diff --git a/cadling/cadling/lib/geometry/uv_grid_extractor.py b/cadling/cadling/lib/geometry/uv_grid_extractor.py
index df6c617..e51c25a 100644
--- a/cadling/cadling/lib/geometry/uv_grid_extractor.py
+++ b/cadling/cadling/lib/geometry/uv_grid_extractor.py
@@ -21,7 +21,6 @@
 # Try importing occwl; if not on sys.path, try adding the vendored location
 try:
     from OCC.Core.TopoDS import TopoDS_Face, TopoDS_Edge
-    from OCC.Core.TopAbs import TopAbs_IN, TopAbs_OUT
     from occwl.face import Face
     from occwl.edge import Edge
     from occwl.uvgrid import uvgrid, ugrid
@@ -33,7 +32,6 @@
         sys.path.insert(0, str(_occwl_path))
         try:
             from OCC.Core.TopoDS import TopoDS_Face, TopoDS_Edge
-            from OCC.Core.TopAbs import TopAbs_IN, TopAbs_OUT
             from occwl.face import Face
             from occwl.edge import Edge
             from occwl.uvgrid import uvgrid, ugrid
@@ -99,19 +97,17 @@ def extract_uv_grid(
                 logger.warning("Failed to extract normal grid from face")
                 return None
 
-            # Compute trimming mask
-            # Get UV values where we sampled
-            _, uv_values = uvgrid(face, num_u=num_u, num_v=num_v, method="point", uvs=True)
-
-            # Create trimming mask by checking if each UV point is inside the trimmed region
-            trimming_mask = np.zeros((num_u, num_v, 1), dtype=np.float32)
-            for i in range(num_u):
-                for j in range(num_v):
-                    uv = uv_values[i, j]
-                    # Use visibility_status: 0=IN, 1=OUT, 2=ON, 3=UNKNOWN
-                    status = face.visibility_status(uv)
-                    # Mark as 1 if inside (TopAbs_IN = 0)
-                    trimming_mask[i, j, 0] = 1.0 if status == TopAbs_IN else 0.0
+            # Compute trimming mask via occwl's "inside" sampling, which returns
+            # a [num_u, num_v, 1] boolean grid (1 where the sample lies inside
+            # the face's trimmed region). This replaces a per-point
+            # face.visibility_status(uv) loop, which raised a gp_Pnt2d SWIG
+            # overload error when handed numpy-float UV coordinates on some
+            # pythonocc/occwl builds and made every face UV-grid fail.
+            inside_grid = uvgrid(face, num_u=num_u, num_v=num_v, method="inside")
+            if inside_grid is None:
+                logger.warning("Failed to extract trimming mask from face")
+                return None
+            trimming_mask = inside_grid.astype(np.float32)
 
             # Stack into [num_u, num_v, 7] array
             uv_grid = np.concatenate([
diff --git a/cadling/cadling/lib/topology/face_identity.py b/cadling/cadling/lib/topology/face_identity.py
index fd910fa..290f701 100644
--- a/cadling/cadling/lib/topology/face_identity.py
+++ b/cadling/cadling/lib/topology/face_identity.py
@@ -39,7 +39,7 @@
     from OCC.Core.TopoDS import TopoDS_Shape, TopoDS_Face, TopoDS_Edge, TopoDS_Vertex
     from OCC.Core.TopExp import TopExp_Explorer
     from OCC.Core.TopAbs import TopAbs_FACE, TopAbs_EDGE, TopAbs_VERTEX
-    from OCC.Core import topods
+    from OCC.Core.TopoDS import topods
 
     HAS_OCC = True
 except ImportError:
diff --git a/cadling/tests/unit/lib/geometry/test_uv_grid_extractor.py b/cadling/tests/unit/lib/geometry/test_uv_grid_extractor.py
index e5cac15..86022f5 100644
--- a/cadling/tests/unit/lib/geometry/test_uv_grid_extractor.py
+++ b/cadling/tests/unit/lib/geometry/test_uv_grid_extractor.py
@@ -266,3 +266,40 @@ def test_edge_grid_sizes(self, real_occ_edges):
             if result is not None:
                 assert result.shape == (num_u, 6)
                 assert np.all(np.isfinite(result))
+
+
+class TestFaceUVGridRegression:
+    """Regression: face UV-grid extraction must SUCCEED on a real face.
+
+    Before the fix, the trimming-mask computation called
+    ``face.visibility_status(uv)`` with numpy-float UV coordinates, which
+    raised a ``gp_Pnt2d`` SWIG overload error on pythonocc/occwl; the broad
+    ``except`` swallowed it and ``extract_uv_grid`` returned ``None`` for
+    *every* face. The other tests here guard their assertions with
+    ``if result is not None:`` and so passed vacuously, hiding the failure.
+    This test asserts success unconditionally on a self-contained box face.
+    """
+
+    @pytest.mark.requires_pythonocc
+    def test_box_face_uv_grid_succeeds(self):
+        pytest.importorskip("OCC")
+        pytest.importorskip("occwl")
+        from OCC.Core.BRepPrimAPI import BRepPrimAPI_MakeBox
+        from OCC.Core.TopAbs import TopAbs_FACE
+        from OCC.Core.TopExp import TopExp_Explorer
+        from OCC.Core.TopoDS import topods
+
+        box = BRepPrimAPI_MakeBox(10.0, 10.0, 10.0).Shape()
+        explorer = TopExp_Explorer(box, TopAbs_FACE)
+        face = topods.Face(explorer.Current())
+
+        result = FaceUVGridExtractor.extract_uv_grid(face, num_u=10, num_v=10)
+        assert result is not None, "face UV-grid extraction must succeed (gp_Pnt2d fix)"
+        assert result.shape == (10, 10, 7)
+        assert np.all(np.isfinite(result))
+
+        trimming = result[:, :, 6]
+        assert np.all((trimming == 0) | (trimming == 1))
+        # A planar box face is fully inside its trimmed region: real material
+        # is sampled (the mask was impossible to populate before the fix).
+        assert trimming.sum() > 0
diff --git a/cadling/tests/unit/lib/topology/test_face_identity.py b/cadling/tests/unit/lib/topology/test_face_identity.py
index ce4ee22..f5beddf 100644
--- a/cadling/tests/unit/lib/topology/test_face_identity.py
+++ b/cadling/tests/unit/lib/topology/test_face_identity.py
@@ -353,3 +353,38 @@ def test_register_all_vertices_no_occ(self):
 
             result = registry.register_all_vertices(mock_shape)
             assert result == {}
+
+
+class TestShapeIdentityRegistryRealShape:
+    """Regression: register_all must populate from a REAL OCC shape.
+
+    Before the fix, face_identity imported ``from OCC.Core import topods``,
+    which raises ``ImportError`` on pythonocc 7.8 ("cannot import name
+    'topods' from 'OCC.Core'"). That set ``HAS_OCC = False`` at module load,
+    so ``register_all_*`` registered nothing and every face/edge index was -1.
+    Every other test in this file mocks the shapes, so the real-OCC path was
+    never exercised and the bug went unnoticed.
+    """
+
+    @pytest.mark.requires_pythonocc
+    def test_register_all_from_real_box(self):
+        pytest.importorskip("OCC")
+        from OCC.Core.BRepPrimAPI import BRepPrimAPI_MakeBox
+
+        from cadling.lib.topology.face_identity import HAS_OCC, ShapeIdentityRegistry
+
+        assert HAS_OCC, "face_identity should detect pythonocc (topods import)"
+
+        box = BRepPrimAPI_MakeBox(10.0, 10.0, 10.0).Shape()
+        registry = ShapeIdentityRegistry()
+        registry.register_all(box)
+
+        # A box solid has 6 faces, 12 edges, 8 vertices.
+        assert registry.num_faces == 6
+        assert registry.num_edges == 12
+        assert registry.num_vertices == 8
+
+        # Index <-> id <-> shape round-trips for a registered face.
+        face_id, face = registry.get_face_by_index(0)
+        assert registry.get_face_index(face_id) == 0
+        assert registry.get_face(face_id) is face