installed lazily by bim.show_openings; tear it down
+    # (along with its persistent depsgraph / undo / redo / load cache handlers)
+    # before the rest of unregister so those handlers can't fire against
+    # half-unloaded module state.
+    opening.DecorationsHandler.uninstall()
+
+    # Network path overlays attach SpaceView3D draw handlers on toggle;
+    # uninstall here so addon disable / Blender shutdown doesn't leak them.
+    decorator.MEPSystemPathDecorator.uninstall()
+    decorator.WallSystemPathDecorator.uninstall()
+
     if not bpy.app.background:
         for tool_data in reversed(tools):
             bpy.utils.unregister_tool(tool_data.tool)
@@ -288,13 +390,11 @@ def unregister():
     del bpy.types.Scene.BIMModelProperties
     del bpy.types.Scene.BIMPolylineProperties
     del bpy.types.Object.BIMArrayProperties
-    del bpy.types.Object.BIMStairProperties
     del bpy.types.Object.BIMSverchokProperties
-    del bpy.types.Object.BIMWindowProperties
-    del bpy.types.Object.BIMDoorProperties
-    del bpy.types.Object.BIMRailingProperties
-    del bpy.types.Object.BIMRoofProperties
+    tool.Parametric.unregister_object_properties()
     del bpy.types.Object.BIMExternalParametricGeometryProperties
+    del bpy.types.Scene.BIMPreviewProperties
+    del bpy.types.WindowManager.BIMParametricEditDialogPrefs
 
     bpy.app.handlers.load_post.remove(handler.load_post)
     bpy.types.VIEW3D_MT_add.remove(ui.add_menu)

src/bonsai/bonsai/bim/module/model/data.py

@@ -51,6 +51,10 @@ class AuthoringData:
 
     @classmethod
     def load(cls, ifc_element_type: Optional[str] = None):
+        # ``is_loaded`` is set first as a recursion guard: one of the data
+        # computations evaluates a PropertyGroup enum's ``items`` callback,
+        # which re-enters this method. Without the guard, load recurses to
+        # RecursionError.
         cls.is_loaded = True
         cls.props = tool.Model.get_model_props()
         cls.data["default_container"] = cls.default_container()

src/bonsai/bonsai/bim/module/model/door.py

@@ -37,7 +37,9 @@ import bonsai.core.root
 import bonsai.tool as tool
 from bonsai.bim.module.drawing import gizmos as gizmo
 from bonsai.bim.module.drawing.gizmos import DimensionGizmoConfig
+from bonsai.bim.module.model.wall_offset_gizmos import WALL_OFFSET_GIZMO_CONFIGS
 from bonsai.bim.module.model.window import create_bm_box, create_bm_window
+from bonsai.bim.parametric_lifecycle import FeatureModifierEditMixin, PickTypeMixin
 
 if TYPE_CHECKING:
     from bonsai.bim.module.model.prop import BIMDoorProperties
@@ -566,103 +568,58 @@ class AddDoor(bpy.types.Operator, tool.Ifc.Operator):
         return {"FINISHED"}
 
 
-class CancelEditingDoor(bpy.types.Operator, tool.Ifc.Operator):
+class _DoorEditMixin(FeatureModifierEditMixin):
+    """Type-specific hooks for door parametric-edit operators. Multi-object —
+    iterates ``tool.Blender.get_selected_objects()`` so a finish/cancel applies
+    to every selected door at once."""
+
+    pset_name = "BBIM_Door"
+
+    @classmethod
+    def _iter_targets(cls, context: bpy.types.Context) -> list[bpy.types.Object]:
+        return tool.Blender.get_selected_objects()
+
+    @classmethod
+    def _is_element_type(cls, element):
+        return tool.Parametric.is_door(element)
+
+    @classmethod
+    def _get_props(cls, obj: bpy.types.Object):
+        return tool.Model.get_door_props(obj)
+
+    @classmethod
+    def _update_modifier_representation(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        update_door_modifier_representation(obj)
+
+
+class CancelEditingDoor(_DoorEditMixin, bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.cancel_editing_door"
     bl_label = "Cancel Editing Door on Selected Objects"
     bl_description = "Cancel editing and revert door parameters to their previous values"
     bl_options = {"REGISTER", "UNDO"}
 
-    def cancel_editing_door_on_object(self, obj: bpy.types.Object) -> None:
-        element = tool.Ifc.get_entity(obj)
-        assert element
-        if not tool.Blender.Modifier.is_door(element):
-            return
-        props = tool.Model.get_door_props(obj)
-        data = json.loads(ifcopenshell.util.element.get_pset(element, "BBIM_Door", "Data"))
-        data.update(data.pop("lining_properties"))
-        data.update(data.pop("panel_properties"))
-
-        # restore previous settings since editing was canceled
-        props.set_props_kwargs_from_ifc_data(data)
-
-        body = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
-        core.switch_representation(
-            tool.Ifc,
-            tool.Geometry,
-            obj=obj,
-            representation=body,
-        )
-
-        props.is_editing = False
-
-    def _execute(self, context: bpy.types.Context) -> set[str]:  # noqa: ARG002
-        for obj in tool.Blender.get_selected_objects():
-            self.cancel_editing_door_on_object(obj)
-        return {"FINISHED"}
+    def _execute(self, context: bpy.types.Context) -> set[str]:
+        return self._cancel_targets(context)
 
 
-class FinishEditingDoor(bpy.types.Operator, tool.Ifc.Operator):
+class FinishEditingDoor(_DoorEditMixin, bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.finish_editing_door"
     bl_label = "Finish Editing Door on Selected Objects"
     bl_description = "Apply changes and finish editing door parameters"
     bl_options = {"REGISTER", "UNDO"}
 
-    def finish_editing_door_on_object(self, obj: bpy.types.Object) -> None:
-        element = tool.Ifc.get_entity(obj)
-        assert element
-        if not tool.Blender.Modifier.is_door(element):
-            return
-        props = tool.Model.get_door_props(obj)
-
-        door_data = props.get_general_kwargs(convert_to_project_units=True)
-        lining_props = props.get_lining_kwargs(convert_to_project_units=True)
-        panel_props = props.get_panel_kwargs(convert_to_project_units=True)
-
-        door_data["lining_properties"] = lining_props
-        door_data["panel_properties"] = panel_props
-
-        props.is_editing = False
-
-        update_door_modifier_representation(obj)
-        element_type = ifcopenshell.util.element.get_type(element)
-        if element_type:
-            tool.Model.mark_thumbnail_for_update(element_type)
-
-        pset = tool.Pset.get_element_pset(element, "BBIM_Door")
-        door_data = tool.Ifc.get().createIfcText(json.dumps(door_data, default=list))
-        ifcopenshell.api.pset.edit_pset(tool.Ifc.get(), pset=pset, properties={"Data": door_data})
-
-    def _execute(self, context: bpy.types.Context) -> set[str]:  # noqa: ARG002
-        for obj in tool.Blender.get_selected_objects():
-            self.finish_editing_door_on_object(obj)
-        return {"FINISHED"}
+    def _execute(self, context: bpy.types.Context) -> set[str]:
+        return self._finish_targets(context)
 
 
-class EnableEditingDoor(bpy.types.Operator, tool.Ifc.Operator):
+class EnableEditingDoor(_DoorEditMixin, bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.enable_editing_door"
     bl_label = "Enable Editing Door on Selected Objects"
     bl_description = "Enter edit mode to modify door parameters interactively"
     bl_options = {"REGISTER", "UNDO"}
 
-    def edit_door_on_obj(self, obj: bpy.types.Object) -> None:
-        element = tool.Ifc.get_entity(obj)
-        assert element
-        if not tool.Blender.Modifier.is_door(element):
-            return
-        props = tool.Model.get_door_props(obj)
-        data = json.loads(ifcopenshell.util.element.get_pset(element, "BBIM_Door", "Data"))
-        data.update(data.pop("lining_properties"))
-        data.update(data.pop("panel_properties"))
-        data.update(tool.Model.get_constituents_props_data(element))
-
-        # required since we could load pset from .ifc and BIMDoorProperties won't be set
-        props.set_props_kwargs_from_ifc_data(data)
-        props.is_editing = True
-
-    def _execute(self, context: bpy.types.Context) -> set[str]:  # noqa: ARG002
-        for obj in tool.Blender.get_selected_objects():
-            self.edit_door_on_obj(obj)
-        return {"FINISHED"}
+    def _execute(self, context: bpy.types.Context) -> set[str]:
+        return self._enable_targets(context)
 
 
 class RemoveDoor(bpy.types.Operator, tool.Ifc.Operator):
@@ -673,7 +630,7 @@ class RemoveDoor(bpy.types.Operator, tool.Ifc.Operator):
     def remove_door_on_object(self, obj: bpy.types.Object) -> None:
         element = tool.Ifc.get_entity(obj)
         assert element
-        if not tool.Blender.Modifier.is_door(element):
+        if not tool.Parametric.is_door(element):
             return
         props = tool.Model.get_door_props(obj)
         props.is_editing = False
@@ -688,12 +645,8 @@ class RemoveDoor(bpy.types.Operator, tool.Ifc.Operator):
 
 
 class ToggleDoorSwing(bpy.types.Operator, tool.Ifc.Operator):
-    """Toggle door swing direction and optionally flip door geometry.
-
-    Shift+Click (when flip_geometry=True): Flip geometry only without changing door direction"""
-
     bl_idname = "bim.toggle_door_swing"
-    bl_label = "Toggle Door Swing"
+    bl_label = "Change Door Swing"
     bl_options = {"REGISTER", "UNDO"}
 
     flip_geometry: bpy.props.BoolProperty(name="Flip Geometry", default=False)
@@ -704,6 +657,15 @@ class ToggleDoorSwing(bpy.types.Operator, tool.Ifc.Operator):
         name="Skip Direction Change", default=False, options={"HIDDEN", "SKIP_SAVE"}
     )
 
+    @classmethod
+    def description(cls, context: bpy.types.Context, properties: bpy.types.OperatorProperties) -> str:
+        if properties.flip_geometry:
+            return (
+                "Swing the door from the opposite side of the wall. "
+                "Shift+click: mirror the door without changing which side it opens to"
+            )
+        return "Move the door hinge to the opposite side"
+
     def invoke(self, context: bpy.types.Context, event: bpy.types.Event) -> set[str]:
         self.skip_direction_change = event.shift
         return self.execute(context)
@@ -730,7 +692,7 @@ class ToggleDoorSwing(bpy.types.Operator, tool.Ifc.Operator):
         if not element:
             return {"CANCELLED"}
 
-        is_door = tool.Blender.Modifier.is_door(element)
+        is_door = tool.Parametric.is_door(element)
 
         if self.flip_geometry:
             tool.Geometry.flip_object(obj, self.flip_local_axes)
@@ -744,20 +706,20 @@ class ToggleDoorSwing(bpy.types.Operator, tool.Ifc.Operator):
         return {"FINISHED"}
 
 
-class CycleDoorType(bpy.types.Operator, tool.Ifc.Operator, gizmo.CycleTypeMixin):
-    """Cycle through available door types. Shift+click to cycle in reverse."""
+class PickDoorType(bpy.types.Operator, tool.Ifc.Operator, PickTypeMixin):
+    """Pick a door type from a popup menu."""
 
-    bl_idname = "bim.cycle_door_type"
-    bl_label = "Cycle Door Type"
+    bl_idname = "bim.pick_door_type"
+    bl_label = "Pick Door Type"
     bl_options = {"REGISTER", "UNDO"}
 
-    element_checker = "is_door"
-    props_getter = "get_door_props"
+    element_checker = tool.Parametric.is_door
+    props_getter = tool.Model.get_door_props
     type_literal = tool.Model.DoorType
     type_attr = "door_type"
 
     def _execute(self, context: bpy.types.Context) -> set[str]:
-        return self._cycle_type(context)
+        return self._pick_type(context)
 
 
 class GizmoDoorEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
@@ -770,7 +732,7 @@ class GizmoDoorEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
     enable_editing_operator = "bim.enable_editing_door"
     finish_editing_operator = "bim.finish_editing_door"
     cancel_editing_operator = "bim.cancel_editing_door"
-    cycle_type_operator = "bim.cycle_door_type"
+    pick_type_operator = "bim.pick_door_type"
 
     # Declarative dimension gizmo configuration with visibility and position
     # matrix_position lambdas replace the get_dimension_matrix_* methods
@@ -877,14 +839,44 @@ class GizmoDoorEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
                 p.get_transom_window_center_z(),
             ),
         ),
+        *WALL_OFFSET_GIZMO_CONFIGS,
     ]
 
-    props_getter = "get_door_props"
+    # Big quarter-arc hit shapes cover much of the door face — without a
+    # negative select_bias they would steal clicks from the small dimension
+    # and edit gizmos drawn on top of them.
+    SWING_ARC_SELECT_BIAS = -1000.0
+    swing_arc_operator = "bim.toggle_door_swing"
+
+    swing_arc_props = [
+        gizmo.SwingArcConfig(
+            name="primary",
+            visibility_condition=lambda p: p.is_editing and "SLIDING" not in p.door_type,
+            hinge_x=lambda p: (
+                p.overall_width if p.door_type.endswith("RIGHT") and "DOUBLE_DOOR" not in p.door_type else 0.0
+            ),
+            hinge_y=lambda p: p.lining_offset,
+            panel_width=lambda p: p.overall_width / 2 if "DOUBLE_DOOR" in p.door_type else p.overall_width,
+            x_mirror=lambda p: p.door_type.endswith("RIGHT") and "DOUBLE_DOOR" not in p.door_type,
+        ),
+        gizmo.SwingArcConfig(
+            name="secondary",
+            visibility_condition=lambda p: p.is_editing
+            and "DOUBLE_DOOR" in p.door_type
+            and "SLIDING" not in p.door_type,
+            hinge_x=lambda p: p.overall_width,
+            hinge_y=lambda p: p.lining_offset,
+            panel_width=lambda p: p.overall_width / 2,
+            x_mirror=lambda _p: True,
+        ),
+    ]
+
+    props_getter = tool.Model.get_door_props
     gizmo_pref_name = "door"
 
     @classmethod
     def is_element_type(cls, element: ifcopenshell.entity_instance) -> bool:
-        return tool.Blender.Modifier.is_door(element)
+        return tool.Parametric.is_door(element)
 
     def get_icon_y_extent(self, props: "BIMDoorProperties") -> tuple[float, float]:
         """Get Y extents for door icon positioning.
@@ -902,24 +894,20 @@ class GizmoDoorEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
         return (furthest_y, furthest_y)
 
     def setup_element_specific_gizmos(self, context: bpy.types.Context) -> None:
-        """Create door-specific swing arc gizmos."""
-        prefs = tool.Blender.get_addon_preferences()
-        inactive_color = prefs.decorator_color_background[:3]
-        special_color = prefs.decorator_color_special[:3]
+        """Create one (main, flip) swing-arc pair per ``swing_arc_props`` entry.
 
-        self.gizmo_door_type = self.create_arc_gizmo(
-            special_color,
-            "bim.toggle_door_swing",
-            prop_path="BIMDoorProperties.door_type",
-            flip_geometry=False,
-        )
-        self.gizmo_flip_arc = self.create_arc_gizmo(
-            inactive_color,
-            "bim.toggle_door_swing",
-            prop_path="BIMDoorProperties.door_type",
-            flip_geometry=True,
-            flip_local_axes="XY",
-        )
+        Stored as ``self.gizmo_swing_arc_<name>`` and ``self.gizmo_swing_arc_<name>_flip``
+        and pinned to ``SWING_ARC_SELECT_BIAS`` so other door gizmos win selection."""
+        prefs = tool.Blender.get_addon_preferences()
+        main_color = prefs.decorator_color_special[:3]
+        flip_color = prefs.decorator_color_background[:3]
+        for cfg in self.swing_arc_props:
+            main = self.create_arc_gizmo(main_color, self.swing_arc_operator, flip_geometry=False)
+            flip = self.create_arc_gizmo(flip_color, self.swing_arc_operator, flip_geometry=True)
+            for gz in (main, flip):
+                gz.select_bias = self.SWING_ARC_SELECT_BIAS
+            setattr(self, f"gizmo_swing_arc_{cfg.name}", main)
+            setattr(self, f"gizmo_swing_arc_{cfg.name}_flip", flip)
 
     def _refresh_element_specific(
         self, context: bpy.types.Context, mw: Matrix, props: "BIMDoorProperties"  # noqa: ARG002
@@ -938,29 +926,23 @@ class GizmoDoorEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
         self._update_view_dependent_dimensions(context, mw, props)
 
     def update_swing_gizmos(self, mw: Matrix, props: "BIMDoorProperties") -> None:
-        """Update swing gizmo position and color based on editing state."""
-        prefs = tool.Blender.get_addon_preferences()
-        door_gizmo_prefs = prefs.gizmos.door
-
-        door_type_visible = self.update_gizmo_visibility(
-            self.gizmo_door_type, props.is_editing, door_gizmo_prefs.swing_arc
-        )
-        flip_arc_visible = self.update_gizmo_visibility(
-            self.gizmo_flip_arc, props.is_editing, door_gizmo_prefs.flip_arc
-        )
-
-        if not door_type_visible and not flip_arc_visible:
-            return
-
-        swing_x_offset = props.overall_width if "RIGHT" in props.door_type else 0.0
-        base_swing_transform = Matrix.Translation(V_(swing_x_offset, props.lining_offset, 0)) @ Matrix.Scale(
-            props.overall_width, 4
-        )
-
-        if door_type_visible:
-            self.gizmo_door_type.matrix_basis = mw @ base_swing_transform
-            self.gizmo_door_type.color = prefs.decorations_colour[:3]
-
-        if flip_arc_visible:
-            mirror_y = Matrix.Scale(-1, 4, (0, 1, 0))
-            self.gizmo_flip_arc.matrix_basis = mw @ base_swing_transform @ mirror_y
+        """Position each declared swing-arc pair per its config + props state."""
+        mirror_y = Matrix.Scale(-1, 4, (0, 1, 0))
+        for cfg in self.swing_arc_props:
+            main = getattr(self, f"gizmo_swing_arc_{cfg.name}")
+            flip = getattr(self, f"gizmo_swing_arc_{cfg.name}_flip")
+            show = cfg.visibility_condition(props)
+            main_visible = self.update_gizmo_visibility(main, show)
+            flip_visible = self.update_gizmo_visibility(flip, show)
+            if not (main_visible or flip_visible):
+                continue
+            x_flip = Matrix.Scale(-1, 4, (1, 0, 0)) if cfg.x_mirror(props) else Matrix.Identity(4)
+            transform = (
+                Matrix.Translation(V_(cfg.hinge_x(props), cfg.hinge_y(props), 0))
+                @ Matrix.Scale(cfg.panel_width(props), 4)
+                @ x_flip
+            )
+            if main_visible:
+                main.matrix_basis = mw @ transform
+            if flip_visible:
+                flip.matrix_basis = mw @ transform @ mirror_y

src/bonsai/bonsai/bim/module/model/host_add_opening_gizmo.py

@@ -0,0 +1,247 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""Generic single-click "Add Opening" gizmo for hosts (walls, slabs, roofs).
+
+One GizmoGroup serves every IFC host type that exposes ``HasOpenings``:
+parametric LAYER2 walls, any ``IfcSlab``, and any ``IfcRoof``. The poll
+guards host-host pairings so this gizmo never overlaps with the existing
+wall-join / extend-vertically gizmos. The positioner dispatches on element
+type — walls use axis-projection + camera-facing-Y math (which requires the
+parametric layer-set); slabs and roofs use a world-Z face bias driven by
+the void object's elevation against the host's bounding box."""
+
+import bpy
+from mathutils import Vector
+
+import bonsai.tool as tool
+from bonsai.bim.module.drawing import gizmos as gizmo
+from bonsai.bim.module.model.opening import is_filling_supported
+from bonsai.bim.module.model.wall import (
+    _get_wall_geom_cached,
+    _wall_camera_facing_icon_y,
+    _wall_gizmo_poll_gate,
+    _WallGeomCachedBillboardingMixin,
+)
+
+
+def is_supported_host(element) -> bool:
+    """Total predicate (None → False). Walls accept either a parametric
+    LAYER2 wall OR a fillet-corner wall (both expose a usable axis +
+    layer-set for the anchor math); slabs and roofs only need the bound
+    box so any IfcSlab / IfcRoof qualifies regardless of parametric
+    modifier state."""
+    if element is None:
+        return False
+    return tool.Parametric.is_path_connectable_wall(element) or element.is_a("IfcSlab") or element.is_a("IfcRoof")
+
+
+def is_supported_filling_or_opening(element) -> bool:
+    """Total predicate for the add-opening gizmo poll. ``None`` (raw Blender
+    mesh) is accepted because the operator converts unclassified meshes
+    into ``IfcOpeningElement`` instances. ``IfcOpeningElement`` is accepted
+    because reassigning an existing opening to a new host is a legal path
+    through the operator. Otherwise defer to the generator's own
+    supported-filling predicate."""
+    if element is None:
+        return True
+    if element.is_a("IfcOpeningElement"):
+        return True
+    return is_filling_supported(element)
+
+
+def _resolve_active_host(context: bpy.types.Context, n_selected: int):
+    """Shared poll prologue: gizmo gate + selection cardinality + active-in-
+    selected + IFC entity lookup + supported-host predicate. Returns the
+    active element on success, ``None`` on any failure — callers chain their
+    feature-specific checks past the early-return."""
+    if not _wall_gizmo_poll_gate(context):
+        return None
+    selected = tool.Blender.get_selected_objects()
+    if len(selected) != n_selected:
+        return None
+    active = context.active_object
+    if active is None or active not in selected:
+        return None
+    element = tool.Ifc.get_entity(active)
+    if not element or not is_supported_host(element):
+        return None
+    return element
+
+
+class GizmoHostAddOpening(bpy.types.GizmoGroup, _WallGeomCachedBillboardingMixin):
+    """Activates when exactly two objects are selected and one is a fillable
+    host (wall / slab / roof) while the other is a valid filling (door /
+    window / existing opening, or a plain Blender mesh).
+
+    Selection-order independent: the host role is identified by class, not
+    by active state. The "+" icon anchors on the host's surface regardless
+    of which object was clicked first. The dispatched ``bim.add_opening``
+    operator also handles either order.
+
+    Per-frame positioning keeps the icon facing the camera as the viewport
+    orbits."""
+
+    bl_idname = "OBJECT_GGT_bim_host_add_opening"
+    bl_label = "Host Add Opening Gizmo"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options = {"3D", "PERSISTENT"}
+
+    @classmethod
+    def poll(cls, context: bpy.types.Context) -> bool:
+        if not _wall_gizmo_poll_gate(context):
+            return False
+        selected = list(tool.Blender.get_selected_objects())
+        if len(selected) != 2:
+            return False
+        active = context.active_object
+        if active is None or active not in selected:
+            return False
+        a_element = tool.Ifc.get_entity(selected[0])
+        b_element = tool.Ifc.get_entity(selected[1])
+        return cls._is_apply_opening_pair(a_element, b_element) or cls._is_apply_opening_pair(b_element, a_element)
+
+    @staticmethod
+    def _is_apply_opening_pair(host_element, filling_element) -> bool:
+        """``host_element`` qualifies as a fillable host AND ``filling_element``
+        qualifies as a filling. Used twice with the operands swapped so the
+        gizmo polls true regardless of which of the two selected objects is
+        active."""
+        if not is_supported_host(host_element):
+            return False
+        if not hasattr(host_element, "HasOpenings"):
+            return False
+        return is_supported_filling_or_opening(filling_element)
+
+    def setup(self, context: bpy.types.Context) -> None:
+        default_color, highlight_color = self.get_decoration_colors()
+        self.add_opening_icon = self.setup_icon_gizmo(
+            "VIEW3D_GT_add_opening", default_color, highlight_color, "bim.add_opening"
+        )
+
+    def position_gizmos(self, context: bpy.types.Context) -> None:
+        selected = list(tool.Blender.get_selected_objects())
+        if len(selected) != 2:
+            return
+        a, b = selected[0], selected[1]
+        a_element = tool.Ifc.get_entity(a)
+        b_element = tool.Ifc.get_entity(b)
+        if is_supported_host(a_element):
+            host_obj, host_element, other = a, a_element, b
+        elif is_supported_host(b_element):
+            host_obj, host_element, other = b, b_element, a
+        else:
+            return
+
+        if tool.Parametric.is_path_connectable_wall(host_element):
+            world_pos = wall_anchor(context, self, host_obj, other)
+        else:
+            world_pos = layer3_anchor(host_obj, other)
+        if world_pos is None:
+            return
+        self.add_opening_icon.matrix_basis = gizmo.billboarded_at(world_pos, gizmo.get_billboard_rotation(context))
+
+
+def wall_anchor(
+    context: bpy.types.Context, group: bpy.types.GizmoGroup, wall_obj: bpy.types.Object, other: bpy.types.Object
+) -> Vector | None:
+    """World-space anchor for the add-opening icon on a wall host: void origin
+    projected onto the wall reference-line X (clamped to wall extents), lifted to
+    the camera-facing wall-local Y."""
+    geom = _get_wall_geom_cached(group, wall_obj)
+    if not geom:
+        return None
+    mw = wall_obj.matrix_world
+    wall_local = mw.inverted() @ other.matrix_world.translation
+    local_x = max(geom["anchor_x"], min(wall_local.x, geom["anchor_x"] + geom["length"]))
+    icon_y = _wall_camera_facing_icon_y(context, mw, geom)
+    base_world = mw @ Vector((local_x, icon_y, 0.0))
+    top_world = mw @ Vector((local_x, icon_y, geom["height"] + gizmo.BaseParametricGizmoGroup.ICON_Z_OFFSET))
+    return gizmo.BaseParametricGizmoGroup.pick_visible_anchor(context, base_world, top_world)
+
+
+def layer3_anchor(host_obj: bpy.types.Object, other: bpy.types.Object) -> Vector:
+    """World-space anchor for the add-opening icon on a LAYER3 host (slab / roof):
+    void's world XY, lifted just above the host's top face. Predictable height
+    regardless of where the void sits vertically — clicking the icon places the
+    opening at the void's XY, and the operator handles the actual cut depth."""
+    bbox = tool.Blender.get_object_world_bounding_box(host_obj)
+    anchor_xy = other.matrix_world.translation.xy
+    top_z = bbox["max_z"] + gizmo.BaseParametricGizmoGroup.ICON_Z_OFFSET
+    return Vector((anchor_xy.x, anchor_xy.y, top_z))
+
+
+def host_toggle_anchor(host_obj: bpy.types.Object) -> Vector:
+    """Object origin XY, lifted just above the topmost mesh vertex. Tracks
+    the parametric origin (useful reference even when the mesh extends
+    asymmetrically) and the visible top face (stays clear of sloped or
+    stepped bodies)."""
+    origin = host_obj.matrix_world.translation
+    top_z = tool.Blender.get_object_world_bounding_box(host_obj)["max_z"] + gizmo.BaseParametricGizmoGroup.ICON_Z_OFFSET
+    return Vector((origin.x, origin.y, top_z))
+
+
+class GizmoHostToggleOpenings(bpy.types.GizmoGroup, _WallGeomCachedBillboardingMixin):
+    """Fallback toggle-openings icon for hosts that lack their own
+    parametric-edit toolbar — slabs today, plus any foreign-authored
+    IfcRoof that carries no BBIM_Roof pset (so ``GizmoRoofEdition`` doesn't
+    poll for it). Walls and parametric roofs already render an idle-row
+    toggle next to the pen and are excluded from this poll.
+
+    When slab parametric-edit lands the slab branch will pen-row-handle
+    its own toggle; updating the exclusion predicate here is the only
+    migration step needed."""
+
+    bl_idname = "OBJECT_GGT_bim_host_toggle_openings"
+    bl_label = "Host Toggle Openings Gizmo"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options = {"3D", "PERSISTENT"}
+
+    @classmethod
+    def poll(cls, context: bpy.types.Context) -> bool:
+        element = _resolve_active_host(context, n_selected=1)
+        if element is None:
+            return False
+        if not tool.Geometry.has_openings(element):
+            return False
+        # Skip when a per-feature parametric-edit gizmo already surfaces
+        # an idle-row toggle for this element — walls and parametric roofs
+        # both render their own toggle in the pen row.
+        if tool.Parametric.is_path_connectable_wall(element):
+            return False
+        if tool.Parametric.is_roof(element):
+            return False
+        return True
+
+    def setup(self, context: bpy.types.Context) -> None:
+        default_color, highlight_color = self.get_decoration_colors()
+        self.toggle_openings_icon = self.setup_icon_gizmo(
+            "VIEW3D_GT_add_opening", default_color, highlight_color, "bim.toggle_host_openings"
+        )
+
+    def position_gizmos(self, context: bpy.types.Context) -> None:
+        host_obj = context.active_object
+        if not host_obj:
+            return
+        self.toggle_openings_icon.matrix_basis = gizmo.billboarded_at(
+            host_toggle_anchor(host_obj), gizmo.get_billboard_rotation(context)
+        )

src/bonsai/bonsai/bim/module/model/mep_bend_preview.py

@@ -0,0 +1,444 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""Bend-preview lifecycle for MEP segment joins.
+
+Holds the four lifecycle operators (Enable / Finish / Cancel /
+EnableFromBend) and the ``GizmoBendPreview`` group that surfaces the
+tunable dimensions and validate/cancel icons during preview. Draft state
+lives at ``Scene.BIMPreviewProperties.bend`` per CLAUDE.md §2.9 (Scene
+for cross-element previews).
+
+The geometry math (``compute_bend_preview_polylines``,
+``_bend_profile_cross_section``, ``_sweep_profile_along_polyline``)
+stays in ``mep.py`` because the commit operator ``MEPAddBend`` reuses
+it; this module imports the polyline helper for per-frame gizmo
+positioning. The GPU lines themselves are drawn by
+``decorator.BendPreviewDecorator``, kept in ``decorator.py`` with its
+sibling decorators."""
+
+from typing import ClassVar
+
+import bpy
+import ifcopenshell.util.element
+import ifcopenshell.util.unit
+from mathutils import Matrix, Vector
+
+import bonsai.tool as tool
+from bonsai.bim.module.drawing import gizmos as gizmo
+from bonsai.bim.module.model import preview_base
+from bonsai.bim.module.model.mep import (
+    _is_bend_fitting,
+    _n_mep_selected,
+    cached_compute_bend_preview_polylines,
+    segments_are_parallel,
+    validate_bend_preconditions,
+)
+
+
+class EnableBendPreview(bpy.types.Operator):
+    """Enter bend-preview mode for two selected MEP segments. Populates
+    scene.BIMPreviewProperties.bend with segment IFC ids and default
+    start_length / end_length / radius; no IFC mutation until finish."""
+
+    bl_idname = "bim.enable_bend_preview"
+    bl_label = "Enter Bend Preview"
+    bl_description = "Begin tuning bend parameters before committing the bend"
+    bl_options = {"REGISTER", "UNDO"}
+
+    @classmethod
+    def poll(cls, context):
+        if not _n_mep_selected(2):
+            cls.poll_message_set("Select exactly 2 MEP segments to bend.")
+            return False
+        return True
+
+    def execute(self, context):
+        selected = tool.Blender.get_selected_objects()
+        active = context.active_object
+        if active is None or active not in selected:
+            self.report({"ERROR"}, "Active object must be one of the selected MEP segments.")
+            return {"CANCELLED"}
+        other = next((o for o in selected if o is not active), None)
+        if other is None:
+            self.report({"ERROR"}, "Two MEP segments must be selected.")
+            return {"CANCELLED"}
+        active_element = tool.Ifc.get_entity(active)
+        other_element = tool.Ifc.get_entity(other)
+        if active_element is None or other_element is None:
+            self.report({"ERROR"}, "Both selected objects must be IFC elements.")
+            return {"CANCELLED"}
+        if segments_are_parallel(active, other):
+            self.report({"ERROR"}, "Bend preview is for non-parallel segments only.")
+            return {"CANCELLED"}
+
+        # Pre-check the same preconditions MEPAddBend enforces so the user
+        # sees the rejection here rather than after tuning a doomed preview.
+        precondition_error = validate_bend_preconditions(active_element, other_element)
+        if precondition_error is not None:
+            self.report({"ERROR"}, precondition_error)
+            return {"CANCELLED"}
+
+        preview_base.sync_uncommitted_moves([active, other])
+
+        props = preview_base.get_preview_props(context, "bend")
+        # Auto-cancel any prior preview so re-clicking join on a different
+        # pair doesn't silently commit the previous tuning.
+        if props is not None and props.is_active:
+            bpy.ops.bim.cancel_bend_preview()
+
+        props.start_segment_id = active_element.id()
+        props.end_segment_id = other_element.id()
+        props.start_length = 0.1
+        props.end_length = 0.1
+        props.radius = 0.2
+        props.is_active = True
+        return {"FINISHED"}
+
+
+class FinishBendPreview(bpy.types.Operator):
+    """Commit the previewed bend with the tuned parameters and exit preview.
+
+    Preview state survives a failed commit so the user can re-tune without
+    re-selecting."""
+
+    bl_idname = "bim.finish_bend_preview"
+    bl_label = "Apply Bend"
+    bl_description = "Commit the bend with the previewed parameters"
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context):
+        return preview_base.commit_preview(
+            self,
+            context,
+            "bend",
+            "mep_add_bend",
+            ("start_segment_id", "end_segment_id", "start_length", "end_length", "radius", "editing_bend_id"),
+        )
+
+
+class CancelBendPreview(bpy.types.Operator):
+    """Exit bend preview without committing."""
+
+    bl_idname = "bim.cancel_bend_preview"
+    bl_label = "Cancel Bend"
+    bl_description = "Discard the previewed bend"
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context):
+        if context.screen is None:
+            return {"CANCELLED"}
+        props = preview_base.get_preview_props(context, "bend")
+        if props is None or not props.is_active:
+            return {"CANCELLED"}
+        preview_base.clear_preview_state(props)
+        return {"FINISHED"}
+
+
+class EnableBendPreviewFromBend(bpy.types.Operator):
+    """Re-open the bend preview on an existing bend fitting.
+
+    Resolves the two connected segments via the bend's ports +
+    ``IfcRelConnectsPorts``, reads parametric values back from the bend's
+    ``BBIM_Fitting`` pset, and flags the preview so committing replaces
+    the existing bend in place."""
+
+    bl_idname = "bim.enable_bend_preview_from_bend"
+    bl_label = "Edit Bend"
+    bl_description = "Re-open the bend preview to retune an existing bend"
+    bl_options = {"REGISTER", "UNDO"}
+
+    @classmethod
+    def poll(cls, context):
+        active = context.active_object
+        if active is None:
+            cls.poll_message_set("No active object.")
+            return False
+        element = tool.Ifc.get_entity(active)
+        if element is None or not _is_bend_fitting(element):
+            cls.poll_message_set("Active object must be a bend fitting.")
+            return False
+        return True
+
+    def execute(self, context):
+        active = context.active_object
+        bend_element = tool.Ifc.get_entity(active)
+        if bend_element is None or not _is_bend_fitting(bend_element):
+            self.report({"ERROR"}, "Active object is not a bend fitting.")
+            return {"CANCELLED"}
+
+        connected_segments: list = []
+        for port in tool.System.get_ports(bend_element):
+            connected_port = tool.System.get_connected_port(port)
+            if connected_port is None:
+                continue
+            related = tool.System.get_port_relating_element(connected_port)
+            if related is not None and related.is_a("IfcFlowSegment") and related not in connected_segments:
+                connected_segments.append(related)
+
+        if len(connected_segments) != 2:
+            self.report(
+                {"ERROR"},
+                f"Bend has {len(connected_segments)} connected segments; need exactly 2 to re-edit.",
+            )
+            return {"CANCELLED"}
+
+        # Read parametric values from the bend type's BBIM_Fitting pset. The
+        # type carries the canonical parameters; querying the occurrence
+        # would force a get_type round-trip and miss user-edited types.
+        bend_type = ifcopenshell.util.element.get_type(bend_element)
+        if bend_type is None:
+            self.report({"ERROR"}, "Bend fitting has no type to read parameters from.")
+            return {"CANCELLED"}
+        bend_type_obj = tool.Ifc.get_object(bend_type)
+        if bend_type_obj is None:
+            self.report({"ERROR"}, "Bend type has no Blender object — cannot read pset.")
+            return {"CANCELLED"}
+        bbim = tool.Model.get_modeling_bbim_pset_data(bend_type_obj, "BBIM_Fitting")
+        if bbim is None:
+            self.report({"ERROR"}, "Bend fitting has no BBIM_Fitting pset — not a parametric bend.")
+            return {"CANCELLED"}
+        data = bbim.get("data_dict", {})
+
+        props = preview_base.get_preview_props(context, "bend")
+        if props is not None and props.is_active:
+            bpy.ops.bim.cancel_bend_preview()
+
+        # Segment order is load-bearing: the bend's lateral sign and z-axis
+        # flip are derived from which segment is "start" vs "end". Re-edit
+        # must reuse the same pairing as the original create so the recreate
+        # lands at the same orientation.
+        start_segment, end_segment = connected_segments
+        props.start_segment_id = start_segment.id()
+        props.end_segment_id = end_segment.id()
+        # Pset values are in IFC native units; scene units come from si_conversion.
+        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
+        props.start_length = float(data.get("start_length", 0.1)) * si_conversion
+        props.end_length = float(data.get("end_length", 0.1)) * si_conversion
+        props.radius = float(data.get("radius", 0.2)) * si_conversion
+        props.editing_bend_id = bend_element.id()
+        props.is_active = True
+        return {"FINISHED"}
+
+
+def _bend_preview_segments(context):
+    """Resolve the two segment objects from the scene-level preview props.
+
+    Re-resolves by IFC id each frame so undo / file reload during preview
+    never dangles a stale bpy reference."""
+    props = context.scene.BIMPreviewProperties.bend
+    ifc_file = tool.Ifc.get()
+    if ifc_file is None or not props.is_active:
+        return None, None
+    try:
+        start_element = ifc_file.by_id(props.start_segment_id)
+        end_element = ifc_file.by_id(props.end_segment_id)
+    except Exception:
+        return None, None
+    start_obj = tool.Ifc.get_object(start_element) if start_element else None
+    end_obj = tool.Ifc.get_object(end_element) if end_element else None
+    return start_obj, end_obj
+
+
+def _gizmo_x_matrix(location: Vector, x_direction: Vector) -> Matrix:
+    """Build a 4x4 matrix placing a gizmo at ``location`` with its local +X
+    axis aligned to ``x_direction`` in world space. ``BIM_GT_gizmo_dimension``
+    draws + drags along local +X by convention."""
+    x = x_direction.normalized()
+    seed = Vector((0, 0, 1)) if abs(x.z) < 0.9 else Vector((1, 0, 0))
+    y = (seed - x * seed.dot(x)).normalized()
+    z = x.cross(y)
+    mat = Matrix.Identity(4)
+    mat[0][:3] = (x.x, y.x, z.x)
+    mat[1][:3] = (x.y, y.y, z.y)
+    mat[2][:3] = (x.z, y.z, z.z)
+    mat.translation = location
+    return mat
+
+
+class GizmoBendPreview(bpy.types.GizmoGroup):
+    """Interactive gizmo group for the bend preview flow.
+
+    Three dimension widgets drag start_length / end_length / radius; two
+    icon gizmos commit or cancel. When the geometry is degenerate the
+    dimensions and validate hide but cancel stays visible so the user
+    always has an exit."""
+
+    bl_idname = "OBJECT_GGT_bim_bend_preview"
+    bl_label = "Bend Preview Gizmos"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options = {"3D", "PERSISTENT"}
+
+    ICON_SCALE: ClassVar[float] = 0.375
+    ICON_SPACING_X: ClassVar[float] = 0.4
+    ICON_Z_OFFSET: ClassVar[float] = 1.5
+
+    @classmethod
+    def poll(cls, context):
+        preview = getattr(context.scene, "BIMPreviewProperties", None)
+        props = preview.bend if preview is not None else None
+        if props is None or not props.is_active:
+            return False
+        if not tool.Blender.are_viewport_gizmos_enabled():
+            return False
+        ifc_file = tool.Ifc.get()
+        if ifc_file is None:
+            return False
+        try:
+            ifc_file.by_id(props.start_segment_id)
+            ifc_file.by_id(props.end_segment_id)
+        except (RuntimeError, KeyError):
+            return False
+        return True
+
+    def setup(self, context):
+        prefs = tool.Blender.get_addon_preferences()
+        default_color = tuple(prefs.decorations_colour[:3])
+        highlight_color = tuple(prefs.decorator_color_selected[:3])
+
+        _props = preview_base.make_props_callback("bend")
+
+        def setup_dimension(attr: str, prop_name: str, invert_delta: bool = False) -> bpy.types.Gizmo:
+            gz = self.gizmos.new("BIM_GT_gizmo_dimension")
+            gz.move_get_cb = preview_base.make_dim_getter(_props, attr)
+            gz.move_set_cb = preview_base.make_dim_setter(_props, attr)
+            gz.axis = Vector((1, 0, 0))
+            gz.invert_delta = invert_delta
+            gz.delta_scale = 1.0
+            gz.prop_name = prop_name
+            gz.gizmo_group = self
+            gz.color = default_color
+            gz.color_highlight = highlight_color
+            gz.alpha = 1.0
+            gz.use_draw_modal = True
+            gz.use_draw_scale = False
+            gz.text_offset_sign = 1
+            gz.text_alignment = gizmo.TextAlignment.CENTER
+            gz.show_start_arrow = False
+            gz.show_end_arrow = True
+            gz.show_extension_lines = False
+            gz.text_formatter = None
+            return gz
+
+        self.start_dim = setup_dimension("start_length", "Start Length")
+        self.end_dim = setup_dimension("end_length", "End Length")
+        self.radius_dim = setup_dimension("radius", "Radius")
+
+        from bonsai.bim.module.drawing.gizmos import BaseParametricGizmoGroup
+
+        self.validate_icon = self.gizmos.new("VIEW3D_GT_validate")
+        self.validate_icon.use_draw_scale = False
+        self.validate_icon.color = BaseParametricGizmoGroup.COLOR_GREEN
+        self.validate_icon.color_highlight = highlight_color
+        self.validate_icon.target_set_operator("bim.finish_bend_preview")
+
+        self.cancel_icon = self.gizmos.new("VIEW3D_GT_cancel")
+        self.cancel_icon.use_draw_scale = False
+        self.cancel_icon.color = BaseParametricGizmoGroup.COLOR_RED
+        self.cancel_icon.color_highlight = highlight_color
+        self.cancel_icon.target_set_operator("bim.cancel_bend_preview")
+
+    def refresh(self, context):
+        self._position_gizmos(context)
+
+    def draw_prepare(self, context):
+        self._position_gizmos(context)
+
+    def _position_gizmos(self, context):
+        """Place gizmos at the bend intersection using the current scene
+        props. Cancel stays visible on degenerate geometry so the user
+        always has an exit; the other widgets hide when there's no defined
+        tangent / arc to anchor them on."""
+        start_obj, end_obj = _bend_preview_segments(context)
+        if start_obj is None or end_obj is None:
+            for gz in (self.start_dim, self.end_dim, self.radius_dim, self.validate_icon, self.cancel_icon):
+                gz.hide = True
+            return
+
+        props = context.scene.BIMPreviewProperties.bend
+        preview = cached_compute_bend_preview_polylines(
+            start_obj, end_obj, props.start_length, props.end_length, props.radius
+        )
+        if not preview["valid"]:
+            for gz in (self.start_dim, self.end_dim, self.radius_dim, self.validate_icon):
+                gz.hide = True
+            self.cancel_icon.hide = False
+            axes = preview.get("invalid_axes") or []
+            if axes:
+                intersection_point = axes[0][1]
+                billboard_rot = gizmo.get_billboard_rotation(context)
+                anchor = intersection_point + Vector((0, 0, self.ICON_Z_OFFSET))
+                self.cancel_icon.matrix_basis = gizmo.billboarded_at(anchor, billboard_rot, scale=self.ICON_SCALE)
+            return
+
+        for gz in (self.start_dim, self.end_dim, self.radius_dim, self.validate_icon, self.cancel_icon):
+            gz.hide = False
+
+        leg_a_far, leg_a_end = preview["leg_a"]
+        leg_b_far, leg_b_end = preview["leg_b"]
+        toward_bend_a = (
+            (leg_a_end - leg_a_far).normalized() if (leg_a_end - leg_a_far).length > 1e-6 else Vector((0, 0, 1))
+        )
+        toward_bend_b = (
+            (leg_b_end - leg_b_far).normalized() if (leg_b_end - leg_b_far).length > 1e-6 else Vector((0, 0, 1))
+        )
+        leg_a_tangent = leg_a_end + toward_bend_a * props.start_length
+        leg_b_tangent = leg_b_end + toward_bend_b * props.end_length
+
+        # axis is set in world space every frame so the drag projection
+        # matches the visual regardless of either segment's matrix_world.
+        self.start_dim.matrix_basis = _gizmo_x_matrix(leg_a_tangent, -toward_bend_a)
+        self.start_dim.axis = -toward_bend_a
+        self.start_dim.set_dimension_length(props.start_length)
+        self.end_dim.matrix_basis = _gizmo_x_matrix(leg_b_tangent, -toward_bend_b)
+        self.end_dim.axis = -toward_bend_b
+        self.end_dim.set_dimension_length(props.end_length)
+
+        arc = preview["arc"]
+        if len(arc) >= 3:
+            mid = len(arc) // 2
+            chord_mid = (arc[0] + arc[-1]) * 0.5
+            toward_mid = arc[mid] - chord_mid
+            if toward_mid.length > 1e-6:
+                toward_mid = toward_mid.normalized()
+                half_chord = (arc[-1] - arc[0]).length * 0.5
+                center_dist = max(0.0, props.radius * props.radius - half_chord * half_chord) ** 0.5
+                arc_center = chord_mid - toward_mid * center_dist
+                radial_out = arc[mid] - arc_center
+                if radial_out.length > 1e-6:
+                    radial_out.normalize()
+                    inward = -radial_out
+                    self.radius_dim.matrix_basis = _gizmo_x_matrix(arc[mid], inward)
+                    self.radius_dim.axis = inward
+                    self.radius_dim.set_dimension_length(props.radius)
+                else:
+                    self.radius_dim.hide = True
+            else:
+                self.radius_dim.hide = True
+        else:
+            self.radius_dim.hide = True
+
+        billboard_rot = gizmo.get_billboard_rotation(context)
+        anchor_base = arc[len(arc) // 2] if arc else (leg_a_end + leg_b_end) * 0.5
+        anchor = anchor_base + Vector((0, 0, self.ICON_Z_OFFSET))
+        offset_x = billboard_rot @ Vector((self.ICON_SPACING_X, 0.0, 0.0))
+        self.validate_icon.matrix_basis = gizmo.billboarded_at(anchor, billboard_rot, scale=self.ICON_SCALE)
+        self.cancel_icon.matrix_basis = gizmo.billboarded_at(anchor + offset_x, billboard_rot, scale=self.ICON_SCALE)

src/bonsai/bonsai/bim/module/model/opening.py

@@ -15,6 +15,8 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 from collections.abc import Sequence
 from math import radians
@@ -41,8 +43,211 @@ from mathutils import Matrix, Vector
 
 import bonsai.core.geometry
 import bonsai.tool as tool
+from bonsai.bim import decorator_cache
 from bonsai.bim.module.drawing.decoration import DecoratorData
 
+# Multi-entry cache for the opening preview's dissolved-edges fallback.
+# Single-entry wouldn't fit: the draw handler iterates every active opening
+# per frame, each with its own mesh. Bumped wholesale on the shared
+# decorator-cache token (depsgraph / undo / redo / load), one slot per
+# (mesh.session_uid, angle_limit). Outlier vs. the per-object caches below —
+# consulted only on world-draw-data miss, so the global wipe rarely fires in
+# steady state and the simpler invalidation is enough.
+_dissolved_edges_cache: dict[
+    tuple[int, float],
+    tuple[list[Vector], list[tuple[int, int]]],
+] = {}
+_dissolved_edges_cache_token: int = -1
+
+
+def _get_cached_dissolved_edges(
+    mesh: bpy.types.Mesh,
+    angle_limit: float = radians(1.0),
+) -> tuple[list[Vector], list[tuple[int, int]]]:
+    global _dissolved_edges_cache_token
+    token = decorator_cache.get_decorator_cache_token()
+    if token != _dissolved_edges_cache_token:
+        _dissolved_edges_cache.clear()
+        _dissolved_edges_cache_token = token
+    key = (mesh.session_uid, angle_limit)
+    cached = _dissolved_edges_cache.get(key)
+    if cached is not None:
+        return cached
+    result = tool.Geometry.get_dissolved_edges(mesh, angle_limit=angle_limit)
+    _dissolved_edges_cache[key] = result
+    return result
+
+
+# Per-object epoch: bumped only when this specific object's transform or geometry
+# updates land in the depsgraph delta. Invalidation work scales with the number
+# of changed objects, not total scene size — moving one object leaves every
+# other entry valid. Bumped by the depsgraph handler below; cleared on
+# undo/redo/load alongside the cache dicts.
+_object_epochs: dict[int, int] = {}
+
+
+@bpy.app.handlers.persistent
+def _bump_object_epochs_for_decoration(*args) -> None:
+    # depsgraph_update_post is called as (scene, depsgraph) in 4.x but the
+    # *args signature follows decorator_cache's defensive idiom.
+    depsgraph = args[1] if len(args) >= 2 else None
+    if depsgraph is None or not hasattr(depsgraph, "updates"):
+        return
+    for u in depsgraph.updates:
+        if not isinstance(u.id, bpy.types.Object):
+            continue
+        if not (u.is_updated_geometry or u.is_updated_transform):
+            continue
+        # u.id is the evaluated COW copy; the cache keys are written from the
+        # original Object (read by the draw handler), and session_uid can
+        # differ across the COW boundary. Resolve to the original before keying.
+        original = getattr(u.id, "original", u.id)
+        if original is None:
+            continue
+        uid = original.session_uid
+        _object_epochs[uid] = _object_epochs.get(uid, 0) + 1
+
+
+@bpy.app.handlers.persistent
+def _clear_decoration_caches_globally(*args) -> None:
+    # Undo/redo/load: depsgraph deltas can't be trusted to describe the
+    # transition, so wipe every per-object cache state.
+    _object_epochs.clear()
+    _world_draw_data_cache.clear()
+    _batch_cache.clear()
+
+
+def _decoration_invalidation_hooks() -> tuple:
+    return (
+        bpy.app.handlers.undo_post,
+        bpy.app.handlers.redo_post,
+        bpy.app.handlers.load_post,
+    )
+
+
+def install_decoration_cache_handlers() -> None:
+    if _bump_object_epochs_for_decoration not in bpy.app.handlers.depsgraph_update_post:
+        bpy.app.handlers.depsgraph_update_post.append(_bump_object_epochs_for_decoration)
+    for hook in _decoration_invalidation_hooks():
+        if _clear_decoration_caches_globally not in hook:
+            hook.append(_clear_decoration_caches_globally)
+
+
+def uninstall_decoration_cache_handlers() -> None:
+    try:
+        bpy.app.handlers.depsgraph_update_post.remove(_bump_object_epochs_for_decoration)
+    except ValueError:
+        pass
+    for hook in _decoration_invalidation_hooks():
+        try:
+            hook.remove(_clear_decoration_caches_globally)
+        except ValueError:
+            pass
+
+
+# Per-object world-space draw payload: line_verts (dissolved or ios_edges-filtered),
+# verts (full mesh, indexed by loop_triangles), edges_indices, tris. Entries are
+# (epoch, payload) tuples; lookup compares epoch to _object_epochs[uid], so a
+# stale entry for an object that didn't change since the last build still hits.
+_world_draw_data_cache: dict[
+    int,
+    tuple[
+        int,
+        tuple[
+            list[tuple[float, float, float]],
+            list[tuple[float, float, float]],
+            list[tuple[int, int]],
+            list[tuple[int, ...]],
+        ],
+    ],
+] = {}
+
+
+def _get_cached_world_draw_data(
+    obj: bpy.types.Object,
+) -> tuple[
+    list[tuple[float, float, float]],
+    list[tuple[float, float, float]],
+    list[tuple[int, int]],
+    list[tuple[int, ...]],
+]:
+    uid = obj.session_uid
+    epoch = _object_epochs.get(uid, 0)
+    entry = _world_draw_data_cache.get(uid)
+    if entry is not None and entry[0] == epoch:
+        return entry[1]
+
+    mw = obj.matrix_world
+    verts = [tuple(mw @ v.co) for v in obj.data.vertices]
+    obj.data.calc_loop_triangles()
+    tris = [tuple(t.vertices) for t in obj.data.loop_triangles]
+
+    ios_edges_attribute = obj.data.attributes.get("ios_edges")
+    if ios_edges_attribute:
+        # Loader-curated edges: read the attribute aligned with bm.edges order.
+        bm = bmesh.new()
+        bm.from_mesh(obj.data)
+        edges_indices = [
+            tuple(v.index for v in e.verts) for i, e in enumerate(bm.edges) if ios_edges_attribute.data[i].value
+        ]
+        bm.free()
+        line_verts = verts
+    else:
+        dissolved, edges_indices = _get_cached_dissolved_edges(obj.data)
+        line_verts = [tuple(mw @ v) for v in dissolved]
+
+    result = (line_verts, verts, edges_indices, tris)
+    _world_draw_data_cache[uid] = (epoch, result)
+    return result
+
+
+# GPUBatch cache: skip per-frame batch_for_shader. Entries are (epoch, batch);
+# lookup compares epoch to _object_epochs[uid] so other objects' batches stay
+# alive when one object's depsgraph delta bumps only its own epoch. The cached
+# batches reference GPU-side buffers tied to Blender's built-in shaders, which
+# are themselves cached by name (gpu.shader.from_builtin returns the same
+# handle each call), so they stay drawable across frames.
+_batch_cache: dict[tuple[int, str], tuple[int, "gpu.types.GPUBatch"]] = {}
+
+# CAD hidden-line convention for the occluded back-pass: world-space dashes so
+# density stays coherent across zoom. Dash + gap = period; dash_width controls
+# the "on" portion.
+_DASH_PERIOD_METERS: float = 0.20
+_DASH_WIDTH_METERS: float = 0.10
+# Solid front pass is rendered wider than the dashed back pass so its halo
+# overpowers the dashed center on visible edges even when the WIRE-display
+# overlay biases the depth buffer at outline pixels.
+_DASH_LINE_WIDTH: float = 1.5
+_SOLID_LINE_WIDTH: float = 2.5
+# Per-iteration default line width used by every non-occlusion draw call in
+# this decorator's ``__call__``. Restored after each occlusion pair so the
+# next draw isn't silently inheriting the wider solid-pass override.
+_DEFAULT_LINE_WIDTH: float = 2.0
+
+
+def _get_cached_batch_or_none(cache_key: tuple[int, str]) -> "gpu.types.GPUBatch | None":
+    uid = cache_key[0]
+    epoch = _object_epochs.get(uid, 0)
+    entry = _batch_cache.get(cache_key)
+    if entry is not None and entry[0] == epoch:
+        return entry[1]
+    return None
+
+
+def _store_batch_in_cache(cache_key: tuple[int, str], batch: "gpu.types.GPUBatch") -> None:
+    uid = cache_key[0]
+    epoch = _object_epochs.get(uid, 0)
+    _batch_cache[cache_key] = (epoch, batch)
+
+
+def is_filling_supported(element) -> bool:
+    """True when Bonsai's opening generator can derive an opening from this
+    element. IFC's schema permits any IfcElement as a filling; Bonsai
+    currently supports only IfcDoor and IfcWindow because those are the
+    classes with OverallWidth/OverallHeight attributes (or their types'
+    ELEVATION_VIEW profiles) that the generator can consume."""
+    return element is not None and element.is_a() in ("IfcDoor", "IfcWindow")
+
 
 class FilledOpeningGenerator:
     def generate(
@@ -50,9 +255,15 @@ class FilledOpeningGenerator:
         filling_obj: bpy.types.Object,
         voided_obj: bpy.types.Object,
         target: Optional[Vector] = None,
+        preserve_placement: bool = False,
     ) -> Union[None, str]:
         """
         :param target: Target opening position. If ommited, cursor position is used.
+        :param preserve_placement: If True, keep ``filling_obj.matrix_world`` as-is
+            and skip the snap-to-wall-axis / rl1-rl2 Z-default logic. The opening
+            is still created at the filling's current world position. Useful
+            when the caller (e.g. the SHIFT-add-opening gizmo flow) has
+            already positioned the filling intentionally.
         :return: None if there was no errors, otherwise returns a string with error message.
         """
         props = tool.Model.get_model_props()
@@ -74,7 +285,7 @@ class FilledOpeningGenerator:
             should_set_z_level = False
 
         # Sometimes, the voided_obj may be an aggregate, which won't have any representation.
-        if voided_obj.data:
+        if not preserve_placement and voided_obj.data:
             raycast = voided_obj.closest_point_on_mesh(voided_obj.matrix_world.inverted() @ target, distance=0.01)
             if not raycast[0]:
                 target = filling_obj.matrix_world.translation.copy()
@@ -207,18 +418,16 @@ class FilledOpeningGenerator:
                 representation = tool.Geometry.get_representation_by_context(voided_element, context)
                 assert representation
 
-                bonsai.core.geometry.switch_representation(
-                    tool.Ifc,
-                    tool.Geometry,
-                    obj=voided_obj,
-                    representation=representation,
-                )
+                tool.Geometry.recut_host(voided_obj, representation)
 
     def regenerate_from_type(self, usecase_path: str, ifc_file: ifcopenshell.file, settings: dict[str, Any]) -> None:
         relating_type = settings["relating_type"]
 
-        for related_object in settings["related_objects"]:
-            self._regenerate_from_type(related_object)
+        # Filling type-switch on an array of fillings fans out N host recuts —
+        # one per related object — without batching. Coalesce them.
+        with tool.Geometry.batch_host_recut():
+            for related_object in settings["related_objects"]:
+                self._regenerate_from_type(related_object)
 
     def _regenerate_from_type(self, related_object: ifcopenshell.entity_instance) -> None:
         filling = related_object
@@ -267,12 +476,7 @@ class FilledOpeningGenerator:
             representation = tool.Geometry.get_active_representation(voided_obj)
             if not representation:
                 continue
-            bonsai.core.geometry.switch_representation(
-                tool.Ifc,
-                tool.Geometry,
-                obj=voided_obj,
-                representation=representation,
-            )
+            tool.Geometry.recut_host(voided_obj, representation)
 
     def generate_opening_from_filling(
         self,
@@ -407,6 +611,31 @@ class RecalculateFill(bpy.types.Operator, tool.Ifc.Operator):
         return context.selected_objects
 
     def _execute(self, context):
+        # N selected fillings × M voided host parts would fire N×M host recuts
+        # without batching. Coalesce per host.
+        with tool.Geometry.batch_host_recut():
+            return self._recalculate_fills(context)
+
+    def _recalculate_fills(self, context):
+        # Refresh each selected filling's mapped opening source before
+        # recutting the host. Dedup by source id covers the common shared-
+        # source case in one rewrite while leaving unrelated sibling sources
+        # untouched.
+        seen_source_ids: set[int] = set()
+        for obj in context.selected_objects:
+            element = tool.Ifc.get_entity(obj)
+            if not element or not element.FillsVoids:
+                continue
+            opening = element.FillsVoids[0].RelatingOpeningElement
+            body = tool.Geometry.get_body_representation(opening)
+            if body is None:
+                continue
+            source = tool.Geometry.resolve_mapped_representation(body)
+            if source.id() in seen_source_ids:
+                continue
+            seen_source_ids.add(source.id())
+            tool.Model.regenerate_filling_opening_body(element)
+
         for obj in context.selected_objects:
             element = tool.Ifc.get_entity(obj)
             if not element or not element.FillsVoids:
@@ -435,12 +664,7 @@ class RecalculateFill(bpy.types.Operator, tool.Ifc.Operator):
                 if building_obj and building_obj.data:
                     representation = tool.Geometry.get_active_representation(building_obj)
                     if representation:
-                        bonsai.core.geometry.switch_representation(
-                            tool.Ifc,
-                            tool.Geometry,
-                            obj=building_obj,
-                            representation=representation,
-                        )
+                        tool.Geometry.recut_host(building_obj, representation)
 
         # Refresh cut decorator
         DecoratorData.cut_cache.clear()
@@ -558,6 +782,29 @@ class AddBoolean(Operator, tool.Ifc.Operator):
         tool.Root.reload_item_decorator()
 
 
+class ToggleHostOpenings(Operator, tool.Ifc.Operator):
+    bl_idname = "bim.toggle_host_openings"
+    bl_label = "Toggle Openings"
+    bl_description = "Show or hide opening fills (doors and windows) in the viewport\n\nHotkey: Alt+O"
+    bl_options = {"REGISTER", "UNDO"}
+
+    @classmethod
+    def poll(cls, context):
+        if not tool.Model.has_selected_ifc_objects():
+            cls.poll_message_set("No IFC objects selected.")
+            return False
+        return True
+
+    def _execute(self, context: bpy.types.Context) -> set[str]:
+        # Opening visibility is independent of host geometry — don't commit any
+        # active parametric edit; the user can keep editing the host.
+        if tool.Model.get_model_props().openings:
+            bpy.ops.bim.edit_openings(apply_all=True)
+        else:
+            bpy.ops.bim.show_openings()
+        return {"FINISHED"}
+
+
 class ShowOpenings(Operator, tool.Ifc.Operator):
     bl_idname = "bim.show_openings"
     bl_label = "Show Openings"
@@ -739,27 +986,29 @@ class EditOpenings(Operator, tool.Ifc.Operator):
         for opening_element in opening_elements:
             opening_obj = tool.Ifc.get_object(opening_element)
 
-            similar_openings = bonsai.core.geometry.get_similar_openings(tool.Ifc, opening_element)
-            similar_openings_building_objs = bonsai.core.geometry.get_similar_openings_building_objs(
-                tool.Ifc, similar_openings
-            )
-            building_objs.update(similar_openings_building_objs)
-
             if opening_obj:
-                if tool.Ifc.is_edited(opening_obj):
-                    tool.Geometry.run_geometry_update_representation(obj=opening_obj)
-                    bonsai.core.geometry.edit_similar_opening_placement(
-                        tool.Geometry, opening_element, similar_openings
-                    )
-                elif tool.Ifc.is_moved(opening_obj):
-                    bonsai.core.geometry.edit_object_placement(tool.Ifc, tool.Geometry, tool.Surveyor, obj=opening_obj)
+                opening_edited = tool.Ifc.is_edited(opening_obj)
+                opening_moved = tool.Ifc.is_moved(opening_obj)
+                # Sibling walls only need a viewport-level refresh when the
+                # opening's shape or placement actually changed — a pure
+                # show/hide toggle leaves them in their existing state.
+                if opening_edited or opening_moved:
+                    similar_openings = bonsai.core.geometry.get_similar_openings(tool.Ifc, opening_element)
+                    similar_openings_building_objs = bonsai.core.geometry.get_similar_openings_building_objs(
+                        tool.Ifc, similar_openings
+                    )
+                    building_objs.update(similar_openings_building_objs)
+                    if opening_edited:
+                        tool.Geometry.run_geometry_update_representation(obj=opening_obj)
+                    else:
+                        bonsai.core.geometry.edit_object_placement(
+                            tool.Ifc, tool.Geometry, tool.Surveyor, obj=opening_obj
+                        )
                     bonsai.core.geometry.edit_similar_opening_placement(
                         tool.Geometry, opening_element, similar_openings
                     )
+                    building_objs.update(self.get_all_building_objects_of_similar_openings(opening_element))
 
-                building_objs.update(
-                    self.get_all_building_objects_of_similar_openings(opening_element)
-                )  # NB this has nothing to do with clone similar_opening
                 tool.Ifc.unlink(element=opening_element)
                 if props.representation_obj == opening_obj:
                     props.representation_obj = None
@@ -797,6 +1046,12 @@ class CloneOpening(Operator, tool.Ifc.Operator):
         return True
 
     def _execute(self, context):
+        # The voided host may be an aggregate whose parts each get recut.
+        # Coalesce per host so a many-parts aggregate doesn't fan out.
+        with tool.Geometry.batch_host_recut():
+            return self._clone_opening(context)
+
+    def _clone_opening(self, context):
         # NOTE: Operator displayed in UI only with IfcOpeningElement being active.
         ifc_file = tool.Ifc.get()
         objects = bpy.context.selected_objects
@@ -826,12 +1081,7 @@ class CloneOpening(Operator, tool.Ifc.Operator):
                 continue
             representation = tool.Geometry.get_active_representation(obj)
             assert representation
-            bonsai.core.geometry.switch_representation(
-                tool.Ifc,
-                tool.Geometry,
-                obj=obj,
-                representation=representation,
-            )
+            tool.Geometry.recut_host(obj, representation)
 
         return {"FINISHED"}
 
@@ -941,7 +1191,6 @@ class SelectBoolean(Operator):
         return {"FINISHED"}
 
 
-# TODO: merge with ProfileDecorator?
 class DecorationsHandler:
     installed = None
 
@@ -951,6 +1200,7 @@ class DecorationsHandler:
             cls.uninstall()
         handler = cls()
         cls.installed = SpaceView3D.draw_handler_add(handler, (context,), "WINDOW", "POST_VIEW")
+        install_decoration_cache_handlers()
 
     @classmethod
     def uninstall(cls):
@@ -959,15 +1209,79 @@ class DecorationsHandler:
         except ValueError:
             pass
         cls.installed = None
+        uninstall_decoration_cache_handlers()
 
-    def draw_batch(self, shader_type, content_pos, color, indices=None):
+    def _get_or_build_batch(self, shader, shader_type, content_pos, indices=None, cache_key=None):
+        if cache_key is not None:
+            cached = _get_cached_batch_or_none(cache_key)
+            if cached is not None:
+                return cached
         if not tool.Blender.validate_shader_batch_data(content_pos, indices):
-            return
-        shader = self.line_shader if shader_type == "LINES" else self.shader
+            return None
         batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
+        if cache_key is not None:
+            _store_batch_in_cache(cache_key, batch)
+        return batch
+
+    def draw_batch(self, shader_type, content_pos, color, indices=None, cache_key=None):
+        shader = self.line_shader if shader_type == "LINES" else self.shader
+        batch = self._get_or_build_batch(shader, shader_type, content_pos, indices, cache_key=cache_key)
+        if batch is None:
+            return
         shader.uniform_float("color", color)
         batch.draw(shader)
 
+    def _draw_lines_with_occlusion(self, verts, color, edges_indices, cache_key=None):
+        # Two-pass CAD hidden-line convention. Both passes use POLYLINE_UNIFORM_COLOR.
+        #
+        # The solid front pass is rendered WIDER than the dashed back pass so it
+        # produces a halo around the line center, beyond the depth-bias zone that
+        # Blender's overlay engine writes when an opening is set to WIRE display.
+        # Without the width difference, the wire bias makes the center-pixel
+        # ``LESS_EQUAL`` comparison fail (line ends up slightly behind the biased
+        # wire depth) so the solid pass would lose to the dashed back pass even
+        # on visible edges. The halo gives the solid pass enough screen-space to
+        # overpower the dashed pattern visually.
+        #
+        # Dashed renders first at the standard width so the solid overlay's wider
+        # halo cleanly hides it on visible edges; on occluded edges the solid
+        # ``LESS_EQUAL`` pass fails against the wall depth and the dashed remains.
+        front_batch = self._get_or_build_batch(self.line_shader, "LINES", verts, edges_indices, cache_key=cache_key)
+        if front_batch is None:
+            return
+
+        dashed_cache_key = (cache_key[0], cache_key[1] + "_dashed") if cache_key is not None else None
+        dash_batch = None
+        if dashed_cache_key is not None:
+            dash_batch = _get_cached_batch_or_none(dashed_cache_key)
+        if dash_batch is None:
+            dash_verts, dash_edges = tool.Blender.build_dashed_line_segments(
+                verts, edges_indices, _DASH_PERIOD_METERS, _DASH_WIDTH_METERS
+            )
+            dash_batch = self._get_or_build_batch(self.line_shader, "LINES", dash_verts, dash_edges)
+            if dash_batch is not None and dashed_cache_key is not None:
+                _store_batch_in_cache(dashed_cache_key, dash_batch)
+
+        original_depth_test = gpu.state.depth_test_get()
+        front_color = list(color)
+        front_color[3] = 1.0
+        self.line_shader.uniform_float("color", front_color)
+
+        if dash_batch is not None:
+            self.line_shader.uniform_float("lineWidth", _DASH_LINE_WIDTH)
+            gpu.state.depth_test_set("ALWAYS")
+            dash_batch.draw(self.line_shader)
+
+        self.line_shader.uniform_float("lineWidth", _SOLID_LINE_WIDTH)
+        gpu.state.depth_test_set("LESS_EQUAL")
+        front_batch.draw(self.line_shader)
+
+        # Restore the per-iteration default set at the top of __call__ so
+        # subsequent draws (the HalfSpaceSolid arrow, future call-sites) are
+        # not silently affected by the front-pass width override.
+        self.line_shader.uniform_float("lineWidth", _DEFAULT_LINE_WIDTH)
+        gpu.state.depth_test_set(original_depth_test)
+
     def __call__(self, context):
         props = tool.Model.get_model_props()
         if not props.openings:
@@ -1001,7 +1315,7 @@ class DecorationsHandler:
             self.line_shader.bind()  # required to be able to change uniforms of the shader
             # POLYLINE_UNIFORM_COLOR specific uniforms
             self.line_shader.uniform_float("viewportSize", (context.region.width, context.region.height))
-            self.line_shader.uniform_float("lineWidth", 2.0)
+            self.line_shader.uniform_float("lineWidth", _DEFAULT_LINE_WIDTH)
 
             # general shader
             self.shader = gpu.shader.from_builtin("UNIFORM_COLOR")
@@ -1039,23 +1353,18 @@ class DecorationsHandler:
                 self.draw_batch("LINES", verts, selected_elements_color, selected_edges)
                 self.draw_batch("POINTS", unselected_vertices, unselected_elements_color)
                 self.draw_batch("POINTS", selected_vertices, selected_elements_color)
+                tool.Blender.draw_bmesh_face_tris(bm, verts, transparent_color(special_elements_color), self.draw_batch)
             else:
-                bm = bmesh.new()
-                bm.from_mesh(obj.data)
-
-                verts = [tuple(obj.matrix_world @ v.co) for v in bm.verts]
-                if ios_edges_attribute := obj.data.attributes.get("ios_edges"):
-                    edges = [e for i, e in enumerate(bm.edges) if ios_edges_attribute.data[i].value]
-                else:
-                    edges = bm.edges
-                edges_indices = [tuple([v.index for v in e.verts]) for e in edges]
-
+                line_verts, verts, edges_indices, tris = _get_cached_world_draw_data(obj)
                 color = selected_elements_color if obj in context.selected_objects else special_elements_color
-                self.draw_batch("LINES", verts, color, edges_indices)
-
-            obj.data.calc_loop_triangles()
-            tris = [tuple(t.vertices) for t in obj.data.loop_triangles]
-            self.draw_batch("TRIS", verts, transparent_color(special_elements_color), tris)
+                self._draw_lines_with_occlusion(line_verts, color, edges_indices, cache_key=(obj.session_uid, "lines"))
+                self.draw_batch(
+                    "TRIS",
+                    verts,
+                    transparent_color(special_elements_color),
+                    tris,
+                    cache_key=(obj.session_uid, "tris"),
+                )
 
             if "HalfSpaceSolid" in obj.name:
                 # Arrow shape
@@ -1069,7 +1378,4 @@ class DecorationsHandler:
                 ]
                 edges = [(0, 1), (1, 2), (1, 3), (1, 4), (1, 5)]
                 color = selected_elements_color if obj in context.selected_objects else special_elements_color
-                self.draw_batch("LINES", verts, color, edges)
-
-            if obj.mode != "EDIT":
-                bm.free()
+                self._draw_lines_with_occlusion(verts, color, edges, cache_key=(obj.session_uid, "arrow"))

src/bonsai/bonsai/bim/module/model/polyline.py

@@ -75,6 +75,7 @@ class PolylineOperator:
         self.is_typing = False
         self.snap_angle = None
         self.snapping_points = []
+        self.unit_scale = 1.0
         self.instructions = {
             "Cycle Input": {"icons": True, "keys": ["EVENT_TAB"]},
             "Distance Input": {"icons": True, "keys": ["EVENT_D"]},

src/bonsai/bonsai/bim/module/model/preview_base.py

@@ -0,0 +1,274 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""Shared helpers for Bonsai's parametric preview flows.
+
+Multiple Bonsai features follow the same Scene-level preview pattern:
+
+    Enable<X>Preview   — validates a selection, populates draft state on
+                         ``Scene.BIMPreviewProperties.<x>``, flips ``is_active``.
+    Gizmo<X>Preview    — polls on ``is_active``, surfaces tunable widgets +
+                         validate/cancel icons.
+    <X>PreviewDecorator — GPU lines drawn while ``is_active`` is True.
+    Finish<X>Preview   — direct ``bpy.ops.bim.<verb>(...)`` call with kwargs
+                         read off the draft state, then clears it.
+    Cancel<X>Preview   — pure state reset.
+
+The MEP bend and wall fillet flows are the two current callers. They write
+their Finish / Cancel operators directly, matching the convention used
+throughout the rest of ``bim/module/model/`` for operator-to-operator
+dispatch (explicit ``bpy.ops.bim.X(kwarg=value)`` at the call site, no
+string indirection). This module hosts the cross-cutting accessors only;
+no base class layer.
+
+The GPU draw-handler lifecycle for ``<X>PreviewDecorator`` lives on the
+feature-neutral ``tool.Blender.ViewportDecorator`` base, which every
+viewport decorator (preview or otherwise) inherits from."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from typing import Any
+
+import bpy
+
+import bonsai.tool as tool
+
+# --- Props accessors ---------------------------------------------------------
+
+
+def get_preview_props(context: bpy.types.Context, attr: str):
+    """Resolve a child preview PropertyGroup under ``Scene.BIMPreviewProperties``.
+
+    Returns ``None`` if the umbrella isn't attached yet — true briefly
+    during addon register and during plug-out, so polls / draw callbacks
+    must defend against ``None`` rather than assuming the prop is always
+    available. Also tolerates contexts without a ``scene`` attribute
+    (test mocks built from ``SimpleNamespace``)."""
+    scene = getattr(context, "scene", None)
+    if scene is None:
+        return None
+    preview = getattr(scene, "BIMPreviewProperties", None)
+    return getattr(preview, attr, None) if preview is not None else None
+
+
+def is_preview_active(context: bpy.types.Context, attr: str) -> bool:
+    """``True`` while a specific preview is open. Used by sibling gizmo
+    polls to hide themselves so the preview is the only interactive
+    surface in the viewport (the bend / fillet preview groups take over
+    the same selection's icon stack)."""
+    props = get_preview_props(context, attr)
+    return bool(props is not None and props.is_active)
+
+
+def any_preview_active(context: bpy.types.Context) -> bool:
+    """``True`` if any registered preview is currently open. Sister gizmo
+    polls call this to hide themselves uniformly during ANY preview, so a
+    new preview registered in ``PREVIEW_CANCEL_OPS`` automatically gates
+    every parametric gizmo without each one growing a specific check."""
+    for attr, _op_name in PREVIEW_CANCEL_OPS:
+        if is_preview_active(context, attr):
+            return True
+    return False
+
+
+# --- Lazy closure factories --------------------------------------------------
+#
+# Used by preview gizmo groups when wiring ``BIM_GT_gizmo_dimension``'s
+# ``move_get_cb`` / ``move_set_cb`` callbacks. The closures re-resolve
+# ``bpy.context.scene`` per CALL rather than capturing it at setup() time
+# — the captured Scene's RNA struct can be freed on file open / undo, and
+# referencing a freed struct crashes Blender. Lazy lookup survives the
+# whole undo / reload lifecycle.
+
+
+def make_props_callback(attr: str) -> Callable[[], Any]:
+    """Return a zero-arg callable that lazily fetches the preview props.
+
+    Equivalent to ``getattr(bpy.context.scene.BIMPreviewProperties, attr)``
+    with full defensiveness against missing scene / missing umbrella."""
+
+    def _props():
+        scene = bpy.context.scene
+        preview = getattr(scene, "BIMPreviewProperties", None) if scene else None
+        return getattr(preview, attr, None) if preview is not None else None
+
+    return _props
+
+
+def make_dim_getter(props_callback: Callable[[], Any], field: str) -> Callable[[], float]:
+    """Factory for ``BIM_GT_gizmo_dimension.move_get_cb`` reading a single
+    FloatProperty off the live preview state. Returns ``0.0`` defensively
+    when the props are temporarily unavailable so the widget doesn't crash
+    Blender during plug-out / reload."""
+
+    def _get() -> float:
+        props = props_callback()
+        return getattr(props, field) if props is not None else 0.0
+
+    return _get
+
+
+def make_dim_setter(
+    props_callback: Callable[[], Any],
+    field: str,
+    min_value: float = 0.001,
+) -> Callable[[float], None]:
+    """Factory for ``BIM_GT_gizmo_dimension.move_set_cb`` writing a single
+    FloatProperty + tagging viewport areas for redraw so the GPU preview
+    decorator tracks the value live during drag. Clamps at ``min_value``
+    to match the FloatProperty's declared lower bound."""
+
+    def _set(value: float) -> None:
+        props = props_callback()
+        if props is None:
+            return
+        setattr(props, field, max(min_value, float(value)))
+        tool.Blender.update_all_viewports()
+
+    return _set
+
+
+# --- Shared Enable lifecycle helpers -----------------------------------------
+
+
+def sync_uncommitted_moves(objects: list) -> None:
+    """Push any Blender-side translation / rotation of ``objects`` back to
+    their IFC ``ObjectPlacement`` before a preview decorator starts reading
+    ``obj.matrix_world`` per frame.
+
+    Without this sync, a user who grabbed-moved an object but didn't commit
+    the move sees the live preview at the dragged position while the final
+    commit lands at the stale IFC position — a confusing "where did my
+    preview go?" experience. Both bend and fillet enable paths call this
+    on the relevant pair just before activating the preview."""
+    for obj in objects:
+        tool.Geometry.commit_placement_if_moved(obj, apply_scale=False)
+
+
+def clear_preview_state(props: bpy.types.PropertyGroup) -> None:
+    """Reset a preview PropertyGroup to its idle state on commit / cancel.
+
+    Sets ``is_active`` to False and zeros every ``IntProperty`` whose name
+    ends in ``_id`` (the entity-reference convention every preview follows).
+    Other fields are left at their last value — defaults are re-applied on
+    the next enable, so leaving them alone avoids a redundant write."""
+    props.is_active = False
+    for name, rna in props.bl_rna.properties.items():
+        if name.endswith("_id") and rna.type == "INT":
+            setattr(props, name, 0)
+
+
+# --- Standard Finish flow ----------------------------------------------------
+
+
+def commit_preview(
+    operator: bpy.types.Operator,
+    context: bpy.types.Context,
+    attr: str,
+    target_op_name: str,
+    kwarg_names: tuple[str, ...],
+) -> set[str]:
+    """Standard Finish-Preview dispatch: validate context + active preview,
+    read kwargs off the draft, call ``bpy.ops.bim.<target_op_name>(**kwargs)``,
+    and clear the preview on success.
+
+    The dispatched operator's own ``self.report({"ERROR"})`` paths are promoted
+    by ``bpy.ops`` to ``RuntimeError`` — catching it here surfaces the message
+    to the user via ``operator.report`` rather than leaving Blender's operator
+    state half-broken (which silently disables downstream gizmo polls).
+
+    Returns the dispatched operator's result set verbatim so callers can
+    pass it straight back from their own ``execute``."""
+    if context.screen is None:
+        return {"CANCELLED"}
+    props = get_preview_props(context, attr)
+    if props is None or not props.is_active:
+        return {"CANCELLED"}
+    if tool.Ifc.get() is None:
+        operator.report({"ERROR"}, "No IFC file loaded.")
+        return {"CANCELLED"}
+    kwargs = {name: getattr(props, name) for name in kwarg_names}
+    try:
+        result = getattr(bpy.ops.bim, target_op_name)(**kwargs)
+    except RuntimeError as exc:
+        operator.report({"ERROR"}, str(exc))
+        return {"CANCELLED"}
+    if "FINISHED" in result:
+        clear_preview_state(props)
+    return result
+
+
+# --- Esc dispatch ------------------------------------------------------------
+
+PREVIEW_CANCEL_OPS: tuple[tuple[str, str], ...] = (
+    ("bend", "cancel_bend_preview"),
+    ("wall_fillet", "cancel_wall_fillet_preview"),
+)
+"""Registry of ``(child PointerProperty on Scene.BIMPreviewProperties, bim
+operator name)`` consulted by the Esc handler. Adding a new preview means
+appending one tuple; the forward-compat test pins that every preview
+PropertyGroup with ``is_active`` has an entry here."""
+
+
+def try_cancel_active_preview(context: bpy.types.Context) -> bool:
+    """Cancel every registered preview that is currently active.
+
+    Returns ``True`` iff at least one preview was cancelled. Multiple
+    previews can be simultaneously active (e.g. a stale bend preview opened
+    just before the user starts a wall fillet) — one Esc must clear them
+    all rather than forcing the user to tap Esc once per preview.
+
+    Tags 3D viewports for redraw on success — the Esc keymap entry runs
+    outside a viewport mouse event so the gizmo poll wouldn't re-evaluate
+    until the next interaction without an explicit redraw."""
+    cancelled = False
+    for attr, op_name in PREVIEW_CANCEL_OPS:
+        if is_preview_active(context, attr):
+            getattr(bpy.ops.bim, op_name)()
+            cancelled = True
+    if cancelled:
+        tool.Blender.update_all_viewports(context)
+    return cancelled
+
+
+def discard_pending_previews(scene: bpy.types.Scene) -> None:
+    """Clear every active preview under ``Scene.BIMPreviewProperties`` so
+    saved preview state never resurfaces on file load.
+
+    Mirrors ``tool.Parametric.heal_stale_edit_flags`` for the object-level
+    parametric-edit lifecycle — except previews are *discarded* rather than
+    validated. A preview's only UI cue is its in-viewport widget; reloading
+    a ``.blend`` saved mid-preview restores the flag but not the surrounding
+    user attention, and a stuck ``is_active`` silently hides every sibling
+    gizmo poll gated on it.
+
+    Iterates ``PREVIEW_CANCEL_OPS`` so any preview registered for Esc
+    cancellation is automatically covered here too. Sets ``is_active``
+    directly rather than dispatching the cancel operator: load_post may
+    fire before ``bpy.context.screen`` is reattached, and the cancel
+    operators bail on ``context.screen is None``."""
+    preview = getattr(scene, "BIMPreviewProperties", None)
+    if preview is None:
+        return
+    for attr, _op_name in PREVIEW_CANCEL_OPS:
+        child = getattr(preview, attr, None)
+        if child is not None and getattr(child, "is_active", False):
+            child.is_active = False

src/bonsai/bonsai/bim/module/model/profile.py

@@ -1002,6 +1002,14 @@ class EnableEditingExtrusionAxis(bpy.types.Operator, tool.Ifc.Operator):
     def _execute(self, context):
         self.unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
         obj = context.active_object
+
+        # Commit any in-progress parametric (gizmo) draft on this object
+        # before switching to axis-edit. Otherwise the in-memory draft
+        # state is overwritten when the axis mesh is imported below,
+        # silently discarding the user's pending dimension edits.
+        if feature := tool.Parametric.is_object_editing(obj):
+            tool.Parametric.commit_object_draft(obj, feature.finish_op)
+
         element = tool.Ifc.get_entity(obj)
 
         axis = ifcopenshell.util.representation.get_representation(element, "Model", "Axis", "GRAPH_VIEW")
@@ -1157,7 +1165,8 @@ class DrawPolylineProfile(bpy.types.Operator, PolylineOperator, tool.Ifc.Operato
                         DumbProfileJoiner().join_V(profile2["obj"], profile1["obj"])
                         if connect_IfcFlowSegments:
                             bpy.ops.bim.mep_connect_elements(
-                                obj1_name=profile1["obj"].name, obj2_name=profile2["obj"].name
+                                obj1_guid=tool.Ifc.get_entity(profile1["obj"]).GlobalId,
+                                obj2_guid=tool.Ifc.get_entity(profile2["obj"]).GlobalId,
                             )
 
     def modal(self, context, event):

src/bonsai/bonsai/bim/module/model/prop.py

@@ -15,6 +15,8 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 import math
 from collections.abc import Callable
@@ -31,8 +33,10 @@ from bonsai.bim.module.drawing.decoration import CutDecorator
 from bonsai.bim.module.model.data import AuthoringData
 from bonsai.bim.module.model.decorator import (
     BoundingBoxDecorator,
+    MEPSystemPathDecorator,
     SlabDirectionDecorator,
     WallAxisDecorator,
+    WallSystemPathDecorator,
 )
 from bonsai.bim.module.model.door import update_door_modifier_bmesh
 from bonsai.bim.module.model.window import update_window_modifier_bmesh
@@ -101,8 +105,12 @@ def update_type_page(self: "BIMModelProperties", context: bpy.types.Context) ->
 
 
 def update_relating_array_from_object(self: "BIMArrayProperties", context: bpy.types.Context) -> None:
-    bpy.ops.bim.enable_editing_array(item=self.is_editing)
-    return
+    # Skip the cleanup-time clear: Finish/Cancel sets relating_array_object back to None,
+    # which has no source to hydrate from. Only the user-driven pick (None → some array)
+    # should auto-enter edit on the picked source's layer 0.
+    if self.relating_array_object is None:
+        return
+    bpy.ops.bim.enable_editing_array(item=0)
 
 
 def is_object_array_applicable(self: "BIMArrayProperties", obj: bpy.types.Object) -> bool:
@@ -126,6 +134,19 @@ def update_slab_direction_decorator(self: "BIMModelProperties", context: bpy.typ
         SlabDirectionDecorator.uninstall()
 
 
+def update_paths_decorator(self: "BIMModelProperties", context: bpy.types.Context) -> None:
+    """Unified toggle for connected-element path overlays. Drives both the
+    MEP and wall path decorators — each decorator's ``draw`` short-circuits
+    when its kind of element isn't selected, so leaving both installed is
+    cheap and lets one toggle cover any connected-element family."""
+    if self.show_paths:
+        MEPSystemPathDecorator.install(bpy.context)
+        WallSystemPathDecorator.install(bpy.context)
+    else:
+        MEPSystemPathDecorator.uninstall()
+        WallSystemPathDecorator.uninstall()
+
+
 def update_measure_xyz(self: "BIMModelProperties", context: bpy.types.Context) -> None:
     if self.show_bounding_box:
         BoundingBoxDecorator.install(context)
@@ -193,14 +214,36 @@ def update_stair(self: "BIMStairProperties", context: bpy.types.Context) -> None
         _get_updater("stair", "regenerate_stair_mesh")(obj)
 
 
+def update_wall(self: "BIMWallProperties", context: bpy.types.Context) -> None:
+    """Regenerate wall mesh preview when property changes. Does NOT touch IFC."""
+    obj = context.active_object
+    if obj and self.is_editing:
+        _get_updater("wall", "regenerate_wall_mesh_from_props")(obj)
+
+
+def update_wall_offset_baseline(self: "BIMWallProperties", context: bpy.types.Context) -> None:
+    """Recompute the preview-only ``offset`` when the draft baseline cycles. Does not touch IFC.
+
+    ``offset`` itself has no ``update`` callback on purpose — adding one would make
+    every baseline cycle rebuild the bmesh twice (once via offset's callback, once
+    explicitly below)."""
+    obj = context.active_object
+    if not (obj and self.is_editing):
+        return
+    t = self.thickness
+    if self.desired_offset_baseline == "CENTER":
+        self.offset = -t / 2
+    elif self.desired_offset_baseline == "INTERIOR":
+        self.offset = -t
+    else:  # EXTERIOR
+        self.offset = 0.0
+    _get_updater("wall", "regenerate_wall_mesh_from_props")(obj)
+
+
 def update_railing(self: "BIMRailingProperties", context: bpy.types.Context) -> None:
     """Regenerate railing mesh when property changes."""
     if self.is_editing:
-        # Only FRAMELESS_PANEL can update live via bmesh.
-        # WALL_MOUNTED_HANDRAIL geometry is generated from IFC representation,
-        # so it only updates on "Finish Editing" to avoid modifying IFC during preview.
-        if self.railing_type == "FRAMELESS_PANEL":
-            _get_updater("railing", "update_railing_modifier_bmesh")(context)
+        _get_updater("railing", "update_railing_modifier_bmesh")(context)
 
 
 def update_roof(self: "BIMRoofProperties", context: bpy.types.Context) -> None:
@@ -210,6 +253,20 @@ def update_roof(self: "BIMRoofProperties", context: bpy.types.Context) -> None:
         _get_updater("roof", "update_roof_modifier_bmesh")(obj)
 
 
+def update_pipe_segment(self: "BIMPipeSegmentProperties", context: bpy.types.Context) -> None:
+    """Regenerate pipe-segment preview mesh from props during edit. Does NOT touch IFC."""
+    obj = context.active_object
+    if obj and self.is_editing:
+        _get_updater("mep", "regenerate_pipe_segment_mesh_from_props")(obj)
+
+
+def update_duct_segment(self: "BIMDuctSegmentProperties", context: bpy.types.Context) -> None:
+    """Regenerate duct-segment preview mesh from props during edit. Does NOT touch IFC."""
+    obj = context.active_object
+    if obj and self.is_editing:
+        _get_updater("mep", "regenerate_duct_segment_mesh_from_props")(obj)
+
+
 class BIMModelProperties(PropertyGroup):
     ifc_class: bpy.props.EnumProperty(items=get_ifc_class, name="Construction Class", update=update_ifc_class)
     relating_type_id: bpy.props.EnumProperty(
@@ -312,6 +369,19 @@ class BIMModelProperties(PropertyGroup):
         default=False,
         update=update_slab_direction_decorator,
     )
+    show_paths: bpy.props.BoolProperty(
+        name="Show Paths",
+        default=False,
+        update=update_paths_decorator,
+        description=(
+            "Trace the connected element path from the selected element. For "
+            "walls, follows IfcRelConnectsPathElements and draws each "
+            "connected wall's reference axis with endpoint dots. For MEP "
+            "elements, follows IfcRelConnectsPorts and draws each segment's "
+            "axis plus a port-to-port spider for each fitting. Toggle off to "
+            "skip the BFS traversal entirely."
+        ),
+    )
 
     prev_transform_orientation_slot_type: bpy.props.StringProperty(name="Previous Gizmo Orientation Type")
     prev_show_gizmo_object_translate: bpy.props.BoolProperty(name="Previous Gizmo Translate")
@@ -359,6 +429,7 @@ class BIMModelProperties(PropertyGroup):
         offset: float
         show_wall_axis: bool
         show_slab_direction: bool
+        show_paths: bool
 
         prev_transform_orientation_slot_type: str
         prev_show_gizmo_object_translate: bool
@@ -369,8 +440,13 @@ class BIMModelProperties(PropertyGroup):
 
 
 class BIMArrayProperties(PropertyGroup):
-    is_editing: bpy.props.IntProperty(
-        default=-1, description="Currently edited array index. -1 if not in array editing mode."
+    is_editing: bpy.props.BoolProperty(
+        default=False,
+        description="True while an array layer is in parametric edit mode. The specific layer is in editing_item_index.",
+    )
+    editing_item_index: bpy.props.IntProperty(
+        default=-1,
+        description="Index of the array layer currently being edited; -1 when not in edit mode.",
     )
     count: bpy.props.IntProperty(name="Count", default=0, min=0)
     x: bpy.props.FloatProperty(name="X", default=0, subtype="DISTANCE")
@@ -386,6 +462,15 @@ class BIMArrayProperties(PropertyGroup):
         name="Method",
         default="OFFSET",
     )
+    per_child_opening: bpy.props.BoolProperty(
+        name="Per-Child Opening",
+        description=(
+            "When the array parent fills a wall (or any voidable host), give each array child its own opening + "
+            "filling pair so the host is cut once per child. Disable to leave the host uncut by the children — "
+            "only the parent's original opening remains"
+        ),
+        default=True,
+    )
     relating_array_object: bpy.props.PointerProperty(
         type=bpy.types.Object,
         name="Copy Array Properties",
@@ -394,13 +479,15 @@ class BIMArrayProperties(PropertyGroup):
     )
 
     if TYPE_CHECKING:
-        is_editing: int
+        is_editing: bool
+        editing_item_index: int
         count: int
         x: float
         y: float
         z: float
         use_local_space: bool
         method: Literal["OFFSET", "DISTRIBUTE"]
+        per_child_opening: bool
         sync_children: bool
         relating_array_object: Union[bpy.types.Object, None]
 
@@ -1631,6 +1718,133 @@ class BIMRoofProperties(PropertyGroup):
             setattr(target_props, prop_name, prop_value)
 
 
+class BIMSlabProperties(PropertyGroup):
+    """Transient state for the slab disconnect-access gizmo.
+
+    ``is_editing`` flips True when the user clicks the pen icon on a slab
+    that has wall connections — gating the per-wall disconnect icons in
+    ``GizmoSlabUnjoinWalls`` so they're hidden until the user opts in. No
+    IFC draft state lives here: the disconnect operator commits directly,
+    so this PropertyGroup carries only the UI gate."""
+
+    is_editing: bpy.props.BoolProperty(name="Slab Edit Active", default=False, options={"SKIP_SAVE"})
+
+    if TYPE_CHECKING:
+        is_editing: bool
+
+
+class BIMWallProperties(PropertyGroup):
+    """Transient draft state for parametric wall gizmo editing.
+
+    Populated from IFC on `bim.enable_editing_wall`, mutated by gizmo drags during edit
+    (preview only — no IFC writes), and either committed by `bim.finish_editing_wall`
+    or discarded by `bim.cancel_editing_wall`.
+
+    The `snap_*` fields are the values captured on enable; `finish_editing_wall` compares
+    current vs snap to skip unchanged params and guarantee a no-op session leaves the
+    IFC file byte-identical.
+    """
+
+    is_editing: bpy.props.BoolProperty(
+        default=False,
+        description="True while wall parametric edit mode is active.",
+    )
+    mesh_dirty: bpy.props.BoolProperty(
+        default=False,
+        options={"HIDDEN", "SKIP_SAVE"},
+        description=(
+            "True while the visible mesh is the preview box; cleared once the real "
+            "IFC-derived geometry is restored (on commit or cancel)."
+        ),
+    )
+    length: bpy.props.FloatProperty(
+        name="Length",
+        default=1.0,
+        min=0.01,
+        subtype="DISTANCE",
+        update=update_wall,
+        description="Wall length along its reference axis (preview value; committed on finish).",
+    )
+    height: bpy.props.FloatProperty(
+        name="Height",
+        default=3.0,
+        min=0.01,
+        subtype="DISTANCE",
+        update=update_wall,
+        description="Wall vertical height (preview value; committed on finish).",
+    )
+    x_angle: bpy.props.FloatProperty(
+        name="Slope (X Angle)",
+        default=0.0,
+        soft_min=-math.pi / 3,
+        soft_max=math.pi / 3,
+        subtype="ANGLE",
+        update=update_wall,
+        description="Slope angle: tilt of the wall's top face along +Y (preview value; committed on finish).",
+    )
+    thickness: bpy.props.FloatProperty(
+        name="Thickness",
+        default=0.2,
+        min=0.001,
+        subtype="DISTANCE",
+        description="Wall thickness captured from IFC at edit-enable; not gizmo-bound.",
+    )
+    offset: bpy.props.FloatProperty(
+        name="Offset",
+        default=0.0,
+        subtype="DISTANCE",
+        description="Layer-set offset captured from IFC at edit-enable; driven by desired_offset_baseline.",
+    )
+    desired_offset_baseline: bpy.props.EnumProperty(
+        items=[
+            ("EXTERIOR", "Exterior", "Reference axis at the exterior face"),
+            ("CENTER", "Center", "Reference axis at the wall centreline"),
+            ("INTERIOR", "Interior", "Reference axis at the interior face"),
+        ],
+        name="Desired Offset Baseline",
+        default="CENTER",
+        update=update_wall_offset_baseline,
+        description="Which face of the wall the reference axis aligns to (preview value; committed on finish).",
+    )
+    anchor_x: bpy.props.FloatProperty(
+        default=0.0,
+        subtype="DISTANCE",
+        description="Local-X of the wall's axis polyline start, so the preview box lands where the IFC mesh does.",
+    )
+
+    snap_length: bpy.props.FloatProperty(description="Snapshot of length at edit-enable; commit skips no-op writes.")
+    snap_height: bpy.props.FloatProperty(description="Snapshot of height at edit-enable; commit skips no-op writes.")
+    snap_thickness: bpy.props.FloatProperty(
+        description="Snapshot of thickness at edit-enable; commit skips no-op writes."
+    )
+    snap_offset: bpy.props.FloatProperty(description="Snapshot of offset at edit-enable; commit skips no-op writes.")
+    snap_x_angle: bpy.props.FloatProperty(
+        subtype="ANGLE",
+        description="Snapshot of x_angle at edit-enable; commit skips no-op writes.",
+    )
+    snap_offset_baseline: bpy.props.StringProperty(
+        default="",
+        description="Snapshot of desired_offset_baseline at edit-enable; commit skips no-op writes.",
+    )
+
+    if TYPE_CHECKING:
+        is_editing: bool
+        mesh_dirty: bool
+        length: float
+        height: float
+        x_angle: float
+        thickness: float
+        offset: float
+        desired_offset_baseline: Literal["EXTERIOR", "CENTER", "INTERIOR"]
+        anchor_x: float
+        snap_length: float
+        snap_height: float
+        snap_thickness: float
+        snap_offset: float
+        snap_x_angle: float
+        snap_offset_baseline: str
+
+
 class SnapMousePoint(PropertyGroup):
     x: bpy.props.FloatProperty(name="X")
     y: bpy.props.FloatProperty(name="Y")
@@ -1762,3 +1976,236 @@ class BIMExternalParametricGeometryProperties(bpy.types.PropertyGroup):
         geometry_source: Literal["GEONODES", "IFCSVERCHOK"]
         geo_nodes: Union[bpy.types.GeometryNodeTree, None]
         sverchok_nodes: Union[sverchok.node_tree.SverchCustomTree, None]
+
+
+class BIMPipeSegmentProperties(PropertyGroup):
+    """Transient draft state for parametric pipe-segment gizmo editing."""
+
+    is_editing: bpy.props.BoolProperty(
+        default=False,
+        description="True while pipe-segment parametric edit mode is active.",
+    )
+    mesh_dirty: bpy.props.BoolProperty(
+        default=False,
+        options={"HIDDEN", "SKIP_SAVE"},
+        description=(
+            "True while the visible mesh is the preview shape; cleared once the "
+            "real IFC-derived geometry is restored (on commit or cancel)."
+        ),
+    )
+    length: bpy.props.FloatProperty(
+        name="Length",
+        default=1.0,
+        min=0.01,
+        subtype="DISTANCE",
+        update=update_pipe_segment,
+        description="Pipe-segment extrusion length (preview value; committed on finish).",
+    )
+    snap_length: bpy.props.FloatProperty(
+        description="Snapshot of length at edit-enable; commit skips no-op writes.",
+    )
+    snap_object_scale_z: bpy.props.FloatProperty(
+        default=1.0,
+        description=(
+            "Snapshot of obj.scale.z at edit-enable. Cancel / no-op-finish restore "
+            "this exact value so a user's non-identity pre-edit scale isn't silently "
+            "zeroed by the scale-based preview."
+        ),
+    )
+
+    if TYPE_CHECKING:
+        is_editing: bool
+        mesh_dirty: bool
+        length: float
+        snap_length: float
+        snap_object_scale_z: float
+
+
+class BIMDuctSegmentProperties(PropertyGroup):
+    """Transient draft state for parametric duct-segment gizmo editing."""
+
+    is_editing: bpy.props.BoolProperty(
+        default=False,
+        description="True while duct-segment parametric edit mode is active.",
+    )
+    mesh_dirty: bpy.props.BoolProperty(
+        default=False,
+        options={"HIDDEN", "SKIP_SAVE"},
+        description=(
+            "True while the visible mesh is the preview shape; cleared once the "
+            "real IFC-derived geometry is restored (on commit or cancel)."
+        ),
+    )
+    length: bpy.props.FloatProperty(
+        name="Length",
+        default=1.0,
+        min=0.01,
+        subtype="DISTANCE",
+        update=update_duct_segment,
+        description="Duct-segment extrusion length (preview value; committed on finish).",
+    )
+    snap_length: bpy.props.FloatProperty(
+        description="Snapshot of length at edit-enable; commit skips no-op writes.",
+    )
+    snap_object_scale_z: bpy.props.FloatProperty(
+        default=1.0,
+        description=(
+            "Snapshot of obj.scale.z at edit-enable. Cancel / no-op-finish restore "
+            "this exact value so a user's non-identity pre-edit scale isn't silently "
+            "zeroed by the scale-based preview."
+        ),
+    )
+
+    if TYPE_CHECKING:
+        is_editing: bool
+        mesh_dirty: bool
+        length: float
+        snap_length: float
+        snap_object_scale_z: float
+
+
+class BIMBendPreviewProperties(PropertyGroup):
+    """Scene-level pending state for the bend-creation preview flow.
+
+    Scene-level (not per-object) because the bend involves two segments by
+    IFC id — neither alone owns the draft."""
+
+    is_active: bpy.props.BoolProperty(
+        default=False,
+        options={"SKIP_SAVE"},
+        description="True while the bend-creation preview flow is active.",
+    )
+    start_segment_id: bpy.props.IntProperty(
+        default=0,
+        options={"SKIP_SAVE"},
+        description="IFC element id of the start (active) segment.",
+    )
+    end_segment_id: bpy.props.IntProperty(
+        default=0,
+        options={"SKIP_SAVE"},
+        description="IFC element id of the end (other selected) segment.",
+    )
+    start_length: bpy.props.FloatProperty(
+        name="Start Length",
+        default=0.1,
+        min=0.001,
+        subtype="DISTANCE",
+        description="Length of the bend fitting's tangent leg on the start (active) segment side",
+    )
+    end_length: bpy.props.FloatProperty(
+        name="End Length",
+        default=0.1,
+        min=0.001,
+        subtype="DISTANCE",
+        description="Length of the bend fitting's tangent leg on the end (other) segment side",
+    )
+    radius: bpy.props.FloatProperty(
+        name="Radius",
+        default=0.2,
+        min=0.001,
+        subtype="DISTANCE",
+        description="Inner radius of the bend curve",
+    )
+    editing_bend_id: bpy.props.IntProperty(
+        default=0,
+        options={"SKIP_SAVE"},
+        description=(
+            "IFC element id of an existing bend fitting being re-edited "
+            "(non-zero only on the pen-icon re-edit flow). The create "
+            "operator deletes this bend + its port connections before "
+            "recreating with the new parameters."
+        ),
+    )
+
+    if TYPE_CHECKING:
+        is_active: bool
+        start_segment_id: int
+        end_segment_id: int
+        start_length: float
+        end_length: float
+        radius: float
+        editing_bend_id: int
+
+
+class BIMWallFilletPreviewProperties(PropertyGroup):
+    """Scene-level pending state for the wall-fillet preview flow.
+
+    Scene-level because the fillet spans two walls and commits a third
+    (corner) wall between them. ``SKIP_SAVE`` fields throughout."""
+
+    is_active: bpy.props.BoolProperty(
+        default=False,
+        options={"SKIP_SAVE"},
+        description="True while the wall-fillet preview flow is active.",
+    )
+    wall_a_id: bpy.props.IntProperty(
+        default=0,
+        options={"SKIP_SAVE"},
+        description=(
+            "IFC element id of the active wall — the corner wall inherits its "
+            "material layer set, height, x_angle, and type."
+        ),
+    )
+    wall_b_id: bpy.props.IntProperty(
+        default=0,
+        options={"SKIP_SAVE"},
+        description="IFC element id of the other selected wall.",
+    )
+    radius: bpy.props.FloatProperty(
+        name="Radius",
+        default=0.5,
+        soft_min=-10.0,
+        soft_max=10.0,
+        subtype="DISTANCE",
+        unit="LENGTH",
+        options={"SKIP_SAVE"},
+        description="Radius of the circular arc connecting the two walls.",
+    )
+    editing_corner_id: bpy.props.IntProperty(
+        default=0,
+        options={"SKIP_SAVE"},
+        description=(
+            "IFC element id of an existing fillet corner being re-edited "
+            "(non-zero only on the pen-icon re-edit flow). The create "
+            "operator deletes this corner + its connections before recreating "
+            "with the new radius."
+        ),
+    )
+
+    if TYPE_CHECKING:
+        is_active: bool
+        wall_a_id: int
+        wall_b_id: int
+        radius: float
+        editing_corner_id: int
+
+
+class BIMPreviewProperties(PropertyGroup):
+    """Umbrella for parametric-edit preview drafts attached to ``Scene``."""
+
+    bend: bpy.props.PointerProperty(type=BIMBendPreviewProperties)
+    wall_fillet: bpy.props.PointerProperty(type=BIMWallFilletPreviewProperties)
+
+    if TYPE_CHECKING:
+        bend: BIMBendPreviewProperties
+        wall_fillet: BIMWallFilletPreviewProperties
+
+
+class BIMParametricEditDialogPrefs(PropertyGroup):
+    """Session-scoped flag for the parametric-edit pen-icon dispatcher.
+
+    Attached to ``WindowManager`` so the state lives for one Blender session
+    and resets on restart — the right scope for "don't show this again for
+    this session" toggles."""
+
+    suppress_shared_rep_warning: bpy.props.BoolProperty(
+        name="Suppress shared-representation warning",
+        description=(
+            "When true, the pen-icon dispatcher skips the shared-geometry "
+            "confirmation dialog. Resets on Blender restart."
+        ),
+        default=False,
+    )
+
+    if TYPE_CHECKING:
+        suppress_shared_rep_warning: bool

src/bonsai/bonsai/bim/module/model/railing.py

@@ -18,6 +18,7 @@
 
 
 import json
+import math
 from typing import Any
 
 import bmesh
@@ -27,13 +28,24 @@ import ifcopenshell.api.geometry
 import ifcopenshell.api.pset
 import ifcopenshell.util.representation
 import ifcopenshell.util.unit
-from mathutils import Vector
+from mathutils import Matrix, Vector
 
 import bonsai.core.geometry
 import bonsai.core.root
 import bonsai.tool as tool
+from bonsai.bim.module.drawing import gizmos as gizmo
+from bonsai.bim.module.drawing.gizmos import DimensionGizmoConfig
+from bonsai.bim.module.model import prop
 from bonsai.bim.module.model.data import RailingData, refresh
 from bonsai.bim.module.model.decorator import ProfileDecorator
+from bonsai.bim.parametric_lifecycle import (
+    CycleTypeMixin,
+    PathPreservingEditMixin,
+    PickTypeMixin,
+)
+from bonsai.tool.cad import WELD_TOLERANCE
+
+V_ = tool.Blender.V_
 
 # reference:
 # https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcRailing.htm
@@ -92,7 +104,6 @@ def update_railing_modifier_ifc_data(context: bpy.types.Context) -> None:
         si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
 
         representation_data = {
-            "railing_type": props.railing_type,
             "context": body,
             "railing_path": railing_path,
             "use_manual_supports": props.use_manual_supports,
@@ -125,6 +136,56 @@ def update_bbim_railing_pset(element: ifcopenshell.entity_instance, railing_data
     ifcopenshell.api.pset.edit_pset(tool.Ifc.get(), pset=pset, properties={"Data": railing_data})
 
 
+def generate_wall_mounted_handrail_preview(
+    obj: bpy.types.Object,
+    props: "prop.BIMRailingProperties",
+    path_data: dict[str, Any],
+    si_conversion: float,
+) -> None:
+    """Viewport-only WALL_MOUNTED_HANDRAIL preview: rebuild ``obj.data`` from the same
+    geometry helper the IFC representation builder uses, without writing any IFC."""
+    railing_path = [Vector(v) * si_conversion for v in path_data["verts"]]
+    looped_path = path_data["edges"][-1][-1] == path_data["edges"][0][0]
+
+    geom = ifcopenshell.api.geometry.compute_wall_mounted_handrail_geometry(
+        railing_path=railing_path,
+        support_spacing=props.support_spacing,
+        railing_diameter=props.railing_diameter,
+        clear_width=props.clear_width,
+        height=props.height,
+        use_manual_supports=props.use_manual_supports,
+        terminal_type=props.terminal_type,
+        looped_path=looped_path,
+        unit_scale=1.0,  # props are already SI; bypass the IFC project-units conversion
+    )
+
+    bm = tool.Blender.get_bmesh_for_mesh(obj.data, clean=True)
+
+    tool.Cad.sweep_disk_along_polyline(
+        bm,
+        [Vector(p) for p in geom.handrail_polyline],
+        geom.handrail_radius,
+        arc_indices=geom.handrail_arc_point_indices,
+    )
+
+    for support in geom.supports:
+        tool.Cad.sweep_disk_along_polyline(
+            bm,
+            [Vector(p) for p in support.arc_polyline],
+            support.arc_radius,
+        )
+        tool.Cad.add_disk_extrusion(
+            bm,
+            Vector(support.disk_position),
+            support.disk_radius,
+            support.disk_depth,
+            support.disk_z_rotation,
+        )
+
+    bmesh.ops.recalc_face_normals(bm, faces=bm.faces[:])
+    tool.Blender.apply_bmesh(obj.data, bm)
+
+
 def update_railing_modifier_bmesh(context: bpy.types.Context) -> None:
     """before using should make sure that Data contains up-to-date information.
     If BBIM Pset just changed should call refresh() before updating bmesh
@@ -140,6 +201,13 @@ def update_railing_modifier_bmesh(context: bpy.types.Context) -> None:
     path_data = RailingData.data["path_data"]
 
     si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
+
+    # WALL_MOUNTED_HANDRAIL renders the preview from the compute helper; IFC stays
+    # untouched until Finish Editing rebuilds the representation.
+    if not props.is_editing_path and props.railing_type == "WALL_MOUNTED_HANDRAIL":
+        generate_wall_mounted_handrail_preview(obj, props, path_data, si_conversion)
+        return
+
     # need to make sure we support edit mode
     # since users will probably be in edit mode when they'll be changing railing path
     bm = tool.Blender.get_bmesh_for_mesh(obj.data, clean=True)
@@ -165,8 +233,6 @@ def update_railing_modifier_bmesh(context: bpy.types.Context) -> None:
         thickness = props.thickness
         spacing = props.spacing
 
-        # spacing
-        # split each edge in 3 segments by 0.5 * spacing by x-y plane
         main_edges = bm.edges[:]
         for main_edge in main_edges:
             bm_split_edge_at_offset(main_edge, spacing)
@@ -211,7 +277,7 @@ def update_railing_modifier_bmesh(context: bpy.types.Context) -> None:
         bmesh.ops.dissolve_edges(bm, edges=edges_to_dissolve)
         bmesh.ops.dissolve_verts(bm, verts=verts_to_dissolve)
         # to remove unnecessary verts in 0 spacing case
-        bmesh.ops.remove_doubles(bm, verts=bm.verts, dist=0.0001)
+        bmesh.ops.remove_doubles(bm, verts=bm.verts, dist=WELD_TOLERANCE)
 
         bmesh.ops.recalc_face_normals(bm, faces=bm.faces[:])
 
@@ -271,8 +337,8 @@ def get_path_data(obj: bpy.types.Object) -> dict[str, Any]:
             segments.append((i - 1, 0))
             break
 
-        # skip path verts if they just go vertical to avoid errors
-        if (v.co.xy - prev_v.co.xy).length <= 0.0001:
+        # Vertical-only segments project to a degenerate XY edge; skip to avoid divide-by-zero downstream.
+        if (v.co.xy - prev_v.co.xy).length <= WELD_TOLERANCE:
             continue
 
         points.append(v.co)
@@ -406,68 +472,630 @@ class CopyRailingParameters(bpy.types.Operator, tool.Ifc.Operator):
         return {"FINISHED"}
 
 
-class EnableEditingRailing(bpy.types.Operator, tool.Ifc.Operator):
-    bl_idname = "bim.enable_editing_railing"
-    bl_label = "Enable Editing Railing"
-    bl_options = {"REGISTER"}
+class _RailingEditMixin(PathPreservingEditMixin):
+    """Single-object (active_object) railing-edit hooks; path_data is preserved
+    through the edit (path editing is a separate operator family)."""
 
-    def _execute(self, context):
-        obj = context.active_object
-        assert obj
-        props = tool.Model.get_railing_props(obj)
-        data = tool.Model.get_modeling_bbim_pset_data(obj, "BBIM_Railing")["data_dict"]
+    pset_name = "BBIM_Railing"
+
+    @classmethod
+    def _is_element_type(cls, element):
+        return tool.Parametric.is_railing(element)
+
+    @classmethod
+    def _get_props(cls, obj: bpy.types.Object):
+        return tool.Model.get_railing_props(obj)
+
+    @classmethod
+    def _post_load_data(cls, data: dict) -> dict:
+        # BIMRailingProperties.path_data is a StringProperty holding JSON.
         data["path_data"] = json.dumps(data["path_data"])
+        return data
 
-        # required since we could load pset from .ifc and BIMRailingProperties won't be set
-        props.set_props_kwargs_from_ifc_data(data)
+    @classmethod
+    def _update_pset(cls, element, data: dict) -> None:
+        update_bbim_railing_pset(element, data)
 
-        props.is_editing = True
-        return {"FINISHED"}
+    @classmethod
+    def _update_modifier_ifc_data(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        update_railing_modifier_ifc_data(context)
 
-
-class CancelEditingRailing(bpy.types.Operator, tool.Ifc.Operator):
-    bl_idname = "bim.cancel_editing_railing"
-    bl_label = "Cancel Editing Railing"
-    bl_options = {"REGISTER"}
-
-    def _execute(self, context):
-        obj = context.active_object
-        assert obj
-        data = tool.Model.get_modeling_bbim_pset_data(obj, "BBIM_Railing")["data_dict"]
+    @classmethod
+    def _restore_viewport_after_cancel(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        """WALL_MOUNTED_HANDRAIL reloads the committed Body; others rebuild the preview bmesh."""
         props = tool.Model.get_railing_props(obj)
-
-        # restore previous settings since editing was canceled
-        props.set_props_kwargs_from_ifc_data(data)
+        if props.railing_type == "WALL_MOUNTED_HANDRAIL":
+            element = tool.Ifc.get_entity(obj)
+            assert element
+            body = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
+            if body:
+                bonsai.core.geometry.switch_representation(
+                    tool.Ifc,
+                    tool.Geometry,
+                    obj=obj,
+                    representation=body,
+                )
+            return
         update_railing_modifier_bmesh(context)
 
-        props.is_editing = False
-        return {"FINISHED"}
 
-
-class FinishEditingRailing(bpy.types.Operator, tool.Ifc.Operator):
-    bl_idname = "bim.finish_editing_railing"
-    bl_label = "Finish Editing Railing"
-    bl_options = {"REGISTER"}
+class EnableEditingRailing(_RailingEditMixin, bpy.types.Operator, tool.Ifc.Operator):
+    bl_idname = "bim.enable_editing_railing"
+    bl_label = "Enable Editing Railing"
+    bl_options = {"REGISTER", "UNDO"}
 
     def _execute(self, context):
-        obj = context.active_object
-        assert obj
-        element = tool.Ifc.get_entity(obj)
-        assert element
-        props = tool.Model.get_railing_props(obj)
+        return self._enable_targets(context)
 
-        pset_data = tool.Model.get_modeling_bbim_pset_data(bpy.context.active_object, "BBIM_Railing")
-        path_data = pset_data["data_dict"]["path_data"]
 
-        railing_data = props.get_general_kwargs(convert_to_project_units=True)
-        railing_data["path_data"] = path_data
-        props.is_editing = False
+class CancelEditingRailing(_RailingEditMixin, bpy.types.Operator, tool.Ifc.Operator):
+    bl_idname = "bim.cancel_editing_railing"
+    bl_label = "Cancel Editing Railing"
+    bl_options = {"REGISTER", "UNDO"}
 
-        update_bbim_railing_pset(element, railing_data)
-        update_railing_modifier_ifc_data(context)
+    def _execute(self, context):
+        return self._cancel_targets(context)
+
+
+class FinishEditingRailing(_RailingEditMixin, bpy.types.Operator, tool.Ifc.Operator):
+    bl_idname = "bim.finish_editing_railing"
+    bl_label = "Finish Editing Railing"
+    bl_options = {"REGISTER", "UNDO"}
+
+    def _execute(self, context):
+        return self._finish_targets(context)
+
+
+class CycleRailingType(bpy.types.Operator, tool.Ifc.Operator, CycleTypeMixin):
+    """Cycle railing_type (FRAMELESS_PANEL ↔ WALL_MOUNTED_HANDRAIL). Shift+click reverses."""
+
+    bl_idname = "bim.cycle_railing_type"
+    bl_label = "Cycle Railing Type"
+    bl_options = {"REGISTER", "UNDO"}
+
+    element_checker = tool.Parametric.is_railing
+    props_getter = tool.Model.get_railing_props
+    type_literal = tool.Model.RailingType
+    type_attr = "railing_type"
+
+    def _execute(self, context: bpy.types.Context) -> set[str]:
+        return self._cycle_type(context)
+
+
+class ToggleRailingUseManualSupports(bpy.types.Operator):
+    """Flip use_manual_supports on the active WALL_MOUNTED_HANDRAIL railing.
+
+    No-op unless a parametric edit is active and the railing is wall-mounted.
+    """
+
+    bl_idname = "bim.toggle_railing_use_manual_supports"
+    bl_label = "Toggle Railing Manual Supports"
+    bl_description = "Switch between automatic support spacing and manual per-vertex placement"
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context):
+        resolved = tool.Model.resolve_active_props_for_edit(
+            context,
+            tool.Model.get_railing_props,
+            subtype=("railing_type", "WALL_MOUNTED_HANDRAIL"),
+        )
+        if resolved is None:
+            return {"CANCELLED"}
+        _obj, props = resolved
+        props.use_manual_supports = not props.use_manual_supports
         return {"FINISHED"}
 
 
+class PickRailingTerminalType(bpy.types.Operator, tool.Ifc.Operator, PickTypeMixin):
+    """Pick ``terminal_type`` for the active WALL_MOUNTED_HANDRAIL railing."""
+
+    bl_idname = "bim.pick_railing_terminal_type"
+    bl_label = "Pick Railing Terminal Type"
+    bl_description = "Pick the cap geometry applied at the rail ends"
+    bl_options = {"REGISTER", "UNDO"}
+
+    skip_element_check = True
+    props_getter = tool.Model.get_railing_props
+    type_literal = prop.CapType
+    type_attr = "terminal_type"
+
+    def _execute(self, context: bpy.types.Context) -> set[str]:
+        if (
+            tool.Model.resolve_active_props_for_edit(
+                context,
+                tool.Model.get_railing_props,
+                subtype=("railing_type", "WALL_MOUNTED_HANDRAIL"),
+            )
+            is None
+        ):
+            return {"CANCELLED"}
+        return self._pick_type(context)
+
+
+def _format_attr_distance(attr_name: str):
+    """text_formatter that renders the named property as a distance, ignoring the
+    dimension's visible-length argument (which is fixed for schematic gizmos)."""
+    return lambda p, _v: tool.Unit.format_distance(getattr(p, attr_name))
+
+
+class GizmoRailingSchematic(bpy.types.GizmoGroup, gizmo.BaseSchematicGizmoGroup):
+    """Schematic-frame parametric editor for railings. Mutually exclusive with path-edit mode."""
+
+    bl_idname = "OBJECT_GGT_bim_railing_edition"
+    bl_label = "Railing Editing Gizmo"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options = {"3D", "PERSISTENT"}
+
+    enable_editing_operator = "bim.enable_editing_railing"
+    finish_editing_operator = "bim.finish_editing_railing"
+    cancel_editing_operator = "bim.cancel_editing_railing"
+    cycle_type_operator = "bim.cycle_railing_type"
+
+    props_getter = tool.Model.get_railing_props
+    gizmo_pref_name = "railing"
+
+    # Schematic-local layout. +X → screen RIGHT, +Y → screen UP, +Z → toward viewer
+    # (post billboard rotation). Each dimension is anchored alongside the feature it
+    # measures so the label, not the bar length, carries the value.
+    SCHEMATIC_MESH_HEIGHT_FRAC = 0.9  # Mesh top edge in schematic-local +Y
+    SCHEMATIC_MESH_WIDTH_FRAC = 0.7  # Mesh side edges in schematic-local ±X
+    SCHEMATIC_MESH_RAIL_Y_FRAC = SCHEMATIC_MESH_HEIGHT_FRAC / 2  # WALL_MOUNTED_HANDRAIL rail centreline
+    SCHEMATIC_MESH_DEPTH_FRAC = 0.06  # Panel depth — small so the schematic reads as slabs not boxes
+    # WALL_MOUNTED_HANDRAIL dimensions — fractions of schematic_box_size so they
+    # scale with the host group's box size.
+    SCHEMATIC_RAIL_RADIUS_FRAC = 0.05
+    SCHEMATIC_RAIL_CLEAR_FRAC = 0.5  # Stylised — wider than real-world for visible bracket arm
+    SCHEMATIC_RAIL_INSET_FRAC = 0.08  # Wall extends past the outermost support on both sides
+
+    @classmethod
+    def schematic_rail_radius(cls) -> float:
+        return cls.schematic_box_size * cls.SCHEMATIC_RAIL_RADIUS_FRAC
+
+    @classmethod
+    def schematic_rail_clear(cls) -> float:
+        return cls.schematic_box_size * cls.SCHEMATIC_RAIL_CLEAR_FRAC
+
+    # Axonometric 3/4 view: +Z projects down-and-left so the depth axis
+    # is visibly separated from the back face. Without the X tilt, panel
+    # thickness (schematic-local Z) collapses to a near-horizontal bar.
+    schematic_view_rotation = Matrix.Rotation(math.radians(20), 4, "X") @ Matrix.Rotation(math.radians(-25), 4, "Y")
+
+    # Hover a dimension → highlight the schematic edges tagged with the matching feature.
+    # Tags are written by the mesh builders. "spacing" is empty space (no edges) so it's
+    # absent from this map and gracefully no-ops on hover.
+    schematic_attr_to_feature = {
+        "height": "panel_height",
+        "thickness": "panel_thickness",
+        "railing_diameter": "rail_tube",
+        "clear_width": "bracket",
+        "support_spacing": "bracket",
+    }
+
+    schematic_dimension_props = [
+        # ── FRAMELESS_PANEL ─────────────────────────────────────────────
+        DimensionGizmoConfig(
+            attr_name="height",
+            axis=(0, 1, 0),
+            min_value=0.01,
+            # Gated to FRAMELESS_PANEL: in WALL_MOUNTED_HANDRAIL, height only
+            # feeds TO_FLOOR / TO_END_POST_AND_FLOOR terminals so dragging it
+            # is a no-op under the default "180" terminal.
+            visibility_condition=lambda p: p.railing_type == "FRAMELESS_PANEL",
+            matrix_position=lambda p: Vector((-GizmoRailingSchematic.SCHEMATIC_MESH_WIDTH_FRAC / 2 - 0.08, 0.0, 0.0)),
+            schematic_visible_length=SCHEMATIC_MESH_HEIGHT_FRAC,
+            text_formatter=_format_attr_distance("height"),
+        ),
+        DimensionGizmoConfig(
+            attr_name="thickness",
+            axis=(0, 0, 1),  # panel depth — projects to a true depth direction under the 3/4 tilt
+            min_value=0.005,
+            visibility_condition=lambda p: p.railing_type == "FRAMELESS_PANEL",
+            matrix_position=lambda p: Vector(
+                (
+                    (
+                        -GizmoRailingSchematic.SCHEMATIC_MESH_WIDTH_FRAC / 2
+                        - GizmoRailingSchematic.SCHEMATIC_MESH_GAP_HALF_WIDTH
+                    )
+                    / 2,
+                    GizmoRailingSchematic.SCHEMATIC_MESH_HEIGHT_FRAC + 0.05,
+                    -GizmoRailingSchematic.SCHEMATIC_MESH_DEPTH_FRAC / 2,
+                )
+            ),
+            schematic_visible_length=0.4,  # longer than default to survive depth foreshortening
+            text_formatter=_format_attr_distance("thickness"),
+        ),
+        DimensionGizmoConfig(
+            attr_name="spacing",
+            axis=(1, 0, 0),
+            min_value=0.0,  # zero-spacing collapses the picket gap into a single continuous panel
+            visibility_condition=lambda p: p.railing_type == "FRAMELESS_PANEL",
+            matrix_position=lambda p: Vector((0.0, -0.1, 0.0)),
+            text_formatter=_format_attr_distance("spacing"),
+        ),
+        # ── WALL_MOUNTED_HANDRAIL ──────────────────────────────────────
+        DimensionGizmoConfig(
+            attr_name="railing_diameter",
+            axis=(0, 1, 0),
+            min_value=0.001,
+            visibility_condition=lambda p: p.railing_type == "WALL_MOUNTED_HANDRAIL",
+            matrix_position=lambda p: Vector(
+                (
+                    -GizmoRailingSchematic.SCHEMATIC_MESH_WIDTH_FRAC / 2 - 0.05,
+                    GizmoRailingSchematic.SCHEMATIC_MESH_RAIL_Y_FRAC - 0.09,
+                    GizmoRailingSchematic.schematic_rail_clear(),
+                )
+            ),
+            text_formatter=_format_attr_distance("railing_diameter"),
+        ),
+        DimensionGizmoConfig(
+            attr_name="clear_width",
+            axis=(0, 0, 1),  # +Z is the wall-to-rail perpendicular axis under the 3/4 tilt
+            min_value=0.001,
+            visibility_condition=lambda p: p.railing_type == "WALL_MOUNTED_HANDRAIL",
+            matrix_position=lambda p: Vector(
+                (
+                    0.0,
+                    GizmoRailingSchematic.SCHEMATIC_MESH_RAIL_Y_FRAC,
+                    0.0,
+                )
+            ),
+            schematic_visible_length=0.36,  # 2× default so the call-out survives depth projection
+            text_formatter=_format_attr_distance("clear_width"),
+        ),
+        DimensionGizmoConfig(
+            attr_name="support_spacing",
+            axis=(1, 0, 0),
+            min_value=0.05,
+            visibility_condition=lambda p: (p.railing_type == "WALL_MOUNTED_HANDRAIL" and not p.use_manual_supports),
+            matrix_position=lambda p: Vector(
+                (
+                    -GizmoRailingSchematic.SCHEMATIC_MESH_WIDTH_FRAC / 2
+                    + GizmoRailingSchematic.SCHEMATIC_RAIL_INSET_FRAC,
+                    -0.18,
+                    0.0,
+                )
+            ),
+            # Bare names (not Gizmo…SCHEMATIC_…) because the class is still under construction here.
+            schematic_visible_length=SCHEMATIC_MESH_WIDTH_FRAC - 2 * SCHEMATIC_RAIL_INSET_FRAC,
+            text_formatter=_format_attr_distance("support_spacing"),
+        ),
+    ]
+
+    @classmethod
+    def is_element_type(cls, element: ifcopenshell.entity_instance) -> bool:
+        return tool.Parametric.is_railing(element)
+
+    @classmethod
+    def schematic_cache_key(cls, props) -> tuple:
+        """Cache the schematic mesh by ``railing_type`` — proportions are fixed
+        per type, so the bmesh build runs at most twice across a session
+        (once for ``FRAMELESS_PANEL``, once for ``WALL_MOUNTED_HANDRAIL``)
+        rather than once per draw call."""
+        return (props.railing_type,)
+
+    def setup_element_specific_gizmos(self, context: bpy.types.Context) -> None:
+        """Create the WALL_MOUNTED_HANDRAIL-only affordances on the schematic.
+
+        Two static lock glyphs (open/closed) for toggling
+        ``use_manual_supports``: instantiate both and let the per-frame state
+        query pick which one to show. State-aware icons use a static pair
+        rather than a single dynamic gizmo to avoid ``prop_path`` resolution
+        in the render path.
+
+        Plus a cycle-glyph at the rail end that opens the ``terminal_type``
+        popup when clicked.
+        """
+        default_color, highlight_color = self.get_decoration_colors()
+
+        self.lock_open_gizmo, self.lock_closed_gizmo = self.create_icon_gizmo_lock_pair(
+            "bim.toggle_railing_use_manual_supports",
+            open_color=default_color,
+        )
+
+        self.terminal_gizmo = self.gizmos.new("VIEW3D_GT_menu")
+        self.terminal_gizmo.color = default_color
+        self.terminal_gizmo.color_highlight = highlight_color
+        self.terminal_gizmo.use_draw_scale = False
+        self.terminal_gizmo.alpha = 0.8
+        self.terminal_gizmo.target_set_operator("bim.pick_railing_terminal_type")
+
+    def _refresh_element_specific(self, context: bpy.types.Context, mw: "Matrix", props) -> None:
+        """Position and gate the WALL_MOUNTED_HANDRAIL-only gizmos.
+
+        - Lock glyphs: only WALL_MOUNTED_HANDRAIL while editing. Show
+          ``lock_open`` when ``use_manual_supports`` is True, the closed
+          padlock when False ("auto-spacing is locked to support_spacing").
+        - Terminal gizmo: same gating, positioned just past the right rail
+          end so it reads as "configure the rail's end cap".
+        """
+        super()._refresh_element_specific(context, mw, props)
+
+        # ``draw_prepare`` can fire on a freshly recreated GizmoGroup instance
+        # before ``setup_element_specific_gizmos`` has populated the lock /
+        # terminal attributes (Blender 5.x recreates per-region groups on
+        # reload). Bail out cheaply; the next refresh after setup completes
+        # will reposition them correctly.
+        if not hasattr(self, "lock_open_gizmo"):
+            return
+
+        # Single gate for all WALL_MOUNTED_HANDRAIL extras.
+        active = props.is_editing and not props.is_editing_path and props.railing_type == "WALL_MOUNTED_HANDRAIL"
+
+        if not active:
+            self.lock_open_gizmo.hide = True
+            self.lock_closed_gizmo.hide = True
+            self.terminal_gizmo.hide = True
+            return
+
+        billboard_rot = self._frame_billboard_rot
+        view_rotation = self.schematic_view_rotation
+        anchor = self._compute_schematic_anchor(props, mw, billboard_rot)
+
+        # ── Lock glyphs for use_manual_supports ──────────────────────────
+        # Sit just above the wall's bottom line, near the centre of the
+        # schematic — visually grouped with the dimension it controls
+        # (support_spacing) without overlapping the arrow tail below.
+        is_manual = bool(props.use_manual_supports)
+        self.lock_open_gizmo.hide = not is_manual
+        self.lock_closed_gizmo.hide = is_manual
+        lock_local = Vector((0.0, 0.05, 0.0))
+        lock_world = anchor + billboard_rot @ view_rotation @ lock_local
+        lock_matrix = gizmo.billboarded_at(lock_world, billboard_rot, 0.09)
+        self.lock_open_gizmo.matrix_basis = lock_matrix
+        self.lock_closed_gizmo.matrix_basis = lock_matrix
+
+        # ── Terminal-type popup gizmo at the right rail end ──────────────
+        # Pushed well past the right wall edge so the icon doesn't crowd
+        # the wall outline or the bracket attach point. At rail height and
+        # rail depth so it reads as "attached to the rail terminal".
+        self.terminal_gizmo.hide = False
+        terminal_local = Vector(
+            (
+                self.SCHEMATIC_MESH_WIDTH_FRAC / 2 + 0.25,
+                self.SCHEMATIC_MESH_RAIL_Y_FRAC,
+                self.schematic_rail_clear(),
+            )
+        )
+        terminal_world = anchor + billboard_rot @ view_rotation @ terminal_local
+        self.terminal_gizmo.matrix_basis = gizmo.billboarded_at(terminal_world, billboard_rot, 0.18)
+
+    def update_editing_gizmos(
+        self, context: bpy.types.Context, mw: "Matrix", props: "prop.BIMRailingProperties"
+    ) -> None:
+        """Hide the pen gizmo while polyline path-edit is active; reposition the cycle icon.
+
+        The base class shows the pen gizmo whenever ``is_editing`` is False,
+        which is the case during path-edit too. Allowing the user to click
+        through into parametric edit while the polyline mesh is open in EDIT
+        mode mixes two distinct editing states and leaves a stale draft if
+        they cancel out — block the entry point instead. The operator itself
+        is intentionally not guarded (callers via scripting can still invoke
+        it); this is the UX-level enforcement.
+
+        The cycle icon defaults to the editing icon row (next to validate /
+        cancel) via the parent's positioning. We move it to just above the
+        schematic mesh so it reads as "cycle the railing type *shown here*"
+        — associated with the preview the user is interacting with, not a
+        generic editing button at the bottom of the schematic.
+        """
+        super().update_editing_gizmos(context, mw, props)
+        if props.is_editing_path:
+            self.pen_gizmo.hide = True
+
+        if props.is_editing and not props.is_editing_path:
+            billboard_rot = self._frame_billboard_rot
+            view_rotation = self.schematic_view_rotation
+            anchor = self._compute_schematic_anchor(props, mw, billboard_rot)
+            # Comfortably above the mesh top edge so the icon doesn't crowd
+            # the ``thickness`` / ``clear_width`` dimension callouts that
+            # already sit just above the panel/wall.
+            cycle_local = Vector((0.0, self.SCHEMATIC_MESH_HEIGHT_FRAC + 0.25, 0.0))
+            world_pos = anchor + billboard_rot @ view_rotation @ cycle_local
+            # 30% smaller than the editing-icon-row default (0.30 → 0.21):
+            # the cycle is a tertiary affordance compared to pen/validate/cancel.
+            self.cycle_gizmo.matrix_basis = gizmo.billboarded_at(world_pos, billboard_rot, 0.21)
+
+    @classmethod
+    def build_schematic_mesh(cls, props) -> "bmesh.types.BMesh":
+        """Build a wireframe preview of the railing in schematic-local coordinates.
+
+        FRAMELESS_PANEL renders as a box whose proportions track the bound
+        properties (height / thickness / spacing); WALL_MOUNTED_HANDRAIL
+        renders as a horizontal tube with two L-shaped supports whose
+        proportions track railing_diameter / clear_width / support_spacing.
+        Both are scaled to fit inside ``[-schematic_box_size, +schematic_box_size]``
+        on each axis so the schematic reads the same regardless of absolute
+        property values.
+
+        The mesh is decorative — clicks land on the labeled sliders, not on
+        the preview geometry. See ``BaseSchematicGizmoGroup`` for the
+        draw-handler lifecycle.
+        """
+        bm = bmesh.new()
+        if props.railing_type == "FRAMELESS_PANEL":
+            cls._build_frameless_panel_schematic(bm, props)
+        else:
+            cls._build_wall_mounted_handrail_schematic(bm, props)
+        return bm
+
+    # Schematic-local half-width of the visible gap between the two panel boxes.
+    # Conveys the "spacing" semantic at a glance — the user sees two pickets
+    # separated by air, with the spacing dimension emerging from that gap.
+    SCHEMATIC_MESH_GAP_HALF_WIDTH = 0.05
+
+    @classmethod
+    def _build_frameless_panel_schematic(cls, bm: "bmesh.types.BMesh", props) -> None:
+        """Stylised panel: two wireframe boxes with a visible gap between them.
+
+        The box edges sit at the ``SCHEMATIC_MESH_*_FRAC`` positions
+        (matching where the dimension gizmos anchor), so each dimension line
+        visually starts at the geometry feature it measures. Internal
+        proportions are stable across drags — the actual values are shown
+        through the dimension labels, while the schematic communicates
+        which feature each label refers to. The gap between the two boxes
+        (set by ``SCHEMATIC_MESH_GAP_HALF_WIDTH``) gives the "spacing"
+        dimension a real visual referent.
+
+        Edges are tagged on a string layer so hover-highlight can colour
+        the geometric feature being measured: vertical edges → height,
+        depth edges → thickness. The X-aligned edges along the panel
+        width are untagged (they don't correspond to a single dimension).
+        """
+        hw = cls.SCHEMATIC_MESH_WIDTH_FRAC / 2
+        hd = cls.SCHEMATIC_MESH_DEPTH_FRAC / 2
+        h_top = cls.SCHEMATIC_MESH_HEIGHT_FRAC
+        gap = cls.SCHEMATIC_MESH_GAP_HALF_WIDTH
+
+        layer_name = cls.SCHEMATIC_FEATURE_LAYER_NAME
+        feat_layer = bm.edges.layers.string.get(layer_name) or bm.edges.layers.string.new(layer_name)
+
+        # Edge index → feature tag for one box. Order matches the (a, b)
+        # tuple order below: bottom ring (4) + top ring (4) + verticals (4).
+        edge_tags_per_box = (
+            b"",  # (0,1) bottom-back, X-aligned
+            b"panel_thickness",  # (1,2) bottom-right, Z-aligned
+            b"",  # (2,3) bottom-front, X-aligned
+            b"panel_thickness",  # (3,0) bottom-left, Z-aligned
+            b"",  # (4,5) top-back, X-aligned
+            b"panel_thickness",  # (5,6) top-right, Z-aligned
+            b"",  # (6,7) top-front, X-aligned
+            b"panel_thickness",  # (7,4) top-left, Z-aligned
+            b"panel_height",  # (0,4) vertical back-left
+            b"panel_height",  # (1,5) vertical back-right
+            b"panel_height",  # (2,6) vertical front-right
+            b"panel_height",  # (3,7) vertical front-left
+        )
+
+        # Build two separate wireframe boxes — one on each side of the central
+        # gap. The boxes share the same Y range (0..h_top) and Z range (±hd)
+        # but split the X range so the gap from -gap to +gap stays empty.
+        for x_left, x_right in ((-hw, -gap), (gap, hw)):
+            corners = [
+                bm.verts.new((x_left, 0.0, -hd)),
+                bm.verts.new((x_right, 0.0, -hd)),
+                bm.verts.new((x_right, 0.0, hd)),
+                bm.verts.new((x_left, 0.0, hd)),
+                bm.verts.new((x_left, h_top, -hd)),
+                bm.verts.new((x_right, h_top, -hd)),
+                bm.verts.new((x_right, h_top, hd)),
+                bm.verts.new((x_left, h_top, hd)),
+            ]
+            for tag, (a, b) in zip(
+                edge_tags_per_box,
+                (
+                    (0, 1),
+                    (1, 2),
+                    (2, 3),
+                    (3, 0),  # bottom ring
+                    (4, 5),
+                    (5, 6),
+                    (6, 7),
+                    (7, 4),  # top ring
+                    (0, 4),
+                    (1, 5),
+                    (2, 6),
+                    (3, 7),  # vertical edges
+                ),
+            ):
+                edge = bm.edges.new((corners[a], corners[b]))
+                if tag:
+                    edge[feat_layer] = tag
+
+    @classmethod
+    def _build_wall_mounted_handrail_schematic(cls, bm: "bmesh.types.BMesh", props) -> None:
+        """Stylised wall-mounted handrail: wall outline, hex tube, two L-brackets.
+
+        Three visual elements convey "rail mounted on a wall":
+
+        - **Wall outline** — a wireframe rectangle in the YZ plane at ``z=0``,
+          extending slightly past the rail ends so the wall reads as a
+          surface the rail is *attached to* rather than a coincident frame.
+        - **Handrail tube** — a hexagonal cross-section extruded along ±X
+          at ``z=+clear_s`` (in front of the wall), at ``y=rail_y``.
+        - **L-shaped brackets** at each rail end — from the rail centreline
+          drop a short distance, then run perpendicular back to the wall
+          plane. Mirrors the standard wall-mount bracket geometry: a
+          horizontal arm holding the rail off the wall, a vertical drop
+          attaching to the rail.
+
+        Like ``_build_frameless_panel_schematic``, the schematic uses fixed
+        proportions so the dimension gizmos' anchor points stay aligned
+        with the geometry features regardless of property values.
+        """
+        half_len = cls.SCHEMATIC_MESH_WIDTH_FRAC / 2
+        wall_top = cls.SCHEMATIC_MESH_HEIGHT_FRAC
+        rail_y = cls.SCHEMATIC_MESH_RAIL_Y_FRAC  # rail sits at half wall height
+        radius_s = cls.schematic_rail_radius()
+        clear_s = cls.schematic_rail_clear()
+
+        layer_name = cls.SCHEMATIC_FEATURE_LAYER_NAME
+        feat_layer = bm.edges.layers.string.get(layer_name) or bm.edges.layers.string.new(layer_name)
+
+        # ── Wall outline (rectangle at z=0, slightly wider than the rail) ──
+        # Spans the full schematic height; the rail attaches in the middle,
+        # so the wall reads as "continuing past the rail above and below".
+        # Wall edges stay untagged — they're background context, not a
+        # feature any dimension measures.
+        wall_extra = 0.08
+        wall_x_left = -half_len - wall_extra
+        wall_x_right = half_len + wall_extra
+        wall_corners = [
+            bm.verts.new((wall_x_left, 0.0, 0.0)),
+            bm.verts.new((wall_x_right, 0.0, 0.0)),
+            bm.verts.new((wall_x_right, wall_top, 0.0)),
+            bm.verts.new((wall_x_left, wall_top, 0.0)),
+        ]
+        for a, b in ((0, 1), (1, 2), (2, 3), (3, 0)):
+            bm.edges.new((wall_corners[a], wall_corners[b]))
+
+        # ── Handrail tube (hex cross-section in YZ, extruded along X) ──────
+        # Centred on the rail centreline at (±(half_len - rail_inset),
+        # rail_y, +clear_s) — in front of the wall plane at z=0. The tube
+        # is shorter than the wall so the wall visibly extends past it on
+        # both sides; the L-brackets sit at the tube ends, so the leftmost
+        # bracket no longer coincides with the wall's left edge.
+        rail_inset = cls.SCHEMATIC_RAIL_INSET_FRAC
+        rail_x_left = -half_len + rail_inset
+        rail_x_right = half_len - rail_inset
+        segments = 6
+        ring_left, ring_right = [], []
+        for i in range(segments):
+            theta = 2 * math.pi * i / segments
+            dy = math.cos(theta) * radius_s
+            dz = math.sin(theta) * radius_s
+            ring_left.append(bm.verts.new((rail_x_left, rail_y + dy, clear_s + dz)))
+            ring_right.append(bm.verts.new((rail_x_right, rail_y + dy, clear_s + dz)))
+        # All hex-tube edges tagged "rail_tube" so they highlight together
+        # when the railing_diameter dimension is hovered.
+        for i in range(segments):
+            j = (i + 1) % segments
+            e_left = bm.edges.new((ring_left[i], ring_left[j]))
+            e_right = bm.edges.new((ring_right[i], ring_right[j]))
+            e_axial = bm.edges.new((ring_left[i], ring_right[i]))
+            e_left[feat_layer] = b"rail_tube"
+            e_right[feat_layer] = b"rail_tube"
+            e_axial[feat_layer] = b"rail_tube"
+
+        # ── L-brackets at each rail end (rail → drop → wall) ───────────────
+        # Bracket attach points follow the rail ends, so they're pulled
+        # inward by ``rail_inset`` from the wall edges. From the rail
+        # centreline, drop ``bracket_drop`` in Y, then run perpendicular
+        # back to the wall plane (z=0). The L shape reads as a wall-mount
+        # bracket under the 3/4 tilt. Both bracket segments tagged
+        # "bracket" so they highlight when clear_width OR support_spacing
+        # is hovered (both dimensions measure features of the supports).
+        bracket_drop = 0.06
+        for x in (rail_x_left, rail_x_right):
+            v_rail = bm.verts.new((x, rail_y, clear_s))
+            v_corner = bm.verts.new((x, rail_y - bracket_drop, clear_s))
+            v_wall = bm.verts.new((x, rail_y - bracket_drop, 0.0))
+            e1 = bm.edges.new((v_rail, v_corner))
+            e2 = bm.edges.new((v_corner, v_wall))
+            e1[feat_layer] = b"bracket"
+            e2[feat_layer] = b"bracket"
+
+
 class FlipRailingPathOrder(bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.flip_railing_path_order"
     bl_label = "Flip Railing Path Order"
@@ -511,6 +1139,16 @@ class EnableEditingRailingPath(bpy.types.Operator, tool.Ifc.Operator):
         [o.select_set(False) for o in context.selected_objects if o != obj]
         assert obj
         props = tool.Model.get_railing_props(obj)
+
+        # Auto-commit any in-progress parametric draft before switching to
+        # path-edit. ``set_props_kwargs_from_ifc_data`` a few lines below
+        # overwrites props with the pset's stored values — without committing
+        # first, anything the user dragged on a dimension gizmo (height,
+        # diameter, …) would be silently discarded the moment path-edit
+        # starts.
+        if props.is_editing:
+            tool.Parametric.commit_object_draft(obj, "bim.finish_editing_railing")
+
         data = tool.Model.get_modeling_bbim_pset_data(obj, "BBIM_Railing")["data_dict"]
         # required since we could load pset from .ifc and BIMRoofProperties won't be set
         props.set_props_kwargs_from_ifc_data(data)

src/bonsai/bonsai/bim/module/model/roof.py

@@ -17,8 +17,8 @@
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
 
 import json
-from math import cos, pi, radians, tan
-from typing import Any, Literal, Union
+from math import atan2, cos, degrees, pi, radians, tan
+from typing import Any, ClassVar, Literal, Union
 
 import bmesh
 import bpy
@@ -32,8 +32,11 @@ from mathutils import Quaternion, Vector
 
 import bonsai.core.root
 import bonsai.tool as tool
+from bonsai.bim.module.drawing import gizmos as gizmo
+from bonsai.bim.module.drawing.gizmos import DimensionGizmoConfig, IconSlot
 from bonsai.bim.module.model.data import RoofData, refresh
 from bonsai.bim.module.model.decorator import ProfileDecorator
+from bonsai.bim.parametric_lifecycle import CycleTypeMixin, PathPreservingEditMixin
 
 # reference:
 # https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcRoof.htm
@@ -210,7 +213,13 @@ def generate_hipped_roof_bmesh(
 
     new_verts = [bm.verts.new(v) for v in verts]
     new_edges = [bm.edges.new([new_verts[vi] for vi in edge]) for edge in edges]
-    new_faces = [bm.faces.new([new_verts[vi] for vi in face]) for face in faces]
+    # Skip degenerate faces. ``bpypolyskel.polygonize`` can emit a face whose
+    # vertex list contains the same index twice on certain footprint /
+    # slope combinations (the straight-skeleton collapses two ridge events
+    # onto the same vertex). ``bm.faces.new`` rejects those with
+    # ``found the same (BMVert) used multiple times``; dropping them keeps
+    # the rest of the roof intact instead of aborting the whole rebuild.
+    new_faces = [bm.faces.new([new_verts[vi] for vi in face]) for face in faces if len(set(face)) == len(face)]
 
     if mode == "HEIGHT":  # Calculate the angle we ended up with.
         new_faces[0].normal_update()
@@ -396,6 +405,11 @@ def generate_hipped_roof_bmesh(
         if is_internal:
             faces_to_delete.add(face)
     bmesh.ops.delete(bm, geom=list(faces_to_delete), context="FACES")
+    # Final pass: ``remove_doubles`` + internal-face deletion above can leave
+    # the bottom slab faces flipped at low slopes, where the kernel's
+    # "outward" inference becomes ambiguous on near-flat geometry. Recompute
+    # once more on the final topology so the eave plane points down.
+    bmesh.ops.recalc_face_normals(bm, faces=bm.faces[:])
     return bm
 
 
@@ -608,61 +622,169 @@ class AddRoof(bpy.types.Operator, tool.Ifc.Operator):
         tool.Model.add_body_representation(obj)
 
 
-class EnableEditingRoof(bpy.types.Operator, tool.Ifc.Operator):
-    bl_idname = "bim.enable_editing_roof"
-    bl_label = "Enable Editing Roof"
-    bl_options = {"REGISTER"}
+class _RoofEditMixin(PathPreservingEditMixin):
+    """Type-specific hooks for roof parametric-edit operators. Single-object
+    (active_object). ``path_data`` is preserved through the edit; the separate
+    ``Enable/Finish/CancelEditingRoofPath`` operators handle path editing."""
 
-    def _execute(self, context):
-        obj = context.active_object
-        assert obj
-        props = tool.Model.get_roof_props(obj)
-        data = tool.Model.get_modeling_bbim_pset_data(obj, "BBIM_Roof")["data_dict"]
-        # required since we could load pset from .ifc and BIMRoofProperties won't be set
-        props.set_props_kwargs_from_ifc_data(data)
-        props.is_editing = True
-        return {"FINISHED"}
+    pset_name = "BBIM_Roof"
 
+    @classmethod
+    def _is_element_type(cls, element):
+        return tool.Parametric.is_roof(element)
 
-class CancelEditingRoof(bpy.types.Operator, tool.Ifc.Operator):
-    bl_idname = "bim.cancel_editing_roof"
-    bl_label = "Cancel Editing Roof"
-    bl_options = {"REGISTER"}
+    @classmethod
+    def _get_props(cls, obj: bpy.types.Object):
+        return tool.Model.get_roof_props(obj)
 
-    def _execute(self, context):
-        obj = context.active_object
-        assert obj
-        data = tool.Model.get_modeling_bbim_pset_data(obj, "BBIM_Roof")["data_dict"]
-        props = tool.Model.get_roof_props(obj)
+    @classmethod
+    def _update_pset(cls, element, data: dict) -> None:
+        update_bbim_roof_pset(element, data)
 
-        # restore previous settings since editing was canceled
-        props.set_props_kwargs_from_ifc_data(data)
+    @classmethod
+    def _update_modifier_ifc_data(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        update_roof_modifier_ifc_data(context)
+
+    @classmethod
+    def _update_modifier_bmesh(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
         update_roof_modifier_bmesh(obj)
 
-        props.is_editing = False
-        return {"FINISHED"}
+    @classmethod
+    def _restore_viewport_after_cancel(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        """Rebuild the roof bmesh from the just-restored draft props so the
+        viewport reverts to the pre-edit geometry. Same helper the modal
+        edits use, just driven by the cancelled props instead of in-flight
+        drag values."""
+        update_roof_modifier_bmesh(obj)
 
 
-class FinishEditingRoof(bpy.types.Operator, tool.Ifc.Operator):
-    bl_idname = "bim.finish_editing_roof"
-    bl_label = "Finish Editing Roof"
-    bl_options = {"REGISTER"}
+EnableEditingRoof, FinishEditingRoof, CancelEditingRoof = tool.Parametric.build_edit_lifecycle(
+    "roof",
+    _RoofEditMixin,
+    labels=(
+        ("Enable Editing Roof", ""),
+        ("Finish Editing Roof", ""),
+        ("Cancel Editing Roof", ""),
+    ),
+    module_name=__name__,
+)
 
-    def _execute(self, context):
-        obj = context.active_object
-        element = tool.Ifc.get_entity(obj)
-        props = tool.Model.get_roof_props(obj)
 
-        pset_data = tool.Model.get_modeling_bbim_pset_data(obj, "BBIM_Roof")
-        path_data = pset_data["data_dict"]["path_data"]
+# Fixed horizontal run for the slope gizmo: the draggable value is the
+# vertical rise at this distance from the anchor, in the rise/run convention.
+_ROOF_SLOPE_REFERENCE_RUN = 1.0
+# One degree shy of vertical; avoids tan() blow-up when the user drags the
+# rise handle past the gizmo's anchor.
+_ROOF_MAX_SLOPE_ANGLE = pi / 2 - 0.001
 
-        roof_data = props.get_general_kwargs(convert_to_project_units=True)
-        roof_data["path_data"] = path_data
-        props.is_editing = False
 
-        update_bbim_roof_pset(element, roof_data)
-        update_roof_modifier_ifc_data(context)
-        return {"FINISHED"}
+def _roof_has_openings() -> bool:
+    """``visible_when`` predicate for the toggle_openings idle slot. True iff
+    the active object's IFC element exposes a non-empty HasOpenings inverse."""
+    obj = bpy.context.active_object
+    if obj is None:
+        return False
+    element = tool.Ifc.get_entity(obj)
+    if element is None:
+        return False
+    return tool.Geometry.has_openings(element)
+
+
+class CycleRoofGenerationMethod(bpy.types.Operator, tool.Ifc.Operator, CycleTypeMixin):
+    """Cycle the roof generation method (HEIGHT ↔ ANGLE). Shift+click cycles in reverse."""
+
+    bl_idname = "bim.cycle_roof_generation_method"
+    bl_label = "Cycle Roof Generation Method"
+    bl_options = {"REGISTER", "UNDO"}
+
+    element_checker = tool.Parametric.is_roof
+    props_getter = tool.Model.get_roof_props
+    type_literal = tool.Model.RoofGenerationMethod
+    type_attr = "generation_method"
+
+    def _execute(self, context: bpy.types.Context) -> set[str]:
+        return self._cycle_type(context)
+
+
+class GizmoRoofEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
+    bl_idname = "OBJECT_GGT_bim_roof_edition"
+    bl_label = "Roof Editing Gizmo"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options = {"3D", "PERSISTENT"}
+
+    enable_editing_operator = "bim.enable_editing_roof"
+    finish_editing_operator = "bim.finish_editing_roof"
+    cancel_editing_operator = "bim.cancel_editing_roof"
+    cycle_type_operator = "bim.cycle_roof_generation_method"
+
+    # Positions for all three dimensions are set per-frame by the position
+    # override below; no static ``matrix_position`` is needed.
+    dimension_gizmo_props = [
+        DimensionGizmoConfig(
+            attr_name="height",
+            axis=(0, 0, 1),
+            min_value=0.01,
+            visibility_condition=lambda p: p.generation_method == "HEIGHT",
+        ),
+        DimensionGizmoConfig(
+            attr_name="angle",
+            axis=(0, 0, 1),
+            prop_name="Slope",
+            min_value=0.0,
+            visibility_condition=lambda p: p.generation_method == "ANGLE",
+            compute_value=lambda p: tan(p.angle) * _ROOF_SLOPE_REFERENCE_RUN,
+            apply_value=lambda p, rise: setattr(
+                p, "angle", min(_ROOF_MAX_SLOPE_ANGLE, max(0.0, atan2(rise, _ROOF_SLOPE_REFERENCE_RUN)))
+            ),
+            text_formatter=lambda p, rise: (f"{tool.Unit.format_distance(rise)} ({degrees(p.angle):.1f}°)"),
+        ),
+        DimensionGizmoConfig(
+            attr_name="roof_thickness",
+            axis=(0, 0, -1),
+            min_value=0.001,
+            # The line shows the perpendicular slab thickness (matching the
+            # pset value and the drag delta); the true vertical span is
+            # ``roof_thickness / cos(angle)``, longer than what is drawn.
+        ),
+    ]
+
+    props_getter = tool.Model.get_roof_props
+    gizmo_pref_name = "roof"
+
+    idle_slots: ClassVar[tuple[IconSlot, ...]] = (
+        IconSlot(
+            name="toggle_openings",
+            gizmo_idname="VIEW3D_GT_add_opening",
+            operator="bim.toggle_host_openings",
+            visible_when=lambda gg: _roof_has_openings(),
+        ),
+    )
+
+    @classmethod
+    def is_element_type(cls, element: ifcopenshell.entity_instance) -> bool:
+        return tool.Parametric.is_roof(element)
+
+    def _update_dimension_gizmo_positions(self, context: bpy.types.Context, mw, props) -> None:  # noqa: ARG002
+        """Anchor every dimension gizmo at the object origin. Each gizmo's
+        declared axis (height/slope along +Z, thickness along -Z) separates
+        them in 3D so they don't visually collide despite sharing a
+        position; the height + slope gizmos themselves are mutually
+        exclusive via ``visibility_condition`` on ``generation_method``."""
+        origin = Vector((0.0, 0.0, 0.0))
+        self.set_dimension_gizmo_position("height", mw, origin, (0, 0, 1))
+        self.set_dimension_gizmo_position("angle", mw, origin, (0, 0, 1))
+        self.set_dimension_gizmo_position("roof_thickness", mw, origin, (0, 0, -1))
+
+    def get_element_height(self, props) -> float:  # noqa: ARG002
+        """Object-local Z of the mesh's topmost vertex, so the pen / validate /
+        cancel / cycle row anchors visibly above sloped or stepped roof
+        bodies rather than at the parametric ``props.height`` which may not
+        match the rendered apex on ANGLE-generation roofs."""
+        obj = bpy.context.active_object
+        if obj is None or not getattr(obj, "bound_box", None):
+            return 1.0
+        return max(c[2] for c in obj.bound_box)
 
 
 class EnableEditingRoofPath(bpy.types.Operator, tool.Ifc.Operator):

src/bonsai/bonsai/bim/module/model/slab.py

@@ -271,7 +271,7 @@ class DumbSlabPlaner:
                 # For instances, a 30 degrees angled extrusion with positive direction has the same extrusion direction as a
                 # -150 degrees angled extrusion with negative direction. The difference lies in the object's rotation.
                 # This means that things can get messy if the user changes the object x angle somehow. We have to figure out an alternative approach.
-                existing_x_angle = obj.rotation_euler.x
+                existing_x_angle = tool.Model.get_existing_x_angle(extrusion)
                 existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, 0, tolerance=0.001) else existing_x_angle
                 existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, pi, tolerance=0.001) else existing_x_angle
                 existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, 2 * pi, tolerance=0.001) else existing_x_angle
@@ -620,6 +620,14 @@ class EnableEditingExtrusionProfile(bpy.types.Operator, tool.Ifc.Operator):
     def _execute(self, context):
         self.unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
         obj = context.active_object
+
+        # Commit any in-progress parametric (gizmo) draft on this object
+        # before switching to profile-edit. Otherwise the in-memory draft
+        # state is overwritten when the profile mesh is imported below,
+        # silently discarding the user's pending dimension edits.
+        if feature := tool.Parametric.is_object_editing(obj):
+            tool.Parametric.commit_object_draft(obj, feature.finish_op)
+
         element = tool.Ifc.get_entity(obj)
 
         body = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
@@ -991,3 +999,74 @@ class RecalculateSlab(bpy.types.Operator, tool.Ifc.Operator):
 
         tool.Model.recalculate_walls(walls)
         return {"FINISHED"}
+
+
+class EnableEditingSlab(bpy.types.Operator, tool.Ifc.Operator):
+    """Open the slab disconnect-access mode. Pure UI toggle: flips
+    ``obj.BIMSlabProperties.is_editing`` so the per-wall disconnect
+    gizmos surface on the slab. ``tool.Ifc.Operator`` base because the
+    parametric framework's universal dispatcher routes through
+    ``tool.Parametric.run_bim_op``, which only accepts that subclass for
+    undo-safe lifecycle. No IFC mutation."""
+
+    bl_idname = "bim.enable_editing_slab"
+    bl_label = "Edit Slab Connections"
+    bl_description = "Show disconnect icons for every wall clipped to this slab"
+    bl_options = {"REGISTER", "UNDO"}
+
+    @classmethod
+    def poll(cls, context):
+        obj = context.active_object
+        if obj is None:
+            return False
+        element = tool.Ifc.get_entity(obj)
+        return element is not None and element.is_a("IfcSlab")
+
+    def _execute(self, context):
+        context.active_object.BIMSlabProperties.is_editing = True
+        return {"FINISHED"}
+
+
+class CancelEditingSlab(bpy.types.Operator, tool.Ifc.Operator):
+    """Close the slab disconnect-access mode."""
+
+    bl_idname = "bim.cancel_editing_slab"
+    bl_label = "Close Slab Edit"
+    bl_description = "Hide the slab disconnect icons"
+    bl_options = {"REGISTER", "UNDO"}
+
+    @classmethod
+    def poll(cls, context):
+        obj = context.active_object
+        if obj is None:
+            return False
+        element = tool.Ifc.get_entity(obj)
+        return element is not None and element.is_a("IfcSlab")
+
+    def _execute(self, context):
+        context.active_object.BIMSlabProperties.is_editing = False
+        return {"FINISHED"}
+
+
+class FinishEditingSlab(bpy.types.Operator, tool.Ifc.Operator):
+    """Close the slab disconnect-access mode. Same body as Cancel — slab
+    edit is a pure UI gate with no IFC draft to commit; the framework
+    requires both ``bim.finish_editing_<name>`` and
+    ``bim.cancel_editing_<name>`` to exist by name convention."""
+
+    bl_idname = "bim.finish_editing_slab"
+    bl_label = "Finish Slab Edit"
+    bl_description = "Hide the slab disconnect icons"
+    bl_options = {"REGISTER", "UNDO"}
+
+    @classmethod
+    def poll(cls, context):
+        obj = context.active_object
+        if obj is None:
+            return False
+        element = tool.Ifc.get_entity(obj)
+        return element is not None and element.is_a("IfcSlab")
+
+    def _execute(self, context):
+        context.active_object.BIMSlabProperties.is_editing = False
+        return {"FINISHED"}

src/bonsai/bonsai/bim/module/model/stair.py

@@ -15,6 +15,8 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 import json
 
@@ -29,7 +31,13 @@ from mathutils import Matrix, Vector
 import bonsai.core.root
 import bonsai.tool as tool
 from bonsai.bim.module.drawing import gizmos as gizmo
-from bonsai.bim.module.drawing.gizmos import DimensionGizmoConfig
+from bonsai.bim.module.drawing.gizmos import (
+    COLOR_GREEN,
+    COLOR_RED,
+    DimensionGizmoConfig,
+    IconSlot,
+)
+from bonsai.bim.parametric_lifecycle import IntegerInputDialogMixin, PickTypeMixin
 from bonsai.tool.numeric_input import (
     IntegerInputState,
     run_integer_input_modal,
@@ -37,7 +45,7 @@ from bonsai.tool.numeric_input import (
 )
 
 V_ = tool.Blender.V_
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, ClassVar
 
 from bmesh.types import BMVert
 from bpy.props import IntProperty
@@ -262,7 +270,6 @@ class FinishEditingStair(bpy.types.Operator, tool.Ifc.Operator):
 
         # Use the special method that includes custom_tread_lock for IFC storage
         data = props.get_props_kwargs_for_ifc_export(convert_to_project_units=True)
-        props.is_editing = False
         regenerate_stair_mesh(obj)
         tool.Model.add_body_representation(obj)
 
@@ -272,6 +279,7 @@ class FinishEditingStair(bpy.types.Operator, tool.Ifc.Operator):
 
         # update IfcStairFlight properties
         update_ifc_stair_props(obj)
+        props.is_editing = False
         return {"FINISHED"}
 
 
@@ -376,6 +384,20 @@ class AdjustStairTreads(bpy.types.Operator):
         return {"FINISHED"}
 
 
+class InputStairTreads(IntegerInputDialogMixin, bpy.types.Operator):
+    """Popup-dialog entry point for typing a new ``number_of_treads`` value.
+    Bound to the world-space ``xN`` count label in the stair edit row."""
+
+    bl_idname = "bim.input_stair_treads"
+    bl_label = "Set Number of Treads"
+    bl_description = "Type the number of treads for this stair"
+    bl_options = {"REGISTER", "UNDO"}
+
+    number_of_treads: IntProperty(name="Number of Treads", default=1, min=1)
+    attr_name = "number_of_treads"
+    props_getter = staticmethod(tool.Model.get_stair_props)
+
+
 class SetStairTreads(bpy.types.Operator):
     """Set the number of treads to a specific value."""
 
@@ -421,20 +443,20 @@ class SetStairTreads(bpy.types.Operator):
         return f"Number of Treads: {input_str}_{validity}  |  Enter to confirm, Esc to cancel"
 
 
-class CycleStairType(bpy.types.Operator, gizmo.CycleTypeMixin):
-    """Cycle through stair types. Shift+click to cycle in reverse."""
+class PickStairType(bpy.types.Operator, PickTypeMixin):
+    """Pick a stair type from a popup menu."""
 
-    bl_idname = "bim.cycle_stair_type"
-    bl_label = "Cycle Stair Type"
+    bl_idname = "bim.pick_stair_type"
+    bl_label = "Pick Stair Type"
     bl_options = {"REGISTER", "UNDO"}
 
-    props_getter = "get_stair_props"
+    props_getter = tool.Model.get_stair_props
     type_literal = tool.Model.StairType
     type_attr = "stair_type"
     skip_element_check = True
 
     def execute(self, context: bpy.types.Context) -> set[str]:
-        return self._cycle_type(context)
+        return self._pick_type(context)
 
 
 # Tread run accessors - callbacks that delegate to BIMStairProperties methods
@@ -460,20 +482,47 @@ class GizmoStairEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
     bl_region_type = "WINDOW"
     bl_options = {"3D", "PERSISTENT"}
 
-    # === Stair-Specific Icon Layout (meters) ===
-    # Additional icons for stair editing, positioned after standard icons:
-    #   [Validate] [Cancel] [Cycle] [TreadLock] [Plus] [Minus]
-    ICON_TREAD_LOCK_X = 1.24  # X position for tread lock toggle icon
-    ICON_PLUS_X = 1.61  # X position for add tread (+) icon
-    ICON_MINUS_X = 1.98  # X position for remove tread (-) icon
+    # === Stair-Specific Icon Layout ===
+    # Row order: [Validate] [Cancel] [Cycle] [TreadLock] [xN] [Plus] [Minus]
+    # The base class assigns X positions from ``feature_slots`` tuple order —
+    # adding an icon is a one-line append, no hardcoded X constant.
     ICON_PLUS_MINUS_SCALE = 0.24  # Scale for plus/minus icons (slightly larger)
     ICON_CYCLE_SCALE = 0.3  # Scale for cycle type icon
+    ICON_COUNT_LABEL_SCALE = 0.36  # Scale for the xN tread-count label
     ICON_Z_OFFSET = 0.5  # Z offset above geometry for editing icons
 
+    feature_slots: ClassVar[tuple[IconSlot, ...]] = (
+        IconSlot(
+            name="tread_lock",
+            gizmo_idname="VIEW3D_GT_lock",
+            variants=("open", "closed"),
+            operator="bim.toggle_stair_property",
+            color=(1.0, 1.0, 1.0),
+            operator_props=(("property_name", "custom_tread_lock"),),
+        ),
+        IconSlot(name="tread_count_label", placeholder=True),
+        IconSlot(
+            name="plus",
+            gizmo_idname="VIEW3D_GT_plus",
+            operator="bim.adjust_stair_treads",
+            scale=ICON_PLUS_MINUS_SCALE,
+            color=COLOR_GREEN,
+            operator_props=(("increment", 1),),
+        ),
+        IconSlot(
+            name="minus",
+            gizmo_idname="VIEW3D_GT_minus",
+            operator="bim.adjust_stair_treads",
+            scale=ICON_PLUS_MINUS_SCALE,
+            color=COLOR_RED,
+            operator_props=(("increment", -1),),
+        ),
+    )
+
     enable_editing_operator = "bim.enable_editing_stair"
     finish_editing_operator = "bim.finish_editing_stair"
     cancel_editing_operator = "bim.cancel_editing_stair"
-    cycle_type_operator = "bim.cycle_stair_type"
+    pick_type_operator = "bim.pick_stair_type"
 
     def get_icon_y_extent(self, props: "BIMStairProperties") -> tuple[float, float]:
         """Get Y extents for stair icon positioning.
@@ -578,83 +627,91 @@ class GizmoStairEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
     ]
 
     # Metadata-driven dispatch for props and preferences
-    props_getter = "get_stair_props"
+    props_getter = tool.Model.get_stair_props
     gizmo_pref_name = "stair"
 
     @classmethod
     def is_element_type(cls, element: ifcopenshell.entity_instance) -> bool:
-        return tool.Blender.Modifier.is_stair(element)
+        return tool.Parametric.is_stair(element)
 
     def setup_element_specific_gizmos(self, context: bpy.types.Context) -> None:
-        """Create stair-specific icon gizmos (lock, plus, minus)."""
-        self.lock_gizmo = self.create_icon_gizmo(
-            "VIEW3D_GT_lock",
-            self.COLOR_BLUE,
+        """Create the total-length lock as an open/closed pair plus the
+        ``xN`` tread-count label. Lock click toggles
+        ``props.total_length_lock``; the per-frame update hook picks which
+        member is visible. Anchored to the stair's far X end (not the edit
+        row) so it's positioned by ``_update_lock_gizmo_position`` rather
+        than the toolbar slot system.
+
+        The count label binds to ``bim.input_stair_treads`` (popup dialog)
+        for click-to-type input and sits at the X reserved by the
+        ``tread_count_label`` placeholder slot in ``feature_slots``."""
+        self.total_length_lock_open_gizmo, self.total_length_lock_closed_gizmo = self.create_icon_gizmo_lock_pair(
             "bim.toggle_stair_property",
-            prop_path="BIMStairProperties.total_length_lock",
+            self.COLOR_BLUE,
             property_name="total_length_lock",
         )
-        self.tread_lock_gizmo = self.create_icon_gizmo(
-            "VIEW3D_GT_lock",
-            (1.0, 1.0, 1.0),
-            "bim.toggle_stair_property",
-            prop_path="BIMStairProperties.custom_tread_lock",
-            property_name="custom_tread_lock",
-        )
-        self.plus_gizmo = self.create_icon_gizmo(
-            "VIEW3D_GT_plus", self.COLOR_GREEN, "bim.adjust_stair_treads", increment=1
-        )
-        self.minus_gizmo = self.create_icon_gizmo(
-            "VIEW3D_GT_minus", self.COLOR_RED, "bim.adjust_stair_treads", increment=-1
-        )
+        default_color, highlight_color = self.get_decoration_colors()
+        self.tread_count_label_gizmo = self.gizmos.new("BIM_GT_count_label")
+        self.tread_count_label_gizmo.use_draw_scale = False
+        self.tread_count_label_gizmo.color = default_color
+        self.tread_count_label_gizmo.color_highlight = highlight_color
+        self.tread_count_label_gizmo.alpha = 0.8
+        self.tread_count_label_gizmo.target_set_operator("bim.input_stair_treads")
 
-    def _refresh_element_specific(self, context: bpy.types.Context, mw: Matrix, props: "BIMStairProperties") -> None:
-        """Update stair-specific lock and tread count gizmos."""
-        billboard_rot = gizmo.get_billboard_rotation(context)
-        self.update_lock_gizmo(mw, props, billboard_rot)
+    def _refresh_element_specific(
+        self, context: bpy.types.Context, mw: Matrix, props: "BIMStairProperties"  # noqa: ARG002
+    ) -> None:
+        """Update stair-specific lock and tread count gizmos. Lock positioning is
+        handled per-frame in the dimension-positioning hook."""
+        self.update_lock_gizmo(props)
         self.update_tread_lock_gizmo(props)
         self.update_tread_count_gizmos(props)
 
-    def update_lock_gizmo(self, mw: Matrix, props: "BIMStairProperties", billboard_rot: Matrix) -> None:
-        """Update lock gizmo visibility, color, and position."""
-        gizmo_prefs = self.get_gizmo_prefs()
-        if not self.update_gizmo_visibility(self.lock_gizmo, props.is_editing, gizmo_prefs.lock):
-            return  # Hidden, skip positioning
-
-        self.lock_gizmo.color = self.COLOR_RED if props.total_length_lock else self.COLOR_GREEN
-
-        total_run = props.get_total_run()
-        local_transform = (
-            Matrix.Translation(Vector((total_run + self.ICON_Z_OFFSET, -self.GIZMO_OFFSET, -self.GIZMO_OFFSET)))
-            @ billboard_rot
-            @ Matrix.Scale(self.EDITING_ICON_SCALE, 4)
-        )
-        self.lock_gizmo.matrix_basis = mw @ local_transform
+    def update_lock_gizmo(self, props: "BIMStairProperties") -> None:
+        """Show the open/closed total-length lock variant matching
+        ``props.total_length_lock``. Positioning is handled per-frame by
+        the dimension-positioning hook."""
+        if not hasattr(self, "total_length_lock_open_gizmo"):
+            return
+        if not props.is_editing:
+            self.total_length_lock_open_gizmo.hide = True
+            self.total_length_lock_closed_gizmo.hide = True
+            return
+        self.total_length_lock_open_gizmo.hide = props.total_length_lock
+        self.total_length_lock_closed_gizmo.hide = not props.total_length_lock
 
     def update_tread_lock_gizmo(self, props: "BIMStairProperties") -> None:
-        """Update visibility of tread lock gizmo. Positioning is handled in _update_editing_icon_positions."""
-        if not hasattr(self, "tread_lock_gizmo"):
+        """Show the open/closed lock variant matching ``props.custom_tread_lock``.
+
+        Both pair members share an X position (set by the base's slot
+        positioning); this picks which one is visible per frame so a state
+        flip can't reveal both at once."""
+        if not hasattr(self, "tread_lock_open_gizmo"):
             return
-        gizmo_prefs = self.get_gizmo_prefs()
-        self.update_gizmo_visibility(self.tread_lock_gizmo, props.is_editing, gizmo_prefs.lock)
+        if not props.is_editing:
+            self.tread_lock_open_gizmo.hide = True
+            self.tread_lock_closed_gizmo.hide = True
+            return
+        self.tread_lock_open_gizmo.hide = props.custom_tread_lock
+        self.tread_lock_closed_gizmo.hide = not props.custom_tread_lock
 
     def update_tread_count_gizmos(self, props: "BIMStairProperties") -> None:
-        """Update visibility of +/- tread count gizmos. Positioning is handled in _update_editing_icon_positions."""
+        """Update visibility of the +/- tread count gizmos and the ``xN``
+        label. Positioning is handled in ``_update_editing_icon_positions``."""
         if not hasattr(self, "plus_gizmo") or not hasattr(self, "minus_gizmo"):
             return
-        gizmo_prefs = self.get_gizmo_prefs()
-        self.update_gizmo_visibility(self.plus_gizmo, props.is_editing, gizmo_prefs.plus)
+        self.update_gizmo_visibility(self.plus_gizmo, props.is_editing)
         # Minus has additional condition: number_of_treads > 1
-        self.update_gizmo_visibility(
-            self.minus_gizmo, props.is_editing and props.number_of_treads > 1, gizmo_prefs.minus
-        )
+        self.update_gizmo_visibility(self.minus_gizmo, props.is_editing and props.number_of_treads > 1)
+        if hasattr(self, "tread_count_label_gizmo"):
+            self.update_gizmo_visibility(self.tread_count_label_gizmo, props.is_editing)
 
     def _update_dimension_gizmo_positions(
-        self, context: bpy.types.Context, mw: Matrix, props: "BIMStairProperties"
+        self, context: bpy.types.Context, mw: Matrix, props: "BIMStairProperties"  # noqa: ARG002
     ) -> None:
         """Update dimension gizmo positions based on camera view direction."""
-        viewing_from_negative_y, viewing_from_negative_x = self.get_local_view_direction(context, mw)
-        billboard_rot = gizmo.get_billboard_rotation(context)
+        viewing_from_negative_y, viewing_from_negative_x = self._frame_view_dir
+        billboard_rot = self._frame_billboard_rot
         total_run = props.get_total_run()
         riser_height = props.get_riser_height()
 
@@ -725,10 +782,12 @@ class GizmoStairEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
         billboard_rot: Matrix,
         total_run: float,
     ) -> None:
-        """Update lock gizmo position based on Y view direction."""
+        """Update lock gizmo pair position based on Y view direction. Writes
+        the matrix on both members so a state flip can't reveal a stale pose."""
         y_pos = self.get_y_position_for_view(props, viewing_from_negative_y, use_offset=True)
-        self.set_icon_gizmo_position(
-            "lock_gizmo",
+        self.set_icon_gizmo_pair_position(
+            "total_length_lock_open_gizmo",
+            "total_length_lock_closed_gizmo",
             mw,
             total_run + self.ICON_Z_OFFSET,
             y_pos,
@@ -740,30 +799,47 @@ class GizmoStairEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
     def _update_editing_icon_positions(
         self, mw: Matrix, props: "BIMStairProperties", viewing_from_negative_y: bool, billboard_rot: Matrix
     ) -> None:
-        """Update editing icon positions, flipping Y based on viewing angle."""
+        """Reposition the editing icons at stair's view-dependent Y. The base
+        class's update_editing_gizmos already placed them at the default
+        ``get_icon_y_offset`` Y — this overrides with the stair-specific
+        ``get_icon_y_for_view`` flip so the icons land on the side the
+        camera is looking from."""
         if not props.is_editing:
             return
 
         icon_z = props.height + self.ICON_Z_OFFSET
         y_pos = self.get_icon_y_for_view(props, viewing_from_negative_y)
+        slot_x = self._slot_x_positions()
 
         self.set_icon_gizmo_position("validate_gizmo", mw, 0, y_pos, icon_z, billboard_rot)
         self.set_icon_gizmo_position("cancel_gizmo", mw, self.ICON_CANCEL_X, y_pos, icon_z, billboard_rot)
         self.set_icon_gizmo_position(
             "cycle_gizmo", mw, self.ICON_CYCLE_X, y_pos, icon_z, billboard_rot, scale=self.ICON_CYCLE_SCALE
         )
-        self.set_icon_gizmo_position(
-            "tread_lock_gizmo",
+        self.set_icon_gizmo_pair_position(
+            "tread_lock_open_gizmo",
+            "tread_lock_closed_gizmo",
             mw,
-            self.ICON_TREAD_LOCK_X,
+            slot_x["tread_lock"],
             y_pos,
             icon_z - self.EDITING_ICON_SCALE / 2,
             billboard_rot,
             scale=self.EDITING_ICON_SCALE,
         )
         self.set_icon_gizmo_position(
-            "plus_gizmo", mw, self.ICON_PLUS_X, y_pos, icon_z, billboard_rot, scale=self.ICON_PLUS_MINUS_SCALE
+            "plus_gizmo", mw, slot_x["plus"], y_pos, icon_z, billboard_rot, scale=self.ICON_PLUS_MINUS_SCALE
         )
         self.set_icon_gizmo_position(
-            "minus_gizmo", mw, self.ICON_MINUS_X, y_pos, icon_z, billboard_rot, scale=self.ICON_PLUS_MINUS_SCALE
+            "minus_gizmo", mw, slot_x["minus"], y_pos, icon_z, billboard_rot, scale=self.ICON_PLUS_MINUS_SCALE
         )
+        if hasattr(self, "tread_count_label_gizmo"):
+            self.tread_count_label_gizmo.set_count(int(props.number_of_treads))
+            self.set_icon_gizmo_position(
+                "tread_count_label_gizmo",
+                mw,
+                slot_x["tread_count_label"],
+                y_pos,
+                icon_z,
+                billboard_rot,
+                scale=self.ICON_COUNT_LABEL_SCALE,
+            )

src/bonsai/bonsai/bim/module/model/ui.py

@@ -22,6 +22,7 @@ from collections.abc import Iterable
 from typing import TYPE_CHECKING, Any
 
 import bpy
+import ifcopenshell.util.unit
 from bpy.types import Panel
 
 import bonsai.bim
@@ -237,11 +238,11 @@ class BIM_PT_array(bpy.types.Panel):
 
             for i, array in enumerate(ArrayData.data["parameters"]["data_dict"]):
                 box = self.layout.box()
-                if props.is_editing == i:
+                if props.editing_item_index == i:
                     row = box.row(align=True)
                     row.prop(props, "count", icon="MOD_ARRAY")
-                    row.operator("bim.edit_array", icon="CHECKMARK", text="").item = i
-                    row.operator("bim.disable_editing_array", icon="CANCEL", text="")
+                    row.operator("bim.finish_editing_array", icon="CHECKMARK", text="")
+                    row.operator("bim.cancel_editing_array", icon="CANCEL", text="")
                     row = box.row(align=True)
                     row.prop(props, "method")
                     row = box.row(align=True)
@@ -303,6 +304,8 @@ class BIM_PT_stair(bpy.types.Panel):
             row = self.layout.row(align=True)
             row.label(text="Stair parameters", icon="IPO_CONSTANT")
 
+            si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
+
             if props.is_editing:
                 calculated_params = tool.Model.get_active_stair_calculated_params()
                 row = self.layout.row(align=True)
@@ -322,22 +325,61 @@ class BIM_PT_stair(bpy.types.Panel):
                         row.label(text=f"{prop_name}:")
                         row = self.layout.row(align=True)
                         for prop_value_item in prop_value:
-                            row.label(text=str(prop_value_item))
+                            if isinstance(prop_value_item, float):
+                                row.label(text=tool.Unit.format_distance(prop_value_item * si_conversion))
+                            else:
+                                row.label(text=str(prop_value_item))
                     else:
                         row.label(text=prop_name)
-                        row.label(text=str(prop_value))
+                        if isinstance(prop_value, float):
+                            row.label(text=tool.Unit.format_distance(prop_value * si_conversion))
+                        else:
+                            row.label(text=str(prop_value))
 
             # calculated properties
             for prop_name, prop_value in calculated_params.items():
                 row = self.layout.row(align=True)
                 row.label(text=prop_name)
-                row.label(text=str(prop_value))
+                if isinstance(prop_value, float):
+                    row.label(text=tool.Unit.format_distance(prop_value * si_conversion))
+                else:
+                    row.label(text=str(prop_value))
         else:
             row = self.layout.row()
             row.label(text="No Stair Found")
             row.operator("bim.add_stair", icon="ADD", text="")
 
 
+class BIM_PT_wall(bpy.types.Panel):
+    bl_label = "Wall"
+    bl_idname = "BIM_PT_wall"
+    bl_space_type = "PROPERTIES"
+    bl_region_type = "WINDOW"
+    bl_context = "scene"
+    bl_options = {"DEFAULT_CLOSED"}
+    bl_parent_id = "BIM_PT_tab_parametric_geometry"
+
+    @classmethod
+    def poll(cls, context):
+        obj = context.active_object
+        if not obj:
+            return False
+        element = tool.Ifc.get_entity(obj)
+        return bool(element) and tool.Parametric.is_wall(element)
+
+    def draw(self, context):
+        obj = context.active_object
+        if obj is None:
+            return
+        props = tool.Model.get_wall_props(obj)
+        row = self.layout.row(align=True)
+        if props.is_editing:
+            row.operator("bim.finish_editing_wall", icon="CHECKMARK", text="Finish Editing")
+            row.operator("bim.cancel_editing_wall", icon="CANCEL", text="")
+        else:
+            row.operator("bim.enable_editing_wall", icon="GREASEPENCIL", text="Edit Wall")
+
+
 class BIM_PT_sverchok(bpy.types.Panel):
     bl_label = "Sverchok"
     bl_idname = "BIM_PT_sverchok"

src/bonsai/bonsai/bim/module/model/wall_offset_gizmos.py

@@ -0,0 +1,279 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""Four wall-offset dimension gizmos (left / right / top / bottom) shared by door and
+window edit gizmo groups — both fillings sit in a LAYER2 wall and the offset math is
+identical.
+
+The compute side returns a *signed* value on the X axis (negative when the filling
+is 180°-flipped onto the wall's opposite face) so the gizmo framework auto-flips
+the rendered arrow; the apply side takes ``abs(value)`` because the user-facing
+offset is always positive. Z-axis values are unsigned in both directions.
+
+Fillings are assumed to align with the wall's local X axis to within ±90° — the
+parametric door/window construction path enforces this, and the X-sign math
+falls back to +1 if ``col[0].x`` lands on the ambiguous zero (filling rotated
+exactly 90° in the wall plane).
+
+Every public entry point falls back to a safe no-op when the host-wall chain
+cannot be resolved: reads return 0.0, writes do nothing, and gizmo anchors
+return a filling-relative position. This keeps the gizmos non-crashing when a
+filling momentarily loses its host (e.g. mid-edit, partially-loaded files).
+
+``_GEOM_CACHE`` is module-scoped and persists across tests — tests must call
+``clear_caches()`` between cases."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, NamedTuple, Protocol
+
+from mathutils import Vector
+
+import bonsai.tool as tool
+from bonsai.bim.module.drawing.gizmos import DimensionGizmoConfig
+
+if TYPE_CHECKING:
+    import bpy
+
+
+class FillingProps(Protocol):
+    """Structural subset of door/window props this module touches."""
+
+    id_data: bpy.types.Object
+    overall_width: float
+    overall_height: float
+
+
+# Wall-local frame axis indices. Y (depth) is unused — fillings sit on the wall's centreline.
+_AXIS_X = 0
+_AXIS_Z = 2
+
+
+class _HostWallGeom(NamedTuple):
+    """Cached host-wall geometry in SI metres, wall-local frame. ``height`` is
+    the vertical projection (already accounts for slanted extrusions)."""
+
+    wall_obj: bpy.types.Object
+    height: float
+    axis_min_x: float
+    axis_max_x: float
+
+
+class _AxisExtent(NamedTuple):
+    """``[low, high]`` interval on one wall-local axis; low = near end.
+
+    ``x_sign`` is +1 / -1 for an X-axis filling extent only (carries the
+    180° auto-flip); always 1.0 elsewhere."""
+
+    low: float
+    high: float
+    x_sign: float = 1.0
+
+
+class _Edge(NamedTuple):
+    """Wall edge a gizmo measures to. ``is_max_end=True`` picks right/top, else left/bottom."""
+
+    axis_index: int
+    is_max_end: bool
+
+
+_LEFT = _Edge(axis_index=_AXIS_X, is_max_end=False)
+_RIGHT = _Edge(axis_index=_AXIS_X, is_max_end=True)
+_BOTTOM = _Edge(axis_index=_AXIS_Z, is_max_end=False)
+_TOP = _Edge(axis_index=_AXIS_Z, is_max_end=True)
+
+
+# Avoids repeating the host-wall chain walk + LAYER2 geometry read per gizmo per frame.
+_GEOM_CACHE = tool.Parametric.GenerationKeyedCache()
+
+
+def clear_caches() -> None:
+    _GEOM_CACHE.clear()
+
+
+def _host_wall_geom(filling_obj: bpy.types.Object) -> _HostWallGeom | None:
+    """Cached host-wall geometry for a filling, or ``None`` if any link in
+    filling → opening → wall → LAYER2 extrusion → scene-object resolution breaks."""
+    return _GEOM_CACHE.get_or_compute(filling_obj.name, lambda: _compute_host_wall_geom(filling_obj))
+
+
+def _compute_host_wall_geom(filling_obj: bpy.types.Object) -> _HostWallGeom | None:
+    element = tool.Ifc.get_entity(filling_obj)
+    if not element:
+        return None
+    host_wall = tool.Spatial.get_host_wall(element)
+    if not host_wall:
+        return None
+    wall_obj = tool.Ifc.get_object(host_wall)
+    length_height = tool.Wall.get_length_and_height(host_wall)
+    axis_extent = tool.Wall.get_axis_local_extent(host_wall)
+    # x_angle is None for non-LAYER2 walls — gates entry; the value itself is unused.
+    if not (wall_obj and length_height and axis_extent and tool.Wall.get_x_angle(host_wall) is not None):
+        return None
+    _, height = length_height
+    axis_min_x, axis_max_x = axis_extent
+    return _HostWallGeom(wall_obj=wall_obj, height=height, axis_min_x=axis_min_x, axis_max_x=axis_max_x)
+
+
+def _filling_axis_extent(props: FillingProps, host_wall_obj: bpy.types.Object, axis_index: int) -> _AxisExtent:
+    """Filling footprint on the wall's local axis.
+
+    X-axis extent carries the filling's orientation sign (180° flip onto
+    the opposite face) in ``x_sign``."""
+    filling_in_wall = host_wall_obj.matrix_world.inverted() @ props.id_data.matrix_world
+    origin = filling_in_wall.translation[axis_index]
+    if axis_index == _AXIS_X:
+        # col[0].x is the X-component of the filling's local X axis in the wall-local frame:
+        # +1 when filling's +X aligns with wall's +X, -1 after a 180° Z-flip.
+        x_sign = 1.0 if filling_in_wall.col[0].x >= 0.0 else -1.0
+        signed_width = x_sign * props.overall_width
+        return _AxisExtent(origin + min(0.0, signed_width), origin + max(0.0, signed_width), x_sign)
+    return _AxisExtent(origin, origin + props.overall_height)
+
+
+def _wall_axis_extent(geom: _HostWallGeom, axis_index: int) -> _AxisExtent:
+    """Wall span on one local axis: X = IFC axis-line endpoints (not mesh bound-box,
+    which drifts on trimmed walls); Z = 0 → wall height."""
+    if axis_index == _AXIS_X:
+        return _AxisExtent(geom.axis_min_x, geom.axis_max_x)
+    return _AxisExtent(0.0, geom.height)
+
+
+def _offset_from_extents(filling: _AxisExtent, wall: _AxisExtent, is_max_end: bool) -> float:
+    """Distance from the wall edge to the filling's matching edge on the same axis."""
+    if is_max_end:
+        return wall.high - filling.high
+    return filling.low - wall.low
+
+
+def _translate_along_wall_axis(
+    props: FillingProps, host_wall_obj: bpy.types.Object, delta: float, axis_index: int
+) -> None:
+    """Shift the filling by ``delta`` SI metres along the wall's local axis. Drag
+    operates in the filling's intent frame, not Blender's world frame, so a rotated
+    host wall still tracks correctly."""
+    if delta == 0.0:
+        return
+    direction_world = host_wall_obj.matrix_world.to_3x3().col[axis_index].normalized()
+    props.id_data.matrix_world.translation = props.id_data.matrix_world.translation + direction_world * delta
+
+
+def _get_offset(props: FillingProps, edge: _Edge) -> float:
+    """SI distance from the wall edge to the filling's matching edge on the same axis."""
+    geom = _host_wall_geom(props.id_data)
+    if not geom:
+        return 0.0
+    filling = _filling_axis_extent(props, geom.wall_obj, edge.axis_index)
+    wall = _wall_axis_extent(geom, edge.axis_index)
+    return _offset_from_extents(filling, wall, edge.is_max_end)
+
+
+def _set_offset(props: FillingProps, edge: _Edge, value: float) -> None:
+    """Translate the filling so its offset to ``edge`` becomes ``max(0, value)`` SI metres.
+    Max-end edges (right/top) translate in the opposite direction of near-end edges."""
+    geom = _host_wall_geom(props.id_data)
+    if not geom:
+        return
+    current = _get_offset(props, edge)
+    target = max(0.0, value)
+    delta = (current - target) if edge.is_max_end else (target - current)
+    _translate_along_wall_axis(props, geom.wall_obj, delta, edge.axis_index)
+
+
+def has_host_wall(props: FillingProps) -> bool:
+    """True when the filling resolves to a LAYER2 host wall present in the scene."""
+    return _host_wall_geom(props.id_data) is not None
+
+
+def _edge_position(props: FillingProps, edge: _Edge) -> Vector:
+    """Gizmo anchor in filling-local space, at the wall edge, pointing toward the filling."""
+    geom = _host_wall_geom(props.id_data)
+    if not geom:
+        if edge.axis_index == _AXIS_X:
+            return Vector((0.0, 0.0, props.overall_height / 2))
+        return Vector((props.overall_width / 2, 0.0, props.overall_height if edge.is_max_end else 0.0))
+    wall = _wall_axis_extent(geom, edge.axis_index)
+    edge_value = wall.high if edge.is_max_end else wall.low
+    if edge.axis_index == _AXIS_X:
+        wall_edge_world = geom.wall_obj.matrix_world @ Vector((edge_value, 0.0, 0.0))
+        pos = props.id_data.matrix_world.inverted() @ wall_edge_world
+        return Vector((pos.x, 0.0, props.overall_height / 2))
+    # LAYER2 wall matrix_world is upright, so wall-local Z and filling-local Z differ
+    # only by the filling's Z origin in the wall frame.
+    filling_z_in_wall = _filling_axis_extent(props, geom.wall_obj, axis_index=_AXIS_Z).low
+    return Vector((props.overall_width / 2, 0.0, edge_value - filling_z_in_wall))
+
+
+def _compute_value(props: FillingProps, edge: _Edge) -> float:
+    """Renderer-side value. X-axis edges return a signed value so the gizmo's
+    auto-flip kicks in for fillings on the wall's opposite face; Z-axis returns unsigned."""
+    geom = _host_wall_geom(props.id_data)
+    if not geom:
+        return 0.0
+    filling = _filling_axis_extent(props, geom.wall_obj, edge.axis_index)
+    wall = _wall_axis_extent(geom, edge.axis_index)
+    return filling.x_sign * _offset_from_extents(filling, wall, edge.is_max_end)
+
+
+def _apply_value(props: FillingProps, edge: _Edge, value: float) -> None:
+    """Drag-end commit; X-axis takes ``abs(value)`` since the negative sign in compute
+    is a rendering hint only (user-facing offset is always positive)."""
+    if edge.axis_index == _AXIS_X:
+        _set_offset(props, edge, abs(value))
+    else:
+        _set_offset(props, edge, value)
+
+
+# attr_name identifies the gizmo within its group; values flow through
+# compute/apply, not via a registered property.
+WALL_OFFSET_GIZMO_CONFIGS: list[DimensionGizmoConfig] = [
+    DimensionGizmoConfig(
+        attr_name="host_wall_offset_left",
+        axis=(1, 0, 0),
+        visibility_condition=has_host_wall,
+        compute_value=lambda p: _compute_value(p, _LEFT),
+        apply_value=lambda p, v: _apply_value(p, _LEFT, v),
+        matrix_position=lambda p: _edge_position(p, _LEFT),
+    ),
+    DimensionGizmoConfig(
+        attr_name="host_wall_offset_right",
+        axis=(-1, 0, 0),
+        visibility_condition=has_host_wall,
+        compute_value=lambda p: _compute_value(p, _RIGHT),
+        apply_value=lambda p, v: _apply_value(p, _RIGHT, v),
+        matrix_position=lambda p: _edge_position(p, _RIGHT),
+    ),
+    DimensionGizmoConfig(
+        attr_name="host_wall_offset_bottom",
+        axis=(0, 0, 1),
+        visibility_condition=has_host_wall,
+        compute_value=lambda p: _compute_value(p, _BOTTOM),
+        apply_value=lambda p, v: _apply_value(p, _BOTTOM, v),
+        matrix_position=lambda p: _edge_position(p, _BOTTOM),
+    ),
+    DimensionGizmoConfig(
+        attr_name="host_wall_offset_top",
+        axis=(0, 0, -1),
+        visibility_condition=has_host_wall,
+        compute_value=lambda p: _compute_value(p, _TOP),
+        apply_value=lambda p, v: _apply_value(p, _TOP, v),
+        matrix_position=lambda p: _edge_position(p, _TOP),
+    ),
+]

src/bonsai/bonsai/bim/module/model/window.py

@@ -39,6 +39,8 @@ import bonsai.core.root
 import bonsai.tool as tool
 from bonsai.bim.module.drawing import gizmos as gizmo
 from bonsai.bim.module.drawing.gizmos import DimensionGizmoConfig
+from bonsai.bim.module.model.wall_offset_gizmos import WALL_OFFSET_GIZMO_CONFIGS
+from bonsai.bim.parametric_lifecycle import FeatureModifierEditMixin, PickTypeMixin
 
 if TYPE_CHECKING:
     from bonsai.bim.module.model.prop import BIMWindowProperties
@@ -482,90 +484,53 @@ class AddWindow(bpy.types.Operator, tool.Ifc.Operator):
         return {"FINISHED"}
 
 
-class CancelEditingWindow(bpy.types.Operator, tool.Ifc.Operator):
+class _WindowEditMixin(FeatureModifierEditMixin):
+    """Type-specific hooks for window parametric-edit operators. Single-object
+    by design (window edits target the active object only)."""
+
+    pset_name = "BBIM_Window"
+
+    @classmethod
+    def _is_element_type(cls, element):
+        return tool.Parametric.is_window(element)
+
+    @classmethod
+    def _get_props(cls, obj: bpy.types.Object):
+        return tool.Model.get_window_props(obj)
+
+    @classmethod
+    def _update_modifier_representation(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        update_window_modifier_representation(context)
+
+
+class CancelEditingWindow(_WindowEditMixin, bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.cancel_editing_window"
     bl_label = "Cancel Editing Window"
     bl_description = "Cancel editing and revert window parameters to their previous values"
-    bl_options = {"REGISTER"}
+    bl_options = {"REGISTER", "UNDO"}
 
     def _execute(self, context: bpy.types.Context) -> set[str]:
-        obj = context.active_object
-        assert obj
-        element = tool.Ifc.get_entity(obj)
-        assert element
-        data = json.loads(ifcopenshell.util.element.get_pset(element, "BBIM_Window", "Data"))
-        data.update(data.pop("lining_properties"))
-        data.update(data.pop("panel_properties"))
-        props = tool.Model.get_window_props(obj)
-        props.set_props_kwargs_from_ifc_data(data)
-
-        body = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
-        bonsai.core.geometry.switch_representation(
-            tool.Ifc,
-            tool.Geometry,
-            obj=obj,
-            representation=body,
-        )
-
-        props.is_editing = False
-        return {"FINISHED"}
+        return self._cancel_targets(context)
 
 
-class FinishEditingWindow(bpy.types.Operator, tool.Ifc.Operator):
+class FinishEditingWindow(_WindowEditMixin, bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.finish_editing_window"
     bl_label = "Finish Editing Window"
     bl_description = "Apply changes and finish editing window parameters"
-    bl_options = {"REGISTER"}
+    bl_options = {"REGISTER", "UNDO"}
 
     def _execute(self, context: bpy.types.Context) -> set[str]:
-        obj = context.active_object
-        assert obj
-        element = tool.Ifc.get_entity(obj)
-        assert element
-        props = tool.Model.get_window_props(obj)
-
-        window_data = props.get_general_kwargs(convert_to_project_units=True)
-        lining_props = props.get_lining_kwargs(convert_to_project_units=True)
-        panel_props = props.get_panel_kwargs(convert_to_project_units=True)
-
-        window_data["lining_properties"] = lining_props
-        window_data["panel_properties"] = panel_props
-
-        props.is_editing = False
-
-        update_window_modifier_representation(context)
-        element_type = ifcopenshell.util.element.get_type(element)
-        if element_type:
-            tool.Model.mark_thumbnail_for_update(element_type)
-
-        pset = tool.Pset.get_element_pset(element, "BBIM_Window")
-        window_data = tool.Ifc.get().createIfcText(json.dumps(window_data, default=list))
-        ifcopenshell.api.pset.edit_pset(tool.Ifc.get(), pset=pset, properties={"Data": window_data})
-        return {"FINISHED"}
+        return self._finish_targets(context)
 
 
-class EnableEditingWindow(bpy.types.Operator, tool.Ifc.Operator):
+class EnableEditingWindow(_WindowEditMixin, bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.enable_editing_window"
     bl_label = "Enable Editing Window"
     bl_description = "Enter edit mode to modify window parameters interactively"
-    bl_options = {"REGISTER"}
+    bl_options = {"REGISTER", "UNDO"}
 
     def _execute(self, context: bpy.types.Context) -> set[str]:
-        obj = context.active_object
-        assert obj
-        props = tool.Model.get_window_props(obj)
-        element = tool.Ifc.get_entity(obj)
-        assert element
-        data = json.loads(ifcopenshell.util.element.get_pset(element, "BBIM_Window", "Data"))
-        data.update(data.pop("lining_properties"))
-        data.update(data.pop("panel_properties"))
-        data.update(tool.Model.get_constituents_props_data(element))
-
-        # required since we could load pset from .ifc and BIMWindowProperties won't be set
-        props.set_props_kwargs_from_ifc_data(data)
-
-        props.is_editing = True
-        return {"FINISHED"}
+        return self._enable_targets(context)
 
 
 class RemoveWindow(bpy.types.Operator, tool.Ifc.Operator):
@@ -587,20 +552,20 @@ class RemoveWindow(bpy.types.Operator, tool.Ifc.Operator):
         return {"FINISHED"}
 
 
-class CycleWindowType(bpy.types.Operator, tool.Ifc.Operator, gizmo.CycleTypeMixin):
-    """Cycle through available window types. Shift+click to cycle in reverse."""
+class PickWindowType(bpy.types.Operator, tool.Ifc.Operator, PickTypeMixin):
+    """Pick a window type from a popup menu."""
 
-    bl_idname = "bim.cycle_window_type"
-    bl_label = "Cycle Window Type"
+    bl_idname = "bim.pick_window_type"
+    bl_label = "Pick Window Type"
     bl_options = {"REGISTER", "UNDO"}
 
-    element_checker = "is_window"
-    props_getter = "get_window_props"
+    element_checker = tool.Parametric.is_window
+    props_getter = tool.Model.get_window_props
     type_literal = tool.Model.WindowType
     type_attr = "window_type"
 
     def _execute(self, context: bpy.types.Context) -> set[str]:
-        return self._cycle_type(context)
+        return self._pick_type(context)
 
 
 # Frame accessor factory - creates callbacks that delegate to BIMWindowProperties methods
@@ -638,7 +603,7 @@ class GizmoWindowEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
     enable_editing_operator = "bim.enable_editing_window"
     finish_editing_operator = "bim.finish_editing_window"
     cancel_editing_operator = "bim.cancel_editing_window"
-    cycle_type_operator = "bim.cycle_window_type"
+    pick_type_operator = "bim.pick_window_type"
 
     # matrix_position lambdas replace the get_dimension_matrix_* methods
     dimension_gizmo_props = [
@@ -779,14 +744,15 @@ class GizmoWindowEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
         ),
         # lining_offset is handled specially in _update_dimension_gizmo_positions due to negative value support
         DimensionGizmoConfig(attr_name="lining_offset", axis=(0, 1, 0), min_value=-10.0),
+        *WALL_OFFSET_GIZMO_CONFIGS,
     ]
 
-    props_getter = "get_window_props"
+    props_getter = tool.Model.get_window_props
     gizmo_pref_name = "window"
 
     @classmethod
     def is_element_type(cls, element: ifcopenshell.entity_instance) -> bool:
-        return tool.Blender.Modifier.is_window(element)
+        return tool.Parametric.is_window(element)
 
     def get_icon_y_extent(self, props: "BIMWindowProperties") -> tuple[float, float]:
         """Get Y extents for window icon positioning.

src/bonsai/bonsai/bim/module/model/workspace.py

@@ -841,7 +841,7 @@ class EditObjectUI:
         row = cls.layout.row(align=True)
         row.separator()
         row.label(text="Operations") if ui_context != "TOOL_HEADER" else row
-        cls.draw_regen_operations(row)
+        cls.draw_regen_operations(row, ui_context)
 
         if AuthoringData.data["active_material_usage"] == "LAYER2":
             row = cls.layout.row(align=True) if ui_context != "TOOL_HEADER" else row
@@ -962,20 +962,20 @@ class EditObjectUI:
         return row
 
     @classmethod
-    def draw_regen_operations(cls, row):
-        custom_icon = custom_icon_previews.get("REGEN", custom_icon_previews["IFC"]).icon_id
-
-        if AuthoringData.data["is_regenable_element"]:
-            op = row.operator("bim.hotkey", text="", icon_value=custom_icon)
-            description = "Recalculate Element Geometry\nHotkey: S G"
-            op.hotkey = "S_G"
-            op.description = description.strip()
+    def draw_regen_operations(cls, row, ui_context):
+        # ``AuthoringData.load`` flips ``is_loaded`` at entry as a recursion
+        # guard, so a partial load (any computation along the way raising)
+        # leaves the tail keys unset. ``.get()`` keeps the header draw alive
+        # until the underlying failure is investigated.
+        if AuthoringData.data.get("is_regenable_element"):
+            row = cls.layout.row(align=True) if ui_context != "TOOL_HEADER" else row
+            add_layout_hotkey_operator(row, "Regen", "S_G", "Recalculate Element Geometry", ui_context)
 
         if PortData.data["total_ports"] > 0:
-            op = row.operator("bim.hotkey", text="", icon_value=custom_icon)
-            description = f"{bpy.ops.bim.regenerate_distribution_element.__doc__}\n\nHotkey: S G"
-            op.hotkey = "S_G"
-            op.description = description.strip()
+            row = cls.layout.row(align=True) if ui_context != "TOOL_HEADER" else row
+            add_layout_hotkey_operator(
+                row, "Regen", "S_G", bpy.ops.bim.regenerate_distribution_element.__doc__, ui_context
+            )
 
     @classmethod
     def draw_void(cls, context, row):
@@ -1300,9 +1300,15 @@ class Hotkey(bpy.types.Operator, tool.Ifc.Operator):
                 bpy.ops.bim.generate_space()
             return
         if self.active_material_usage == "LAYER2":
-            bpy.ops.bim.recalculate_wall()
+            if element and tool.Model.has_underside_connection(element):
+                bpy.ops.bim.regenerate_wall_to_underside()
+            else:
+                bpy.ops.bim.recalculate_wall()
         elif self.active_material_usage == "LAYER3":
             bpy.ops.bim.recalculate_slab()
+            wall_objs = tool.Model.get_connected_wall_objs(element)
+            if wall_objs:
+                core.regenerate_wall_to_underside(tool.Ifc, tool.Geometry, tool.Model, wall_objs)
         elif tool.System.get_ports(element):
             bpy.ops.bim.regenerate_distribution_element()
         elif self.active_material_usage == "PROFILE":
@@ -1315,7 +1321,7 @@ class Hotkey(bpy.types.Operator, tool.Ifc.Operator):
                 bpy.ops.bim.recalculate_profile()
         elif self.active_class in ("IfcWindow", "IfcWindowStandardCase", "IfcDoor", "IfcDoorStandardCase"):
             bpy.ops.bim.recalculate_fill()
-        elif self.active_class in ("IfcSpace"):
+        elif self.active_class in ("IfcSpace",):
             bpy.ops.bim.generate_space()
 
     def hotkey_S_M(self):
@@ -1442,10 +1448,7 @@ class Hotkey(bpy.types.Operator, tool.Ifc.Operator):
             bpy.ops.bim.enable_editing_extrusion_axis()
 
     def hotkey_A_O(self):
-        if tool.Model.get_model_props().openings:
-            bpy.ops.bim.edit_openings(apply_all=True)
-        else:
-            bpy.ops.bim.show_openings()
+        bpy.ops.bim.toggle_host_openings()
 
     def hotkey_C_E(self):
         if not bpy.context.selected_objects:

src/bonsai/bonsai/bim/module/nest/decorator.py

@@ -20,7 +20,6 @@ import blf
 import bpy
 import gpu
 import ifcopenshell.util.element
-from bpy.types import SpaceView3D
 from bpy_extras import view3d_utils
 from gpu_extras.batch import batch_for_shader
 from mathutils import Vector
@@ -28,12 +27,6 @@ from mathutils import Vector
 import bonsai.tool as tool
 
 
-def transparent_color(color, alpha=0.1):
-    color = [i for i in color]
-    color[3] = alpha
-    return color
-
-
 def create_bounding_box(objs):
     # Initialize the bounding box coordinates
     min_x, min_y, min_z = float("inf"), float("inf"), float("inf")
@@ -79,26 +72,8 @@ def create_bounding_box(objs):
     return indices, edges
 
 
-class NestDecorator:
-    is_installed = False
-    handlers = []
-
-    @classmethod
-    def install(cls, context):
-        if cls.is_installed:
-            cls.uninstall()
-        handler = cls()
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_nest, (context,), "WINDOW", "POST_VIEW"))
-        cls.is_installed = True
-
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
+class NestDecorator(tool.Blender.ViewportDecorator):
+    draw_method = "draw_nest"
 
     def dotted_line_shader(self):
         vert_out = gpu.types.GPUStageInterfaceInfo("my_interface")
@@ -154,14 +129,6 @@ class NestDecorator:
         shader.uniform_float("u_Scale", 25)
         batch.draw(shader)
 
-    def draw_batch(self, shader_type, content_pos, color, indices=None):
-        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
-            return
-        shader = self.line_shader if shader_type == "LINES" else self.shader
-        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
-        shader.uniform_float("color", color)
-        batch.draw(shader)
-
     def draw_nest(self, context: bpy.types.Context) -> None:
         props = tool.Nest.get_nest_props()
         if props.in_nest_mode:
@@ -226,35 +193,11 @@ class NestDecorator:
             self.draw_custom_batch(line, decorator_color_unselected)
 
 
-class NestModeDecorator:
-    is_installed = False
-    handlers = []
-
-    @classmethod
-    def install(cls, context):
-        if cls.is_installed:
-            cls.uninstall()
-        handler = cls()
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_nest_name, (context,), "WINDOW", "POST_PIXEL"))
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_nest_empty, (context,), "WINDOW", "POST_VIEW"))
-        cls.is_installed = True
-
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
-
-    def draw_batch(self, shader_type, content_pos, color, indices=None):
-        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
-            return
-        shader = self.line_shader if shader_type == "LINES" else self.shader
-        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
-        shader.uniform_float("color", color)
-        batch.draw(shader)
+class NestModeDecorator(tool.Blender.ViewportDecorator):
+    draw_methods = (
+        ("draw_nest_name", "POST_PIXEL"),
+        ("draw_nest_empty", "POST_VIEW"),
+    )
 
     def draw_nest_name(self, context):
         if context.mode == "EDIT_MESH":

src/bonsai/bonsai/bim/module/patch/__init__.py

@@ -21,6 +21,7 @@ import bpy
 from . import operator, prop, ui
 
 classes = (
+    operator.AddIfcPatchPreset,
     operator.ExecuteIfcPatch,
     operator.ExtractSelectedElements,
     operator.RunMigratePatch,
@@ -28,6 +29,7 @@ classes = (
     operator.SelectIfcPatchOutput,
     operator.UpdateIfcPatchArguments,
     prop.BIMPatchProperties,
+    ui.BIM_MT_ifc_patch_presets,
     ui.BIM_PT_patch,
 )
 

src/bonsai/bonsai/bim/module/patch/operator.py

@@ -23,6 +23,7 @@ from typing import TYPE_CHECKING, cast
 import bpy
 import ifcopenshell
 import ifcpatch
+from bl_operators.presets import AddPresetBase
 from bpy_extras.io_utils import ExportHelper, ImportHelper
 
 import bonsai.bim.handler
@@ -77,6 +78,27 @@ class ExecuteIfcPatch(bpy.types.Operator):
             return False
         return True
 
+    def invoke(self, context, event):
+        # Migrating IFC4 → IFC2X3 is lossy (enum drops, IFC4-only classes
+        # become IfcBuildingElementProxy, tessellated meshes get rebuilt as
+        # IfcFacetedBrep). Confirm before running so the user knows.
+        if tool.Patch.migration_is_lossy_downgrade():
+            return context.window_manager.invoke_props_dialog(self, width=480)
+        return self.execute(context)
+
+    def draw(self, context):
+        layout = self.layout
+        layout.label(text="Downgrading to IFC2X3 is lossy.", icon="ERROR")
+        column = layout.column(align=True)
+        column.label(text="Geometry will be preserved as faithfully as possible:")
+        column.label(text="• IfcIndexedPolyCurve → IfcPolyline (arcs approximated by chords)")
+        column.label(text="• IfcPolygonalFaceSet / IfcTriangulatedFaceSet → IfcFacetedBrep")
+        column.separator()
+        column.label(text="The following information is lost:")
+        column.label(text="• IFC4-only classes (IfcLamp, IfcPipeSegment, …) → IfcBuildingElementProxy")
+        column.label(text="• PredefinedType enum values absent from IFC2X3 are dropped")
+        column.label(text="  (original class + enum saved as ObjectType, e.g. 'IfcLamp/COMPACTFLUORESCENT')")
+
     def execute(self, context):
         props = tool.Patch.get_patch_props()
         recipe_name = props.ifc_patch_recipes
@@ -224,3 +246,38 @@ class ExtractSelectedElements(bpy.types.Operator):
         query = tool.Search.get_query_for_selected_elements()
         props.ifc_patch_args_attr[0].string_value = query
         return {"FINISHED"}
+
+
+class AddIfcPatchPreset(AddPresetBase, bpy.types.Operator):
+    """Save / remove ifc-patch argument presets, scoped per recipe.
+
+    Presets live in the standard Blender preset directory under
+    ``bonsai/ifc_patch/<recipe>/`` so a preset created for ``ExtractElements``
+    does not pollute the preset list for ``Migrate``. Persistence across files
+    and sessions is inherited from Blender's preset system."""
+
+    bl_idname = "bim.add_ifc_patch_preset"
+    bl_label = "Add IFC Patch Preset"
+    preset_menu = "BIM_MT_ifc_patch_presets"
+    preset_defines = ["props = bpy.context.scene.BIMPatchProperties"]
+
+    @property
+    def preset_subdir(self) -> str:
+        return tool.Patch.get_preset_subdir()
+
+    @property
+    def preset_values(self) -> list[str]:
+        # `Attribute.get_value_name()` returns the storage field for the
+        # argument's data_type (string_value, bool_value, …). For file
+        # arguments it returns the wrapping PointerProperty (`filepath_value`)
+        # — the scalar path the preset needs is `.single_file` on that.
+        props = tool.Patch.get_patch_props()
+        values = []
+        for i, arg in enumerate(props.ifc_patch_args_attr):
+            field = arg.get_value_name()
+            if not field:
+                continue
+            if arg.data_type == "file":
+                field = f"{field}.single_file"
+            values.append(f"props.ifc_patch_args_attr[{i}].{field}")
+        return values

src/bonsai/bonsai/bim/module/patch/prop.py

@@ -71,6 +71,15 @@ def get_ifcpatch_recipes(self: "BIMPatchProperties", context: bpy.types.Context)
 
 def update_ifc_patch_recipe(self: "BIMPatchProperties", context: bpy.types.Context) -> None:
     bpy.ops.bim.update_ifc_patch_arguments(recipe=self.ifc_patch_recipes)
+    # Blender's script.execute_preset mutates the menu class's bl_label to
+    # the loaded preset's display name (used as a "currently selected"
+    # indicator). The label persists across recipe changes — making the new
+    # recipe's menu falsely show the previous recipe's preset name. Reset
+    # the label to the menu's canonical title so it always matches the
+    # active recipe's preset list.
+    menu_cls = getattr(bpy.types, "BIM_MT_ifc_patch_presets", None)
+    if menu_cls is not None:
+        menu_cls.bl_label = "IFC Patch Presets"
 
 
 class BIMPatchProperties(PropertyGroup):

src/bonsai/bonsai/bim/module/patch/ui.py

@@ -29,6 +29,20 @@ if TYPE_CHECKING:
     from bonsai.bim.prop import Attribute
 
 
+class BIM_MT_ifc_patch_presets(bpy.types.Menu):
+    """Lists ifc-patch presets for the currently selected recipe.
+
+    ``preset_subdir`` is resolved per draw so switching recipes swaps the
+    preset list without re-registering the menu."""
+
+    bl_label = "IFC Patch Presets"
+    preset_operator = "script.execute_preset"
+
+    def draw(self, context: bpy.types.Context) -> None:
+        self.preset_subdir = tool.Patch.get_preset_subdir()
+        bpy.types.Menu.draw_preset(self, context)
+
+
 class BIM_PT_patch(bpy.types.Panel):
     bl_label = "Patch"
     bl_idname = "BIM_PT_patch"
@@ -66,6 +80,11 @@ class BIM_PT_patch(bpy.types.Panel):
                 row.operator("bim.patch_query_from_selected", text="", icon="EYEDROPPER")
 
         if props.ifc_patch_args_attr:
+            preset_row = layout.row(heading="Preset", align=True)
+            preset_row.menu("BIM_MT_ifc_patch_presets", text=BIM_MT_ifc_patch_presets.bl_label)
+            preset_row.operator("bim.add_ifc_patch_preset", text="", icon="ADD")
+            preset_row.operator("bim.add_ifc_patch_preset", text="", icon="REMOVE").remove_active = True
+
             draw_callback = draw_callback_ if props.ifc_patch_recipes == "ExtractElements" else None
             draw_attributes(props.ifc_patch_args_attr, layout, callback=draw_callback)
 

src/bonsai/bonsai/bim/module/project/__init__.py

@@ -28,6 +28,12 @@ classes = (
     operator.AppendLibraryElementByQuery,
     operator.AssignLibraryDeclaration,
     operator.BIM_FH_import_ifc,
+    operator.BIM_OT_apply_pending_opening_cuts,
+    operator.BIM_OT_dismiss_multi_instance_warning,
+    operator.BIM_OT_dismiss_pending_array_repair,
+    operator.BIM_OT_dismiss_pending_opening_cuts,
+    operator.BIM_OT_select_pending_array_repair,
+    operator.BIM_OT_select_pending_opening_cuts,
     operator.BIM_OT_load_clipping_planes,
     operator.BIM_OT_save_clipping_planes,
     operator.ChangeLibraryElement,
@@ -82,6 +88,8 @@ classes = (
     prop.FilterCategory,
     prop.Link,
     prop.EditedObj,
+    prop.PendingArrayRepair,
+    prop.PendingOpeningRecut,
     prop.BIMProjectProperties,
     prop.MeasureToolSettings,
     ui.BIM_MT_new_project,

src/bonsai/bonsai/bim/module/project/data.py

@@ -162,8 +162,8 @@ class ProjectLibraryData:
         library_file = IfcStore.library_file
         if library_file is None or library_file.schema == "IFC2X3":
             return results
-        project = library_file.by_type("IfcProject")[0]
-        results.append((str(project.id()), f"IfcProject {project.Name or 'Unnamed'}", project.Description or ""))
+        root = tool.Project.get_root_context(library_file)
+        results.append((str(root.id()), f"{root.is_a()} {root.Name or 'Unnamed'}", root.Description or ""))
         for library_id, data in cls.data["project_libraries"].items():
             results.append((str(library_id), data["Name"] or "Unnamed", data["Description"] or ""))
         return results

src/bonsai/bonsai/bim/module/project/decorator.py

@@ -42,12 +42,6 @@ def toggle_decorations_on_load(*args):
     # as queried object is linked from separate .blend file.
 
 
-def transparent_color(color, alpha=0.1):
-    color = [i for i in color]
-    color[3] = alpha
-    return color
-
-
 class ProjectDecorator:
     installed = None
 
@@ -80,11 +74,6 @@ class ProjectDecorator:
         unselected_elements_color = self.addon_prefs.decorator_color_unselected
         special_elements_color = self.addon_prefs.decorator_color_special
 
-        def transparent_color(color, alpha=0.1):
-            color = [i for i in color]
-            color[3] = alpha
-            return color
-
         gpu.state.point_size_set(6)
         gpu.state.blend_set("ALPHA")
 
@@ -110,7 +99,9 @@ class ProjectDecorator:
 
         if geom.selected_edges:
             self.draw_batch("LINES", selected_vertices, selected_elements_color, geom.selected_edges)
-            self.draw_batch("TRIS", selected_vertices, transparent_color(selected_elements_color), geom.selected_tris)
+            self.draw_batch(
+                "TRIS", selected_vertices, tool.Blender.transparent_color(selected_elements_color), geom.selected_tris
+            )
 
 
 class ClippingPlaneDecorator:
@@ -145,11 +136,6 @@ class ClippingPlaneDecorator:
         unselected_elements_color = self.addon_prefs.decorator_color_unselected
         special_elements_color = self.addon_prefs.decorator_color_special
 
-        def transparent_color(color, alpha=0.1):
-            color = [i for i in color]
-            color[3] = alpha
-            return color
-
         gpu.state.point_size_set(6)
         gpu.state.blend_set("ALPHA")
 
@@ -210,37 +196,21 @@ class ClippingPlaneDecorator:
 
             if unselected_edges:
                 self.draw_batch("LINES", unselected_vertices, special_elements_color, unselected_edges)
-                self.draw_batch("TRIS", unselected_vertices, transparent_color(special_elements_color), unselected_tris)
+                self.draw_batch(
+                    "TRIS", unselected_vertices, tool.Blender.transparent_color(special_elements_color), unselected_tris
+                )
             if selected_edges:
                 self.draw_batch("LINES", selected_vertices, selected_elements_color, selected_edges)
-                self.draw_batch("TRIS", selected_vertices, transparent_color(selected_elements_color), selected_tris)
+                self.draw_batch(
+                    "TRIS", selected_vertices, tool.Blender.transparent_color(selected_elements_color), selected_tris
+                )
 
 
-class MeasureDecorator:
-    is_installed = False
-    handlers = []
-
-    @classmethod
-    def install(cls, context):
-        if cls.is_installed:
-            cls.uninstall()
-        handler = cls()
-        cls.handlers.append(
-            SpaceView3D.draw_handler_add(handler.draw_measurements_text, (context,), "WINDOW", "POST_PIXEL")
-        )
-        cls.handlers.append(
-            SpaceView3D.draw_handler_add(handler.draw_measurements_poly, (context,), "WINDOW", "POST_VIEW")
-        )
-        cls.is_installed = True
-
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
+class MeasureDecorator(tool.Blender.ViewportDecorator):
+    draw_methods = (
+        ("draw_measurements_text", "POST_PIXEL"),
+        ("draw_measurements_poly", "POST_VIEW"),
+    )
 
     def draw_measurements_text(self, context):
         PolylineDecorator().select_and_draw_measurements_text(context)

src/bonsai/bonsai/bim/module/project/operator.py

@@ -15,6 +15,8 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 import datetime
 import json
@@ -61,6 +63,7 @@ import bonsai.core.project as core
 import bonsai.tool as tool
 from bonsai.bim import export_ifc, import_ifc
 from bonsai.bim.ifc import IfcStore
+from bonsai.bim.module.model import preview_base
 from bonsai.bim.module.model.decorator import FaceAreaDecorator, PolylineDecorator
 from bonsai.bim.module.model.polyline import PolylineOperator
 from bonsai.bim.module.project.data import LinksData, ProjectLibraryData
@@ -278,9 +281,9 @@ class RefreshLibrary(bpy.types.Operator):
         elements = {e for e in elements if not tool.Project.is_element_assigned_to_project_library(e, rels)}
         self.props.add_library_project_library("Unassigned", len(elements), 0, False)
 
-        ifc_project = library_file.by_type("IfcProject")[0]
+        root_context = tool.Project.get_root_context(library_file)
         hierarchy = tool.Project.get_project_hierarchy(library_file)
-        tool.Project.load_project_libraries_to_ui(ifc_project, hierarchy)
+        tool.Project.load_project_libraries_to_ui(root_context, hierarchy)
         return {"FINISHED"}
 
 
@@ -760,7 +763,10 @@ class EditProjectLibrary(bpy.types.Operator):
         previous_parent_library = tool.Project.get_parent_library(project_library)
         new_parent_library = library_file.by_id(int(props.parent_library))
         if previous_parent_library != new_parent_library:
-            if previous_parent_library.is_a("IfcProject"):
+            if previous_parent_library is None:
+                # Edited library was a root in a library-only file; nest it under the new parent.
+                ifcopenshell.api.nest.assign_object(library_file, [project_library], new_parent_library)
+            elif previous_parent_library.is_a("IfcProject"):
                 # Then new one is IfcProjectLibrary.
                 ifcopenshell.api.nest.assign_object(library_file, [project_library], new_parent_library)
             else:  # Previous is IfcProjectLibrary.
@@ -801,9 +807,12 @@ class AddProjectLibrary(bpy.types.Operator):
         props = tool.Project.get_project_props()
         library_file = IfcStore.library_file
         assert library_file
-        project = library_file.by_type("IfcProject")[0]
+        root_context = tool.Project.get_root_context(library_file)
         project_library = ifcopenshell.api.root.create_entity(library_file, "IfcProjectLibrary")
-        ifcopenshell.api.project.assign_declaration(library_file, [project_library], project)
+        if root_context.is_a("IfcProject"):
+            ifcopenshell.api.project.assign_declaration(library_file, [project_library], root_context)
+        else:
+            ifcopenshell.api.nest.assign_object(library_file, [project_library], root_context)
         ProjectLibraryData.load()  # Update enum.
         props.selected_project_library = str(project_library.id())
         props.is_editing_project_library = True
@@ -1110,6 +1119,14 @@ class LoadProject(bpy.types.Operator, IFCFileSelector, ImportHelper):
                     f"Error loading IFC file from filepath '{filepath}'. See logs above in the system console for the details.",
                 )
                 return {"CANCELLED"}
+            if not tool.Ifc.get().by_type("IfcProject"):
+                self.report(
+                    {"ERROR"},
+                    "This file contains no IfcProject. It is likely an IFC project library — "
+                    "load it via Project Setup → Project Library → Select Library File instead.",
+                )
+                IfcStore.purge()
+                return {"CANCELLED"}
             props = tool.Project.get_project_props()
             props.is_loading = True
             props.total_elements = len(tool.Ifc.get().by_type("IfcElement"))
@@ -1220,6 +1237,30 @@ class LoadProjectElements(bpy.types.Operator):
         props = tool.Project.get_project_props()
         props.is_loading = False
 
+        # Stash elements the kernel skipped opening cuts on (HasOpenings > void_limit).
+        # The Project panel banner offers the user a one-click recut.
+        props.pending_opening_recut.clear()
+        if ifc_importer.gross_elements:
+            for element in ifc_importer.gross_elements:
+                item = props.pending_opening_recut.add()
+                item.ifc_definition_id = element.id()
+            self.report(
+                {"WARNING"},
+                f"{len(ifc_importer.gross_elements)} element(s) had too many openings and were loaded without cuts. "
+                f"Apply manually from the Project panel.",
+            )
+
+        props.pending_array_repair.clear()
+        if ifc_importer.broken_arrays:
+            for element in ifc_importer.broken_arrays:
+                item = props.pending_array_repair.add()
+                item.ifc_definition_id = element.id()
+            self.report(
+                {"WARNING"},
+                f"{len(ifc_importer.broken_arrays)} array parent(s) reference missing child GUIDs. "
+                f"Inspect from the Project panel.",
+            )
+
         tool.Project.load_default_thumbnails()
         tool.Project.set_default_context()
         tool.Project.set_default_modeling_dimensions()
@@ -1253,6 +1294,11 @@ class LoadProjectElements(bpy.types.Operator):
             if element.IsDecomposedBy:
                 for subelement in element.IsDecomposedBy[0].RelatedObjects:
                     decomposed_elements.add(subelement)
+            # IfcSurfaceFeature (e.g. road markings) adhere to a host element
+            # via IfcRelAdheresToElement, a [1:1] hierarchical relationship in
+            # the same family as aggregation, containment and nesting (IFC4.3).
+            for rel in getattr(element, "HasSurfaceFeatures", ()):
+                decomposed_elements.update(rel.RelatedSurfaceFeatures)
         if decomposed_elements:
             self.append_decomposed_elements(decomposed_elements)
         elements.update(decomposed_elements)
@@ -1381,6 +1427,7 @@ class LinkIfc(bpy.types.Operator, ImportHelper, tool.Ifc.Operator):
                 new.ifc_definition_id = reference.id()
             new.name = filepath
             new.filepath = filepath
+            new.query = self.query
             bpy.ops.bim.load_link(link_index=-1, use_cache=self.use_cache, query=self.query)
 
 
@@ -1451,6 +1498,10 @@ class LoadLink(bpy.types.Operator, tool.Ifc.Operator):
 
     def _execute(self, context):
         self.link = tool.Project.get_project_props().links[self.link_index]
+        # Fall back to the Link's stored query so callers that omit it
+        # still replay the filter the link was created with.
+        if not self.query and self.link.query:
+            self.query = self.link.query
         filepath = Path(tool.Ifc.resolve_uri(self.link.filepath))
         if not filepath.exists():
             self.report({"ERROR"}, f"File does not exist: '{filepath}'")
@@ -1618,13 +1669,36 @@ class ReloadLink(bpy.types.Operator):
     bl_description = "Reload the selected file"
 
     link_index: bpy.props.IntProperty(name="Link Index")
+    query: bpy.props.StringProperty(
+        name="Query",
+        description=(
+            "Custom selector query to use to load element from a linked model. E.g. 'IfcElement'.\n\n"
+            "Default query - IfcElement, but excluding IfcProxy, IfcSpatialStructureElement, IfcSpatialElement, IfcFeatureElement."
+        ),
+    )
 
     if TYPE_CHECKING:
         link_index: int
+        query: str
+
+    def invoke(self, context, event):
+        link = tool.Project.get_project_props().links[self.link_index]
+        self.query = link.query
+        return context.window_manager.invoke_props_dialog(self)
+
+    def draw(self, context):
+        assert self.layout
+        self.layout.prop(self, "query", placeholder="IfcElement")
 
     def execute(self, context):
+        link = tool.Project.get_project_props().links[self.link_index]
+        # An unset query means the operator was called without the dialog
+        # (e.g. from a script) - preserve the link's stored query instead
+        # of overwriting it with the empty default.
+        if self.properties.is_property_set("query"):
+            link.query = self.query
         bpy.ops.bim.unload_link(link_index=self.link_index)
-        return bpy.ops.bim.load_link(link_index=self.link_index, use_cache=False) or {"FINISHED"}
+        return bpy.ops.bim.load_link(link_index=self.link_index, use_cache=False, query=link.query) or {"FINISHED"}
 
 
 class ToggleLinkSelectability(bpy.types.Operator):
@@ -1903,11 +1977,11 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
 
         self.use_relative_path = tool.Project.get_project_props().use_relative_project_path
         props = tool.Blender.get_bim_props()
-        if (filepath := props.ifc_file) and not self.should_save_as:
-            self.filepath = str(tool.Blender.ensure_blender_path_is_abs(Path(filepath)))
-            return self.execute(context)
-
-        return ExportHelper.invoke(self, context, event)
+        filepath = props.ifc_file
+        if not filepath or self.should_save_as:
+            return ExportHelper.invoke(self, context, event)
+        self.filepath = str(tool.Blender.ensure_blender_path_is_abs(Path(filepath)))
+        return self.execute(context)
 
     def check(self, context):
         # ExportHelper is automatically adjusting suffix to `filename_ext`.
@@ -1933,6 +2007,20 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
         return {"FINISHED"}
 
     def _execute(self, context):
+        committed, failed_commits = tool.Parametric.commit_pending_edits()
+        # Previews are session-transient — discard rather than commit. Sibling
+        # gizmo polls gate on each preview's is_active flag, and a stuck flag
+        # persisted through the save would silently hide them on reload.
+        preview_base.discard_pending_previews(context.scene)
+        # Suffix is appended to the IFC save-success report below so the auto-commit
+        # info isn't immediately overwritten by the success message in Blender's
+        # status bar (only the latest self.report({"INFO"}, ...) sticks).
+        commit_suffix = f" (auto-committed {committed} pending parametric edit(s))" if committed else ""
+        if failed_commits:
+            names = ", ".join(o.name for o in failed_commits)
+            msg = f"Auto-commit failed for {len(failed_commits)} object(s): {names}"
+            print(f"Bonsai: {msg} (their drafts are NOT saved to the IFC file).")
+            self.report({"ERROR"}, msg)
         start = time.time()
         logger = logging.getLogger("ExportIFC")
         path_log = tool.Blender.get_data_dir_path("process.log")
@@ -2001,7 +2089,7 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
                     blendmetadata_path = output_file + suffix
                 self.report(
                     {"INFO"},
-                    f'IFC Project "{os.path.basename(output_file)}" And Metadata File Saved to: {os.path.basename(blendmetadata_path)}',
+                    f'IFC Project "{os.path.basename(output_file)}" And Metadata File Saved to: {os.path.basename(blendmetadata_path)}{commit_suffix}',
                 )
             except Exception as e:
                 self.report({"ERROR"}, f"Failed to save blend metadata file: {e}")
@@ -2011,7 +2099,7 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
                 bpy.ops.wm.save_mainfile(filepath=bpy.data.filepath)
             self.report(
                 {"INFO"},
-                f'IFC Project "{os.path.basename(output_file)}" {"" if not save_blend_file else "And Current Blend File Are"} Saved',
+                f'IFC Project "{os.path.basename(output_file)}" {"" if not save_blend_file else "And Current Blend File Are"} Saved{commit_suffix}',
             )
 
         bonsai.bim.handler.refresh_ui_data()
@@ -3404,3 +3492,149 @@ class GenerateUVMap(bpy.types.Operator):
         tool.Loader.load_generated_uv_map(obj.data)
         self.report({"INFO"}, "Generated UV map for selected mesh.")
         return {"FINISHED"}
+
+
+class BIM_OT_apply_pending_opening_cuts(bpy.types.Operator, tool.Ifc.Operator):
+    """Recompute the wall mesh including opening subtractions for every host
+    that the load-time ``void_limit`` filter skipped. Clears the deferred
+    list on completion so the panel banner disappears."""
+
+    bl_idname = "bim.apply_pending_opening_cuts"
+    bl_label = "Apply Pending Opening Cuts"
+    bl_description = (
+        "Recompute meshes for elements whose openings were skipped at load because they had too many openings"
+    )
+    bl_options = {"REGISTER", "UNDO"}
+
+    def _execute(self, context: bpy.types.Context) -> set[str]:
+        pending = tool.Project.get_project_props().pending_opening_recut
+        applied = 0
+        skipped = 0
+        failed = 0
+        for item in pending:
+            try:
+                element = tool.Ifc.get().by_id(item.ifc_definition_id)
+            except RuntimeError:
+                skipped += 1
+                continue
+            obj = tool.Ifc.get_object(element)
+            if obj is None:
+                skipped += 1
+                continue
+            body = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
+            if body is None:
+                skipped += 1
+                continue
+            try:
+                tool.Geometry.reimport_element_representations(obj, body, apply_openings=True)
+                applied += 1
+            except (RuntimeError, OSError, AttributeError) as exc:
+                # Programmer errors (TypeError, ValueError, etc.) must surface — don't swallow them.
+                failed += 1
+                print(f"apply_pending_opening_cuts: failed to recompute {element} ({exc})")
+
+        pending.clear()
+        message = f"Applied opening cuts to {applied} element(s)."
+        if skipped:
+            message += f" {skipped} entry/entries skipped (entity or object no longer available)."
+        if failed:
+            message += f" {failed} entry/entries failed (see system console)."
+            self.report({"WARNING"}, message)
+        else:
+            self.report({"INFO"}, message)
+        return {"FINISHED"}
+
+
+class BIM_OT_dismiss_pending_opening_cuts(bpy.types.Operator):
+    bl_idname = "bim.dismiss_pending_opening_cuts"
+    bl_label = "Dismiss Pending Opening Cuts"
+    bl_description = "Clear the pending opening-cut list without applying it. Walls stay solid where openings would have been subtracted."
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context: bpy.types.Context) -> set[str]:
+        tool.Project.get_project_props().pending_opening_recut.clear()
+        return {"FINISHED"}
+
+
+class BIM_OT_dismiss_multi_instance_warning(bpy.types.Operator):
+    bl_idname = "bim.dismiss_multi_instance_warning"
+    bl_label = "Dismiss Multi-Instance Warning"
+    bl_description = (
+        "Hide the warning that another Blender instance has this IFC file open. Sticky for the current session."
+    )
+    bl_options = {"REGISTER"}
+
+    def execute(self, context: bpy.types.Context) -> set[str]:
+        from bonsai.bim.ifc import dismiss_multi_instance_warning
+
+        dismiss_multi_instance_warning()
+        return {"FINISHED"}
+
+
+class BIM_OT_select_pending_opening_cuts(bpy.types.Operator):
+    bl_idname = "bim.select_pending_opening_cuts"
+    bl_label = "Select Elements With Skipped Opening Cuts"
+    bl_description = "Select the Blender objects whose openings were skipped at load. Useful for locating which elements need attention."
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context: bpy.types.Context) -> set[str]:
+        ifc_file = tool.Ifc.get()
+        if ifc_file is None:
+            self.report({"INFO"}, "No IFC file loaded.")
+            return {"CANCELLED"}
+        objects: list[bpy.types.Object] = []
+        for item in tool.Project.get_project_props().pending_opening_recut:
+            try:
+                element = ifc_file.by_id(item.ifc_definition_id)
+            except RuntimeError:
+                continue
+            obj = tool.Ifc.get_object(element)
+            if obj is not None:
+                objects.append(obj)
+        if not objects:
+            self.report({"INFO"}, "No matching Blender objects found for the pending list.")
+            return {"CANCELLED"}
+        tool.Blender.set_objects_selection(context, active_object=objects[0], selected_objects=objects)
+        self.report({"INFO"}, f"Selected {len(objects)} element(s).")
+        return {"FINISHED"}
+
+
+class BIM_OT_select_pending_array_repair(bpy.types.Operator):
+    bl_idname = "bim.select_pending_array_repair"
+    bl_label = "Select Array Parents With Missing Children"
+    bl_description = "Select the Blender objects of array parents whose BBIM_Array.Data references children that don't resolve in the file."
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context: bpy.types.Context) -> set[str]:
+        ifc_file = tool.Ifc.get()
+        if ifc_file is None:
+            self.report({"INFO"}, "No IFC file loaded.")
+            return {"CANCELLED"}
+        objects: list[bpy.types.Object] = []
+        for item in tool.Project.get_project_props().pending_array_repair:
+            try:
+                element = ifc_file.by_id(item.ifc_definition_id)
+            except RuntimeError:
+                continue
+            obj = tool.Ifc.get_object(element)
+            if obj is not None:
+                objects.append(obj)
+        if not objects:
+            self.report({"INFO"}, "No matching Blender objects found for the pending list.")
+            return {"CANCELLED"}
+        tool.Blender.set_objects_selection(context, active_object=objects[0], selected_objects=objects)
+        self.report({"INFO"}, f"Selected {len(objects)} array parent(s).")
+        return {"FINISHED"}
+
+
+class BIM_OT_dismiss_pending_array_repair(bpy.types.Operator):
+    bl_idname = "bim.dismiss_pending_array_repair"
+    bl_label = "Dismiss Pending Array Repair"
+    bl_description = (
+        "Clear the pending array-repair list without acting on it. The underlying BBIM_Array.Data stays unchanged."
+    )
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context: bpy.types.Context) -> set[str]:
+        tool.Project.get_project_props().pending_array_repair.clear()
+        return {"FINISHED"}

src/bonsai/bonsai/bim/module/project/prop.py

@@ -98,7 +98,8 @@ def is_editing_project_library_update(self: "BIMProjectProperties", context: bpy
         project_library = library_file.by_id(int(self.selected_project_library))
         self.project_library_attributes.clear()
         bonsai.bim.helper.import_attributes(project_library, self.project_library_attributes)
-        self.parent_library = str(tool.Project.get_parent_library(project_library).id())
+        if parent_library := tool.Project.get_parent_library(project_library):
+            self.parent_library = str(parent_library.id())
         ProjectLibraryData.load()  # Show edit icon in enum.
         return
 
@@ -259,6 +260,11 @@ class Link(PropertyGroup):
         description="STEP ID of the IfcDocumentReference when linked to a parent IFC project. Zero when no parent IFC exists",
         default=0,
     )
+    query: StringProperty(
+        name="Query",
+        description="Selector query used to filter elements when loading the linked model",
+        default="",
+    )
 
     if TYPE_CHECKING:
         name: str
@@ -274,6 +280,7 @@ class Link(PropertyGroup):
         include_in_drawings: bool
         empty_handle: Union[bpy.types.Object, None]
         ifc_definition_id: int
+        query: str
 
 
 class EditedObj(PropertyGroup):
@@ -295,6 +302,28 @@ class LibraryBreadcrumb(PropertyGroup):
         library_id: int
 
 
+class PendingOpeningRecut(PropertyGroup):
+    """One element whose ``HasOpenings`` exceeded ``void_limit`` at load time
+    and was imported without opening subtractions. The user can later apply
+    them on demand from the Project panel banner."""
+
+    ifc_definition_id: IntProperty(name="IFC Definition ID")
+
+    if TYPE_CHECKING:
+        ifc_definition_id: int
+
+
+class PendingArrayRepair(PropertyGroup):
+    """One array parent whose ``BBIM_Array.Data`` references at least one
+    child GUID that does not resolve in the current IFC file. The user can
+    select these parents from the Project panel banner to inspect them."""
+
+    ifc_definition_id: IntProperty(name="IFC Definition ID")
+
+    if TYPE_CHECKING:
+        ifc_definition_id: int
+
+
 class BIMProjectProperties(PropertyGroup):
     is_editing: BoolProperty(name="Is Editing", default=False)
     is_loading: BoolProperty(name="Is Loading", default=False)
@@ -360,6 +389,8 @@ class BIMProjectProperties(PropertyGroup):
         default=30,
         description="Maxium number of openings that object can have. If object has more openings, it will be loaded without openings",
     )
+    pending_opening_recut: CollectionProperty(name="Pending Opening Recut", type=PendingOpeningRecut)
+    pending_array_repair: CollectionProperty(name="Pending Array Repair", type=PendingArrayRepair)
     style_limit: IntProperty(
         name="Style Limit",
         default=300,
@@ -525,6 +556,8 @@ class BIMProjectProperties(PropertyGroup):
         deflection_tolerance: float
         angular_tolerance: float
         void_limit: int
+        pending_opening_recut: bpy.types.bpy_prop_collection_idprop[PendingOpeningRecut]
+        pending_array_repair: bpy.types.bpy_prop_collection_idprop[PendingArrayRepair]
         style_limit: int
         distance_limit: float
         false_origin_mode: Literal["AUTOMATIC", "MANUAL", "DISABLED"]

src/bonsai/bonsai/bim/module/spatial/decorator.py

@@ -18,43 +18,17 @@
 
 import blf
 import gpu
-from bpy.types import SpaceView3D
 from bpy_extras.view3d_utils import location_3d_to_region_2d
-from gpu_extras.batch import batch_for_shader
 from mathutils import Vector
 
 import bonsai.tool as tool
 
 
-class GridDecorator:
-    is_installed = False
-    handlers = []
-
-    @classmethod
-    def install(cls, context):
-        if cls.is_installed:
-            cls.uninstall()
-        handler = cls()
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_text, (context,), "WINDOW", "POST_PIXEL"))
-        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw, (context,), "WINDOW", "POST_VIEW"))
-        cls.is_installed = True
-
-    @classmethod
-    def uninstall(cls):
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
-
-    def draw_batch(self, shader_type, content_pos, color, indices=None):
-        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
-            return
-        shader = self.line_shader if shader_type == "LINES" else self.shader
-        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
-        shader.uniform_float("color", color)
-        batch.draw(shader)
+class GridDecorator(tool.Blender.ViewportDecorator):
+    draw_methods = (
+        ("draw_text", "POST_PIXEL"),
+        ("draw", "POST_VIEW"),
+    )
 
     def draw_text(self, context):
         if not tool.Blender.is_addon_enabled():

src/bonsai/bonsai/bim/module/spatial/operator.py

@@ -302,6 +302,15 @@ class SelectSimilarContainer(bpy.types.Operator):
             is_recursive=self.is_recursive,
         )
         self.is_recursive = True  # <-- forcibly reset
+
+        element = tool.Ifc.get_entity(context.active_object)
+        if element:
+            container = tool.Spatial.get_container(element)
+            if container:
+                result = f'location="{container.Name}"'
+                bpy.context.window_manager.clipboard = result
+                self.report({"INFO"}, f"({result}) was copied to the clipboard.")
+
         return {"FINISHED"}
 
 

src/bonsai/bonsai/bim/module/spatial/prop.py

@@ -128,7 +128,7 @@ def update_grid_is_locked(self: "BIMGridProperties", context: bpy.types.Context)
     if tool.Ifc.get().schema in ("IFC2X3", "IFC4"):
         elements = tool.Ifc.get().by_type("IfcGrid") + tool.Ifc.get().by_type("IfcGridAxis")
     else:
-        elements = tool.Ifc.get().by_type("IfcPositioningElement")
+        elements = tool.Ifc.get().by_type("IfcPositioningElement") + tool.Ifc.get().by_type("IfcGridAxis")
     for element in elements:
         if obj := tool.Ifc.get_object(element):
             if self.is_locked:

src/bonsai/bonsai/bim/module/structural/decorator.py

@@ -31,11 +31,17 @@ import bonsai.tool as tool
 from bonsai.bim.module.structural.load_decoration_data import ShaderInfo
 
 
-class LoadsDecorator:
+class LoadsDecorator(tool.Blender.ViewportDecorator):
     """Decorator to show structural loads in 3D"""
 
-    is_installed = False
-    handlers = []
+    # draw_methods exists to satisfy ViewportDecorator.__init_subclass__'s
+    # method-existence check; the override install below is what actually
+    # registers handlers (the POST_VIEW binding passes no context arg, which
+    # the base's generic install cannot express).
+    draw_methods = (
+        ("draw_load_values", "POST_PIXEL"),
+        ("__call__", "POST_VIEW"),
+    )
     decoration_data = None
     text_info = []
     shader_info = []
@@ -54,15 +60,6 @@ class LoadsDecorator:
         cls.update()
         cls.is_installed = True
 
-    @classmethod
-    def uninstall(cls) -> None:
-        for handler in cls.handlers:
-            try:
-                SpaceView3D.draw_handler_remove(handler, "WINDOW")
-            except ValueError:
-                pass
-        cls.is_installed = False
-
     @classmethod
     def update(cls) -> None:
         cls.decoration_data.update()

src/bonsai/bonsai/bim/module/style/operator.py

@@ -744,7 +744,7 @@ class EnableEditingSurfaceStyle(bpy.types.Operator):
         if self.ifc_class == "IfcSurfaceStyleLighting":
 
             def callback(attribute_name: str, _: object, data: dict[str, Any]) -> None:
-                assert attributes
+                assert attributes is not None
                 color = attributes.add()
                 assert isinstance(color, ColourRgb)
                 color.name = attribute_name
@@ -782,34 +782,40 @@ class EditSurfaceStyle(bpy.types.Operator, tool.Ifc.Operator):
     def _execute(self, context):
         self.props = tool.Style.get_style_props()
         self.style = tool.Ifc.get().by_id(self.props.is_editing_style)
+        prev_update_graph = self.props.update_graph
+        self.props["update_graph"] = False
 
-        style_elements = tool.Style.get_style_elements(self.style)
-        # NOTE: currently this operator is used to edit existing (and only existing) IfcSurfaceStyles
-        # or new or existing IfcSurfaceStyle components (shading, etc)
-        # which is kind of confusing.
-        if self.props.is_editing_class == "IfcSurfaceStyle":
-            self.surface_style = self.style
-        else:
-            self.surface_style = style_elements.get(self.props.is_editing_class, None)
-            self.shading_style = style_elements.get("IfcSurfaceStyleShading", None)
-            self.rendering_style = style_elements.get("IfcSurfaceStyleRendering", None)
-            self.texture_style = style_elements.get("IfcSurfaceStyleWithTextures", None)
+        try:
+            style_elements = tool.Style.get_style_elements(self.style)
 
-        if self.surface_style:
-            result = self.edit_existing_style()
-        else:
-            result = self.add_new_style()
+            # NOTE: currently this operator is used to edit existing (and only existing) IfcSurfaceStyles
+            # or new or existing IfcSurfaceStyle components (shading, etc)
+            # which is kind of confusing.
+            if self.props.is_editing_class == "IfcSurfaceStyle":
+                self.surface_style = self.style
+            else:
+                self.surface_style = style_elements.get(self.props.is_editing_class, None)
+                self.shading_style = style_elements.get("IfcSurfaceStyleShading", None)
+                self.rendering_style = style_elements.get("IfcSurfaceStyleRendering", None)
+                self.texture_style = style_elements.get("IfcSurfaceStyleWithTextures", None)
 
-        if result:
-            return result
+            if self.surface_style:
+                result = self.edit_existing_style()
+            else:
+                result = self.add_new_style()
 
-        tool.Style.disable_editing()
-        core.load_styles(tool.Style, style_type=self.props.style_type)
+            if result:
+                return result
 
-        # restore selected style type
-        material = tool.Ifc.get_object(self.style)
-        msprops = tool.Style.get_material_style_props(material)
-        msprops.active_style_type = msprops.active_style_type
+            tool.Style.disable_editing()
+            core.load_styles(tool.Style, style_type=self.props.style_type)
+
+            # restore selected style type
+            material = tool.Ifc.get_object(self.style)
+            msprops = tool.Style.get_material_style_props(material)
+            msprops.active_style_type = msprops.active_style_type
+        finally:
+            self.props["update_graph"] = prev_update_graph
 
     def edit_existing_style(self) -> None:
         ifc_file = tool.Ifc.get()
@@ -1231,4 +1237,5 @@ class RemoveSurfaceStyle(bpy.types.Operator, tool.Ifc.Operator):
         surface_style = tool.Style.get_style_elements(style)[props.is_editing_class]
         ifcopenshell.api.style.remove_surface_style(ifc_file, surface_style)
         core.disable_editing_style(tool.Style)
+        core.load_styles(tool.Style, style_type=props.style_type)
         return {"FINISHED"}

src/bonsai/bonsai/bim/module/style/prop.py

@@ -185,6 +185,13 @@ class ColourRgb(PropertyGroup):
     # to fit blender.bim.helper.draw_attribute
     is_optional = False
     special_type = ""
+    data_type = ""
+    ifc_class = ""
+    use_explorer_ui = False
+
+    @property
+    def display_name(self):
+        return self.name
 
     def get_value_name(self, *args, **kwargs):
         return "color_value"

src/bonsai/bonsai/bim/module/style/ui.py

@@ -176,8 +176,30 @@ class BIM_PT_styles(Panel):
         row.prop(self.props, "reflectance_method")
 
         if self.props.reflectance_method not in ("PHYSICAL", "NOTDEFINED", "FLAT"):
-            self.layout.label(text="Supported reflectance methods are:")
-            self.layout.label(text="PHYSICAL / NOTDEFINED / FLAT")
+            self.layout.label(
+                text=f"{self.props.reflectance_method} will be skipped: only PHYSICAL / NOTDEFINED / FLAT are supported",
+                icon="ERROR",
+            )
+        elif self.props.reflectance_method in ("PHYSICAL", "NOTDEFINED"):
+            if self.props.specular_colour_class == "IfcColourRgb":
+                self.layout.label(
+                    text="Metallic color is IFC-only in PHYSICAL/NOTDEFINED and does not affect Blender appearance",
+                    icon="ERROR",
+                )
+        elif self.props.reflectance_method == "FLAT":
+            if self.props.diffuse_colour_class == "IfcNormalisedRatioMeasure":
+                self.layout.label(
+                    text="Emissive ratio is IFC-only in FLAT Reflectance method and does not affect Blender appearance",
+                    icon="ERROR",
+                )
+            self.layout.label(
+                text="Specular value is IFC-only in FLAT Reflectance method and does not affect Blender appearance",
+                icon="ERROR",
+            )
+            self.layout.label(
+                text="Highlight value is IFC-only in FLAT Reflectance method and does not affect Blender appearance",
+                icon="ERROR",
+            )
 
         row = self.layout.row(align=True)
         row.label(text="Emissive" if self.props.reflectance_method == "FLAT" else "Diffuse")
@@ -232,6 +254,8 @@ class BIM_PT_styles(Panel):
         row.operator("bim.add_surface_texture", text="", icon="ADD")
         if textures:
             self.layout.prop(self.props, "uv_mode")
+            if self.props.uv_mode in ("Generated", "Camera"):
+                self.layout.label(text="Not available in SOLID Mode", icon="INFO")
 
         for i, texture in enumerate(textures):
             split = self.layout.split(factor=0.30, align=True)
@@ -244,6 +268,22 @@ class BIM_PT_styles(Panel):
             op_clear = row.operator("bim.remove_texture_map", text="", icon="X")
             op_path.texture_map_index = op_clear.texture_map_index = i
 
+            reflectance = self.props.reflectance_method
+            mode = texture.mode
+            if reflectance == "FLAT":
+                if mode != "EMISSIVE":
+                    self.layout.label(
+                        text=f"{mode} will be skipped: only EMISSIVE is supported for Render Reflectance FLAT",
+                        icon="ERROR",
+                    )
+            elif reflectance in ("PHYSICAL", "NOTDEFINED"):
+                _SUPPORTED = {"DIFFUSE", "NORMAL", "METALLICROUGHNESS", "EMISSIVE", "OCCLUSION"}
+                if mode not in _SUPPORTED:
+                    self.layout.label(
+                        text=f"{mode} will be skipped: not supported for Render Reflectance PHYSICAL/NOTDEFINED",
+                        icon="ERROR",
+                    )
+
     def draw_externally_defined_surface_style(self):
         row = self.layout.row()
         op = row.operator("bim.browse_external_style", icon="APPEND_BLEND", text="Append From Blend File")
@@ -252,10 +292,17 @@ class BIM_PT_styles(Panel):
         bonsai.bim.helper.draw_attributes(self.props.external_style_attributes, self.layout, enable_search=True)
 
     def draw_refraction_surface_style(self):
+        self.layout.label(
+            text="Refraction values are IFC-only and do not affect Blender surface appearance",
+            icon="ERROR",
+        )
         bonsai.bim.helper.draw_attributes(self.props.refraction_style_attributes, self.layout, enable_search=True)
-        row = self.layout.row(align=True)
 
     def draw_lighting_surface_style(self):
+        self.layout.label(
+            text="Lighting values are IFC-only and do not affect Blender surface appearance",
+            icon="ERROR",
+        )
         bonsai.bim.helper.draw_attributes(self.props.lighting_style_colours, self.layout)
 
     def draw_edit_ui(self, edit_label: str):

src/bonsai/bonsai/bim/module/system/decorator.py

@@ -15,9 +15,10 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 
-import bmesh
 import bpy
 import gpu
 from bpy.app.handlers import persistent
@@ -30,12 +31,6 @@ ERROR_ELEMENTS_COLOR = (1, 0.2, 0.322, 1)  # RED
 UNSPECIAL_ELEMENT_COLOR = (0.2, 0.2, 0.2, 1)  # GREY
 
 
-def transparent_color(color, alpha=0.1):
-    color = [i for i in color]
-    color[3] = alpha
-    return color
-
-
 @persistent
 def toggle_decorations_on_load(*args):
     props = tool.System.get_system_props()
@@ -78,15 +73,9 @@ class SystemDecorator:
         batch.draw(shader)
 
     def draw_faces(self, bm, vertices_coords):
-        """mutates original bm (triangulates it)
-        so the triangulation edges will be shown too
-        """
-        traingulated_bm = bm
-        bmesh.ops.triangulate(traingulated_bm, faces=traingulated_bm.faces)
-
-        face_indices = [[v.index for v in f.verts] for f in traingulated_bm.faces]
-        faces_color = transparent_color(self.addon_prefs.decorator_color_special)
-        self.draw_batch("TRIS", vertices_coords, faces_color, face_indices)
+        """Submit a non-mutating beauty-triangulated TRIS batch over ``bm``'s faces."""
+        faces_color = tool.Blender.transparent_color(self.addon_prefs.decorator_color_special)
+        tool.Blender.draw_bmesh_face_tris(bm, vertices_coords, faces_color, self.draw_batch)
 
     def __call__(self, context, get_custom_bmesh=None, draw_faces=False, exit_edit_mode_callback=None):
         self.addon_prefs = tool.Blender.get_addon_preferences()
@@ -133,13 +122,15 @@ class SystemDecorator:
         self.shader = gpu.shader.from_builtin("UNIFORM_COLOR")
         self.shader.bind()
 
-        self.draw_batch("LINES", all_vertices, transparent_color(unselected_elements_color), unselected_edges)
+        self.draw_batch(
+            "LINES", all_vertices, tool.Blender.transparent_color(unselected_elements_color), unselected_edges
+        )
         self.draw_batch("LINES", all_vertices, selected_elements_color, selected_edges)
         self.draw_batch("LINES", all_vertices, UNSPECIAL_ELEMENT_COLOR, arc_edges)
         self.draw_batch("LINES", all_vertices, special_elements_color, preview_edges)
         self.draw_batch("LINES", all_vertices, special_elements_color, roof_angle_edges)
 
-        self.draw_batch("POINTS", unselected_vertices, transparent_color(unselected_elements_color, 0.5))
+        self.draw_batch("POINTS", unselected_vertices, tool.Blender.transparent_color(unselected_elements_color, 0.5))
         self.draw_batch("POINTS", error_vertices, ERROR_ELEMENTS_COLOR)
         self.draw_batch("POINTS", special_vertices, special_elements_color)
         self.draw_batch("POINTS", selected_vertices, selected_elements_color)

src/bonsai/bonsai/bim/module/system/operator.py

@@ -317,13 +317,23 @@ class MEPConnectElements(bpy.types.Operator, tool.Ifc.Operator):
     bl_label = "Connect MEP Elements"
     bl_description = "Connects two selected elements by their closest located ports and adjusts them"
     bl_options = {"REGISTER", "UNDO"}
-    obj1_name: bpy.props.StringProperty(name="Object 1")
-    obj2_name: bpy.props.StringProperty(name="Object 2")
+    obj1_guid: bpy.props.StringProperty(name="Object 1 GlobalId")
+    obj2_guid: bpy.props.StringProperty(name="Object 2 GlobalId")
 
     def _execute(self, context):
-        if self.obj1_name and self.obj2_name:
-            obj1 = bpy.data.objects.get(self.obj1_name)
-            obj2 = bpy.data.objects.get(self.obj2_name)
+        if self.obj1_guid and self.obj2_guid:
+            ifc_file = tool.Ifc.get()
+            try:
+                el1_lookup = ifc_file.by_guid(self.obj1_guid)
+                el2_lookup = ifc_file.by_guid(self.obj2_guid)
+            except RuntimeError:
+                self.report({"ERROR"}, "Could not resolve MEP elements from supplied GlobalIds.")
+                return {"CANCELLED"}
+            obj1 = tool.Ifc.get_object(el1_lookup)
+            obj2 = tool.Ifc.get_object(el2_lookup)
+            if not obj1 or not obj2:
+                self.report({"ERROR"}, "Supplied MEP elements have no Blender object bound.")
+                return {"CANCELLED"}
         else:
             if not context.selected_objects or len(context.selected_objects) != 2:
                 self.report({"ERROR"}, "Need to select 2 objects.")

src/bonsai/bonsai/bim/module/type/operator.py

@@ -65,10 +65,28 @@ class AssignType(bpy.types.Operator, tool.Ifc.Operator):
             if active_drawing:
                 active_target_view = tool.Drawing.get_drawing_target_view(active_drawing)
 
+        compatible: list[tuple[bpy.types.Object, ifcopenshell.entity_instance]] = []
+        skipped_classes: set[str] = set()
         for obj in related_objects:
             element = tool.Ifc.get_entity(obj)
             if not element or not element.is_a("IfcObject"):
                 continue
+            if not tool.Type.is_relating_type_compatible(element, relating_type):
+                skipped_classes.add(element.is_a())
+                continue
+            compatible.append((obj, element))
+
+        if skipped_classes:
+            self.report(
+                {"WARNING"},
+                f"Skipped {', '.join(sorted(skipped_classes))}: not a valid occurrence for " f"{relating_type.is_a()}.",
+            )
+
+        if not compatible:
+            self.report({"ERROR"}, f"No selected object can be typed by {relating_type.is_a()}.")
+            return {"CANCELLED"}
+
+        for obj, element in compatible:
             core.assign_type(tool.Ifc, tool.Model, tool.Type, element=element, type=relating_type)
 
             # Switch to the drawing's target view if available
@@ -376,12 +394,22 @@ class DuplicateType(bpy.types.Operator, tool.Ifc.Operator):
         if self.assign_selected_objects:
             selected_objects = tool.Blender.get_selected_objects()
             prefs = tool.Blender.get_addon_preferences()
+            skipped_classes: set[str] = set()
             for selected_obj in selected_objects:
                 selected_element = tool.Ifc.get_entity(selected_obj)
-                if selected_element and selected_element.is_a("IfcObject"):
-                    core.assign_type(tool.Ifc, tool.Model, tool.Type, element=selected_element, type=new)
-                    if prefs.occurrence_name_style == "TYPE":
-                        selected_obj.name = tool.Model.generate_occurrence_name(new, selected_element.is_a())
+                if not selected_element or not selected_element.is_a("IfcObject"):
+                    continue
+                if not tool.Type.is_relating_type_compatible(selected_element, new):
+                    skipped_classes.add(selected_element.is_a())
+                    continue
+                core.assign_type(tool.Ifc, tool.Model, tool.Type, element=selected_element, type=new)
+                if prefs.occurrence_name_style == "TYPE":
+                    selected_obj.name = tool.Model.generate_occurrence_name(new, selected_element.is_a())
+            if skipped_classes:
+                self.report(
+                    {"WARNING"},
+                    f"Skipped {', '.join(sorted(skipped_classes))}: not a valid occurrence for " f"{new.is_a()}.",
+                )
 
         if obj in context.selectable_objects:
             tool.Blender.select_and_activate_single_object(context, new_obj)

src/bonsai/bonsai/bim/module/type/ui.py

@@ -151,7 +151,8 @@ class BIM_PT_type_attributes(Panel):
                 row = layout.row(align=True)
                 row.label(text=attribute["name"])
                 value = get_display_value(attribute["value"])
-                row.label(text=value)
+                op = row.operator("bim.select_similar", text=value, icon="NONE", emboss=False)
+                op.key = "type." + attribute["name"]
 
 
 def add_object_button(self, context):

src/bonsai/bonsai/bim/module/void/operator.py

@@ -26,7 +26,7 @@ import bonsai.bim.handler
 import bonsai.core.geometry
 import bonsai.core.root
 import bonsai.tool as tool
-from bonsai.bim.module.model.opening import FilledOpeningGenerator
+from bonsai.bim.module.model.opening import FilledOpeningGenerator, is_filling_supported
 
 
 class AddOpening(bpy.types.Operator, tool.Ifc.Operator):
@@ -34,11 +34,21 @@ class AddOpening(bpy.types.Operator, tool.Ifc.Operator):
     bl_label = "Apply Opening"
     bl_options = {"REGISTER", "UNDO"}
     bl_description = (
-        "Apply opening objects to an Element.\n\n"
-        "The Element and the openings to be applied should be selected. The order of selection is not important.\n"
-        "Opening can be just a Blender mesh object."
+        "Cuts openings in a wall, slab, or roof using selected shape objects — "
+        "doors, windows, existing openings, or plain (non-IFC) meshes. "
+        "Selection order doesn't matter.\n\n"
+        "Doors and windows also fill the opening. Other IFC classes are currently "
+        "unsupported by the opening generator and get skipped with a warning.\n\n"
+        "Shift+click: keep each opening at its shape object's current position "
+        "instead of snapping to the wall."
     )
 
+    # Toggled by ``invoke`` when the user holds SHIFT during a gizmo / hotkey
+    # click. The filling-opening generator gates its snap-to-wall-axis block
+    # on this flag. HIDDEN + SKIP_SAVE so the flag doesn't surface in the F6
+    # redo panel or persist into saved keymaps.
+    preserve_placement: bpy.props.BoolProperty(default=False, options={"HIDDEN", "SKIP_SAVE"})
+
     @classmethod
     def poll(cls, context):
         if len(context.selected_objects) < 2:
@@ -46,7 +56,17 @@ class AddOpening(bpy.types.Operator, tool.Ifc.Operator):
             return False
         return True
 
+    def invoke(self, context, event):
+        self.preserve_placement = bool(event.shift)
+        return self.execute(context)
+
     def _execute(self, context):
+        # Multi-opening drops on the same host fan out N update_representation
+        # writes + N switch_representation recuts without batching. Coalesce.
+        with tool.Geometry.batch_host_recut():
+            return self._add_openings(context)
+
+    def _add_openings(self, context):
         selected_objects = context.selected_objects
         target_object = selected_objects[0]
 
@@ -66,9 +86,20 @@ class AddOpening(bpy.types.Operator, tool.Ifc.Operator):
                     self.report({"INFO"}, "You can't add an opening to another opening.")
                     continue
                 elif not element1.is_a("IfcOpeningElement") and not element2.is_a("IfcOpeningElement"):
-                    if element1.is_a("IfcWindow") or element1.is_a("IfcDoor"):  # Add a fill to an element.
+                    if is_filling_supported(element1):  # Add a fill to an element.
                         obj1, obj2 = obj2, obj1
-                    FilledOpeningGenerator().generate(obj2, obj1, target=obj2.matrix_world.translation)
+                    elif not is_filling_supported(element2):
+                        self.report(
+                            {"INFO"},
+                            f"Cannot apply {element2.is_a()} as an opening — Bonsai currently supports only IfcDoor and IfcWindow as parametric fillings.",
+                        )
+                        continue
+                    FilledOpeningGenerator().generate(
+                        obj2,
+                        obj1,
+                        target=obj2.matrix_world.translation,
+                        preserve_placement=self.preserve_placement,
+                    )
                     continue
                 elif element1.is_a("IfcOpeningElement") or element2.is_a("IfcOpeningElement"):
                     if element1.is_a("IfcOpeningElement"):  # Reassign an opening to another element.
@@ -148,7 +179,7 @@ class AddOpening(bpy.types.Operator, tool.Ifc.Operator):
                             voided_obj.scale = (1.0, 1.0, 1.0)
                             tool.Ifc.finish_edit(voided_obj)
                         else:
-                            bpy.ops.bim.update_representation(obj=voided_obj.name)
+                            tool.Geometry.update_host_representation(voided_obj)
 
                     if tool.Ifc.is_moved(voided_obj):
                         bonsai.core.geometry.edit_object_placement(
@@ -157,12 +188,7 @@ class AddOpening(bpy.types.Operator, tool.Ifc.Operator):
 
                     representation = tool.Geometry.get_active_representation(voided_obj)
                     assert representation
-                    bonsai.core.geometry.switch_representation(
-                        tool.Ifc,
-                        tool.Geometry,
-                        obj=voided_obj,
-                        representation=representation,
-                    )
+                    tool.Geometry.recut_host(voided_obj, representation)
                 tool.Geometry.lock_scale(voided_obj)
 
             if not has_visible_openings:
@@ -200,12 +226,7 @@ class RemoveOpening(bpy.types.Operator, tool.Ifc.Operator):
             if building_obj and building_obj.data:
                 representation = tool.Geometry.get_active_representation(building_obj)
                 assert representation
-                bonsai.core.geometry.switch_representation(
-                    tool.Ifc,
-                    tool.Geometry,
-                    obj=building_obj,
-                    representation=representation,
-                )
+                tool.Geometry.recut_host(building_obj, representation)
         tool.Geometry.unlock_scale_object_with_openings(obj)
         tool.Geometry.clear_cache(element)
         return {"FINISHED"}

src/bonsai/bonsai/bim/parametric_lifecycle.py

@@ -0,0 +1,656 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""Shared operator mixins for parametric-edit operators.
+
+Edit-lifecycle mixins (Enable / Finish / Cancel):
+    `FeatureModifierEditMixin` — door, window (BBIM_<Type> pset; nested
+        lining/panel properties; Finish + Cancel route through
+        ``ifcopenshell.api.feature``).
+    `PathPreservingEditMixin` — railing, roof (path_data preserved across
+        edit; only general kwargs are user-editable).
+
+Pattern selection (which approach a new feature should adopt):
+    Every parametric edit lifecycle commits to one of three patterns. Pick by
+    answering "does the feature share the Enable→Finish→Cancel shape that
+    one of the existing mixins already encodes?":
+
+    A. Inherit one of the shared mixins below and route through
+       `tool.Parametric.build_edit_lifecycle`:
+
+       - `FeatureModifierEditMixin` when the feature stores its pset as
+         `{general fields} + {lining_properties: {...}} + {panel_properties: {...}}`
+         and Finish must call a per-type `update_<type>_modifier_representation`.
+
+       - `PathPreservingEditMixin` when the feature's pset carries a
+         `path_data` field that survives general-kwarg edits untouched, with
+         a separate Enable/Finish/Cancel lifecycle for path editing itself.
+
+    B. Write a per-feature mixin that subclasses `ParametricEditMixinBase`
+       and provides `_enable_targets` / `_finish_targets` / `_cancel_targets`,
+       then route through `build_edit_lifecycle`. Pick this when the
+       feature's pset roundtrip or representation handling diverges from the
+       shared mixins but the Enable→Finish→Cancel shape still fits.
+
+    C. Declare standalone Enable/Finish/Cancel Operator subclasses (no
+       factory) when the feature's parameter-change logic is sufficiently
+       unique that even a per-feature mixin would force optional hooks or
+       dead branches. Such operators MUST call the matrix_world drift
+       helpers (`tool.Geometry.commit_placement_if_moved` on Enable/Finish,
+       `tool.Geometry.restore_or_rebaseline_placement` on Cancel) — the
+       drift contract is enforced uniformly regardless of which pattern the
+       operators adopt.
+
+    The authoritative list of registered parametric types — and which use
+    `build_edit_lifecycle` vs. standalone operators — lives in
+    `tool/parametric.py`'s `EDIT_TYPES` and is enforced by the registry
+    contract tests.
+
+This module hosts operator-side mixins that import ``bonsai.tool`` freely.
+The lightweight parametric registry consumed at addon-enable time must stay
+free of such imports and lives separately in ``tool/parametric.py``."""
+
+from __future__ import annotations
+
+import json
+from collections.abc import Callable
+from typing import ClassVar, get_args
+
+import bpy
+import ifcopenshell.util.element
+from bpy.app.handlers import persistent
+from ifcopenshell import entity_instance
+
+import bonsai.core.geometry
+import bonsai.tool as tool
+
+
+class ParametricEditMixinBase:
+    """Common scaffolding for parametric edit-lifecycle mixins.
+
+    Each per-type subclass provides four hooks:
+
+        ``pset_name``: BBIM_<Type> pset identifier
+        ``_is_element_type(element)``: IFC element predicate
+        ``_get_props(obj)``: PropertyGroup accessor
+        ``_iter_targets(context)``: list of objects to act on (default: ``[active_object]``)
+
+    Drift handling is built in: pre-edit matrix_world drift commits to IFC on
+    Enable, in-edit drag commits on Finish, and Cancel restores the committed
+    IFC placement. This prevents an uncommitted drag from disappearing on
+    Finish or snapping back on Cancel.
+
+    Operator subclasses call one of ``_enable_targets`` / ``_finish_targets`` /
+    ``_cancel_targets`` from their ``_execute`` method."""
+
+    pset_name: ClassVar[str]
+
+    @classmethod
+    def _iter_targets(cls, context: bpy.types.Context) -> list[bpy.types.Object]:
+        obj = context.active_object
+        return [obj] if obj else []
+
+    @classmethod
+    def _is_element_type(cls, element: entity_instance) -> bool:
+        raise NotImplementedError
+
+    @classmethod
+    def _get_props(cls, obj: bpy.types.Object):
+        raise NotImplementedError
+
+    @classmethod
+    def _resolve(cls, obj: bpy.types.Object):
+        """Look up ``(element, props)`` for ``obj`` if it matches this type, else None.
+
+        Common predicate guard for every lifecycle method — collapses the
+        ``element = tool.Ifc.get_entity(obj); assert element; if not is_<type>(element): return``
+        triplet into one call."""
+        element = tool.Ifc.get_entity(obj)
+        if not element or not cls._is_element_type(element):
+            return None
+        return element, cls._get_props(obj)
+
+    @classmethod
+    def _handle_drift_on_enable(cls, obj: bpy.types.Object) -> None:
+        tool.Geometry.commit_placement_if_moved(obj, apply_scale=False)
+
+    @classmethod
+    def _handle_drift_on_finish(cls, obj: bpy.types.Object) -> None:
+        tool.Geometry.commit_placement_if_moved(obj)
+
+    @classmethod
+    def _handle_drift_on_cancel(cls, obj: bpy.types.Object, element: entity_instance) -> None:
+        tool.Geometry.restore_or_rebaseline_placement(obj, element)
+
+    @classmethod
+    def _mark_type_thumbnail_dirty(cls, element: entity_instance) -> None:
+        """Mark the element's type's preview thumbnail for refresh so the
+        property-panel preview reflects post-edit geometry. No-op for
+        occurrences without a backing type."""
+        element_type = ifcopenshell.util.element.get_type(element)
+        if element_type:
+            tool.Model.mark_thumbnail_for_update(element_type)
+
+
+class FeatureModifierEditMixin(ParametricEditMixinBase):
+    """Lifecycle for door- and window-style parametric modifier operators.
+
+    Enable:
+        Read BBIM_<Type> pset JSON → unwrap ``lining_properties`` and
+        ``panel_properties`` → merge constituents data → set draft props →
+        ``is_editing = True``.
+
+    Finish:
+        Gather ``general / lining / panel`` kwargs (project units) → nest →
+        ``is_editing = False`` → call ``_update_modifier_representation`` →
+        mark thumbnail → write back to BBIM_<Type> pset via
+        ``ifcopenshell.api.pset.edit_pset``.
+
+    Cancel:
+        Read BBIM_<Type> pset JSON → unwrap → restore draft props →
+        ``switch_representation`` to the Body representation →
+        ``is_editing = False``."""
+
+    @classmethod
+    def _update_modifier_representation(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        """Hook: call the per-type ``update_<type>_modifier_representation``."""
+        raise NotImplementedError
+
+    @classmethod
+    def _enable_one(cls, obj: bpy.types.Object) -> None:
+        resolved = cls._resolve(obj)
+        if resolved is None:
+            return
+        element, props = resolved
+        cls._handle_drift_on_enable(obj)
+        data = json.loads(ifcopenshell.util.element.get_pset(element, cls.pset_name, "Data"))
+        data.update(data.pop("lining_properties"))
+        data.update(data.pop("panel_properties"))
+        data.update(tool.Model.get_constituents_props_data(element))
+        # required since the pset can be loaded from .ifc and the PropertyGroup
+        # would otherwise still hold its default values
+        props.set_props_kwargs_from_ifc_data(data)
+        props.is_editing = True
+
+    @classmethod
+    def _finish_one(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        resolved = cls._resolve(obj)
+        if resolved is None:
+            return
+        element, props = resolved
+        data = props.get_general_kwargs(convert_to_project_units=True)
+        data["lining_properties"] = props.get_lining_kwargs(convert_to_project_units=True)
+        data["panel_properties"] = props.get_panel_kwargs(convert_to_project_units=True)
+        cls._update_modifier_representation(obj, context)
+        cls._mark_type_thumbnail_dirty(element)
+        tool.Pset.write_bbim_data(element, cls.pset_name, data)
+        cls._handle_drift_on_finish(obj)
+        # Set only on success: if any IFC op above raised, the user's draft survives for retry.
+        props.is_editing = False
+
+    @classmethod
+    def _cancel_one(cls, obj: bpy.types.Object) -> None:
+        resolved = cls._resolve(obj)
+        if resolved is None:
+            return
+        element, props = resolved
+        # Cancel must always clear is_editing — leaving it True after a
+        # restore-failure would block the user from re-entering edit mode and
+        # the next save's stale-flag heal would silently roll back the
+        # cancellation. Wrap the restore in try/finally so the flag flips
+        # even on partial failure.
+        try:
+            data = json.loads(ifcopenshell.util.element.get_pset(element, cls.pset_name, "Data"))
+            data.update(data.pop("lining_properties"))
+            data.update(data.pop("panel_properties"))
+            props.set_props_kwargs_from_ifc_data(data)
+            body = tool.Geometry.get_body_representation(element)
+            bonsai.core.geometry.switch_representation(tool.Ifc, tool.Geometry, obj=obj, representation=body)
+            cls._handle_drift_on_cancel(obj, element)
+        finally:
+            props.is_editing = False
+
+    def _enable_targets(self, context: bpy.types.Context) -> set[str]:
+        for obj in self._iter_targets(context):
+            self._enable_one(obj)
+        return {"FINISHED"}
+
+    def _finish_targets(self, context: bpy.types.Context) -> set[str]:
+        for obj in self._iter_targets(context):
+            self._finish_one(obj, context)
+        return {"FINISHED"}
+
+    def _cancel_targets(self, context: bpy.types.Context) -> set[str]:
+        for obj in self._iter_targets(context):
+            self._cancel_one(obj)
+        return {"FINISHED"}
+
+
+class PathPreservingEditMixin(ParametricEditMixinBase):
+    """Lifecycle for railing- and roof-style parametric modifier operators.
+
+    Distinctive: ``path_data`` is part of the BBIM_<Type> pset but is **not**
+    user-editable through this lifecycle — it survives the edit untouched, only
+    general kwargs are diffed. (Path editing has its own separate operator
+    pair, ``Enable/Finish/CancelEditing<Type>Path``, out of scope here.)
+
+    Enable:
+        Fetch pset data via ``tool.Model.get_modeling_bbim_pset_data`` → set
+        draft props → ``is_editing = True``. The subclass post-load hook
+        can reshape the dict to fit the PropertyGroup's storage layout
+        (e.g., pre-serialise a structured pset value to JSON for a
+        ``StringProperty`` field).
+
+    Finish:
+        Read fresh pset → keep ``path_data`` → gather ``general`` kwargs
+        (project units) → reassemble → ``is_editing = False`` → call
+        ``_update_pset`` (per-type pset writer) → call ``_update_modifier_ifc_data``
+        (per-type geometry commit).
+
+    Cancel:
+        Read fresh pset → restore draft props → call
+        ``_restore_viewport_after_cancel`` (per-type viewport restore — typically
+        rebuilds the bmesh preview, but subclasses may load a different
+        representation entirely) → ``is_editing = False``."""
+
+    @classmethod
+    def _post_load_data(cls, data: dict) -> dict:
+        """Hook: optionally transform the pset data dict after loading and before
+        passing to ``set_props_kwargs_from_ifc_data``. Default: pass-through.
+
+        Override when the PropertyGroup stores a structured pset field as a
+        serialised primitive — e.g., a list/dict value mapped onto a
+        ``StringProperty`` requires JSON-encoding here."""
+        return data
+
+    @classmethod
+    def _update_pset(cls, element: entity_instance, data: dict) -> None:
+        """Hook: per-type pset writer (``update_bbim_<type>_pset``)."""
+        raise NotImplementedError
+
+    @classmethod
+    def _update_modifier_ifc_data(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        """Hook: per-type ``update_<type>_modifier_ifc_data`` — commits the
+        modified geometry to IFC. Signature accepts ``(obj, context)`` so
+        subclasses can forward either argument to their existing helper."""
+        raise NotImplementedError
+
+    @classmethod
+    def _restore_viewport_after_cancel(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        """Hook: restore the viewport mesh to match the just-restored draft props.
+
+        Most subclasses rebuild a bmesh preview from props. Subclasses whose
+        committed IFC representation diverges from the preview may switch
+        the mesh back to the committed representation instead."""
+        raise NotImplementedError
+
+    @classmethod
+    def _enable_one(cls, obj: bpy.types.Object) -> None:
+        resolved = cls._resolve(obj)
+        if resolved is None:
+            return
+        _element, props = resolved
+        cls._handle_drift_on_enable(obj)
+        data = tool.Model.get_modeling_bbim_pset_data(obj, cls.pset_name)["data_dict"]
+        data = cls._post_load_data(data)
+        props.set_props_kwargs_from_ifc_data(data)
+        props.is_editing = True
+
+    @classmethod
+    def _finish_one(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        resolved = cls._resolve(obj)
+        if resolved is None:
+            return
+        element, props = resolved
+        pset_data = tool.Model.get_modeling_bbim_pset_data(obj, cls.pset_name)
+        stored = pset_data["data_dict"]
+        data = props.get_general_kwargs(convert_to_project_units=True)
+        data["path_data"] = stored["path_data"]
+        # Skip the pset commit when the draft is identical to the stored pset:
+        # an Enable → Finish-without-changes cycle should not pollute the
+        # representation list or burn an undo entry. Drift commit still runs
+        # unconditionally — matrix_world drift is independent of pset content.
+        if data != stored:
+            cls._update_pset(element, data)
+            cls._update_modifier_ifc_data(obj, context)
+            cls._mark_type_thumbnail_dirty(element)
+        cls._handle_drift_on_finish(obj)
+        # Set only on success: if any IFC op above raised, the user's draft survives for retry.
+        props.is_editing = False
+
+    @classmethod
+    def _cancel_one(cls, obj: bpy.types.Object, context: bpy.types.Context) -> None:
+        resolved = cls._resolve(obj)
+        if resolved is None:
+            return
+        element, props = resolved
+        try:
+            pset_data = tool.Model.get_modeling_bbim_pset_data(obj, cls.pset_name)
+            stored = pset_data["data_dict"]
+            draft = props.get_general_kwargs(convert_to_project_units=True)
+            draft["path_data"] = stored["path_data"]
+            nothing_changed = draft == stored
+            data = cls._post_load_data(stored)
+            props.set_props_kwargs_from_ifc_data(data)
+            # Skip the viewport rebuild on a no-op cancel: the mesh on screen is
+            # still the committed representation, and the per-type viewport-restore
+            # hook may be expensive (some subclasses reload a high-poly IFC
+            # representation rather than rebuild a preview mesh).
+            if not nothing_changed:
+                cls._restore_viewport_after_cancel(obj, context)
+            cls._handle_drift_on_cancel(obj, element)
+        finally:
+            # Always clear the flag — see ``FeatureModifierEditMixin._cancel_one``
+            # for the rationale.
+            props.is_editing = False
+
+    def _enable_targets(self, context: bpy.types.Context) -> set[str]:
+        for obj in self._iter_targets(context):
+            self._enable_one(obj)
+        return {"FINISHED"}
+
+    def _finish_targets(self, context: bpy.types.Context) -> set[str]:
+        for obj in self._iter_targets(context):
+            self._finish_one(obj, context)
+        return {"FINISHED"}
+
+    def _cancel_targets(self, context: bpy.types.Context) -> set[str]:
+        for obj in self._iter_targets(context):
+            self._cancel_one(obj, context)
+        return {"FINISHED"}
+
+
+# --- Type-selection mixins (Cycle / Pick) ------------------------------------
+
+
+class TypeAccessorBase:
+    """Shared contract for operators that resolve and write a Literal type
+    attribute on a Bonsai PropertyGroup.
+
+    Subclasses define ``element_checker``, ``props_getter``, ``type_literal``,
+    ``type_attr``; ``skip_element_check`` bypasses element validation. Concrete
+    subclasses (``CycleTypeMixin``, ``PickTypeMixin``) add the interaction
+    shape on top.
+
+    Test doubles must be set on the operator instance — the predicates are
+    bound at class-definition time, so patching the underlying tool module
+    has no effect."""
+
+    element_checker: Callable[[entity_instance], bool]
+    props_getter: Callable[[bpy.types.Object], bpy.types.PropertyGroup]
+    type_literal: type
+    type_attr: str
+    skip_element_check: bool = False
+
+    def _resolve_target(self, context: bpy.types.Context) -> bpy.types.Object | None:
+        """Return the active object iff it passes ``element_checker`` (or the
+        check is skipped). ``None`` signals the operator should bail with
+        ``{'CANCELLED'}``."""
+        obj = context.active_object
+        if not obj:
+            return None
+        if not self.skip_element_check:
+            element = tool.Ifc.get_entity(obj)
+            if not element or not self.element_checker(element):
+                return None
+        return obj
+
+
+class CycleTypeMixin(TypeAccessorBase):
+    """Operator mixin that cycles through ``type_literal``'s values.
+
+    Shift-click reverses direction."""
+
+    reverse: bpy.props.BoolProperty(name="Reverse", default=False, options={"HIDDEN", "SKIP_SAVE"})
+
+    def invoke(self, context: bpy.types.Context, event: bpy.types.Event) -> set[str]:
+        self.reverse = event.shift
+        return self.execute(context)
+
+    def _cycle_type(self, context: bpy.types.Context) -> set[str]:
+        obj = self._resolve_target(context)
+        if obj is None:
+            return {"CANCELLED"}
+
+        props = self.props_getter(obj)
+        types = get_args(self.type_literal)
+        current = getattr(props, self.type_attr)
+        idx = types.index(current) if current in types else 0
+        direction = -1 if self.reverse else 1
+        setattr(props, self.type_attr, types[(idx + direction) % len(types)])
+
+        return {"FINISHED"}
+
+
+class PickTypeMixin(TypeAccessorBase):
+    """Operator mixin that opens a popup menu listing ``type_literal``'s values.
+
+    Empty ``value`` ⇒ ``invoke`` opens the popup; non-empty ⇒ the user picked
+    an item and ``_pick_type`` applies it.
+
+    When invoked mid-click (e.g. from a gizmo's ``target_set_operator``), the
+    menu opens only after the originating ``LEFTMOUSE`` releases. Otherwise
+    the still-pressed click flows straight into Blender's drag-through-pick
+    gesture and the menu commits whichever item the cursor drifts over on
+    release. Other invocation paths (command-palette / F3, EXEC_DEFAULT, F6
+    redo) bypass the wait and open the menu immediately.
+
+    The ``value`` StringProperty is declared on this mixin but registered via
+    the concrete Operator subclass's MRO scan — do not instantiate the mixin
+    standalone."""
+
+    # Carries the picked value through invoke→execute; empty default
+    # distinguishes "open popup" from "apply".
+    value: bpy.props.StringProperty(default="", options={"HIDDEN", "SKIP_SAVE"})
+
+    def invoke(self, context: bpy.types.Context, event: bpy.types.Event) -> set[str]:
+        """Open the picker menu, or apply a value that was preset by a
+        menu-item click.
+
+        Routing through ``execute()`` keeps subclass IFC-transaction wrapping
+        in the loop and means F6 redo / ``EXEC_DEFAULT`` reach the apply path."""
+        if self.value:
+            return self.execute(context)
+
+        if self._resolve_target(context) is None:
+            return {"CANCELLED"}
+
+        if event.value == "PRESS":
+            context.window_manager.modal_handler_add(self)
+            return {"RUNNING_MODAL"}
+        return self._open_picker(context)
+
+    def modal(self, context: bpy.types.Context, event: bpy.types.Event) -> set[str]:
+        if event.type == "LEFTMOUSE" and event.value == "RELEASE":
+            self._open_picker(context)
+            # INTERFACE does not remove a modal handler; only FINISHED /
+            # CANCELLED do.
+            return {"CANCELLED"}
+        if event.type in {"RIGHTMOUSE", "ESC"}:
+            return {"CANCELLED"}
+        return {"RUNNING_MODAL"}
+
+    def _open_picker(self, context: bpy.types.Context) -> set[str]:
+        bl_idname = self.bl_idname
+        values = list(get_args(self.type_literal))
+
+        def draw(menu_self, _menu_context):
+            layout = menu_self.layout
+            for v in values:
+                op = layout.operator(bl_idname, text=v)
+                op.value = v
+
+        context.window_manager.popup_menu(draw, title=self.bl_label, icon="MENU_PANEL")
+        # The type change is a two-step interaction: this invocation just OPENS
+        # the menu (no state change yet); a SECOND invocation fires when the
+        # user clicks a menu item — that one writes ``props.<type_attr>`` and
+        # returns FINISHED. By returning INTERFACE here (and not FINISHED), the
+        # menu-open step is excluded from Blender's undo stack so the user
+        # gets exactly ONE undo entry per type change. If we returned FINISHED
+        # here too, the stack would gain a no-op "opened the menu" entry that
+        # Ctrl+Z would dismiss before reverting the actual type change —
+        # confusing UX where the first Ctrl+Z appears to do nothing.
+        return {"INTERFACE"}
+
+    def _pick_type(self, context: bpy.types.Context) -> set[str]:
+        if not self.value:
+            # No-op rather than re-open the menu, so command-palette misuse
+            # doesn't infinite-loop.
+            return {"CANCELLED"}
+
+        obj = self._resolve_target(context)
+        if obj is None:
+            return {"CANCELLED"}
+
+        if self.value not in get_args(self.type_literal):
+            self.report({"WARNING"}, f"Unknown {self.type_attr}: {self.value!r}")
+            return {"CANCELLED"}
+
+        props = self.props_getter(obj)
+        setattr(props, self.type_attr, self.value)
+        return {"FINISHED"}
+
+
+class IntegerInputDialogMixin:
+    """Operator mixin that mirrors a per-feature ``IntProperty`` on the
+    operator into a draft attribute on the active object's parametric props,
+    via Blender's ``invoke_props_dialog`` popup.
+
+    Subclasses declare:
+
+    - ``attr_name`` — name of the IntProperty on the subclass AND of the
+      attribute on the resolved props (same name on both sides).
+    - ``props_getter`` — ``staticmethod(tool.Model.get_<feature>_props)``.
+    - ``requires_editing`` — True iff the operator must no-op outside an
+      active edit lifecycle. Default False.
+    - ``value_min`` — minimum value to clamp to. Default 1."""
+
+    attr_name: ClassVar[str] = ""
+    props_getter: ClassVar[Callable[[bpy.types.Object], bpy.types.PropertyGroup]]
+    requires_editing: ClassVar[bool] = False
+    value_min: ClassVar[int] = 1
+
+    def _resolve_props(self, context: bpy.types.Context) -> bpy.types.PropertyGroup | None:
+        """Return the active object's parametric props if the operator is
+        allowed to fire, ``None`` otherwise (caller bails with ``CANCELLED``)."""
+        obj = context.active_object
+        if not obj:
+            return None
+        props = self.props_getter(obj)
+        if self.requires_editing and not props.is_editing:
+            return None
+        return props
+
+    def invoke(self, context: bpy.types.Context, event: bpy.types.Event) -> set[str]:  # noqa: ARG002
+        props = self._resolve_props(context)
+        if props is None:
+            return {"CANCELLED"}
+        setattr(self, self.attr_name, max(self.value_min, getattr(props, self.attr_name)))
+        return context.window_manager.invoke_props_dialog(self)
+
+    def execute(self, context: bpy.types.Context) -> set[str]:
+        props = self._resolve_props(context)
+        if props is None:
+            return {"CANCELLED"}
+        setattr(props, self.attr_name, max(self.value_min, getattr(self, self.attr_name)))
+        return {"FINISHED"}
+
+
+# --- Undo-resync registry ----------------------------------------------------
+#
+# Per-type regenerators called from ``resync_parametric_drafts_after_undo``
+# (wired into ``bim/handler.py:undo_post`` and ``redo_post``) so the preview
+# mesh of an in-progress parametric draft repaints after Ctrl+Z / Ctrl+Shift+Z.
+#
+# Each regenerator is a one-line lazy-import + call. Lazy imports because
+# ``bonsai.bim.parametric_lifecycle`` loads before ``bim/module/model/*``
+# at addon enable; a module-level import would cycle. Each function-local
+# import lands at first call, after the feature module has registered.
+#
+# Types with no entry — door, window, railing, etc. — are IFC-derived: undo
+# of an IFC mutation already restores the entity, and ``switch_representation``
+# repaints the mesh as a side effect of the next refresh. They don't need a
+# bespoke preview regenerator.
+
+
+def _wall_undo_regenerator(obj: bpy.types.Object) -> None:
+    from bonsai.bim.module.model.wall import regenerate_wall_mesh_from_props
+
+    regenerate_wall_mesh_from_props(obj)
+
+
+def _stair_undo_regenerator(obj: bpy.types.Object) -> None:
+    from bonsai.bim.module.model.stair import regenerate_stair_mesh
+
+    regenerate_stair_mesh(obj)
+
+
+def _roof_undo_regenerator(obj: bpy.types.Object) -> None:
+    from bonsai.bim.module.model.roof import update_roof_modifier_bmesh
+
+    update_roof_modifier_bmesh(obj)
+
+
+UNDO_REGENERATORS: dict[str, Callable[[bpy.types.Object], None]] = {
+    "wall": _wall_undo_regenerator,
+    "stair": _stair_undo_regenerator,
+    "roof": _roof_undo_regenerator,
+}
+
+
+def resync_parametric_drafts_after_undo() -> None:
+    """Re-render preview meshes for every parametric draft currently active.
+
+    Walks all objects, skips any not in a registered parametric edit,
+    dispatches to the per-type regenerator in ``UNDO_REGENERATORS``. A type
+    without an entry is left alone — its preview is either already correct
+    (IFC-derived) or has no draft preview mesh."""
+    for obj in bpy.data.objects:
+        feature = tool.Parametric.is_object_editing(obj)
+        if feature is None:
+            continue
+        regenerator = UNDO_REGENERATORS.get(feature.name)
+        if regenerator is None:
+            continue
+        regenerator(obj)
+    tool.Blender.update_all_viewports()
+
+
+@persistent
+def _resync_on_undo(scene: bpy.types.Scene) -> None:
+    resync_parametric_drafts_after_undo()
+
+
+def install_parametric_lifecycle_handlers() -> None:
+    """Append the undo-resync callback to undo_post and redo_post; idempotent.
+
+    Caller must invoke this AFTER appending the central undo/redo handlers so
+    regenerators see restored IFC state — bpy.app.handlers fire in append order."""
+    for hook in (bpy.app.handlers.undo_post, bpy.app.handlers.redo_post):
+        if _resync_on_undo not in hook:
+            hook.append(_resync_on_undo)
+
+
+def uninstall_parametric_lifecycle_handlers() -> None:
+    for hook in (bpy.app.handlers.undo_post, bpy.app.handlers.redo_post):
+        try:
+            hook.remove(_resync_on_undo)
+        except ValueError:
+            pass

src/bonsai/bonsai/bim/ui.py

@@ -15,6 +15,8 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 import os
 import platform
@@ -37,21 +39,10 @@ from natsort import natsorted
 import bonsai.bim
 import bonsai.bim.helper
 import bonsai.tool as tool
+from bonsai.bim.ifc import is_cache_locked_by_other_process
 from bonsai.bim.module.bsdd.prop import BIMBSDDProperties, BSDDProperty
-from bonsai.bim.module.model.prop import (
-    BIMDoorProperties,
-    BIMRailingProperties,
-    BIMRoofProperties,
-    BIMStairProperties,
-    BIMWindowProperties,
-)
-from bonsai.bim.module.model.ui import (
-    draw_door_properties,
-    draw_railing_properties,
-    draw_roof_properties,
-    draw_stair_properties,
-    draw_window_properties,
-)
+from bonsai.bim.module.model import prop as _model_prop
+from bonsai.bim.module.model import ui as _model_ui
 from bonsai.bim.module.pset.prop import IfcProperty
 from bonsai.bim.prop import Attribute
 
@@ -273,130 +264,32 @@ class BIM_UL_panel_visibilities(bpy.types.UIList):
         row.prop(item, "is_bookmarked", text="", icon="SOLO_ON" if item.is_bookmarked else "SOLO_OFF", emboss=False)
 
 
-class GizmoPreferencesDoor(bpy.types.PropertyGroup):
-    """Property group for door gizmo visibility settings."""
-
-    overall_height: BoolProperty(name="Overall Height", default=True)
-    overall_width: BoolProperty(name="Overall Width", default=True)
-    threshold_thickness: BoolProperty(name="Threshold Thickness", default=True)
-    threshold_depth: BoolProperty(name="Threshold Depth", default=True)
-    threshold_offset: BoolProperty(name="Threshold Offset", default=True)
-    lining_offset: BoolProperty(name="Lining Offset", default=True)
-    lining_depth: BoolProperty(name="Lining Depth", default=True)
-    lining_thickness: BoolProperty(name="Lining Thickness", default=True)
-    transom_offset: BoolProperty(name="Transom Offset", default=True)
-    transom_thickness: BoolProperty(name="Transom Thickness", default=True)
-    casing_thickness: BoolProperty(name="Casing Thickness", default=True)
-    casing_depth: BoolProperty(name="Casing Depth", default=True)
-    swing_arc: BoolProperty(name="Swing Arc", default=True, description="Show door swing direction arc")
-    flip_arc: BoolProperty(name="Flip Arc", default=True, description="Show flip door orientation arc")
-
-    if TYPE_CHECKING:
-        overall_height: bool
-        overall_width: bool
-        threshold_thickness: bool
-        threshold_depth: bool
-        threshold_offset: bool
-        lining_offset: bool
-        lining_depth: bool
-        lining_thickness: bool
-        transom_offset: bool
-        transom_thickness: bool
-        casing_thickness: bool
-        casing_depth: bool
-        swing_arc: bool
-        flip_arc: bool
-
-
-class GizmoPreferencesWindow(bpy.types.PropertyGroup):
-    """Property group for window gizmo visibility settings."""
-
-    overall_height: BoolProperty(name="Overall Height", default=True)
-    overall_width: BoolProperty(name="Overall Width", default=True)
-    lining_offset: BoolProperty(name="Lining Offset", default=True)
-    lining_depth: BoolProperty(name="Lining Depth", default=True)
-    lining_thickness: BoolProperty(name="Lining Thickness", default=True)
-    lining_to_panel_offset_x: BoolProperty(name="Lining to Panel Offset X", default=True)
-    lining_to_panel_offset_y: BoolProperty(name="Lining to Panel Offset Y", default=True)
-    frame_depth: BoolProperty(name="Frame Depth", default=True)
-    frame_thickness: BoolProperty(name="Frame Thickness", default=True)
-    mullion_thickness: BoolProperty(name="Mullion Thickness", default=True)
-    first_mullion_offset: BoolProperty(name="First Mullion Offset", default=True)
-    second_mullion_offset: BoolProperty(name="Second Mullion Offset", default=True)
-    transom_thickness: BoolProperty(name="Transom Thickness", default=True)
-    first_transom_offset: BoolProperty(name="First Transom Offset", default=True)
-    second_transom_offset: BoolProperty(name="Second Transom Offset", default=True)
-
-    if TYPE_CHECKING:
-        overall_height: bool
-        overall_width: bool
-        lining_offset: bool
-        lining_depth: bool
-        lining_thickness: bool
-        lining_to_panel_offset_x: bool
-        lining_to_panel_offset_y: bool
-        frame_depth: bool
-        frame_thickness: bool
-        mullion_thickness: bool
-        first_mullion_offset: bool
-        second_mullion_offset: bool
-        transom_thickness: bool
-        first_transom_offset: bool
-        second_transom_offset: bool
-
-
-class GizmoPreferencesStair(bpy.types.PropertyGroup):
-    """Property group for stair gizmo visibility settings."""
-
-    width: BoolProperty(name="Width", default=True)
-    height: BoolProperty(name="Height", default=True)
-    tread_run: BoolProperty(name="Tread Run", default=True)
-    tread_depth: BoolProperty(name="Tread Depth", default=True)
-    riser_height: BoolProperty(name="Riser Height", default=True)
-    nosing_length: BoolProperty(name="Nosing Length", default=True)
-    nosing_depth: BoolProperty(name="Nosing Depth", default=True)
-    total_length_target: BoolProperty(name="Total Length Target", default=True)
-    base_slab_depth: BoolProperty(name="Base Slab Depth", default=True)
-    top_slab_depth: BoolProperty(name="Top Slab Depth", default=True)
-    lock: BoolProperty(name="Total Length Lock", default=True)
-    plus: BoolProperty(name="Add Tread (+)", default=True)
-    minus: BoolProperty(name="Remove Tread (-)", default=True)
-    cycle: BoolProperty(name="Cycle Stair Type", default=True)
-
-    if TYPE_CHECKING:
-        width: bool
-        height: bool
-        tread_run: bool
-        tread_depth: bool
-        riser_height: bool
-        nosing_length: bool
-        nosing_depth: bool
-        total_length_target: bool
-        base_slab_depth: bool
-        top_slab_depth: bool
-        lock: bool
-        plus: bool
-        minus: bool
-        cycle: bool
-
-
 class GizmoPreferences(bpy.types.PropertyGroup):
-    """Property group for all gizmo visibility settings."""
+    """Aggregator for parametric gizmo visibility settings. One flat bool per
+    parametric feature; controls whether that feature's gizmo group polls
+    visible in the viewport.
+
+    The per-feature ``<name>: BoolProperty`` fields are derived from
+    ``tool.Parametric.EDIT_TYPES`` at module load — adding a new parametric
+    type to the registry automatically surfaces its toggle here, with no
+    parallel hand-maintained list to keep in sync."""
 
     draw_gizmos_in_3d_viewport: BoolProperty(
         name="Draw Gizmos In 3D Viewport",
         default=True,
         description="Show interactive gizmos in the 3D viewport for parametric elements",
     )
-    door: bpy.props.PointerProperty(type=GizmoPreferencesDoor)
-    window: bpy.props.PointerProperty(type=GizmoPreferencesWindow)
-    stair: bpy.props.PointerProperty(type=GizmoPreferencesStair)
 
     if TYPE_CHECKING:
         draw_gizmos_in_3d_viewport: bool
-        door: GizmoPreferencesDoor
-        window: GizmoPreferencesWindow
-        stair: GizmoPreferencesStair
+
+
+for _gizmo_pref_entry in tool.Parametric.EDIT_TYPES:
+    GizmoPreferences.__annotations__[_gizmo_pref_entry.name] = BoolProperty(
+        name=_gizmo_pref_entry.name.replace("_", " ").title(),
+        default=True,
+    )
+del _gizmo_pref_entry
 
 
 class DocPreferences(bpy.types.PropertyGroup):
@@ -492,11 +385,22 @@ class DocPreferences(bpy.types.PropertyGroup):
 
 
 class DefaultParameters(bpy.types.PropertyGroup):
-    door: bpy.props.PointerProperty(type=BIMDoorProperties)
-    window: bpy.props.PointerProperty(type=BIMWindowProperties)
-    railing: bpy.props.PointerProperty(type=BIMRailingProperties)
-    roof: bpy.props.PointerProperty(type=BIMRoofProperties)
-    stair: bpy.props.PointerProperty(type=BIMStairProperties)
+    """Per-type preset values used to seed new parametric instances.
+
+    The ``<name>: PointerProperty`` fields are derived from the subset of
+    ``tool.Parametric.EDIT_TYPES`` flagged ``has_default_parameters=True``,
+    each pointing at the matching ``BIM<Name>Properties`` class. Adding a
+    new entry with that flag automatically surfaces a preferences section
+    and gives the create operator a preset to copy from."""
+
+
+for _default_params_entry in tool.Parametric.EDIT_TYPES:
+    if not _default_params_entry.has_default_parameters:
+        continue
+    DefaultParameters.__annotations__[_default_params_entry.name] = bpy.props.PointerProperty(
+        type=getattr(_model_prop, _default_params_entry.props_attr),
+    )
+del _default_params_entry
 
 
 class BIM_ADDON_preferences(bpy.types.AddonPreferences):
@@ -608,6 +512,15 @@ class BIM_ADDON_preferences(bpy.types.AddonPreferences):
         size=4,
         description="Color of not selected verts/edges (used in profile editing mode)",
     )
+    clip_box_cap_color: bpy.props.FloatVectorProperty(
+        name="Clip Box Caps Color",
+        subtype="COLOR",
+        default=(0.0, 0.0, 0.0, 1.0),
+        min=0.0,
+        max=1.0,
+        size=4,
+        description="Fill color of clip-box cross-section caps",
+    )
     decorator_color_special: bpy.props.FloatVectorProperty(
         name="Special Elements Color",
         subtype="COLOR",
@@ -844,54 +757,13 @@ class BIM_ADDON_preferences(bpy.types.AddonPreferences):
             )
 
     def draw_gizmo_parameters(self, layout: bpy.types.UILayout, context: bpy.types.Context) -> None:
+        """Render one enabled-toggle per parametric feature."""
         layout.label(text="Toggle visibility of gizmos in editing mode")
         box = layout.box()
-        bonsai.bim.helper.draw_expandable_panel(box, context, "Parametric Door", self.draw_door_gizmo_parameters)
-        bonsai.bim.helper.draw_expandable_panel(box, context, "Parametric Window", self.draw_window_gizmo_parameters)
-        bonsai.bim.helper.draw_expandable_panel(box, context, "Parametric Stair", self.draw_stair_gizmo_parameters)
-
-    def draw_door_gizmo_parameters(self, layout: bpy.types.UILayout, context: bpy.types.Context) -> None:
-        from bonsai.bim.module.model.door import GizmoDoorEdition
-
-        door_gizmos = self.gizmos.door
-        gizmo_prop_names = {p.attr_name for p in GizmoDoorEdition.dimension_gizmo_props}
-        # Add special gizmos not in dimension_gizmo_props
-        gizmo_prop_names.update(("swing_arc", "flip_arc"))
-        try:
-            annotations = door_gizmos.__annotations__
-        except AttributeError:
-            annotations = type(door_gizmos).__annotations__
-        for prop in annotations:
-            if prop in gizmo_prop_names:
-                layout.prop(door_gizmos, prop)
-
-    def draw_window_gizmo_parameters(self, layout: bpy.types.UILayout, context: bpy.types.Context) -> None:
-        from bonsai.bim.module.model.window import GizmoWindowEdition
-
-        window_gizmos = self.gizmos.window
-        gizmo_prop_names = {p.attr_name for p in GizmoWindowEdition.dimension_gizmo_props}
-        try:
-            annotations = window_gizmos.__annotations__
-        except AttributeError:
-            annotations = type(window_gizmos).__annotations__
-        for prop in annotations:
-            if prop in gizmo_prop_names:
-                layout.prop(window_gizmos, prop)
-
-    def draw_stair_gizmo_parameters(self, layout: bpy.types.UILayout, context: bpy.types.Context) -> None:
-        from bonsai.bim.module.model.stair import GizmoStairEdition
-
-        stair_gizmos = self.gizmos.stair
-        gizmo_prop_names = {p.attr_name for p in GizmoStairEdition.dimension_gizmo_props}
-        # Add special gizmos not in dimension_gizmo_props
-        special_gizmo_names = {"lock", "plus", "minus", "cycle"}
-        try:
-            annotations = stair_gizmos.__annotations__
-        except AttributeError:
-            annotations = type(stair_gizmos).__annotations__
-        for prop in annotations:
-            if prop in gizmo_prop_names or prop in special_gizmo_names:
-                layout.prop(stair_gizmos, prop)
+        annotations = type(self.gizmos).__annotations__
+        for feature in tool.Parametric.EDIT_TYPES:
+            if feature.name in annotations:
+                box.prop(self.gizmos, feature.name)
 
     def draw_model_settings(self, layout: bpy.types.UILayout, context: bpy.types.Context) -> None:
         layout.prop(self, "occurrence_name_style")
@@ -938,39 +810,29 @@ class BIM_ADDON_preferences(bpy.types.AddonPreferences):
         layout.row().prop(self, "decorator_color_special")
         layout.row().prop(self, "decorator_color_error")
         layout.row().prop(self, "decorator_color_background")
+        bonsai.bim.helper.draw_expandable_panel(
+            layout,
+            context,
+            "Clip Box",
+            self.draw_clip_box_colors,
+        )
+
+    def draw_clip_box_colors(self, layout: bpy.types.UILayout, context: bpy.types.Context) -> None:
+        layout.row().prop(self, "clip_box_cap_color")
 
     def draw_default_parameters(self, layout: bpy.types.UILayout, context: bpy.types.Context) -> None:
         box = layout.box()
-        bonsai.bim.helper.draw_expandable_panel(
-            box,
-            context,
-            "Door",
-            lambda _layout, _context: draw_door_properties(_layout, self.default_parameters.door),
-        )
-        bonsai.bim.helper.draw_expandable_panel(
-            box,
-            context,
-            "Window",
-            lambda _layout, _context: draw_window_properties(_layout, self.default_parameters.window),
-        )
-        bonsai.bim.helper.draw_expandable_panel(
-            box,
-            context,
-            "Railing",
-            lambda _layout, _context: draw_railing_properties(_layout, self.default_parameters.railing),
-        )
-        bonsai.bim.helper.draw_expandable_panel(
-            box,
-            context,
-            "Roof",
-            lambda _layout, _context: draw_roof_properties(_layout, self.default_parameters.roof),
-        )
-        bonsai.bim.helper.draw_expandable_panel(
-            box,
-            context,
-            "Stair",
-            lambda _layout, _context: draw_stair_properties(_layout, self.default_parameters.stair),
-        )
+        for entry in tool.Parametric.EDIT_TYPES:
+            if not entry.has_default_parameters:
+                continue
+            props = getattr(self.default_parameters, entry.name)
+            draw_props = getattr(_model_ui, f"draw_{entry.name}_properties")
+            bonsai.bim.helper.draw_expandable_panel(
+                box,
+                context,
+                entry.name.replace("_", " ").title(),
+                lambda _layout, _context, _draw=draw_props, _props=props: _draw(_layout, _props),
+            )
 
     def draw_other_settings(self, layout: bpy.types.UILayout, context: bpy.types.Context) -> None:
         layout.prop(self, "opening_focus_opacity")
@@ -1088,6 +950,50 @@ class BIM_PT_tabs(Panel):
             op.uri = "https://docs.bonsaibim.org/guides/troubleshooting.html#saving-and-loading-blend-files"
             row.operator("bim.close_blend_warning", text="", icon="CANCEL")
 
+        if is_cache_locked_by_other_process():
+            box = self.layout.box()
+            box.alert = True
+            row = box.row(align=True)
+            row.label(text="IFC Already Open in Another Blender Instance", icon="ERROR")
+            row.operator("bim.dismiss_multi_instance_warning", text="", icon="CANCEL")
+            draw_multiline_text(
+                box.column(align=True),
+                "This file is open in another Blender instance. Editing the same "
+                "IFC from two instances at once can lose your work or display "
+                "outdated geometry. Close the other Blender instances to continue safely.",
+                context=context,
+            )
+
+        pprops = tool.Project.get_project_props()
+        if pending := pprops.pending_opening_recut:
+            box = self.layout.box()
+            box.alert = True
+            box.label(text="Opening Cuts Skipped", icon="ERROR")
+            draw_multiline_text(
+                box.column(align=True),
+                f"{len(pending)} element(s) had too many openings to cut during load. "
+                f"Apply to recompute their meshes, or dismiss to leave them as they are.",
+                context=context,
+            )
+            row = box.row(align=True)
+            row.operator("bim.select_pending_opening_cuts", text="Select Elements", icon="RESTRICT_SELECT_OFF")
+            row.operator("bim.apply_pending_opening_cuts", text="Apply Openings", icon="PLAY")
+            row.operator("bim.dismiss_pending_opening_cuts", text="", icon="CANCEL")
+
+        if pending := pprops.pending_array_repair:
+            box = self.layout.box()
+            box.alert = True
+            box.label(text="Arrays With Missing Children", icon="ERROR")
+            draw_multiline_text(
+                box.column(align=True),
+                f"{len(pending)} array parent(s) reference child GUIDs that don't exist in this file. "
+                f"The arrays loaded incomplete. Select to inspect, or dismiss.",
+                context=context,
+            )
+            row = box.row(align=True)
+            row.operator("bim.select_pending_array_repair", text="Select Elements", icon="RESTRICT_SELECT_OFF")
+            row.operator("bim.dismiss_pending_array_repair", text="", icon="CANCEL")
+
         gprops = tool.Geometry.get_geometry_props()
         # Check that Blender mode and IFC Mode do match.
         if context.mode == "OBJECT" and gprops.mode in ("OBJECT", "ITEM"):
@@ -2039,6 +1945,7 @@ class BIM_PT_decorators_overlay(Panel):
         aggregate_props = tool.Aggregate.get_aggregate_props()
         nest_props = tool.Nest.get_nest_props()
         model_props = tool.Model.get_model_props()
+        system_props = tool.System.get_system_props()
         display_all = overlay.show_overlays
 
         col = layout.column()
@@ -2056,10 +1963,20 @@ class BIM_PT_decorators_overlay(Panel):
         row = col.row(align=True)
         row.prop(model_props, "show_slab_direction", text="Slab Direction")
         row = col.row(align=True)
+        row.prop(model_props, "show_paths", text="Element Paths")
+        row.prop(system_props, "should_draw_decorations", text="System Decorations")
+        row = col.row(align=True)
         row.prop(model_props, "show_bounding_box", text="Bounding Box Dimensions")
         row = col.row(align=True)
         row.prop(model_props, "show_cut_decorator", text="Cut Decorator")
         row.prop(model_props, "show_cut_decorator_fill", text="Fill Cut Decorator")
+        clip_box_props = tool.ClipBox.get_scene_props(context.scene)
+        row = col.row(align=True)
+        # Grey out the toggles when there is no clip box to act on, so the
+        # user can see the controls but can't flip a switch that does nothing.
+        row.enabled = bool(clip_box_props.clip_boxes)
+        row.prop(clip_box_props, "enabled", text="Enable Clipping")
+        row.prop(clip_box_props, "show_caps", text="Show Caps")
 
 
 class BIM_PT_snappping(Panel):

src/bonsai/bonsai/core/aggregate.py

@@ -93,6 +93,8 @@ def enter_aggregate_mode(
     aggregator: type[tool.Aggregate],
     obj: bpy.types.Object,
 ):
+    if not aggregator.get_aggregate_props().in_aggregate_mode:
+        aggregator.save_previous_selection()
     aggregator.update_previous_aggregate_mode_state()
     if aggregator.get_higher_aggregate():
         aggregator.disable_aggregate_mode()
@@ -107,6 +109,7 @@ def exit_aggregate_mode(aggregator: type[tool.Aggregate]):
         aggregator.enable_aggregate_mode(new_obj)
     else:
         aggregator.disable_aggregate_mode()
+        aggregator.restore_previous_selection()
 
 
 class IncompatibleAggregateError(Exception):

src/bonsai/bonsai/core/connection.py

@@ -0,0 +1,113 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+"""Shared post-disconnect cleanup dispatch.
+
+Used by both ``bim.disconnect_elements`` (explicit user disconnect) and the
+connection cascade in ``tool.Geometry.delete_ifc_object`` (implicit
+disconnect-on-delete). Each kind returned by
+:py:meth:`bonsai.tool.connection.Connection.find_rels` /
+:py:meth:`find_rels_for_element` maps to a single arm here, so adding a new
+kind means extending one dispatch table — both call sites benefit
+automatically and the AST forward-compat guard enforces coverage.
+
+The ``subject`` parameter is the entity whose teardown effects the
+disconnect: for ``"path"`` / ``"element"`` / ``"element-top"`` kinds it
+carries an ``IfcRel*`` relationship entity (the rel that gets removed);
+for ``"mep-pair-fitting"`` it carries an ``IfcFlowFitting`` (the fitting
+that gets deleted). The slot is uniform on intent — the dispatch decides
+the teardown mechanism by kind.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import bonsai.core.geometry
+from bonsai.core.model import regenerate_wall_to_underside
+
+if TYPE_CHECKING:
+    import ifcopenshell
+
+    import bonsai.tool as tool
+
+
+def disconnect_rel(
+    ifc: type[tool.Ifc],
+    geometry: type[tool.Geometry],
+    model: type[tool.Model],
+    connection: type[tool.Connection],
+    subject: ifcopenshell.entity_instance,
+    kind: str,
+    elem: ifcopenshell.entity_instance,
+    partner: ifcopenshell.entity_instance,
+    skip_elem_recreate: bool = False,
+    skip_partner_recreate: bool = False,
+) -> None:
+    """Run the post-disconnect cleanup for one connection.
+
+    ``elem`` and ``partner`` are the two endpoints. The ``skip_*_recreate``
+    flags suppress per-side regenerate / recreate work — used by the
+    cascade-on-delete to avoid re-extruding entities that are about to be
+    removed by ``remove_product``. For the disconnect operator (where neither
+    endpoint is being deleted), both flags stay False and the full cleanup
+    runs on both sides.
+    """
+    if kind == "path":
+        bonsai.core.geometry.remove_connection(geometry, connection=subject)
+        if not skip_elem_recreate:
+            elem_obj = ifc.get_object(elem)
+            if elem_obj is not None:
+                model.recreate_wall(elem, elem_obj)
+        if not skip_partner_recreate:
+            partner_obj = ifc.get_object(partner)
+            if partner_obj is not None:
+                model.recreate_wall(partner, partner_obj)
+    elif kind == "element-top":
+        wall, _slab = connection.orient_element_top(subject, elem, partner)
+        ifc.run(
+            "geometry.disconnect_element",
+            relating_element=subject.RelatingElement,
+            related_element=subject.RelatedElement,
+        )
+        # Skip the wall-side regenerate when the wall is itself being deleted —
+        # either it's the elem of this cascade pass, or it's the partner that
+        # was queued earlier in the same batch.
+        if (wall is elem and skip_elem_recreate) or (wall is partner and skip_partner_recreate):
+            return
+        wall_obj = ifc.get_object(wall)
+        if wall_obj is not None:
+            regenerate_wall_to_underside(ifc, geometry, model, [wall_obj])
+    elif kind == "element":
+        ifc.run(
+            "geometry.disconnect_element",
+            relating_element=subject.RelatingElement,
+            related_element=subject.RelatedElement,
+        )
+    elif kind == "mep-pair-fitting":
+        if skip_elem_recreate and subject is elem:
+            return
+        if skip_partner_recreate and subject is partner:
+            return
+        fitting_obj = ifc.get_object(subject)
+        if fitting_obj is not None:
+            geometry.delete_ifc_object(fitting_obj)
+    else:
+        raise ValueError(f"Unknown kind: {kind!r}")

src/bonsai/bonsai/core/drawing.py

@@ -302,9 +302,25 @@ def add_drawing(
         context=drawing.get_body_context(),
         ifc_representation_class=None,
     )
+
+    drawings_parent_group = None
+    for group in ifc.get().by_type("IfcGroup"):
+        if group.Name == "DRAWINGS" and group.ObjectType == "DRAWINGS":
+            drawings_parent_group = group
+            break
+
+    if not drawings_parent_group:
+        drawings_parent_group = ifc.run("group.add_group")
+        ifc.run(
+            "group.edit_group", group=drawings_parent_group, attributes={"Name": "DRAWINGS", "ObjectType": "DRAWINGS"}
+        )
+
     group = ifc.run("group.add_group")
     ifc.run("group.edit_group", group=group, attributes={"Name": drawing_name, "ObjectType": "DRAWING"})
     ifc.run("group.assign_group", group=group, products=[element])
+
+    ifc.run("group.assign_group", group=drawings_parent_group, products=[group])
+
     collector.assign(camera)
     pset = ifc.run("pset.add_pset", product=element, name="EPset_Drawing")
     if drawing.get_unit_system() == "METRIC":
@@ -335,7 +351,22 @@ def add_drawing(
         },
     )
     drawing.setup_shading_styles_path(shading_styles_path)
-    information = ifc.run("document.add_information")
+
+    drawings_parent_document = None
+    for document in ifc.get().by_type("IfcDocumentInformation"):
+        if document.Name == "DRAWINGS" and document.Scope == "DRAWINGS":
+            drawings_parent_document = document
+            break
+
+    if not drawings_parent_document:
+        drawings_parent_document = ifc.run("document.add_information")
+        if ifc.get_schema() == "IFC2X3":
+            attributes = {"DocumentId": "DRAWINGS", "Name": "DRAWINGS", "Scope": "DRAWINGS"}
+        else:
+            attributes = {"Identification": "DRAWINGS", "Name": "DRAWINGS", "Scope": "DRAWINGS"}
+        ifc.run("document.edit_information", information=drawings_parent_document, attributes=attributes)
+
+    information = ifc.run("document.add_information", parent=drawings_parent_document)
     uri = drawing.get_default_drawing_path(drawing_name)
     reference = ifc.run("document.add_reference", information=information)
     if ifc.get_schema() == "IFC2X3":
@@ -363,9 +394,23 @@ def duplicate_drawing(
     drawing_tool.set_name(new_drawing, drawing_name)
     group = drawing_tool.get_drawing_group(new_drawing)
     ifc.run("group.unassign_group", group=group, products=[new_drawing])
+
+    drawings_parent_group = None
+    for parent_group in ifc.get().by_type("IfcGroup"):
+        if parent_group.Name == "DRAWINGS" and parent_group.ObjectType == "DRAWINGS":
+            drawings_parent_group = parent_group
+            break
+
+    if not drawings_parent_group:
+        drawings_parent_group = ifc.run("group.add_group")
+        ifc.run(
+            "group.edit_group", group=drawings_parent_group, attributes={"Name": "DRAWINGS", "ObjectType": "DRAWINGS"}
+        )
+
     new_group = ifc.run("group.add_group")
     ifc.run("group.edit_group", group=new_group, attributes={"Name": drawing_name, "ObjectType": "DRAWING"})
     ifc.run("group.assign_group", group=new_group, products=[new_drawing])
+    ifc.run("group.assign_group", group=drawings_parent_group, products=[new_group])
     if should_duplicate_annotations:
         new_annotations: list[ifcopenshell.entity_instance] = []
         annotation_objs = [ifc.get_object(a) for a in drawing_tool.get_group_elements(group) if a != drawing]
@@ -381,7 +426,21 @@ def duplicate_drawing(
     old_reference = drawing_tool.get_drawing_document(new_drawing)
     ifc.run("document.unassign_document", products=[new_drawing], document=old_reference)
 
-    information = ifc.run("document.add_information")
+    drawings_parent_document = None
+    for document in ifc.get().by_type("IfcDocumentInformation"):
+        if document.Name == "DRAWINGS" and document.Scope == "DRAWINGS":
+            drawings_parent_document = document
+            break
+
+    if not drawings_parent_document:
+        drawings_parent_document = ifc.run("document.add_information")
+        if ifc.get_schema() == "IFC2X3":
+            attributes = {"DocumentId": "DRAWINGS", "Name": "DRAWINGS", "Scope": "DRAWINGS"}
+        else:
+            attributes = {"Identification": "DRAWINGS", "Name": "DRAWINGS", "Scope": "DRAWINGS"}
+        ifc.run("document.edit_information", information=drawings_parent_document, attributes=attributes)
+
+    information = ifc.run("document.add_information", parent=drawings_parent_document)
     uri = drawing_tool.get_default_drawing_path(drawing_name)
     reference = ifc.run("document.add_reference", information=information)
     if ifc.get_schema() == "IFC2X3":
@@ -567,7 +626,8 @@ def sync_references(
 
     for reference_element in potential_reference_elements:
         if not drawing_tool.get_drawing_reference_annotation(drawing, reference_element):
-            if annotation := drawing_tool.generate_reference_annotation(drawing, reference_element, context):
+            annotation = drawing_tool.generate_reference_annotation(drawing, reference_element, context)
+            if annotation:
                 ifc.run("drawing.assign_product", relating_product=reference_element, related_object=annotation)
                 ifc.run("group.assign_group", group=group, products=[annotation])
                 collector.assign(ifc.get_object(annotation))

src/bonsai/bonsai/core/model.py

@@ -15,10 +15,13 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was modified with the assistance of an AI coding tool.
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, Literal, Optional
+import math
+from typing import TYPE_CHECKING, Any, Literal, Optional
 
 if TYPE_CHECKING:
     import bpy
@@ -31,6 +34,24 @@ if TYPE_CHECKING:
     OffsetType = Literal["CENTER", "EXTERIOR", "INTERIOR"]
 
 
+# Arc sample count for fillet preview polylines. 24 samples produces a visually
+# smooth arc at common viewport scales without bloating the GPU batch.
+FILLET_DEFAULT_ARC_RESOLUTION = 24
+# Dot-product floor for treating two wall-axis segments as parallel — below
+# this the projected intersection is too sensitive to floating-point noise
+# to be useful as a junction apex. Calibrated to ~2° from parallel.
+PARALLEL_DOT_THRESHOLD = 0.9994
+# Perpendicular distance (SI metres) under which two parallel wall axes are
+# considered to share the same infinite line. Calibrated to absorb sub-50mm
+# placement drift between authored-joined walls without merging genuinely
+# offset parallel walls.
+COLLINEAR_LINE_TOLERANCE = 0.05
+# Default proximity (SI metres) for classifying a layer offset against the
+# canonical EXTERIOR / CENTER / INTERIOR baselines. Tight enough that ordinary
+# millimetre-scale modelling intent always falls into the nearest baseline.
+BASELINE_OFFSET_TOLERANCE = 0.001
+
+
 def unjoin_walls(
     ifc: type[tool.Ifc],
     blender: type[tool.Blender],
@@ -140,23 +161,84 @@ def align_objects(
     model.align_objects(reference_obj, objs, align_type)
 
 
+def regenerate_wall_to_underside(
+    ifc: type[tool.Ifc],
+    geometry: type[tool.Geometry],
+    model: type[tool.Model],
+    wall_objs: list[bpy.types.Object],
+) -> None:
+    """Re-clip walls to their connected underside objects after the slab has moved.
+
+    When a wall has no remaining slab connections — the case reached after the
+    last TOP rel is severed (via disconnect or via cascade-on-slab-delete) — the
+    stale trim booleans are cleaned up so the wall reverts to its pre-clip
+    extrusion instead of holding orphan ``IfcBooleanResult`` items and a dead
+    ``BBIM_Boolean`` pset.
+    """
+    clipped_objs = []
+    reverted_objs = []
+    for obj in wall_objs:
+        wall = ifc.get_entity(obj)
+        slab_objs = model.get_connected_slab_objs(wall)
+        if not slab_objs:
+            model.remove_wall_to_underside_booleans(wall)
+            reverted_objs.append(obj)
+            continue
+        if ifc.is_moved(obj):
+            geometry.run_edit_object_placement(obj=obj)
+        # Sync each slab's Blender mesh to its current IFC representation before
+        # reading face geometry, so a changed profile is picked up correctly.
+        model.reload_body_representation(slab_objs)
+        model.remove_wall_to_underside_booleans(wall)
+        for slab_obj in slab_objs:
+            clip = model.get_slab_clipping_bmesh(slab_obj)
+            if clip:
+                model.clip_wall_to_slab(wall, clip)
+        clipped_objs.append(obj)
+    refresh_objs = clipped_objs + reverted_objs
+    if refresh_objs:
+        model.reload_body_representation(refresh_objs)
+
+
 def extend_wall_to_slab(
     ifc: type[tool.Ifc],
     geometry: type[tool.Geometry],
     model: type[tool.Model],
-    slab_obj: bpy.types.Object,
+    slab_objs: list[bpy.types.Object],
     wall_objs: list[bpy.types.Object],
 ) -> None:
-    if not (clip := model.get_slab_clipping_bmesh(slab_obj)):
-        return  # Nothing to clip?
-    slab = ifc.get_entity(slab_obj)
+    # If any wall is currently in item mode, exit it before modifying the
+    # representation. Leaving stale item objects around causes delete_ifc_item
+    # to later remove the extrusion (or other pre-boolean items) from inside
+    # the boolean chain, corrupting the IFC model.
+    geom_props = geometry.get_geometry_props()
+    if geom_props.representation_obj in wall_objs:
+        geometry.disable_item_mode()
+    clipped_walls = []
     for obj in wall_objs:
         if ifc.is_moved(obj):
             geometry.run_edit_object_placement(obj=obj)
         wall = ifc.get_entity(obj)
-        model.clip_wall_to_slab(wall, clip)
-        model.connect_wall_to_slab(wall, slab)
-    model.reload_body_representation(wall_objs)
+        # Merge previously connected slabs with newly requested ones so that
+        # re-running the operator never produces duplicate booleans and never
+        # silently discards clips that were applied in an earlier call.
+        existing = model.get_connected_slab_objs(wall)
+        seen = {id(s) for s in existing}
+        all_slab_objs = list(existing) + [s for s in slab_objs if id(s) not in seen]
+        # Remove stale booleans once, then re-clip against the full set.
+        model.remove_wall_to_underside_booleans(wall)
+        did_clip = False
+        for slab_obj in all_slab_objs:
+            clip = model.get_slab_clipping_bmesh(slab_obj)
+            if not clip:
+                continue
+            model.clip_wall_to_slab(wall, clip)
+            model.connect_wall_to_slab(wall, ifc.get_entity(slab_obj))
+            did_clip = True
+        if did_clip:
+            clipped_walls.append(obj)
+    if clipped_walls:
+        model.reload_body_representation(clipped_walls)
 
 
 class RequireTwoWallsError(Exception):
@@ -173,3 +255,438 @@ class RequireAtLeastTwoElements(Exception):
 
 class RequireLayeredElement(Exception):
     pass
+
+
+# --- Wall geometry math (pure) ------------------------------------------------
+# Tuple in / tuple out so these helpers run without ``bpy`` or ``mathutils``.
+# Callers convert ``mathutils.Vector`` at the boundary.
+
+
+def baseline_from_offset(offset: float, thickness: float, tolerance: float = BASELINE_OFFSET_TOLERANCE) -> str:
+    """Classify a numeric layer offset as EXTERIOR / CENTER / INTERIOR.
+
+    Handles both POSITIVE and NEGATIVE direction_sense walls. Returns the
+    closest canonical baseline; falls back to ``"CENTER"`` when nothing is
+    within ``tolerance``."""
+    candidates = (
+        ("EXTERIOR", 0.0),
+        ("CENTER", -thickness / 2),
+        ("INTERIOR", -thickness),
+        ("EXTERIOR", thickness),
+        ("CENTER", thickness / 2),
+        ("INTERIOR", 0.0),
+    )
+    best = min(candidates, key=lambda c: abs(offset - c[1]))
+    return best[0] if abs(offset - best[1]) < tolerance else "CENTER"
+
+
+def project_axis_intersection(
+    seg_a: tuple[tuple[float, float, float], tuple[float, float, float]],
+    seg_b: tuple[tuple[float, float, float], tuple[float, float, float]],
+    parallel_threshold: float,
+) -> Optional[tuple[float, float, float]]:
+    """Compute the 2D (X,Y plane) intersection of two world-space axis segments.
+
+    Each segment is a pair of 3-tuples. Returns the intersection as a 3-tuple
+    (Z is the average of the four input Zs, for visual placement) or ``None`` if
+    the segments are parallel within ``parallel_threshold`` (a dot-product magnitude
+    threshold — see ``PARALLEL_DOT_THRESHOLD`` for the calibrated value)."""
+    p1, p2 = seg_a
+    p3, p4 = seg_b
+    d1x, d1y = p2[0] - p1[0], p2[1] - p1[1]
+    d2x, d2y = p4[0] - p3[0], p4[1] - p3[1]
+    d1_len = (d1x * d1x + d1y * d1y) ** 0.5
+    d2_len = (d2x * d2x + d2y * d2y) ** 0.5
+    if d1_len < 1e-9 or d2_len < 1e-9:
+        return None
+    dot = (d1x * d2x + d1y * d2y) / (d1_len * d2_len)
+    if abs(dot) >= parallel_threshold:
+        return None
+    denom = d1x * d2y - d1y * d2x
+    if abs(denom) < 1e-9:
+        return None
+    t = ((p3[0] - p1[0]) * d2y - (p3[1] - p1[1]) * d2x) / denom
+    ix = p1[0] + t * d1x
+    iy = p1[1] + t * d1y
+    iz = (p1[2] + p2[2] + p3[2] + p4[2]) / 4
+    return (ix, iy, iz)
+
+
+def opening_is_past_cut(min_t: float, cut_percentage: float) -> bool:
+    """True when the opening's near edge sits past the cut on the t axis.
+
+    Strict inequality is load-bearing: a boundary touch or NaN keeps the
+    opening on both walls — the safe default when extent resolution fails."""
+    return min_t > cut_percentage
+
+
+def opening_is_before_cut(max_t: float, cut_percentage: float) -> bool:
+    """True when the opening's far edge sits before the cut on the t axis."""
+    return max_t < cut_percentage
+
+
+def opening_straddles_cut(min_t: float, max_t: float, cut_percentage: float) -> bool:
+    """True when the opening's extent crosses the cut on the t axis."""
+    return min_t < cut_percentage < max_t
+
+
+WallJoinState = Literal["joined", "collinear", "intersect", "none"]
+
+
+def classify_wall_join_state(
+    seg_a: tuple[tuple[float, float, float], tuple[float, float, float]],
+    seg_b: tuple[tuple[float, float, float], tuple[float, float, float]],
+    are_joined: bool,
+    parallel_threshold: float,
+    collinear_tolerance: float,
+) -> tuple[WallJoinState, Optional[tuple[float, float, float]]]:
+    """Classify a wall pair's geometric state — ``(state, intersection)``.
+
+    Priority: ``"joined"`` (caller-supplied flag) → ``"collinear"`` →
+    ``"intersect"`` (projected point returned) → ``"none"`` (parallel,
+    non-collinear)."""
+    if are_joined:
+        return "joined", None
+    if are_axes_collinear(seg_a, seg_b, parallel_threshold, collinear_tolerance):
+        return "collinear", None
+    intersection = project_axis_intersection(seg_a, seg_b, parallel_threshold)
+    if intersection is None:
+        return "none", None
+    return "intersect", intersection
+
+
+def wall_join_preview_lines(
+    seg_a: tuple[tuple[float, float, float], tuple[float, float, float]],
+    seg_b: tuple[tuple[float, float, float], tuple[float, float, float]],
+    intersection: tuple[float, float, float],
+) -> list[tuple[tuple[float, float, float], tuple[float, float, float]]]:
+    """Two segments showing each wall axis extending to ``intersection``.
+
+    Each segment runs from the input axis's nearest endpoint to the
+    intersection, held at that wall's own Z. Returned in input order
+    ``[floor_a, floor_b]``."""
+    ix, iy, _ = intersection
+
+    def _nearest(seg: tuple[tuple[float, float, float], tuple[float, float, float]]) -> tuple[float, float, float]:
+        return min(seg, key=lambda p: (p[0] - ix) ** 2 + (p[1] - iy) ** 2)
+
+    near_a = _nearest(seg_a)
+    near_b = _nearest(seg_b)
+    return [
+        (near_a, (ix, iy, near_a[2])),
+        (near_b, (ix, iy, near_b[2])),
+    ]
+
+
+def resolve_extend_walls_target(
+    target_obj: Any,
+    objs: list[Any],
+    reverse: bool,
+) -> tuple[Any, list[Any]]:
+    """Pick which object is the extend-target and which are extended.
+
+    Default direction: ``objs`` are extended to meet ``target_obj``.
+    Reversed direction (``reverse=True``) swaps the pair — equivalent to
+    having passed them in the opposite order. The swap is well-defined only
+    for the 1+1 case (one target + one other); for ``n>1`` it would be
+    ambiguous, so the default direction is preserved instead."""
+    if reverse and target_obj is not None and len(objs) == 1:
+        return objs[0], [target_obj]
+    return target_obj, objs
+
+
+def displacement_from_x_angle(height: float, x_angle: float) -> float:
+    """Top-edge horizontal displacement for a wall of given vertical ``height``
+    and slope ``x_angle`` (radians). Inverse of ``x_angle_from_displacement``."""
+    return height * math.tan(x_angle)
+
+
+def x_angle_from_displacement(height: float, displacement: float) -> float:
+    """Recover slope ``x_angle`` (radians) from a top-edge horizontal displacement.
+
+    ``height`` is clamped to ``max(height, 1e-6)`` so zero-height walls map
+    cleanly to ``±π/2`` instead of dividing by zero."""
+    return math.atan2(displacement, max(height, 1e-6))
+
+
+def vertical_height_from_extrusion_depth(extrusion_depth: float, x_angle: float) -> float:
+    """Vertical height of a wall given its slanted extrusion depth and slope.
+
+    ``IfcExtrudedAreaSolid.Depth`` measures along the (possibly slanted) extrusion
+    direction. The vertical height the user thinks of is ``depth * cos(x_angle)``.
+    Unit-agnostic: the result is in the same units as ``extrusion_depth``."""
+    return extrusion_depth * abs(math.cos(x_angle))
+
+
+def extrusion_depth_from_vertical_height(vertical_height: float, x_angle: float) -> float:
+    """``vertical_height / cos(x_angle)`` with ``cos`` clamped at ``1e-6`` to
+    stay finite near ``±π/2``."""
+    return vertical_height / max(abs(math.cos(x_angle)), 1e-6)
+
+
+def length_and_height_from_extrusion(
+    extrusion_depth: float,
+    x_angle: float,
+    reference_line_x_extent: float,
+    unit_scale: float,
+) -> tuple[float, float]:
+    """SI ``(length, vertical_height)`` of a LAYER2 wall.
+
+    Height is the *vertical* projection of the slanted depth, not the
+    slanted depth itself."""
+    length = reference_line_x_extent * unit_scale
+    height = vertical_height_from_extrusion_depth(extrusion_depth * unit_scale, x_angle)
+    return length, height
+
+
+def are_axes_collinear(
+    seg_a: tuple[tuple[float, float, float], tuple[float, float, float]],
+    seg_b: tuple[tuple[float, float, float], tuple[float, float, float]],
+    parallel_threshold: float = PARALLEL_DOT_THRESHOLD,
+    line_tolerance: float = COLLINEAR_LINE_TOLERANCE,
+) -> bool:
+    """True if both axis segments lie on the same infinite line in plan.
+
+    Two conditions: directions must be (anti-)parallel within ``parallel_threshold``,
+    AND any endpoint of B must lie on A's infinite line within ``line_tolerance``.
+    Plan-only (Z ignored)."""
+    d1x, d1y = seg_a[1][0] - seg_a[0][0], seg_a[1][1] - seg_a[0][1]
+    d2x, d2y = seg_b[1][0] - seg_b[0][0], seg_b[1][1] - seg_b[0][1]
+    d1_len = (d1x * d1x + d1y * d1y) ** 0.5
+    d2_len = (d2x * d2x + d2y * d2y) ** 0.5
+    if d1_len < 1e-9 or d2_len < 1e-9:
+        return False
+    if abs((d1x * d2x + d1y * d2y) / (d1_len * d2_len)) < parallel_threshold:
+        return False
+    # Project seg_b[0] onto the infinite line through seg_a; the perpendicular
+    # distance to the original point tells us how far off the line B sits.
+    nx, ny = d1x / d1_len, d1y / d1_len
+    dx, dy = seg_b[0][0] - seg_a[0][0], seg_b[0][1] - seg_a[0][1]
+    t = dx * nx + dy * ny
+    proj_x = seg_a[0][0] + nx * t
+    proj_y = seg_a[0][1] + ny * t
+    perp_x = seg_b[0][0] - proj_x
+    perp_y = seg_b[0][1] - proj_y
+    return (perp_x * perp_x + perp_y * perp_y) ** 0.5 < line_tolerance
+
+
+def closest_endpoint_midpoint(
+    seg_a: tuple[tuple[float, float, float], tuple[float, float, float]],
+    seg_b: tuple[tuple[float, float, float], tuple[float, float, float]],
+) -> tuple[float, float, float]:
+    """Midpoint of the closest endpoint pair between two segments."""
+    endpoints_a = (seg_a[0], seg_a[1])
+    endpoints_b = (seg_b[0], seg_b[1])
+
+    def _distance_sq(p: tuple[float, float, float], q: tuple[float, float, float]) -> float:
+        return (p[0] - q[0]) ** 2 + (p[1] - q[1]) ** 2 + (p[2] - q[2]) ** 2
+
+    closest_pair = min(((a, b) for a in endpoints_a for b in endpoints_b), key=lambda pair: _distance_sq(*pair))
+    a, b = closest_pair
+    return ((a[0] + b[0]) / 2, (a[1] + b[1]) / 2, (a[2] + b[2]) / 2)
+
+
+def compute_path_connection_location(
+    seg_self: tuple[tuple[float, float, float], tuple[float, float, float]],
+    self_conn_type: str,
+    seg_other: tuple[tuple[float, float, float], tuple[float, float, float]],
+    other_conn_type: str,
+    parallel_threshold: float = PARALLEL_DOT_THRESHOLD,
+) -> tuple[float, float, float]:
+    """World-space location of a single ``IfcRelConnectsPathElements`` between
+    two wall axes.
+
+    Priority: ``self``'s ATSTART/ATEND endpoint → ``other``'s ATSTART/ATEND
+    endpoint → axis intersection → closest-endpoint midpoint fallback."""
+    if self_conn_type == "ATSTART":
+        return seg_self[0]
+    if self_conn_type == "ATEND":
+        return seg_self[1]
+    if other_conn_type == "ATSTART":
+        return seg_other[0]
+    if other_conn_type == "ATEND":
+        return seg_other[1]
+    intersection = project_axis_intersection(seg_self, seg_other, parallel_threshold)
+    if intersection is not None:
+        return intersection
+    return closest_endpoint_midpoint(seg_self, seg_other)
+
+
+def _vec_sub(a: tuple[float, float, float], b: tuple[float, float, float]) -> tuple[float, float, float]:
+    return (a[0] - b[0], a[1] - b[1], a[2] - b[2])
+
+
+def _vec_dot(a: tuple[float, float, float], b: tuple[float, float, float]) -> float:
+    return a[0] * b[0] + a[1] * b[1] + a[2] * b[2]
+
+
+def _vec_cross(a: tuple[float, float, float], b: tuple[float, float, float]) -> tuple[float, float, float]:
+    return (a[1] * b[2] - a[2] * b[1], a[2] * b[0] - a[0] * b[2], a[0] * b[1] - a[1] * b[0])
+
+
+def _vec_length(v: tuple[float, float, float]) -> float:
+    return (v[0] * v[0] + v[1] * v[1] + v[2] * v[2]) ** 0.5
+
+
+def _rotate_around_axis(
+    v: tuple[float, float, float],
+    axis: tuple[float, float, float],
+    angle: float,
+) -> tuple[float, float, float]:
+    """Rotate ``v`` around unit-length ``axis`` by ``angle`` radians."""
+    cos_a = math.cos(angle)
+    sin_a = math.sin(angle)
+    dot = _vec_dot(axis, v)
+    cross = _vec_cross(axis, v)
+    k = 1.0 - cos_a
+    return (
+        v[0] * cos_a + cross[0] * sin_a + axis[0] * dot * k,
+        v[1] * cos_a + cross[1] * sin_a + axis[1] * dot * k,
+        v[2] * cos_a + cross[2] * sin_a + axis[2] * dot * k,
+    )
+
+
+def compute_fillet_polylines(
+    seg_a: tuple[tuple[float, float, float], tuple[float, float, float]],
+    seg_b: tuple[tuple[float, float, float], tuple[float, float, float]],
+    radius: float,
+    arc_resolution: int = FILLET_DEFAULT_ARC_RESOLUTION,
+    parallel_threshold: float = PARALLEL_DOT_THRESHOLD,
+) -> dict:
+    """Preview polylines for a circular fillet at the junction of two axes.
+
+    Returns a dict with ``valid``, ``reason``, ``intersection``, ``tangent_a``
+    / ``tangent_b``, ``arc`` (``arc_resolution + 1`` samples), ``arc_center``,
+    ``arc_radius``, ``sweep_angle``, ``sweep_axis``, ``tangent_offset``,
+    ``wall_a_join_side`` / ``wall_b_join_side`` (ATSTART/ATEND/None),
+    ``invalid_radius`` (tangent overshoots — arc + tangents still populated
+    for warning rendering), and ``invalid_axes`` (set on parallel)."""
+    blank: dict = {
+        "valid": False,
+        "reason": None,
+        "intersection": None,
+        "tangent_a": None,
+        "tangent_b": None,
+        "arc": [],
+        "arc_center": None,
+        "arc_radius": radius,
+        "sweep_angle": 0.0,
+        "sweep_axis": None,
+        "tangent_offset": 0.0,
+        "wall_a_join_side": None,
+        "wall_b_join_side": None,
+        "invalid_radius": False,
+        "invalid_axes": None,
+    }
+
+    intersection = project_axis_intersection(seg_a, seg_b, parallel_threshold)
+    if intersection is None:
+        return {**blank, "reason": "parallel", "invalid_axes": [seg_a, seg_b]}
+
+    def _classify(seg, ipt):
+        d0 = (seg[0][0] - ipt[0]) ** 2 + (seg[0][1] - ipt[1]) ** 2 + (seg[0][2] - ipt[2]) ** 2
+        d1 = (seg[1][0] - ipt[0]) ** 2 + (seg[1][1] - ipt[1]) ** 2 + (seg[1][2] - ipt[2]) ** 2
+        if d0 <= d1:
+            return seg[0], seg[1], "ATSTART"
+        return seg[1], seg[0], "ATEND"
+
+    near_a, far_a, side_a = _classify(seg_a, intersection)
+    near_b, far_b, side_b = _classify(seg_b, intersection)
+
+    # Direction along each segment AWAY from the corner. ``far - intersection``
+    # handles both the shared-corner and extended-axes cases uniformly.
+    dir_a_raw = _vec_sub(far_a, intersection)
+    dir_b_raw = _vec_sub(far_b, intersection)
+    far_len_a = _vec_length(dir_a_raw)
+    far_len_b = _vec_length(dir_b_raw)
+    if far_len_a < 1e-9 or far_len_b < 1e-9:
+        return {**blank, "reason": "near_collinear", "intersection": intersection}
+    dir_a = (dir_a_raw[0] / far_len_a, dir_a_raw[1] / far_len_a, dir_a_raw[2] / far_len_a)
+    dir_b = (dir_b_raw[0] / far_len_b, dir_b_raw[1] / far_len_b, dir_b_raw[2] / far_len_b)
+
+    cos_angle = max(-1.0, min(1.0, _vec_dot(dir_a, dir_b)))
+    angle = math.acos(cos_angle)
+    sweep_angle = math.pi - angle
+    if sweep_angle < 1e-3 or sweep_angle > math.pi - 1e-3:
+        return {
+            **blank,
+            "reason": "near_collinear",
+            "intersection": intersection,
+            "sweep_angle": sweep_angle,
+            "wall_a_join_side": side_a,
+            "wall_b_join_side": side_b,
+        }
+
+    tangent_offset = radius * math.tan(sweep_angle / 2)
+    tangent_a = (
+        intersection[0] + dir_a[0] * tangent_offset,
+        intersection[1] + dir_a[1] * tangent_offset,
+        intersection[2] + dir_a[2] * tangent_offset,
+    )
+    tangent_b = (
+        intersection[0] + dir_b[0] * tangent_offset,
+        intersection[1] + dir_b[1] * tangent_offset,
+        intersection[2] + dir_b[2] * tangent_offset,
+    )
+
+    plane_normal_raw = _vec_cross(dir_a, dir_b)
+    pn_len = _vec_length(plane_normal_raw)
+    if pn_len < 1e-9:
+        return {**blank, "reason": "near_collinear", "intersection": intersection}
+    plane_normal = (
+        plane_normal_raw[0] / pn_len,
+        plane_normal_raw[1] / pn_len,
+        plane_normal_raw[2] / pn_len,
+    )
+
+    perp_a = _vec_cross(plane_normal, dir_a)
+    if _vec_dot(perp_a, dir_b) < 0:
+        perp_a = (-perp_a[0], -perp_a[1], -perp_a[2])
+
+    arc_center = (
+        tangent_a[0] + perp_a[0] * radius,
+        tangent_a[1] + perp_a[1] * radius,
+        tangent_a[2] + perp_a[2] * radius,
+    )
+
+    v_a = _vec_sub(tangent_a, arc_center)
+    v_b = _vec_sub(tangent_b, arc_center)
+    sweep_axis = plane_normal
+    if _vec_dot(_vec_cross(v_a, v_b), plane_normal) < 0:
+        sweep_axis = (-plane_normal[0], -plane_normal[1], -plane_normal[2])
+
+    arc_points: list[tuple[float, float, float]] = []
+    for i in range(arc_resolution + 1):
+        t = i / arc_resolution
+        rotated = _rotate_around_axis(v_a, sweep_axis, sweep_angle * t)
+        arc_points.append(
+            (
+                arc_center[0] + rotated[0],
+                arc_center[1] + rotated[1],
+                arc_center[2] + rotated[2],
+            )
+        )
+
+    # Overshoot check only for convex fillets (positive ``tangent_offset``);
+    # the inverted-fillet case puts tangents past the intersection.
+    invalid_radius = tangent_offset > 0 and (tangent_offset > far_len_a or tangent_offset > far_len_b)
+
+    return {
+        "valid": not invalid_radius,
+        "reason": "invalid_radius" if invalid_radius else None,
+        "intersection": intersection,
+        "tangent_a": tangent_a,
+        "tangent_b": tangent_b,
+        "arc": arc_points,
+        "arc_center": arc_center,
+        "arc_radius": radius,
+        "sweep_angle": sweep_angle,
+        "sweep_axis": sweep_axis,
+        "tangent_offset": tangent_offset,
+        "wall_a_join_side": side_a,
+        "wall_b_join_side": side_b,
+        "leg_a_available": far_len_a,
+        "leg_b_available": far_len_b,
+        "invalid_radius": invalid_radius,
+        "invalid_axes": None,
+    }

src/bonsai/bonsai/core/product.py

@@ -0,0 +1,65 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+from __future__ import annotations
+
+import math
+from collections.abc import Iterable
+from typing import TYPE_CHECKING
+
+import bonsai.core.geometry
+
+if TYPE_CHECKING:
+    import bpy
+
+    import bonsai.tool as tool
+
+
+Z_ROTATION_ALIGNMENT_TOLERANCE = 1e-9
+
+
+def _z_rotation_diff(target_z: float, source_z: float) -> float:
+    """Signed Z-Euler difference wrapped to [-π, π]."""
+    return (target_z - source_z + math.pi) % (2 * math.pi) - math.pi
+
+
+def copy_z_rotation_to_selected(
+    ifc: type[tool.Ifc],
+    geometry: type[tool.Geometry],
+    surveyor: type[tool.Surveyor],
+    *,
+    active: bpy.types.Object,
+    targets: Iterable[bpy.types.Object],
+    flip: bool = False,
+) -> int:
+    """Apply ``active``'s Z-Euler rotation to each target."""
+    source_z = surveyor.get_z_rotation(active)  # ty: ignore[missing-argument]
+    if flip:
+        source_z += math.pi
+    rotated = 0
+    for obj in targets:
+        target_z = surveyor.get_z_rotation(obj)  # ty: ignore[missing-argument]
+        if abs(_z_rotation_diff(target_z, source_z)) < Z_ROTATION_ALIGNMENT_TOLERANCE:
+            continue
+        surveyor.set_z_rotation(obj, source_z)  # ty: ignore[missing-argument]
+        rotated += 1
+        if ifc.get_entity(obj) is not None:
+            bonsai.core.geometry.edit_object_placement(ifc, geometry, surveyor, obj=obj)
+    return rotated

src/bonsai/bonsai/core/root.py

@@ -20,8 +20,6 @@ from __future__ import annotations
 
 from typing import TYPE_CHECKING, Optional
 
-import ifcopenshell.util.element
-
 if TYPE_CHECKING:
     import bpy
     import ifcopenshell
@@ -58,31 +56,12 @@ def copy_class(
             geometry.change_object_data(obj, data, is_global=True)
             geometry.rename_object(data, geometry.get_representation_name(ifc.get_entity(data)))
         # Only assign styles if element doesn't get them from material
-        if not _has_material_styles(ifc, new):
+        if not root.has_material_styles(new):
             root.assign_body_styles(new, obj)
     collector.assign(obj)
     return new
 
 
-def _has_material_styles(ifc: type[tool.Ifc], element: ifcopenshell.entity_instance) -> bool:
-    """Check if element has styles defined through its material.
-
-    Returns True if any constituent material has a style representation,
-    which means styles should NOT be applied directly to the geometry.
-    """
-    materials = ifcopenshell.util.element.get_materials(element)
-
-    if not materials:
-        return False
-
-    # Check if any of the constituent materials have styles
-    for material in materials:
-        if hasattr(material, "HasRepresentation") and material.HasRepresentation:
-            return True
-
-    return False
-
-
 def assign_class(
     ifc: type[tool.Ifc],
     collector: type[tool.Collector],

src/bonsai/bonsai/core/spatial.py

@@ -64,10 +64,11 @@ def assign_container(
         spatial.disable_editing(obj)
         all_elements.add(root_element)
         all_elements.update(spatial.get_decomposition(root_element))
-    if products := [e for e in root_elements if spatial.can_contain(container, root_element)]:
+    if products := [e for e in root_elements if spatial.can_contain(container, e)]:
         ifc.run("spatial.assign_container", products=products, relating_structure=container)
     for element in all_elements:
-        collector.assign(ifc.get_object(element))
+        if obj := ifc.get_object(element):
+            collector.assign(obj)
 
 
 def enable_editing_container(spatial: type[tool.Spatial], obj: bpy.types.Object) -> None:

src/bonsai/bonsai/core/tool.py

@@ -195,6 +195,14 @@ class Collector:
     def assign(cls, obj, should_clean_users_collection=False): pass
 
 
+@interface
+class Connection:
+    def find_rel(cls, elem_a, elem_b): pass
+    def find_rels(cls, elem_a, elem_b): pass
+    def find_rels_for_element(cls, elem): pass
+    def orient_element_top(cls, rel, elem_a, elem_b): pass
+
+
 @interface
 class Context:
     def clear_context(cls): pass
@@ -415,6 +423,17 @@ class Drawing:
     def update_embedded_svg_location(cls, uri, old_location, new_location): pass
 
 
+@interface
+class Duplicate:
+    def get_decomposition_relationships(cls, objs): pass
+    def get_connection_relationships(cls, objs): pass
+    def get_port_connection_relationships(cls, objs): pass
+    def recreate_decompositions(cls, relationships, old_to_new): pass
+    def recreate_connections(cls, relationship, old_to_new): pass
+    def recreate_port_connections(cls, snapshot, old_to_new): pass
+    def consume_warnings(cls): pass
+
+
 @interface
 class Feature:
     def add_feature(cls, featured_obj, featured_objs): pass
@@ -445,6 +464,7 @@ class Geometry:
     def get_representation_name(cls, representation): pass
     def get_styles(cls, obj): pass
     def get_total_representation_items(cls, obj): pass
+    def has_axis_representation(cls, element): pass
     def has_data_users(cls, data): pass
     def has_material_style_override(cls, obj): pass
     def import_representation_parameters(cls, data): pass
@@ -668,6 +688,9 @@ class Model:
     def export_profile(cls, obj, position=None): pass
     def generate_occurrence_name(cls, element_type, ifc_class): pass
     def get_extrusion(cls, representation): pass
+    def get_connected_slab_objs(cls, wall): pass
+    def get_connected_wall_objs(cls, slab): pass
+    def has_underside_connection(cls, element): pass
     def get_manual_booleans(cls, element): pass
     def get_material_layer_parameters(cls, element): pass
     def get_slab_clipping_bmesh(cls, obj): pass
@@ -679,10 +702,13 @@ class Model:
     def load_openings(cls, openings): pass
     def purge_scene_openings(cls): pass
     def recalculate_walls(cls, objs): pass
+    def recreate_wall(cls, element, obj): pass
     def regenerate_array(cls, parent, data): pass
     def regenerate_profile(cls, obj): pass
     def regenerate_slab(cls, obj): pass
     def reload_body_representation(cls, obj_or_objects): pass
+    def remove_wall_to_underside_booleans(cls, wall): pass
+    def strip_underside_booleans(cls, wall): pass
     def replace_object_ifc_representation(cls, ifc_file, ifc_context, obj, new_representation): pass
 
 
@@ -776,6 +802,12 @@ class Profile:
     def get_profile(cls, element): pass
 
 
+@interface
+class Parametric:
+    def get_geom_generation(cls): pass
+    def refresh_post_commit(cls, operator) -> None: pass
+
+
 @interface
 class Pset:
     def add_proposed_property(cls, name, value, props): pass
@@ -859,13 +891,13 @@ class Root:
     def assign_body_styles(cls, element, obj): pass
     def copy_representation(cls, source, dest): pass
     def does_type_have_representations(cls, element): pass
-    def get_decomposition_relationships(cls, objs): pass
     def get_default_container(cls): pass
     def get_element_representation(cls, element, context): pass
     def get_element_type(cls, element): pass
     def get_object_name(cls, obj): pass
     def get_object_representation(cls, obj): pass
     def get_representation_context(cls, representation): pass
+    def has_material_styles(cls, element): pass
     def is_containable(cls, element): pass
     def is_drawing_annotation(cls, element): pass
     def is_element_a(cls, element, ifc_class): pass
@@ -873,7 +905,6 @@ class Root:
     def is_in_nest_mode(cls, element): pass
     def is_spatial_element(cls, element): pass
     def link_object_data(cls, source_obj, destination_obj): pass
-    def recreate_decompositions(cls, relationships, old_to_new): pass
     def run_geometry_add_representation(cls, obj=None, context=None, ifc_representation_class=None, profile_set_usage=None): pass
     def set_object_name(cls, obj, element): pass
 
@@ -1017,6 +1048,8 @@ class Spatial:
     def get_container(cls, element): pass
     def get_decomposed_elements(cls, container, recursive): pass
     def get_decomposition(cls, element): pass
+    def get_host_element(cls, filling): pass
+    def get_host_wall(cls, filling): pass
     def get_object_matrix(cls, obj): pass
     def get_relative_object_matrix(cls, target_obj, relative_to_obj): pass
     def get_root_element(cls, element): pass
@@ -1137,6 +1170,8 @@ class Style:
 @interface
 class Surveyor:
     def get_absolute_matrix(cls, obj): pass
+    def get_z_rotation(cls, obj): pass
+    def set_z_rotation(cls, obj, z): pass
 
 
 @interface
@@ -1173,6 +1208,7 @@ class Type:
     def get_representation_context(cls, representation): pass
     def get_type_occurrences(cls, element_type): pass
     def has_material_usage(cls, element): pass
+    def is_relating_type_compatible(cls, occurrence, relating_type): pass
     def record_material_usage_attributes(cls, element): pass
     def restore_material_usage_attributes(cls, element, usage_attributes): pass
     def run_geometry_add_representation(cls, obj=None, context=None, ifc_representation_class=None, profile_set_usage=None): pass
@@ -1203,6 +1239,42 @@ class Voider:
     def void(cls, opening_obj, building_obj): pass
 
 
+@interface
+class Array:
+    def bake_children_transform(cls, parent_element, item): pass
+    def constrain_children_to_parent(cls, parent_element): pass
+    def get_all_children_objects(cls, parent_element): pass
+    def get_all_objects(cls, parent_element): pass
+    def get_child_layer_index(cls, child_element): pass
+    def get_children_objects(cls, modifier_data): pass
+    def get_modifiers_data(cls, parent_element): pass
+    def get_parent_element(cls, element): pass
+    def get_parent_object(cls, element): pass
+    def remove_constraints(cls, parent_element): pass
+    def set_children_lock_state(cls, parent_element, item, lock_state): pass
+
+
+@interface
+class Slab:
+    def read_geometry(cls, obj): pass
+
+
+@interface
+class Wall:
+    def collinear_boundary_world(cls, seg_a, seg_b): pass
+    def compute_wall_fillet_geometry(cls, wall_a_obj, wall_b_obj, radius, arc_resolution): pass
+    def get_axis_local_extent(cls, wall): pass
+    def get_length_and_height(cls, wall): pass
+    def get_world_reference_line(cls, obj): pass
+    def get_x_angle(cls, wall): pass
+    def has_layer2_usage(cls, wall): pass
+    def is_straight_axis(cls, wall): pass
+    def path_connection_location_world(cls, seg_self, self_conn_type, seg_other, other_conn_type, parallel_threshold): pass
+    def read_geometry(cls, obj): pass
+    def validate_for_parametric_edit(cls, obj): pass
+    def walk_connected_walls(cls, start_element, node_cap): pass
+
+
 @interface
 class Web:
     pass

src/bonsai/bonsai/tool/__init__.py

@@ -20,6 +20,7 @@
 # ruff: noqa: F401
 
 from bonsai.tool.aggregate import Aggregate
+from bonsai.tool.array import Array
 from bonsai.tool.attribute import Attribute
 from bonsai.tool.bcf import Bcf
 from bonsai.tool.blender import Blender
@@ -29,7 +30,9 @@ from bonsai.tool.bsdd import Bsdd
 from bonsai.tool.cad import Cad
 from bonsai.tool.clash import Clash
 from bonsai.tool.classification import Classification
+from bonsai.tool.clip_box import ClipBox
 from bonsai.tool.collector import Collector
+from bonsai.tool.connection import Connection
 from bonsai.tool.context import Context
 from bonsai.tool.cost import Cost
 from bonsai.tool.covering import Covering
@@ -37,6 +40,7 @@ from bonsai.tool.debug import Debug
 from bonsai.tool.demo import Demo
 from bonsai.tool.document import Document
 from bonsai.tool.drawing import Drawing
+from bonsai.tool.duplicate import Duplicate
 from bonsai.tool.feature import Feature
 from bonsai.tool.geometry import Geometry
 from bonsai.tool.georeference import Georeference
@@ -51,6 +55,7 @@ from bonsai.tool.misc import Misc
 from bonsai.tool.model import Model
 from bonsai.tool.nest import Nest
 from bonsai.tool.owner import Owner
+from bonsai.tool.parametric import Parametric
 from bonsai.tool.patch import Patch
 from bonsai.tool.polyline import Polyline
 from bonsai.tool.profile import Profile
@@ -63,6 +68,7 @@ from bonsai.tool.resource import Resource
 from bonsai.tool.root import Root
 from bonsai.tool.search import Search
 from bonsai.tool.sequence import Sequence
+from bonsai.tool.slab import Slab
 from bonsai.tool.snap import Snap
 from bonsai.tool.spatial import Spatial
 from bonsai.tool.structural import Structural
@@ -72,4 +78,5 @@ from bonsai.tool.system import System
 from bonsai.tool.tester import Tester
 from bonsai.tool.type import Type
 from bonsai.tool.unit import Unit
+from bonsai.tool.wall import Wall
 from bonsai.tool.web import Web