diff --git a/.github/workflows/build_osx.yml b/.github/workflows/build_osx.yml
index b4de5e2e8c..f76964506e 100644
--- a/.github/workflows/build_osx.yml
+++ b/.github/workflows/build_osx.yml
@@ -88,10 +88,15 @@ jobs:
           # actually drops ifcopenshell.document.rdb.dylib into
           # site-packages/ifcopenshell/ (see the commit that added this
           # gate for the full history + the rocksdb/macdeployqt write-up).
+          # --shared mirrors build_rocky.yml after 27249770e: builds
+          # IfcOpenShell as shared libs so each plug-in dylib references
+          # libIfcParse / libIfcGeom via @rpath instead of statically
+          # embedding them — the dominant size win for BonsaiViewer.app
+          # (per-plugin libs go from ~30-50 MB to a few MB).
           CXXFLAGS="-O3" CFLAGS="-O3 ${DARWIN_C_SOURCE}" ADD_COMMIT_SHA=1 BUILD_CFG=Release \
             BUILD_BONSAIVIEWER=ON QT_DIR="${QT_DIR}" \
             IFCOS_BUILD_PYTHON_WRAPPER=off \
-            python3 ./nix/build-all.py -v --diskcleanup ${MAC_INTEL} \
+            python3 ./nix/build-all.py -v --diskcleanup --shared ${MAC_INTEL} \
             | tee build.log
 
       - name: Upload Build Logs
diff --git a/src/bonsaiviewer/CMakeLists.txt b/src/bonsaiviewer/CMakeLists.txt
index 179eee2a2e..0dac4dd59d 100644
--- a/src/bonsaiviewer/CMakeLists.txt
+++ b/src/bonsaiviewer/CMakeLists.txt
@@ -180,6 +180,13 @@ if(APPLE)
     install(CODE [[
         file(GLOB _ifc_plugins
              "${CMAKE_INSTALL_PREFIX}/lib/ifcopenshell.*.dylib")
+        # Skip ifcopenshell.geometry.writer.*.dylib — those are heavy
+        # schema-specific OBJ / glTF / DAE / STP / IGS / SVG / TTL export
+        # converters. BonsaiViewer is a viewer; it never writes geometry
+        # out, so they're pure deadweight. Mirrors the Rocky workflow's
+        # filter in `stage_runtime_payload` (see 27249770e). Cuts the
+        # macOS .app by ~100-150 MB.
+        list(FILTER _ifc_plugins EXCLUDE REGEX "ifcopenshell\\.geometry\\.writer\\.")
         if(_ifc_plugins)
             message(STATUS "Staging IfcOpenShell plug-ins into BonsaiViewer.app/Contents/Frameworks")
             file(COPY ${_ifc_plugins}