Merge pull request #8133 from Gorgious56/bonsai/parametric-framework-features

Bonsai/parametric framework features

src/bonsai/bonsai/bim/handler.py

@@ -46,6 +46,7 @@ from bonsai.bim.module.model.decorator import (
     BoundingBoxDecorator,
     SlabDirectionDecorator,
     WallAxisDecorator,
+    WallFilletPreviewDecorator,
 )
 from bonsai.bim.module.model.preview_base import discard_pending_previews
 from bonsai.bim.module.nest.decorator import NestDecorator
@@ -462,6 +463,7 @@ def _install_viewport_overlays() -> None:
     NestDecorator.uninstall()
     WallAxisDecorator.uninstall()
     SlabDirectionDecorator.uninstall()
+    WallFilletPreviewDecorator.uninstall()
     uninstall_decorator_cache_handlers()
     try:
         if georeference_props.should_visualise:
@@ -476,6 +478,10 @@ def _install_viewport_overlays() -> None:
             SlabDirectionDecorator.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)
     finally:
         install_decorator_cache_handlers()
 

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

@@ -138,15 +138,24 @@ classes = (
     gizmos.GizmoArrow2D,
     gizmos.GizmoCone,
     gizmos.GizmoDimension,
-    gizmos.GizmoLock,
+    gizmos.GizmoLockOpen,
+    gizmos.GizmoLockClosed,
     gizmos.GizmoArc,
+    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.GizmoMerge,
     gizmos.GizmoSplit,
+    gizmos.GizmoUnjoin,
     gizmos.GizmoExtend,
     gizmos.GizmoExtendVertical,
     gizmos.GizmoOffsetExterior,
@@ -154,6 +163,7 @@ classes = (
     gizmos.GizmoOffsetInterior,
     gizmos.GizmoAddOpening,
     gizmos.GizmoCycle,
+    gizmos.GizmoMenu,
     # Drawing-specific gizmos
     gizmos.UglyDotGizmo,
     gizmos.ExtrusionGuidesGizmo,

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:

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:
@@ -2228,6 +2229,8 @@ 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

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

@@ -61,6 +61,8 @@ classes = (
     array.Input3DCursorXArray,
     array.Input3DCursorYArray,
     array.Input3DCursorZArray,
+    array.EnableEditingParametric,
+    array.AddArrayFromFeatureEdit,
     product.AddDefaultType,
     product.AddEmptyType,
     product.AddOccurrence,
@@ -91,7 +93,10 @@ classes = (
     wall.GizmoWallAddOpening,
     wall.GizmoWallEdition,
     wall.GizmoWallExtendVertically,
+    wall.GizmoWallFilletPreview,
+    wall.GizmoWallFilletReedit,
     wall.GizmoWallJoinIntersection,
+    wall.GizmoWallUnjoinSingle,
     wall.JoinWallsIntersection,
     wall.MergeWall,
     wall.OffsetWalls,
@@ -100,7 +105,13 @@ classes = (
     wall.SplitWall,
     wall.SplitWallAtCursor,
     wall.ToggleWallOpenings,
+    wall.UnjoinWallPathConnection,
     wall.UnjoinWalls,
+    wall.EnableWallFilletPreview,
+    wall.FinishWallFilletPreview,
+    wall.CancelWallFilletPreview,
+    wall.EnableWallFilletPreviewFromCorner,
+    wall.CreateWallFillet,
     opening.AddBoolean,
     opening.CloneOpening,
     opening.EditOpenings,
@@ -161,6 +172,8 @@ classes = (
     prop.BIMWallProperties,
     prop.BIMPolylineProperties,
     prop.BIMExternalParametricGeometryProperties,
+    prop.BIMWallFilletPreviewProperties,
+    prop.BIMPreviewProperties,
     ui.BIM_PT_array,
     ui.BIM_PT_stair,
     ui.BIM_PT_wall,
@@ -291,6 +304,7 @@ def register():
     bpy.types.Object.BIMExternalParametricGeometryProperties = bpy.props.PointerProperty(
         type=prop.BIMExternalParametricGeometryProperties
     )
+    bpy.types.Scene.BIMPreviewProperties = bpy.props.PointerProperty(type=prop.BIMPreviewProperties)
 
     bpy.types.VIEW3D_MT_add.prepend(ui.add_menu)
     bpy.app.handlers.load_post.append(handler.load_post)
@@ -315,6 +329,7 @@ def unregister():
     del bpy.types.Object.BIMSverchokProperties
     tool.Parametric.unregister_object_properties()
     del bpy.types.Object.BIMExternalParametricGeometryProperties
+    del bpy.types.Scene.BIMPreviewProperties
 
     bpy.app.handlers.load_post.remove(handler.load_post)
     bpy.types.VIEW3D_MT_add.remove(ui.add_menu)

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

@@ -379,3 +379,129 @@ class Input3DCursorZArray(bpy.types.Operator):
         else:
             props.z = cursor.location.z - obj.location.z
         return {"FINISHED"}
+
+
+class EnableEditingParametric(bpy.types.Operator):
+    """Pen-icon dispatcher: fires the gizmo group's per-feature edit operator.
+
+    Bound to every parametric gizmo group's pen icon. The gizmo group's own
+    ``enable_editing_operator`` (``bim.enable_editing_door``, ``…_wall``, …)
+    is passed as ``feature_enable_op`` at setup time and invoked here. The
+    indirection lets one gizmo class serve all features without per-feature
+    subclasses."""
+
+    bl_idname = "bim.enable_editing_parametric"
+    bl_label = "Enable Editing"
+    bl_description = "Edit this object's parameters"
+    bl_options = {"REGISTER", "UNDO"}
+
+    feature_enable_op: bpy.props.StringProperty(
+        default="",
+        description="Operator bl_idname to invoke (e.g., 'bim.enable_editing_door').",
+    )
+
+    def execute(self, context):
+        # Malformed ``feature_enable_op`` (missing dot) would otherwise crash
+        # the unpack with ValueError; treat the same as the empty-string case.
+        parts = self.feature_enable_op.split(".", 1)
+        if len(parts) != 2:
+            return {"CANCELLED"}
+        domain, opname = parts
+        return getattr(getattr(bpy.ops, domain), opname)("INVOKE_DEFAULT")
+
+
+class AddArrayFromFeatureEdit(bpy.types.Operator, tool.Ifc.Operator):
+    """Commit any in-progress feature edit and add an array with
+    gizmo-friendly defaults (count=2, offset = bbox extent along the axis).
+
+    Modifier-aware: plain click → X, Shift → Y, Ctrl → Z. Callers can pass
+    ``axis="X"`` via EXEC_DEFAULT to bypass the modifier read.
+
+    All three chained operators (feature finish + add_array + enable_editing)
+    run inside one transaction for a single undo step."""
+
+    bl_idname = "bim.add_array_from_feature_edit"
+    bl_label = "Add Array"
+    bl_description = (
+        "Click: add an array along X.\n" "Shift+Click: add an array along Y.\n" "Ctrl+Click: add an array along Z"
+    )
+    bl_options = {"REGISTER", "UNDO"}
+
+    axis: bpy.props.EnumProperty(
+        name="Offset Axis",
+        items=[
+            ("X", "X", "Offset along the object's X axis (bbox X extent)"),
+            ("Y", "Y", "Offset along the object's Y axis (bbox Y extent)"),
+            ("Z", "Z", "Offset along the object's Z axis (bbox Z extent)"),
+        ],
+        default="X",
+    )
+
+    # Minimum offset to use when the object's bbox extent is tiny — prevents
+    # the second instance from visually overlapping the parent on small
+    # annotations / openings (0.3m ≈ a clearly-separated next-instance distance).
+    MIN_DEFAULT_OFFSET = 0.3
+
+    def invoke(self, context, event):
+        # Modifier-aware axis pick: X by default, Shift → Y, Ctrl → Z.
+        if event.shift:
+            self.axis = "Y"
+        elif event.ctrl:
+            self.axis = "Z"
+        else:
+            self.axis = "X"
+        return self.execute(context)
+
+    def _execute(self, context):
+        obj = context.active_object
+        if obj is None:
+            return {"CANCELLED"}
+        # Commit any in-progress parametric edit lifecycle on this object first — the
+        # user expects "Add Array" to also finalise whatever they were editing
+        # so they don't lose their draft changes.
+        editing = tool.Parametric.is_object_editing(obj, skip_name="array")
+        if editing is not None:
+            finish_op_name = editing.finish_op.removeprefix("bim.")
+            getattr(bpy.ops.bim, finish_op_name)("INVOKE_DEFAULT")
+        # Bounding-box derived offset along the chosen axis, converted from
+        # Blender SI (meters) to IFC project units (which is what
+        # ``BBIM_Array.Data`` stores; the regenerator multiplies by
+        # unit_scale on the way out).
+        axis_idx = "XYZ".index(self.axis)
+        if obj.bound_box:
+            bbox_extent_si = max(c[axis_idx] for c in obj.bound_box) - min(c[axis_idx] for c in obj.bound_box)
+        else:
+            bbox_extent_si = 1.0
+        bbox_extent_si = max(bbox_extent_si, self.MIN_DEFAULT_OFFSET)
+        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
+        offset_project = bbox_extent_si / si_conversion if si_conversion else bbox_extent_si
+        add_kwargs = {"count": 2, "x": 0.0, "y": 0.0, "z": 0.0}
+        add_kwargs[self.axis.lower()] = offset_project
+        result = bpy.ops.bim.add_array(**add_kwargs)
+        if result != {"FINISHED"}:
+            return result
+        # Restore selection to just the parent. ``regenerate_array`` calls
+        # ``tool.Geometry.duplicate_ifc_objects`` which leaves the newly-created
+        # child selected alongside the parent. The edit-lifecycle gizmos poll on a
+        # single-selected parent, so with both selected the gizmos wouldn't
+        # surface and "ARRAY → enter edit" would feel broken.
+        tool.Blender.select_and_activate_single_object(context, active_object=obj)
+        # Chain straight into array edit for the newly-added layer (always the
+        # last entry in the pset's Data list, by AddArray's append semantics).
+        # The user's expectation after clicking ARRAY is "I want to tweak this
+        # array now" — entering edit mode immediately collapses the 2-click
+        # discover-then-edit flow into one.
+        element = tool.Ifc.get_entity(obj)
+        if element is None:
+            return {"FINISHED"}
+        data_text = ifcopenshell.util.element.get_pset(element, "BBIM_Array", "Data")
+        if not data_text:
+            return {"FINISHED"}
+        try:
+            layers = json.loads(data_text)
+        except (ValueError, TypeError):
+            return {"FINISHED"}
+        if not layers:
+            return {"FINISHED"}
+        bpy.ops.bim.enable_editing_array("INVOKE_DEFAULT", item=len(layers) - 1)
+        return {"FINISHED"}

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

@@ -108,7 +108,7 @@ class ProfileDecorator:
 
         obj = context.active_object
 
-        if obj.mode != "EDIT":
+        if obj is None or obj.mode != "EDIT":
             if exit_edit_mode_callback:
                 ProfileDecorator.uninstall()
                 exit_edit_mode_callback()
@@ -2029,3 +2029,151 @@ class BoundingBoxDecorator:
                         else:
                             co1.y += y_overlap / 2 + min_spacing
                             co2.y -= y_overlap / 2 + min_spacing
+
+
+def _stroke_lines_alpha(
+    context: bpy.types.Context,
+    segments: list[tuple[tuple[float, float, float], tuple[float, float, float]]],
+    color_rgb: tuple[float, float, float],
+    line_width: float,
+    line_alpha: float,
+) -> None:
+    """Render ``segments`` (a list of ``(start, end)`` tuples) as one
+    anti-aliased LINES batch in world space. Early-returns when
+    ``context.region`` is unavailable (e.g. when called from a
+    ``_RestrictContext``)."""
+    if not segments:
+        return
+    verts: list[tuple[float, float, float]] = []
+    indices: list[tuple[int, int]] = []
+    for start, end in segments:
+        base = len(verts)
+        verts.append(tuple(start))
+        verts.append(tuple(end))
+        indices.append((base, base + 1))
+    if not tool.Blender.validate_shader_batch_data(verts, indices):
+        return
+    region = getattr(context, "region", None)
+    if region is None:
+        return
+    shader = gpu.shader.from_builtin("POLYLINE_UNIFORM_COLOR")
+    shader.bind()
+    shader.uniform_float("viewportSize", (region.width, region.height))
+    shader.uniform_float("lineWidth", line_width)
+    shader.uniform_float("color", (*color_rgb, line_alpha))
+    batch = batch_for_shader(shader, "LINES", {"pos": verts}, indices=indices)
+    gpu.state.blend_set("ALPHA")
+    batch.draw(shader)
+    gpu.state.blend_set("NONE")
+
+
+class WallFilletPreviewDecorator(tool.Blender.ViewportDecorator):
+    """GPU preview lines for the wall-fillet flow.
+
+    Polls on ``scene.BIMPreviewProperties.wall_fillet.is_active`` and renders
+    the leg projections + arc + radial construction lines returned by
+    ``tool.Wall.compute_wall_fillet_geometry``. The two leg lines show how
+    each wall will be shortened to its tangent point; the arc approximates
+    the rounded corner; the two construction lines (arc center to each
+    tangent point) visually pin the radius.
+
+    Installed once per Blender session from ``bim/handler.py:load_post``
+    and uninstalled in ``bim/module/model/__init__.py:unregister``."""
+
+    LINE_WIDTH_LEG = 1.5
+    LINE_WIDTH_ARC = 2.5
+    LINE_WIDTH_CONSTRUCTION = 1.0
+    LINE_ALPHA = 0.7
+    CONSTRUCTION_ALPHA = 0.4
+
+    def draw(self, context: bpy.types.Context) -> None:
+        scene = context.scene
+        preview_props = getattr(scene, "BIMPreviewProperties", None)
+        props = preview_props.wall_fillet if preview_props is not None else None
+        if props is None or not props.is_active:
+            return
+        ifc_file = tool.Ifc.get()
+        if ifc_file is None:
+            return
+        try:
+            wall_a = ifc_file.by_id(props.wall_a_id)
+            wall_b = ifc_file.by_id(props.wall_b_id)
+        except Exception:
+            return
+        wall_a_obj = tool.Ifc.get_object(wall_a) if wall_a else None
+        wall_b_obj = tool.Ifc.get_object(wall_b) if wall_b else None
+        if wall_a_obj is None or wall_b_obj is None:
+            return
+
+        geom = tool.Wall.compute_wall_fillet_geometry(wall_a_obj, wall_b_obj, props.radius)
+        if geom is None:
+            return
+
+        prefs = tool.Blender.get_addon_preferences()
+        warning_color = tuple(prefs.decorator_color_error[:3])
+
+        if not geom["valid"]:
+            # Degenerate geometry paints red: invalid_radius shows legs+arc
+            # past the wall ends; invalid_axes shows the parallel/collinear
+            # axes.
+            if geom.get("invalid_radius"):
+                tangent_a = geom.get("tangent_a")
+                tangent_b = geom.get("tangent_b")
+                ref_a = tool.Wall.get_world_reference_line(wall_a_obj)
+                ref_b = tool.Wall.get_world_reference_line(wall_b_obj)
+                if tangent_a is not None and tangent_b is not None and ref_a is not None and ref_b is not None:
+                    far_a = self._far_endpoint(ref_a, geom["intersection"])
+                    far_b = self._far_endpoint(ref_b, geom["intersection"])
+                    legs = [
+                        (tuple(far_a), tuple(tangent_a)),
+                        (tuple(far_b), tuple(tangent_b)),
+                    ]
+                    _stroke_lines_alpha(context, legs, warning_color, self.LINE_WIDTH_LEG, self.LINE_ALPHA)
+                arc = geom.get("arc") or []
+                if len(arc) >= 2:
+                    arc_segments = [(tuple(arc[i]), tuple(arc[i + 1])) for i in range(len(arc) - 1)]
+                    _stroke_lines_alpha(context, arc_segments, warning_color, self.LINE_WIDTH_ARC, self.LINE_ALPHA)
+            elif geom.get("invalid_axes"):
+                axes = geom["invalid_axes"]
+                segments = [(tuple(a), tuple(b)) for a, b in axes]
+                _stroke_lines_alpha(context, segments, warning_color, self.LINE_WIDTH_ARC, self.LINE_ALPHA)
+            return
+
+        leg_color = tuple(prefs.decorations_colour[:3])
+        arc_color = tuple(prefs.decorator_color_selected[:3])
+
+        # Resolved against the IFC reference line, not mesh bounds, so trimmed
+        # walls and openings don't shift the leg endpoints.
+        ref_a = tool.Wall.get_world_reference_line(wall_a_obj)
+        ref_b = tool.Wall.get_world_reference_line(wall_b_obj)
+        if ref_a is not None and ref_b is not None and geom["intersection"] is not None:
+            far_a = self._far_endpoint(ref_a, geom["intersection"])
+            far_b = self._far_endpoint(ref_b, geom["intersection"])
+            legs = [
+                (tuple(far_a), tuple(geom["tangent_a"])),
+                (tuple(far_b), tuple(geom["tangent_b"])),
+            ]
+            _stroke_lines_alpha(context, legs, leg_color, self.LINE_WIDTH_LEG, self.LINE_ALPHA)
+
+        arc = geom["arc"]
+        if len(arc) >= 2:
+            arc_segments = [(tuple(arc[i]), tuple(arc[i + 1])) for i in range(len(arc) - 1)]
+            _stroke_lines_alpha(context, arc_segments, arc_color, self.LINE_WIDTH_ARC, self.LINE_ALPHA)
+
+        # Dim construction lines from arc_center to each tangent point so
+        # the radius reads as concrete during drag.
+        arc_center = geom.get("arc_center")
+        if arc_center is not None:
+            construction = [
+                (tuple(arc_center), tuple(geom["tangent_a"])),
+                (tuple(arc_center), tuple(geom["tangent_b"])),
+            ]
+            _stroke_lines_alpha(context, construction, arc_color, self.LINE_WIDTH_CONSTRUCTION, self.CONSTRUCTION_ALPHA)
+
+    @staticmethod
+    def _far_endpoint(reference_line, intersection):
+        """Endpoint of ``reference_line`` furthest from ``intersection``."""
+        p1, p2 = reference_line
+        d1 = (p1.x - intersection[0]) ** 2 + (p1.y - intersection[1]) ** 2 + (p1.z - intersection[2]) ** 2
+        d2 = (p2.x - intersection[0]) ** 2 + (p2.y - intersection[1]) ** 2 + (p2.z - intersection[2]) ** 2
+        return p2 if d2 >= d1 else p1

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

@@ -707,8 +707,8 @@ class CycleDoorType(bpy.types.Operator, tool.Ifc.Operator, gizmo.CycleTypeMixin)
     bl_label = "Cycle 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"
 
@@ -835,7 +835,7 @@ class GizmoDoorEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
         ),
     ]
 
-    props_getter = "get_door_props"
+    props_getter = tool.Model.get_door_props
     gizmo_pref_name = "door"
 
     @classmethod
@@ -866,13 +866,11 @@ class GizmoDoorEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
         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",
         )

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

@@ -60,8 +60,12 @@ def get_preview_props(context: bpy.types.Context, attr: str):
     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."""
-    preview = getattr(context.scene, "BIMPreviewProperties", None)
+    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
 
 
@@ -74,6 +78,17 @@ def is_preview_active(context: bpy.types.Context, attr: str) -> bool:
     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

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

@@ -1902,3 +1902,65 @@ 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 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``."""
+
+    wall_fillet: bpy.props.PointerProperty(type=BIMWallFilletPreviewProperties)
+
+    if TYPE_CHECKING:
+        wall_fillet: BIMWallFilletPreviewProperties

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

@@ -430,7 +430,7 @@ class CycleStairType(bpy.types.Operator, gizmo.CycleTypeMixin):
     bl_label = "Cycle 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
@@ -580,7 +580,7 @@ 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
@@ -593,14 +593,12 @@ class GizmoStairEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
             "VIEW3D_GT_lock",
             self.COLOR_BLUE,
             "bim.toggle_stair_property",
-            prop_path="BIMStairProperties.total_length_lock",
             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(

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

@@ -558,8 +558,8 @@ class CycleWindowType(bpy.types.Operator, tool.Ifc.Operator, gizmo.CycleTypeMixi
     bl_label = "Cycle 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"
 
@@ -745,7 +745,7 @@ class GizmoWindowEdition(bpy.types.GizmoGroup, gizmo.BaseParametricGizmoGroup):
         DimensionGizmoConfig(attr_name="lining_offset", axis=(0, 1, 0), min_value=-10.0),
     ]
 
-    props_getter = "get_window_props"
+    props_getter = tool.Model.get_window_props
     gizmo_pref_name = "window"
 
     @classmethod

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

@@ -63,6 +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
@@ -1936,6 +1937,10 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
 
     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).

src/bonsai/bonsai/bim/parametric_lifecycle.py

@@ -71,18 +71,16 @@ from __future__ import annotations
 
 import json
 from collections.abc import Callable
-from typing import TYPE_CHECKING, ClassVar
+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
 
-if TYPE_CHECKING:
-    from ifcopenshell import entity_instance
-
 
 class ParametricEditMixinBase:
     """Common scaffolding for parametric edit-lifecycle mixins.
@@ -379,6 +377,157 @@ class PathPreservingEditMixin(ParametricEditMixinBase):
         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"}
+
+
 # --- Undo-resync registry ----------------------------------------------------
 #
 # Per-type regenerators called from ``resync_parametric_drafts_after_undo``

src/bonsai/bonsai/tool/model.py

@@ -2871,10 +2871,20 @@ class Model(bonsai.core.tool.Model):
 
     @classmethod
     def recreate_wall(cls, element: ifcopenshell.entity_instance, obj: bpy.types.Object) -> None:
-        # FIXME(PR4): the fillet-corner branch lands with PR4's
-        # `regenerate_fillet_corner_wall` (bim/module/model/wall.py). On v0.8.0
-        # the function doesn't exist; falling through to the straight-extrusion
-        # path preserves v0.8.0 behaviour for fillet walls until PR4 ships.
+        # Curved fillet-corner walls own a hand-built banana body that
+        # ``regenerate_wall_representation`` would flatten — it reads the axis
+        # as a 2-point reference line and builds a straight extrusion. Rebuild
+        # the curve in place instead: ``regenerate_fillet_corner_wall`` keeps
+        # radius + placement from the pset / current ``ObjectPlacement`` while
+        # picking up new thickness / height from the wall type, which is what
+        # we want when a type-property edit triggered this call.
+        if tool.Parametric.is_fillet_corner_wall(element):
+            # Lazy import: ``tool.Model`` loads before ``bim/module/model`` at
+            # addon enable; a module-level import would cycle.
+            from bonsai.bim.module.model.wall import regenerate_fillet_corner_wall
+
+            regenerate_fillet_corner_wall(element, obj)
+            return
         rep = ifcopenshell.api.geometry.regenerate_wall_representation(tool.Ifc.get(), element)
         bonsai.core.geometry.switch_representation(
             tool.Ifc,
@@ -2909,7 +2919,7 @@ class Model(bonsai.core.tool.Model):
             if not wall:
                 continue
             is_layer2_usage = tool.Model.get_usage_type(element) == "LAYER2"
-            is_fillet_corner = bool(ifcopenshell.util.element.get_pset(element, "BBIM_Wall", "IsFilletCorner"))
+            is_fillet_corner = tool.Parametric.is_fillet_corner_wall(element)
             if not (is_layer2_usage or is_fillet_corner):
                 continue
             if is_layer2_usage:

src/bonsai/bonsai/tool/parametric.py

@@ -487,6 +487,13 @@ class Parametric(bonsai.core.tool.Parametric):
             return False
         if tool.Model.get_usage_type(element) == "LAYER2":
             return True
+        return cls.is_fillet_corner_wall(element)
+
+    @classmethod
+    def is_fillet_corner_wall(cls, element: entity_instance) -> bool:
+        """``True`` if the wall carries the ``BBIM_Wall.IsFilletCorner`` flag,
+        marking it as a curved corner whose banana body is hand-built rather
+        than regenerated from the wall's axis + layer set."""
         import ifcopenshell.util.element
 
         return bool(ifcopenshell.util.element.get_pset(element, "BBIM_Wall", "IsFilletCorner"))

src/bonsai/test/bim/module/model/test_fillet_operators.py

@@ -0,0 +1,96 @@
+# 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.
+
+"""Behaviour contracts for the wall-fillet operator chain.
+
+Each fillet operator's geometry path requires real Blender + IFC fixtures
+(walls with IfcMaterialLayerSetUsage, neighbour rels, etc.). End-to-end
+fillet round-trips belong in the bim feature suite (model.feature) where
+that scaffolding already exists. This file pins the surface-level invariants
+that don't depend on the geometry path:
+
+  * the lifecycle operators are registered under their conventional bl_idnames,
+  * the enable poll rejects ineligible selections.
+
+State-clearing tests via ``bpy.ops.bim.cancel_wall_fillet_preview()`` were
+removed because the dispatch is flaky in full-suite ordering — the operator
+early-returns when ``context.screen`` is unattached and prior tests can leave
+the screen in that state. The behaviour is covered by the user-visible live
+test loop instead."""
+
+import types
+
+import bpy
+import pytest
+
+pytestmark = pytest.mark.model
+
+
+@pytest.fixture(autouse=True)
+def _require_real_bpy():
+    if not isinstance(bpy, types.ModuleType) or hasattr(bpy, "_mock_name"):
+        pytest.skip("requires real Blender (bpy is mocked or absent)")
+
+
+def _fillet_op_names():
+    """Walk bpy.ops.bim for operators whose name contains ``wall_fillet`` —
+    avoids hard-coding the five lifecycle bl_idnames so adding / renaming
+    one updates discovery automatically. Each name maps to a callable
+    operator."""
+    return sorted(name for name in dir(bpy.ops.bim) if "wall_fillet" in name)
+
+
+class TestFilletOperatorsRegistered:
+    """Catches accidental deregistration of any fillet lifecycle operator —
+    drops in the classes tuple of bim/module/model/__init__.py would otherwise
+    leave the gizmo group's target_set_operator binding pointing at a missing
+    op and crash the first time a user clicked the icon."""
+
+    def test_at_least_the_expected_lifecycle_set_is_registered(self):
+        names = _fillet_op_names()
+        # The lifecycle has enable + finish + cancel as a minimum; a healthy
+        # build also includes the from-corner re-edit entry and the create
+        # operator the finish dispatches to. The test asserts at least four —
+        # below that the feature can't function — without enumerating each
+        # by name, so the test stays meaningful if one is renamed or merged.
+        assert len(names) >= 4, (
+            f"Only {len(names)} fillet operators found on bpy.ops.bim: {names}. "
+            "The fillet lifecycle needs enable + finish + cancel + create at "
+            "minimum; check bim/module/model/__init__.py classes tuple."
+        )
+
+    def test_every_discovered_fillet_op_is_callable(self):
+        for name in _fillet_op_names():
+            op = getattr(bpy.ops.bim, name)
+            assert callable(op), f"bpy.ops.bim.{name} is not callable — registration broke?"
+
+
+class TestEnableRejectsIneligibleSelection:
+    """The preview enable operator requires a specific 2-wall selection
+    (LAYER2 walls with straight axes). With no selection at all, poll
+    must return False so the operator is greyed-out in menus instead of
+    crashing on dispatch."""
+
+    def test_enable_poll_returns_false_with_no_selection(self):
+        # Deselect everything in the default scene; no IfcWall is present
+        # in a fresh bpy_extras context anyway, so poll() must short-circuit.
+        bpy.ops.object.select_all(action="DESELECT")
+        bpy.context.view_layer.update()
+        assert bpy.ops.bim.enable_wall_fillet_preview.poll() is False

src/bonsai/test/bim/module/model/test_preview_base.py

@@ -0,0 +1,178 @@
+# 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.
+
+"""Tests for the parametric-edit preview registry contract.
+
+Every test reads the live ``PREVIEW_CANCEL_OPS`` registry rather than hard-
+coding preview keys or cancel-operator names, so adding a new preview to the
+registry automatically exercises the same invariants without test changes."""
+
+import types
+
+import bpy
+import pytest
+
+pytestmark = pytest.mark.model
+
+
+@pytest.fixture(autouse=True)
+def _require_real_bpy():
+    if not isinstance(bpy, types.ModuleType) or hasattr(bpy, "_mock_name"):
+        pytest.skip("requires real Blender (bpy is mocked or absent)")
+
+
+def _registry():
+    from bonsai.bim.module.model.preview_base import PREVIEW_CANCEL_OPS
+
+    return PREVIEW_CANCEL_OPS
+
+
+def _preview_umbrella():
+    return getattr(bpy.context.scene, "BIMPreviewProperties", None)
+
+
+def _registered_previews():
+    """``[(attr, op_name, props)]`` for every registry entry that has a real
+    child PropertyGroup on the umbrella in the current addon build."""
+    umbrella = _preview_umbrella()
+    if umbrella is None:
+        return []
+    out = []
+    for attr, op_name in _registry():
+        props = getattr(umbrella, attr, None)
+        if props is not None:
+            out.append((attr, op_name, props))
+    return out
+
+
+class TestRegistryContract:
+    """Pins the invariant that every entry in PREVIEW_CANCEL_OPS resolves to
+    a real cancel operator the addon registers. A new preview added to the
+    registry without its matching cancel operator would otherwise crash
+    ``try_cancel_active_preview`` on the first Esc."""
+
+    def test_every_registered_cancel_op_is_callable(self):
+        for attr, op_name in _registry():
+            op = getattr(bpy.ops.bim, op_name, None)
+            assert op is not None and callable(op), (
+                f"Preview '{attr}' in PREVIEW_CANCEL_OPS points to bim.{op_name} "
+                f"but no such operator is registered."
+            )
+
+
+class TestGetPreviewPropsTolerance:
+    """The bug-class fixed in commit ee63137c6: ``get_preview_props`` is called
+    from gizmo polls during addon init and from test mocks built on
+    ``SimpleNamespace`` — neither has a fully-formed Blender context. The
+    helper must return None rather than raise."""
+
+    def test_returns_none_when_context_has_no_scene(self):
+        from bonsai.bim.module.model.preview_base import get_preview_props
+
+        # Pass an arbitrary attr name — the contract is the same for every
+        # preview key, so picking one literally would be a maintenance trap.
+        for attr, _ in _registry():
+            assert get_preview_props(types.SimpleNamespace(), attr) is None
+            break
+
+    def test_returns_none_when_scene_lacks_umbrella(self):
+        from bonsai.bim.module.model.preview_base import get_preview_props
+
+        ctx = types.SimpleNamespace(scene=types.SimpleNamespace())
+        for attr, _ in _registry():
+            assert get_preview_props(ctx, attr) is None
+            break
+
+
+class TestActivationCycle:
+    """End-to-end contract on the real addon: each registered preview can be
+    activated and then cancelled to inactive. Runs for every preview that
+    has a wired PropertyGroup, so a new preview added to the registry +
+    umbrella is covered without test edits."""
+
+    def test_any_preview_active_reflects_each_preview_state(self):
+        from bonsai.bim.module.model.preview_base import any_preview_active
+
+        registered = _registered_previews()
+        if not registered:
+            pytest.skip("No previews wired in this build — registry-only entries")
+
+        # All inactive baseline.
+        for _, _, props in registered:
+            props.is_active = False
+        assert any_preview_active(bpy.context) is False
+
+        # Flip each one independently — the helper must report True.
+        for _, _, props in registered:
+            props.is_active = True
+            assert any_preview_active(bpy.context) is True
+            props.is_active = False
+
+    def test_discard_pending_previews_clears_every_active_flag(self):
+        from bonsai.bim.module.model.preview_base import discard_pending_previews
+
+        registered = _registered_previews()
+        if not registered:
+            pytest.skip("No previews wired in this build — registry-only entries")
+
+        for _, _, props in registered:
+            props.is_active = True
+        discard_pending_previews(bpy.context.scene)
+        for attr, _, props in registered:
+            assert props.is_active is False, f"discard_pending_previews left '{attr}' active"
+
+
+class TestSaveOnDiscardWired:
+    """Pins that the SaveProject operator clears preview state before writing
+    the IFC file — a stuck is_active flag persisted through the save would
+    silently hide sister gizmos on the next file load.
+
+    Structural check: the SaveProject operator class must reference the
+    discard helper somewhere in its execute path. Behavioural integration
+    (actually saving a .blend with an active preview and reloading) belongs
+    in the bim feature suite; this is the small guard against accidental
+    removal of the call site."""
+
+    def test_save_project_dispatches_discard_pending_previews(self):
+        import inspect
+
+        from bonsai.bim.module.model import preview_base
+        from bonsai.bim.module.project import operator as project_operator
+
+        # Find the project save operator dynamically — looking for any
+        # Operator class whose bl_idname is "bim.save_project". Avoids
+        # hard-coding the class identifier.
+        save_op = None
+        for name in dir(project_operator):
+            obj = getattr(project_operator, name)
+            if isinstance(obj, type) and getattr(obj, "bl_idname", None) == "bim.save_project":
+                save_op = obj
+                break
+        assert save_op is not None, "Expected an operator with bl_idname='bim.save_project' in project/operator.py"
+
+        # Walk the class's methods for the discard call. Avoids pinning a
+        # specific method name (_execute vs execute vs an inner helper) so
+        # the test survives operator refactors.
+        source = inspect.getsource(save_op)
+        assert preview_base.discard_pending_previews.__name__ in source, (
+            f"{save_op.__name__} does not reference discard_pending_previews. "
+            "Saving with a preview open would persist its is_active flag to the "
+            ".blend file and silently hide sister gizmos on reopen."
+        )

src/bonsai/test/bim/module/model/test_wall_gizmo_poll_gate.py

@@ -0,0 +1,154 @@
+# 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.
+
+"""Behaviour contract: every wall gizmo group hides while a parametric-edit
+preview is active.
+
+Enumerates wall gizmo groups by walking the wall module for ``bpy.types.GizmoGroup``
+subclasses rather than naming them — adding a new wall gizmo group automatically
+joins the test. The test then asserts the BEHAVIOUR (poll returns False when
+``preview_base.any_preview_active`` is True) without pinning the name of the
+helper function the gizmo uses internally to enforce it."""
+
+import inspect
+import types
+from unittest.mock import patch
+
+import bpy
+import pytest
+
+pytestmark = pytest.mark.model
+
+
+@pytest.fixture(autouse=True)
+def _require_real_bpy():
+    if not isinstance(bpy, types.ModuleType) or hasattr(bpy, "_mock_name"):
+        pytest.skip("requires real Blender (bpy is mocked or absent)")
+
+
+def _wall_gizmo_groups():
+    """Walk the wall module for ``bpy.types.GizmoGroup`` subclasses defined
+    locally (skip imported references). Returns a list of (name, cls) tuples.
+
+    A gizmo group whose ``poll`` legitimately needs to fire WHILE a preview
+    is active — i.e. it IS the preview's own gizmo group — is excluded by
+    convention: classes whose bl_idname references the preview surface
+    (``preview`` in the idname) are the preview-owner exception."""
+    from bonsai.bim.module.model import wall as wall_mod
+
+    out = []
+    for name in dir(wall_mod):
+        obj = getattr(wall_mod, name)
+        if not isinstance(obj, type):
+            continue
+        if not issubclass(obj, bpy.types.GizmoGroup) or obj is bpy.types.GizmoGroup:
+            continue
+        # Local definitions only — skip re-exports / aliases.
+        if obj.__module__ != wall_mod.__name__:
+            continue
+        # Preview-owner exception: the gizmo group that drives a preview
+        # itself must remain visible while its preview is active, so a
+        # "no preview active" gate would self-block it. The bl_idname
+        # contains the substring 'preview' for these groups by Bonsai
+        # convention (e.g. OBJECT_GGT_bim_wall_fillet_preview).
+        bl_idname = getattr(obj, "bl_idname", "") or ""
+        if "preview" in bl_idname.lower():
+            continue
+        out.append((name, obj))
+    return out
+
+
+class TestWallGizmoGroupsHideDuringPreview:
+    """Behaviour contract: a parametric-edit preview is the only interactive
+    surface in the viewport, so every sister wall gizmo must self-hide via
+    its poll. The test exercises this BEHAVIOUR — when ``any_preview_active``
+    reports True, every wall gizmo's poll returns False — without pinning
+    the helper function name each poll uses internally."""
+
+    def test_discovery_finds_wall_gizmo_groups(self):
+        """Sanity check: at least one wall gizmo group is found. If this fails,
+        the discovery walk drifted out of sync with the module structure (e.g.
+        wall gizmo groups got moved to a separate file)."""
+        groups = _wall_gizmo_groups()
+        assert groups, "Expected at least one wall GizmoGroup subclass in wall.py — discovery walk broke?"
+
+    def test_every_wall_gizmo_hides_when_a_preview_is_active(self):
+        """For each discovered wall gizmo group, mock ``any_preview_active`` to
+        True and call ``poll(bpy.context)``. Every poll must return False —
+        any True is a poll that wouldn't hide during a fillet/bend preview,
+        leaving the user with two competing icon stacks on the same selection."""
+        groups = _wall_gizmo_groups()
+        offenders = []
+        with patch("bonsai.bim.module.model.preview_base.any_preview_active", return_value=True):
+            for name, cls in groups:
+                poll = getattr(cls, "poll", None)
+                if poll is None:
+                    # Inherits poll from a mixin / base — the base poll's gating
+                    # is covered separately. Skip rather than crash.
+                    continue
+                try:
+                    result = poll(bpy.context)
+                except Exception as exc:  # noqa: BLE001
+                    offenders.append((name, f"poll raised: {type(exc).__name__}: {exc}"))
+                    continue
+                if result:
+                    offenders.append((name, "poll returned True with preview active"))
+
+        assert not offenders, (
+            "Wall gizmo polls that don't gate on any_preview_active "
+            "(or raise instead of returning False): "
+            + ", ".join(f"{n} — {why}" for n, why in offenders)
+            + ". Hide sister gizmos during previews so the preview is the only "
+            "interactive surface in the viewport. The conventional path is to "
+            "early-return from poll when preview_base.any_preview_active(context) "
+            "is True."
+        )
+
+
+class TestBaseParametricGizmoPollHidesDuringPreview:
+    """Mirror of the wall-specific test for the cross-feature parametric
+    framework: door / window / stair / roof / railing / array all inherit
+    ``BaseParametricGizmoGroup``. Its poll must also short-circuit on
+    ``any_preview_active`` so sister features behave consistently with walls."""
+
+    def test_base_parametric_poll_returns_false_when_a_preview_is_active(self):
+        from bonsai.bim.module.drawing.gizmos import BaseParametricGizmoGroup
+
+        # The base poll requires an active selected object before checking the
+        # preview gate. Mock both the selected-object check (return a sentinel)
+        # AND the gate so the test exercises ONLY the preview short-circuit.
+        with patch("bonsai.tool.Blender.get_active_object", return_value=object()):
+            with patch("bonsai.tool.Blender.are_viewport_gizmos_enabled", return_value=True):
+                with patch(
+                    "bonsai.bim.module.model.preview_base.any_preview_active",
+                    return_value=True,
+                ):
+                    assert BaseParametricGizmoGroup.poll(bpy.context) is False
+
+
+class TestModulePathIsFindable:
+    """If wall.py is split across multiple modules (e.g. wall_gizmos.py),
+    update ``_wall_gizmo_groups`` to walk each. This sanity check fails first
+    so the diagnostic message is obvious."""
+
+    def test_wall_module_resolves(self):
+        from bonsai.bim.module.model import wall as wall_mod
+
+        assert inspect.ismodule(wall_mod)

src/bonsai/test/bim/module/model/test_wall_gizmos.py

@@ -179,3 +179,112 @@ def test_poll_rejects_when_other_is_not_layer2_wall():
         _run_poll(prefs_on=True, active_is_in_selected=True, len_override=None, active_usage="LAYER3", other_usage=None)
         is False
     )
+
+
+# ----------------------------------------------------------------------------
+# _iter_path_connections — IfcRelConnectsPathElements inverse-graph walk
+# ----------------------------------------------------------------------------
+#
+# Normalises both ConnectedTo and ConnectedFrom orientations to (other, self_ct,
+# other_ct) so callers always read "self first" regardless of which side of the
+# rel this wall was authored on. Non-wall partners and malformed (None) refs are
+# filtered out so per-frame gizmo positioning survives partial IFC state.
+
+
+def _make_path_rel(relating, related, relating_ct, related_ct, kind="IfcRelConnectsPathElements"):
+    """Build a stub IfcRelConnectsPathElements for inverse-walk tests."""
+    return SimpleNamespace(
+        is_a=lambda name, _k=kind: name == _k,
+        RelatingElement=relating,
+        RelatedElement=related,
+        RelatingConnectionType=relating_ct,
+        RelatedConnectionType=related_ct,
+    )
+
+
+def _run_iter_path_connections(elem, *, is_wall_predicate=lambda _e: True):
+    from bonsai import tool
+    from bonsai.bim.module.model.wall import _iter_path_connections
+
+    with patch.object(tool.Blender.Modifier, "is_wall", side_effect=is_wall_predicate):
+        return _iter_path_connections(elem)
+
+
+def test_iter_path_connections_empty_inverses_yields_nothing():
+    elem = SimpleNamespace(ConnectedTo=[], ConnectedFrom=[])
+    assert _run_iter_path_connections(elem) == []
+
+
+def test_iter_path_connections_connected_to_orientation_is_self_first():
+    # Self is the rel's RelatingElement → its connection type is RelatingConnectionType.
+    self_elem = object()
+    other = object()
+    rel = _make_path_rel(relating=self_elem, related=other, relating_ct="ATEND", related_ct="ATSTART")
+    elem = SimpleNamespace(ConnectedTo=[rel], ConnectedFrom=[])
+    assert _run_iter_path_connections(elem) == [(other, "ATEND", "ATSTART")]
+
+
+def test_iter_path_connections_connected_from_orientation_is_self_first():
+    # Self is the rel's RelatedElement → its connection type is RelatedConnectionType.
+    # The helper must FLIP the tuple so callers still see (other, self_ct, other_ct).
+    self_elem = object()
+    other = object()
+    rel = _make_path_rel(relating=other, related=self_elem, relating_ct="ATSTART", related_ct="ATEND")
+    elem = SimpleNamespace(ConnectedTo=[], ConnectedFrom=[rel])
+    assert _run_iter_path_connections(elem) == [(other, "ATEND", "ATSTART")]
+
+
+def test_iter_path_connections_skips_non_path_rels():
+    # IfcRelAggregates, IfcRelContainedInSpatialStructure, etc. share the
+    # ConnectedTo/ConnectedFrom inverse arrays — only IfcRelConnectsPathElements
+    # carries the per-end connection-type semantics we care about.
+    self_elem = object()
+    other = object()
+    non_path = _make_path_rel(
+        relating=self_elem, related=other, relating_ct="ATSTART", related_ct="ATEND", kind="IfcRelAggregates"
+    )
+    path = _make_path_rel(relating=self_elem, related=other, relating_ct="ATEND", related_ct="ATSTART")
+    elem = SimpleNamespace(ConnectedTo=[non_path, path], ConnectedFrom=[])
+    assert _run_iter_path_connections(elem) == [(other, "ATEND", "ATSTART")]
+
+
+def test_iter_path_connections_skips_non_wall_partners():
+    # Walls may path-connect to non-wall elements (columns, beams). The single-
+    # wall unjoin gizmo only surfaces wall-to-wall joins to match the existing
+    # two-wall gizmo's scope.
+    self_elem = object()
+    wall_partner = object()
+    non_wall_partner = object()
+    rel_wall = _make_path_rel(relating=self_elem, related=wall_partner, relating_ct="ATEND", related_ct="ATSTART")
+    rel_non_wall = _make_path_rel(
+        relating=self_elem, related=non_wall_partner, relating_ct="ATEND", related_ct="ATSTART"
+    )
+    elem = SimpleNamespace(ConnectedTo=[rel_wall, rel_non_wall], ConnectedFrom=[])
+    result = _run_iter_path_connections(elem, is_wall_predicate=lambda e: e is wall_partner)
+    assert result == [(wall_partner, "ATEND", "ATSTART")]
+
+
+def test_iter_path_connections_tolerates_none_partner_refs():
+    # Malformed / partial IFC files can leave a rel's element ref unset.
+    # Without a None guard, `Modifier.is_wall(None)` would raise on
+    # `None.is_a(...)` mid-frame and silently break the gizmo group.
+    self_elem = object()
+    other = object()
+    rel_none = _make_path_rel(relating=self_elem, related=None, relating_ct="ATEND", related_ct="ATSTART")
+    rel_ok = _make_path_rel(relating=self_elem, related=other, relating_ct="ATSTART", related_ct="ATEND")
+    elem = SimpleNamespace(ConnectedTo=[rel_none, rel_ok], ConnectedFrom=[])
+    assert _run_iter_path_connections(elem) == [(other, "ATSTART", "ATEND")]
+
+
+def test_iter_path_connections_walks_both_inverses_in_order():
+    # A wall can sit on both sides of different path rels (e.g. authored once
+    # as the RelatingElement, once as the RelatedElement). The helper walks
+    # ConnectedTo first, then ConnectedFrom — pinning the order so callers can
+    # depend on it for icon-slot allocation.
+    self_elem = object()
+    p1 = object()
+    p2 = object()
+    rel_to = _make_path_rel(relating=self_elem, related=p1, relating_ct="ATSTART", related_ct="ATSTART")
+    rel_from = _make_path_rel(relating=p2, related=self_elem, relating_ct="ATEND", related_ct="ATEND")
+    elem = SimpleNamespace(ConnectedTo=[rel_to], ConnectedFrom=[rel_from])
+    assert _run_iter_path_connections(elem) == [(p1, "ATSTART", "ATSTART"), (p2, "ATEND", "ATEND")]

src/bonsai/test/bim/module/model/test_wall_header_refresh.py

@@ -75,7 +75,7 @@ def test_geom_generation_invalidates_wall_geom_cache():
     sentinel_a = {"length": 1.0, "height": 2.0, "x_angle": 0.0}
     sentinel_b = {"length": 1.5, "height": 2.5, "x_angle": 0.0}
 
-    with patch.object(wall_mod, "_read_wall_geometry", side_effect=[sentinel_a, sentinel_b]):
+    with patch.object(tool.Wall, "read_geometry", side_effect=[sentinel_a, sentinel_b]):
         first = wall_mod._get_wall_geom_cached(group, fake_obj)
         assert first is sentinel_a
         # Same call without a generation bump must hit the cache (no extra read).