Bonsai patch: lossy-downgrade popup + per-recipe preset menu

Two new UX features in the IFC Patch panel, both backed by helpers on
bonsai.tool.Patch.

Lossy-downgrade confirmation popup. When the user picks the Migrate
recipe with a target schema older than the source's (IFC4 -> IFC2X3,
IFC4X3 -> IFC2X3), ExecuteIfcPatch.invoke shows a properties dialog
listing what's preserved vs lost: IfcIndexedPolyCurve flattened with
arcs approximated, IfcPolygonalFaceSet / IfcTriangulatedFaceSet
converted to IfcFacetedBrep, IFC4-only IfcElement subclasses (IfcLamp,
IfcPipeSegment, IfcGeographicElement, ...) demoted to
IfcBuildingElementProxy with the original class + PredefinedType
encoded into ObjectType, and PredefinedType enum values absent from
IFC2X3 dropped. The user explicitly approves before the recipe runs.

The popup is gated on tool.Patch.migration_is_lossy_downgrade() which
resolves the source schema via header-only parsing
(tool.Patch._patch_source_schema reads the first ~2KB and matches a
FILE_SCHEMA regex, then normalises via ifcopenshell.util.schema.
get_fallback_schema). Avoids a full ifcopenshell.open() on every
Execute click — multi-second saving on large files. The target schema
is looked up by argument name rather than position so it survives
recipe-parameter reordering.

Per-recipe preset menu. New BIM_MT_ifc_patch_presets + AddIfcPatchPreset
wire Blender's standard preset system into the panel. Each recipe gets
its own preset subdirectory (bonsai/ifc_patch/<RecipeName>/), so a
preset saved for ExtractElements does not pollute the Migrate preset
list. The preset operator uses Attribute.get_value_name() (single
source of truth for data_type -> storage-field mapping) to build the
preset_values list dynamically per recipe.

The recipe-change callback resets
BIM_MT_ifc_patch_presets.bl_label to the canonical title — Blender's
script.execute_preset mutates the menu's bl_label to the loaded
preset's name as a "currently-selected" indicator, and without an
explicit reset the previous recipe's preset name would falsely advertise
itself in the new recipe's menu.

tool.Patch gains get_preset_subdir, migration_is_lossy_downgrade,
_patch_source_schema as cross-cutting helpers. _SCHEMA_AGE module
constant provides the ordering used by the downgrade-detection
predicate.

Test coverage: 12 bim-lane tests under test/bim/module/patch/. The
truth table for migration_is_lossy_downgrade covers IFC4/IFC4X3 source
x downgrade/upgrade/same-schema target x Migrate/non-Migrate recipe.
The schema-sniffing tests write a real IFC4X3_ADD2 file to disk and
assert the helper resolves it to IFC4X3 (regression for the original
startswith iteration-order bug). An end-to-end test drives
bpy.ops.bim.execute_ifc_patch with an in-memory IfcLamp source and
verifies the on-disk IFC2X3 file contains a single
IfcBuildingElementProxy with ObjectType "IfcLamp/COMPACTFLUORESCENT"
and the original GlobalId preserved.

Generated with the assistance of an AI coding tool.

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/tool/patch.py

@@ -18,18 +18,33 @@
 
 from __future__ import annotations
 
+import re
 from typing import TYPE_CHECKING, Any
 
 import bpy
 import ifcopenshell
+import ifcopenshell.util.schema
 import ifcpatch
 
 import bonsai.core.tool
+import bonsai.tool
 
 if TYPE_CHECKING:
     from bonsai.bim.module.patch.prop import BIMPatchProperties
 
 
+# Lower index = older schema. Used to detect downgrades vs upgrades.
+_SCHEMA_AGE = {"IFC2X3": 0, "IFC4": 1, "IFC4X3": 2}
+
+# Pretty-printed argument name for the ``Migrate`` recipe's schema parameter
+# (see UpdateIfcPatchArguments.pretty_arg_name in bim/module/patch/operator.py).
+_MIGRATE_SCHEMA_ARG_NAME = "Schema"
+
+# Match a STEP-encoded FILE_SCHEMA header: ``FILE_SCHEMA(('IFC4'));`` and the
+# IFC4X3_ADD2 / IFC2X3_TC1 variants. Captures the bare schema identifier.
+_IFC_FILE_SCHEMA_RE = re.compile(r"FILE_SCHEMA\s*\(\s*\(\s*'([^']+)'", re.IGNORECASE)
+
+
 class Patch(bonsai.core.tool.Patch):
     @classmethod
     def get_patch_props(cls) -> BIMPatchProperties:
@@ -54,6 +69,63 @@ class Patch(bonsai.core.tool.Patch):
             "SplitByBuildingStorey",
         )
 
+    @classmethod
+    def get_preset_subdir(cls) -> str:
+        """Resolve the preset subdirectory for the currently selected recipe.
+
+        Returns a stable string for the ``-`` placeholder so the menu and save
+        operator remain usable when no real recipe has been picked yet."""
+        recipe = cls.get_patch_props().ifc_patch_recipes or "-"
+        return f"bonsai/ifc_patch/{recipe}"
+
+    @classmethod
+    def migration_is_lossy_downgrade(cls) -> bool:
+        """``True`` when the currently configured patch is the ``Migrate``
+        recipe targeting an older schema than the input file. Used to gate
+        the destructive-migration confirmation dialog."""
+        props = cls.get_patch_props()
+        if props.ifc_patch_recipes != "Migrate":
+            return False
+        target_schema = next(
+            (arg.get_value() for arg in props.ifc_patch_args_attr if arg.name == _MIGRATE_SCHEMA_ARG_NAME),
+            None,
+        )
+        if not target_schema:
+            return False
+        source_schema = cls._patch_source_schema()
+        if not source_schema:
+            return False
+        return _SCHEMA_AGE.get(target_schema, -1) < _SCHEMA_AGE.get(source_schema, -1)
+
+    @classmethod
+    def _patch_source_schema(cls) -> str:
+        """Resolve the IFC schema of the configured input without parsing the
+        full file. For loaded-from-memory the schema is in the entity_instance
+        wrapper; for disk paths we read only the STEP file header (first ~2KB)
+        rather than ``ifcopenshell.open`` which parses the whole file."""
+        props = cls.get_patch_props()
+        if props.should_load_from_memory:
+            ifc_file = bonsai.tool.Ifc.get()
+            return ifc_file.schema if ifc_file else ""
+        if not props.ifc_patch_input:
+            return ""
+        try:
+            with open(props.ifc_patch_input, "rb") as f:
+                header = f.read(2048).decode("utf-8", errors="ignore")
+        except OSError:
+            return ""
+        match = _IFC_FILE_SCHEMA_RE.search(header)
+        if not match:
+            return ""
+        # Collapse IFC4X3_ADD2 / IFC2X3_TC1 / IFC4_ADD2 / IFC4X1 etc. to their
+        # base via the canonical normaliser — handles longest-prefix-first
+        # ordering correctly (IFC4X3 before IFC4) so we don't misclassify
+        # IFC4X3 files as IFC4.
+        try:
+            return ifcopenshell.util.schema.get_fallback_schema(match.group(1).upper())
+        except AssertionError:
+            return ""
+
     @classmethod
     def post_process_patch_arguments(cls, recipe: str, args: list[Any]) -> list[Any]:
         if recipe == "ExtractElements":

src/bonsai/test/bim/module/patch/test_execute_downgrade_e2e.py

@@ -0,0 +1,70 @@
+# 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 tempfile
+from pathlib import Path
+
+import bpy
+import ifcopenshell
+import pytest
+
+import bonsai.tool as tool
+from test.bim.bootstrap import NewFile
+
+pytestmark = pytest.mark.patch
+
+
+class TestExecuteIfcPatchDowngradeEndToEnd(NewFile):
+    """Drives the full panel flow the user sees: load IFC4 in memory, pick
+    Migrate + IFC2X3, click Execute, get an IFC2X3 file on disk with the
+    expected IfcBuildingElementProxy fallback + ObjectType encoding.
+
+    A regression here means a real user clicking Execute either crashes
+    Blender, produces a broken file, or silently drops type information
+    that the recipe is supposed to preserve via ObjectType."""
+
+    def test_ifc4_with_ifclamp_downgrades_to_ifc2x3_with_proxy_and_object_type(self):
+        ifc = ifcopenshell.file(schema="IFC4")
+        ifc.create_entity("IfcLamp", GlobalId="2K6Z3DR8X37AS9XFvX8GcW", PredefinedType="COMPACTFLUORESCENT")
+        tool.Ifc.set(ifc)
+
+        props = tool.Patch.get_patch_props()
+        props.should_load_from_memory = True
+        props.ifc_patch_recipes = "Migrate"
+        next(a for a in props.ifc_patch_args_attr if a.name == "Schema").enum_value = "IFC2X3"
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            output_path = Path(tmpdir) / "downgraded.ifc"
+            props.ifc_patch_output = str(output_path)
+
+            result = bpy.ops.bim.execute_ifc_patch()
+
+            assert result == {"FINISHED"}
+            assert output_path.exists(), "Recipe ran but no output file was written"
+
+            written = ifcopenshell.open(str(output_path))
+            assert written.schema == "IFC2X3"
+            proxies = written.by_type("IfcBuildingElementProxy")
+            assert len(proxies) == 1, "IfcLamp should fall back to a single IfcBuildingElementProxy"
+            assert proxies[0].ObjectType == "IfcLamp/COMPACTFLUORESCENT", (
+                "Original class + PredefinedType must be encoded into ObjectType "
+                "so the downgrade isn't a total information loss"
+            )
+            assert proxies[0].GlobalId == "2K6Z3DR8X37AS9XFvX8GcW"

src/bonsai/test/bim/module/patch/test_lossy_downgrade.py

@@ -0,0 +1,131 @@
+# 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 tempfile
+from pathlib import Path
+
+import bpy
+import ifcopenshell
+import pytest
+
+import bonsai.tool as tool
+from test.bim.bootstrap import NewFile
+
+pytestmark = pytest.mark.patch
+
+
+def _set_patch_state(*, recipe: str, target_schema: str | None, source_ifc: ifcopenshell.file | None = None) -> None:
+    """Drive the BIMPatchProperties into the configuration that a user produces
+    by picking Recipe + Schema in the panel + checking "Load from memory".
+    Setting the recipe fires UpdateIfcPatchArguments which builds the dynamic
+    args collection — only then can we assign the schema arg's enum_value."""
+    props = tool.Patch.get_patch_props()
+    if source_ifc is not None:
+        tool.Ifc.set(source_ifc)
+        props.should_load_from_memory = True
+    props.ifc_patch_recipes = recipe  # update callback builds ifc_patch_args_attr
+    if target_schema is not None:
+        schema_arg = next(a for a in props.ifc_patch_args_attr if a.name == "Schema")
+        schema_arg.enum_value = target_schema
+
+
+class TestMigrationIsLossyDowngrade(NewFile):
+    """Pins the predicate that gates ``ExecuteIfcPatch.invoke``'s
+    confirmation popup. Every row of the truth table corresponds to a real
+    user-facing flow — wrong answers either nag the user on safe migrations
+    or silently let lossy ones through with no warning."""
+
+    def test_ifc4_to_ifc2x3_in_memory_is_lossy(self):
+        ifc = ifcopenshell.file(schema="IFC4")
+        _set_patch_state(recipe="Migrate", target_schema="IFC2X3", source_ifc=ifc)
+        assert tool.Patch.migration_is_lossy_downgrade() is True
+
+    def test_ifc4x3_to_ifc2x3_in_memory_is_lossy(self):
+        # Regression for the gate that originally only fired for self.file.schema == "IFC4",
+        # silently leaving IFC4X3 sources crashing on IFC4-only geometry.
+        ifc = ifcopenshell.file(schema="IFC4X3")
+        _set_patch_state(recipe="Migrate", target_schema="IFC2X3", source_ifc=ifc)
+        assert tool.Patch.migration_is_lossy_downgrade() is True
+
+    def test_ifc2x3_to_ifc4_upgrade_is_not_lossy(self):
+        ifc = ifcopenshell.file(schema="IFC2X3")
+        _set_patch_state(recipe="Migrate", target_schema="IFC4", source_ifc=ifc)
+        assert tool.Patch.migration_is_lossy_downgrade() is False
+
+    def test_ifc4_to_ifc4_same_schema_is_not_lossy(self):
+        ifc = ifcopenshell.file(schema="IFC4")
+        _set_patch_state(recipe="Migrate", target_schema="IFC4", source_ifc=ifc)
+        assert tool.Patch.migration_is_lossy_downgrade() is False
+
+    def test_non_migrate_recipe_is_not_lossy(self):
+        # The popup only ever applies to the Migrate recipe — other recipes
+        # (ExtractElements, TessellateElements, …) handle their own warnings.
+        ifc = ifcopenshell.file(schema="IFC4")
+        _set_patch_state(recipe="ExtractElements", target_schema=None, source_ifc=ifc)
+        assert tool.Patch.migration_is_lossy_downgrade() is False
+
+    def test_no_source_set_is_not_lossy(self):
+        # Without an input file or in-memory IFC, the predicate cannot tell
+        # what the source schema is — defaults to False so the popup doesn't
+        # block harmless cases where the user is still configuring the panel.
+        props = tool.Patch.get_patch_props()
+        props.ifc_patch_recipes = "Migrate"
+        schema_arg = next(a for a in props.ifc_patch_args_attr if a.name == "Schema")
+        schema_arg.enum_value = "IFC2X3"
+        assert tool.Patch.migration_is_lossy_downgrade() is False
+
+
+class TestPatchSourceSchemaSniff(NewFile):
+    """End-to-end pin on the header-only schema parsing. The IFC4X3 misdetection
+    bug originally lived in this code path — a raw startswith(\"IFC4\") loop
+    matching IFC4X3_ADD2 before the IFC4X3 base check was reached."""
+
+    def test_in_memory_ifc4x3_source_resolves_to_ifc4x3(self):
+        ifc = ifcopenshell.file(schema="IFC4X3")
+        tool.Ifc.set(ifc)
+        props = tool.Patch.get_patch_props()
+        props.should_load_from_memory = True
+        assert tool.Patch._patch_source_schema() == "IFC4X3"
+
+    def test_file_path_ifc4x3_add2_source_resolves_to_ifc4x3(self):
+        # Writes a real .ifc file with IFC4X3_ADD2 in the FILE_SCHEMA header
+        # and confirms the regex + get_fallback_schema normaliser correctly
+        # collapse it to IFC4X3, not IFC4.
+        with tempfile.TemporaryDirectory() as tmpdir:
+            ifc_path = Path(tmpdir) / "sample.ifc"
+            ifc_path.write_text(
+                "ISO-10303-21;\n"
+                "HEADER;\n"
+                "FILE_DESCRIPTION((''),'2;1');\n"
+                "FILE_NAME('','2026',(''),(''),'','','');\n"
+                "FILE_SCHEMA(('IFC4X3_ADD2'));\n"
+                "ENDSEC;\n"
+                "DATA;\nENDSEC;\nEND-ISO-10303-21;\n"
+            )
+            props = tool.Patch.get_patch_props()
+            props.should_load_from_memory = False
+            props.ifc_patch_input = str(ifc_path)
+            assert tool.Patch._patch_source_schema() == "IFC4X3"
+
+    def test_missing_input_returns_empty_string(self):
+        props = tool.Patch.get_patch_props()
+        props.should_load_from_memory = False
+        props.ifc_patch_input = ""
+        assert tool.Patch._patch_source_schema() == ""

src/bonsai/test/bim/module/patch/test_preset_label_reset.py

@@ -0,0 +1,55 @@
+# 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
+import pytest
+
+import bonsai.tool as tool
+from test.bim.bootstrap import NewFile
+
+pytestmark = pytest.mark.patch
+
+
+class TestPresetMenuLabelResetsOnRecipeChange(NewFile):
+    """Blender's ``script.execute_preset`` mutates the menu class's bl_label
+    to the loaded preset's display name as a "currently-selected" indicator.
+    Without a recipe-change callback, that label persists into the next
+    recipe's menu — falsely advertising a preset that belongs to a
+    different recipe's subdir and isn't selectable from the new menu."""
+
+    def test_changing_recipe_restores_canonical_label(self):
+        # Simulate the state Blender leaves after the user picked a preset
+        # for the previous recipe.
+        menu_cls = bpy.types.BIM_MT_ifc_patch_presets
+        menu_cls.bl_label = "Structural"
+
+        # Switching the recipe must fire update_ifc_patch_recipe, which
+        # resets the menu label.
+        props = tool.Patch.get_patch_props()
+        props.ifc_patch_recipes = "Migrate"
+
+        assert menu_cls.bl_label == "IFC Patch Presets"
+
+    def test_canonical_label_is_used_when_no_preset_was_loaded(self):
+        # Fresh state — label is the bl_label-default from the class declaration.
+        menu_cls = bpy.types.BIM_MT_ifc_patch_presets
+        props = tool.Patch.get_patch_props()
+        props.ifc_patch_recipes = "ExtractElements"
+        assert menu_cls.bl_label == "IFC Patch Presets"