Show resolved unit symbols in read-only Pset/Qto view; add write-back and fallback regression tests

Previously, unit symbols only appeared while a Pset/Qto was in edit mode
(pencil icon) -- the read-only summary view read raw {name: value} dicts
straight from ifcopenshell.util.element.get_psets(), a completely separate
path from the Attribute/unit_symbol machinery, so it never showed a label
even after the earlier fixes. This matters for the "someone in the field
just looking at values" use case, not just editing.

- bim/module/pset/data.py: switch to get_psets(verbose=True) to get each
  property's own entity id, then resolve its unit symbol the same
  override-aware way the edit-mode path does (tool.Pset.get_unit_symbol_for_prop).
  Falls back gracefully (empty symbol) for IfcPreDefinedPropertySet
  attributes, which aren't IfcProperty entities and can't carry a Unit
  override.
- bim/module/pset/ui.py: read-only value button now shows "250 mm" instead
  of just "250".

Also adds the regression tests planned but not yet committed:
- test/tool/test_pset.py: edit a property with its own Unit override and
  write it back, confirming no rescale and the override survives.
- test/bim/test_prop.py (new): get_display_name() falls back to the plain
  name (no crash) when no unit is resolvable or the project has no units
  assigned at all.

src/bonsai/bonsai/bim/helper.py

@@ -236,11 +236,9 @@ def import_attribute(
     elif data_type == "integer":
         new.int_value = 0 if new.is_null else int(data[attribute.name()])
     elif data_type == "float":
-        attribute_type = attribute.type_of_attribute()
-        if attribute_type._is("IfcLengthMeasure"):
-            new.special_type = "LENGTH"
-        elif attribute_type._is("IfcForceMeasure"):
-            new.special_type = "FORCE"
+        measure_class = attribute.type_of_attribute().declared_type().name()
+        new.special_type = tool.Pset.get_special_type_for_measure_class(measure_class)
+        new.unit_symbol = tool.Pset.get_unit_symbol_for_special_type(new.special_type, tool.Ifc.get())
         new.float_value = 0.0 if new.is_null else float(data[attribute.name()])
     elif data_type == "enum":
         attribute_type = attribute.type_of_attribute()

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

@@ -54,7 +54,7 @@ class Data:
         ifc_file = tool.Ifc.get()
         results = []
         psetqtos = ifcopenshell.util.element.get_psets(
-            element, psets_only=psets_only, qtos_only=qtos_only, should_inherit=False
+            element, psets_only=psets_only, qtos_only=qtos_only, should_inherit=False, verbose=True
         )
         for name, data in sorted(psetqtos.items()):
             pset = ifc_file.by_id(data["id"])
@@ -69,13 +69,28 @@ class Data:
                     "id": data["id"],
                     "Name": name,
                     "is_expanded": is_expanded.get(data["id"], True),
-                    "Properties": [{"Name": k, "NominalValue": v} for k, v in sorted(data.items()) if k != "id"],
+                    "Properties": [
+                        cls.property_display_data(ifc_file, k, v) for k, v in sorted(data.items()) if k != "id"
+                    ],
                     "shared_pset_uses": len(pset_uses),
                     "has_template": has_template,
                 }
             )
         return sorted(results, key=lambda v: v["Name"])
 
+    @classmethod
+    def property_display_data(cls, ifc_file: ifcopenshell.file, name: str, verbose_value: Any) -> dict[str, Any]:
+        # Predefined property sets (e.g. IfcDoorPanelProperties) expose plain
+        # attribute values even in verbose mode, since they're typed IFC
+        # attributes rather than IfcProperty entities with their own id/Unit.
+        if not isinstance(verbose_value, dict):
+            return {"Name": name, "NominalValue": verbose_value, "UnitSymbol": ""}
+
+        unit_symbol = ""
+        if (prop_id := verbose_value.get("id")) and (prop_entity := ifc_file.by_id(prop_id)):
+            unit_symbol = tool.Pset.get_unit_symbol_for_prop(prop_entity, ifc_file)
+        return {"Name": name, "NominalValue": verbose_value["value"], "UnitSymbol": unit_symbol}
+
     @classmethod
     def format_pset_enum(cls, psets):
         enum_items = []

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

@@ -203,9 +203,10 @@ def draw_psetqto_ui(
                 row = box.row(align=True)
                 row.scale_y = 0.8
                 row.label(text=prop["Name"])
-                op = row.operator(
-                    "bim.select_similar", text=get_display_value(nominal_value), icon="NONE", emboss=False
-                )
+                display_value = get_display_value(nominal_value)
+                if unit_symbol := prop["UnitSymbol"]:
+                    display_value = f"{display_value} {unit_symbol}"
+                op = row.operator("bim.select_similar", text=display_value, icon="NONE", emboss=False)
                 op.key = '"' + pset["Name"].replace('"', '\\"') + '"."' + prop["Name"].replace('"', '\\"') + '"'
                 # calculate sum of all selected objects
                 if active_operator:

src/bonsai/bonsai/bim/prop.py

@@ -21,7 +21,6 @@ import os
 from typing import TYPE_CHECKING, Any, Literal, Union, assert_never, get_args
 
 import bpy
-import ifcopenshell.util.unit
 from bpy.props import (
     BoolProperty,
     CollectionProperty,
@@ -250,44 +249,19 @@ def set_numerical_value(self: "Attribute", value_name: str, new_value: Union[flo
     self[value_name] = new_value
 
 
-def get_length_value(self: "Attribute") -> float:
-    si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-    return self.float_value * si_conversion
-
-
-def set_length_value(self: "Attribute", value: float) -> None:
-    si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-    self.float_value = value / si_conversion
-
-
 def get_display_name(self: "Attribute") -> str:
-    DISPLAY_UNIT_TYPES = ("AREA", "VOLUME", "FORCE")
     name = self.name
-    if not self.special_type or self.special_type not in DISPLAY_UNIT_TYPES:
+    if not self.unit_symbol:
         return name
-
-    unit_type = f"{self.special_type}UNIT"
-    project_unit = ifcopenshell.util.unit.get_project_unit(tool.Ifc.get(), unit_type)
-    if not project_unit:
-        return name
-
-    unit_symbol = ifcopenshell.util.unit.get_unit_symbol(project_unit)
-    return f"{name}, {unit_symbol}"
+    return f"{name}, {self.unit_symbol}"
 
 
 AttributeDataType = Literal["string", "integer", "float", "boolean", "enum", "file", "list[string]"]
-AttributeSpecialType = Literal[
-    "",
-    "DATE",
-    "DATETIME",
-    "LENGTH",
-    "AREA",
-    "VOLUME",
-    "FORCE",
-    "LOGICAL",
-    "URI",
-    "DURATION",
-]
+# Either "", "DATE", "DATETIME", "LOGICAL", "URI", "DURATION", or an
+# IfcUnitEnum/IfcDerivedUnitEnum value with the "UNIT" suffix stripped (e.g.
+# "LENGTH", "PRESSURE", "MODULUSOFELASTICITY") as returned by
+# tool.Pset.get_special_type_for_prop().
+AttributeSpecialType = str
 
 
 class Attribute(PropertyGroup):
@@ -318,9 +292,6 @@ class Attribute(PropertyGroup):
         get=lambda self: float(self.get("float_value", 0.0)),
         set=set_float_value,
     )
-    length_value: FloatProperty(
-        name="Value", description=tooltip, get=get_length_value, set=set_length_value, unit="LENGTH"
-    )
     enum_items: StringProperty(name="Value")
     """Json serialized mapping of enum items:
         Typically a dictionary of string identifiers to item names.
@@ -342,6 +313,7 @@ class Attribute(PropertyGroup):
     value_max: FloatProperty(description="This is used to validate int_value and float_value")
     value_max_constraint: BoolProperty(default=False, description="True if the numerical value has an upper bound")
     special_type: StringProperty(name="Special Value Type", default="")
+    unit_symbol: StringProperty(name="Unit Symbol", default="")
     use_explorer_ui: BoolProperty()
     metadata: StringProperty(name="Metadata", description="For storing some additional information about the attribute")
     update: StringProperty(name="Update", description="Custom update function to be executed")
@@ -357,7 +329,6 @@ class Attribute(PropertyGroup):
         bool_value: bool
         int_value: int
         float_value: float
-        length_value: float
         enum_items: str
         enum_items_dynamic: str
         enum_descriptions: bpy.types.bpy_prop_collection_idprop[StrProperty]
@@ -373,6 +344,7 @@ class Attribute(PropertyGroup):
         value_min_constraint: bool
         value_max: float
         value_max_constraint: bool
+        unit_symbol: str
         use_explorer_ui: bool
         metadata: str
         update: str
@@ -430,8 +402,6 @@ class Attribute(PropertyGroup):
         elif data_type == "integer":
             return "int_value"
         elif data_type == "float":
-            if display_only and self.special_type == "LENGTH":
-                return "length_value"
             return "float_value"
         elif data_type == "enum":
             return "enum_value"

src/bonsai/bonsai/tool/pset.py

@@ -26,6 +26,7 @@ import ifcopenshell
 import ifcopenshell.api.pset
 import ifcopenshell.util.attribute
 import ifcopenshell.util.element
+import ifcopenshell.util.unit
 
 import bonsai.bim.helper
 import bonsai.bim.schema
@@ -168,42 +169,72 @@ class Pset(bonsai.core.tool.Pset):
             pset_id=0, pset_name=cls.get_pset_name(obj, obj_type), pset_type="PSET", obj=obj, obj_type=obj_type
         )
 
+    # Templates for quantities can specify their kind via TemplateType (e.g.
+    # "Q_LENGTH") instead of PrimaryMeasureType. IfcQuantityCount has no
+    # associated measure/unit, so it is intentionally absent here.
+    QUANTITY_TEMPLATE_TYPE_TO_SPECIAL_TYPE = {
+        "Q_LENGTH": "LENGTH",
+        "Q_AREA": "AREA",
+        "Q_VOLUME": "VOLUME",
+        "Q_WEIGHT": "MASS",
+        "Q_TIME": "TIME",
+    }
+
     @classmethod
-    def get_special_type_for_prop(
-        cls, prop_or_prop_template: ifcopenshell.entity_instance
-    ) -> Literal["LENGTH"] | Literal["AREA"] | Literal["VOLUME"] | Literal["URI"] | Literal[""]:
-        special_type = ""
+    def get_special_type_for_measure_class(cls, measure_class: str) -> str:
+        """Get the ``special_type`` (an IfcUnitEnum value with "UNIT" stripped) for an IFC measure class.
+
+        :param measure_class: An IFC measure class name, e.g. "IfcLengthMeasure".
+        :return: E.g. "LENGTH", or "" if the class has no associated unit type.
+        """
+        if not measure_class.endswith("Measure"):
+            return ""
+        unit_type = ifcopenshell.util.unit.get_measure_unit_type(measure_class)
+        return unit_type[: -len("UNIT")] if unit_type.endswith("UNIT") else ""
+
+    @classmethod
+    def get_special_type_for_prop(cls, prop_or_prop_template: ifcopenshell.entity_instance) -> str:
+        """Classify a property/quantity/template by its measure type.
+
+        :return: An IfcUnitEnum value with the "UNIT" suffix stripped (e.g.
+            "LENGTH", "PRESSURE"), "URI" for IfcURIReference, or "" if the
+            value has no associated unit type.
+        """
         if prop_or_prop_template.is_a("IfcPropertyTemplate"):
             primary_measure_type = prop_or_prop_template.PrimaryMeasureType
-            template_type = prop_or_prop_template.TemplateType
-            if primary_measure_type in ("IfcPositiveLengthMeasure", "IfcLengthMeasure") or template_type == "Q_LENGTH":
-                special_type = "LENGTH"
-            elif primary_measure_type == "IfcAreaMeasure" or template_type == "Q_AREA":
-                special_type = "AREA"
-            elif primary_measure_type == "IfcVolumeMeasure" or template_type == "Q_VOLUME":
-                special_type = "VOLUME"
-            elif primary_measure_type == "IfcURIReference":
-                special_type = "URI"
-        else:
-            if prop_or_prop_template.is_a("IfcPropertySingleValue"):
-                value = prop_or_prop_template.NominalValue
-                if value is not None:
-                    value_type = value.is_a()
-                    if value_type in ("IfcLengthMeasure", "IfcPositiveLengthMeasure"):
-                        special_type = "LENGTH"
-                    elif value_type == "IfcAreaMeasure":
-                        special_type = "AREA"
-                    elif value_type == "IfcVolumeMeasure":
-                        special_type = "VOLUME"
-            elif prop_or_prop_template.is_a("IfcPhysicalSimpleQuantity"):
-                prop_class = prop_or_prop_template.is_a()
-                if prop_class == "IfcQuantityArea":
-                    special_type = "AREA"
-                elif prop_class == "IfcQuantityVolume":
-                    special_type = "VOLUME"
-                elif prop_class == "IfcQuantityLength":
-                    special_type = "LENGTH"
-        return special_type
+            if primary_measure_type == "IfcURIReference":
+                return "URI"
+            if primary_measure_type:
+                return cls.get_special_type_for_measure_class(primary_measure_type)
+            return cls.QUANTITY_TEMPLATE_TYPE_TO_SPECIAL_TYPE.get(prop_or_prop_template.TemplateType, "")
+        elif prop_or_prop_template.is_a("IfcPropertySingleValue"):
+            value = prop_or_prop_template.NominalValue
+            if value is not None:
+                return cls.get_special_type_for_measure_class(value.is_a())
+        elif prop_or_prop_template.is_a("IfcPhysicalSimpleQuantity"):
+            entity = prop_or_prop_template.wrapped_data.declaration().as_entity()
+            measure_class = entity.attribute_by_index(3).type_of_attribute().declared_type().name()
+            return cls.get_special_type_for_measure_class(measure_class)
+        return ""
+
+    @classmethod
+    def get_unit_symbol_for_special_type(cls, special_type: str, ifc_file: ifcopenshell.file) -> str:
+        """Get the project's default unit symbol for a `special_type` (see `get_special_type_for_prop`).
+
+        Used where there's no property instance to check for a `Unit` override
+        (e.g. a template, or a native IFC entity attribute, neither of which
+        can carry one).
+        """
+        if not special_type or special_type == "URI":
+            return ""
+        unit = ifcopenshell.util.unit.get_project_unit(ifc_file, f"{special_type}UNIT")
+        return ifcopenshell.util.unit.get_unit_symbol(unit) if unit else ""
+
+    @classmethod
+    def get_unit_symbol_for_prop(cls, prop: ifcopenshell.entity_instance, ifc_file: ifcopenshell.file) -> str:
+        """Get the unit symbol for an existing property/quantity, respecting its own `Unit` override."""
+        unit = ifcopenshell.util.unit.get_property_unit(prop, ifc_file)
+        return ifcopenshell.util.unit.get_unit_symbol(unit) if unit else ""
 
     @classmethod
     def import_pset_from_existing(
@@ -283,6 +314,7 @@ class Pset(bonsai.core.tool.Pset):
                 metadata.is_null = value is None
                 metadata.is_optional = True
                 metadata.special_type = cls.get_special_type_for_prop(prop)
+                metadata.unit_symbol = cls.get_unit_symbol_for_prop(prop, tool.Ifc.get())
                 metadata.set_value(metadata.get_value_default() if metadata.is_null else value)
                 process_prop_description(metadata)
 
@@ -360,6 +392,7 @@ class Pset(bonsai.core.tool.Pset):
         metadata.is_optional = True
         metadata.data_type = cls.get_prop_template_primitive_type(prop_template)
         metadata.special_type = cls.get_special_type_for_prop(prop_template)
+        metadata.unit_symbol = cls.get_unit_symbol_for_special_type(metadata.special_type, tool.Ifc.get())
 
         if metadata.data_type == "string":
             metadata.string_value = "" if metadata.is_null else str(data[prop_template.Name])
@@ -409,6 +442,8 @@ class Pset(bonsai.core.tool.Pset):
                 cls.import_single_value_from_template(pset_template, prop_template, simplified_data, props)
 
             elif prop_template.TemplateType.startswith("Q_"):
+                if prop_data:
+                    continue  # Existing quantity will be added later by import_pset_from_existing.
                 cls.import_single_value_from_template(pset_template, prop_template, simplified_data, props)
 
             elif prop_template.TemplateType == "P_ENUMERATEDVALUE":
@@ -470,6 +505,7 @@ class Pset(bonsai.core.tool.Pset):
         metadata.is_null = value is None
         metadata.is_optional = True
         metadata.special_type = special_type
+        metadata.unit_symbol = cls.get_unit_symbol_for_special_type(special_type, tool.Ifc.get())
         metadata.set_value(metadata.get_value_default() if metadata.is_null else value)
 
     @classmethod

src/bonsai/test/bim/feature/pset.feature

@@ -361,31 +361,22 @@ Scenario: Edit pset length property
     Given an empty IFC project
     And I press "mesh.add_stair"
     And the variable "pset" is "tool.Pset.get_element_pset(tool.Ifc.get_entity(bpy.context.active_object), 'Pset_StairFlightCommon').id()"
-    And the variable "si_conversion" is "ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())"
     And I press "bim.enable_pset_editing(pset_id={pset}, obj='IfcStairFlight/StairFlight', obj_type='Object')"
 
     # Testing IfcPositiveLengthMeasure type of prop
     Then "active_object.PsetProperties.properties['TreadLength'].metadata.special_type" is "LENGTH"
     And "active_object.PsetProperties.properties['TreadLength'].metadata.float_value" is "250"
-    And "active_object.PsetProperties.properties['TreadLength'].metadata.length_value" is roughly "0.25"
 
     When I set "active_object.PsetProperties.properties['TreadLength'].metadata.float_value" to "350"
     Then "active_object.PsetProperties.properties['TreadLength'].metadata.float_value" is roughly "350"
 
-    When I set "active_object.PsetProperties.properties['TreadLength'].metadata.length_value" to "0.45"
-    Then "active_object.PsetProperties.properties['TreadLength'].metadata.float_value" is roughly "450"
-
     # Testing IfcLengthMeasure type of prop
     Then "active_object.PsetProperties.properties['NosingLength'].metadata.special_type" is "LENGTH"
     And "active_object.PsetProperties.properties['NosingLength'].metadata.float_value" is "0.0"
-    And "active_object.PsetProperties.properties['NosingLength'].metadata.length_value" is roughly "0.0"
 
     When I set "active_object.PsetProperties.properties['NosingLength'].metadata.float_value" to "350"
     Then "active_object.PsetProperties.properties['NosingLength'].metadata.float_value" is roughly "350"
 
-    When I set "active_object.PsetProperties.properties['NosingLength'].metadata.length_value" to "0.45"
-    Then "active_object.PsetProperties.properties['NosingLength'].metadata.float_value" is roughly "450"
-
     When I press "bim.edit_pset(obj='IfcStairFlight/StairFlight', obj_type='Object')"
     Then nothing happens
 
@@ -394,19 +385,14 @@ Scenario: Edit qset length property
     And I press "mesh.add_stair"
     And I press "bim.perform_quantity_take_off"
     And the variable "pset" is "tool.Pset.get_element_pset(tool.Ifc.get_entity(bpy.context.active_object), 'Qto_StairFlightBaseQuantities').id()"
-    And the variable "si_conversion" is "ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())"
     And I press "bim.enable_pset_editing(pset_id={pset}, obj='IfcStairFlight/StairFlight', obj_type='Object')"
 
     # Testing Q_LENGTH type of prop
     Then "active_object.PsetProperties.properties['Length'].metadata.special_type" is "LENGTH"
     And "active_object.PsetProperties.properties['Length'].metadata.float_value" is roughly "2156.485"
-    And "active_object.PsetProperties.properties['Length'].metadata.length_value" is roughly "2.156"
 
     When I set "active_object.PsetProperties.properties['Length'].metadata.float_value" to "350"
-    Then "active_object.PsetProperties.properties['Length'].metadata.length_value" is roughly "0.35"
-
-    When I set "active_object.PsetProperties.properties['Length'].metadata.length_value" to "0.45"
-    Then "active_object.PsetProperties.properties['Length'].metadata.float_value" is roughly "450"
+    Then "active_object.PsetProperties.properties['Length'].metadata.float_value" is roughly "350"
 
     When I press "bim.edit_pset(obj='IfcStairFlight/StairFlight', obj_type='Object')"
     Then nothing happens

src/bonsai/test/bim/test_prop.py

@@ -0,0 +1,79 @@
+# 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/>.
+
+import bpy
+import ifcopenshell
+import ifcopenshell.api.pset
+import ifcopenshell.api.root
+import ifcopenshell.api.unit
+
+import bonsai.tool as tool
+from test.bim.bootstrap import NewFile
+
+
+def import_single_property(ifc, element, prop):
+    """Import a single existing IfcProperty into a real, addon-registered
+    PsetProperties collection, exactly as the property editor does, and
+    return its `metadata` (an `Attribute`)."""
+    pset = ifcopenshell.api.pset.add_pset(ifc, product=element, name="Pset_Test")
+    pset.HasProperties = [prop]
+    obj = bpy.data.objects.new(prop.Name, None)
+    tool.Ifc.link(element, obj)
+    props = obj.PsetProperties
+    tool.Pset.import_pset_from_existing(pset, props, None)
+    return props.properties[prop.Name].metadata
+
+
+class TestGetDisplayName(NewFile):
+    def test_appends_the_resolved_unit_symbol(self):
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcProject")
+        pressure = ifcopenshell.api.unit.add_si_unit(ifc, unit_type="PRESSUREUNIT")
+        ifcopenshell.api.unit.assign_unit(ifc, units=[pressure])
+
+        element = ifc.createIfcWall()
+        prop = ifc.createIfcPropertySingleValue(Name="Foo", NominalValue=ifc.createIfcPressureMeasure(5.0))
+        metadata = import_single_property(ifc, element, prop)
+
+        assert metadata.display_name == "Foo, Pa"
+
+    def test_falls_back_to_the_plain_name_when_no_unit_is_resolvable(self):
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcProject")
+        # No units assigned to the project at all -- nothing to resolve.
+
+        element = ifc.createIfcWall()
+        prop = ifc.createIfcPropertySingleValue(Name="Foo", NominalValue=ifc.createIfcPressureMeasure(5.0))
+        metadata = import_single_property(ifc, element, prop)
+
+        assert metadata.unit_symbol == ""
+        assert metadata.display_name == "Foo"
+
+    def test_falls_back_to_the_plain_name_for_a_non_measure_property(self):
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcProject")
+
+        element = ifc.createIfcWall()
+        prop = ifc.createIfcPropertySingleValue(Name="Foo", NominalValue=ifc.createIfcText("Bar"))
+        metadata = import_single_property(ifc, element, prop)
+
+        assert metadata.unit_symbol == ""
+        assert metadata.display_name == "Foo"

src/bonsai/test/tool/test_pset.py

@@ -20,6 +20,8 @@ import bpy
 import ifcopenshell
 import ifcopenshell.api
 import ifcopenshell.api.pset
+import ifcopenshell.api.root
+import ifcopenshell.api.unit
 
 import bonsai.core.tool
 import bonsai.tool as tool
@@ -52,3 +54,80 @@ class TestIsPsetEmpty(NewFile):
         assert subject.is_pset_empty(pset) is False
         ifcopenshell.api.pset.edit_pset(ifc, pset=pset, properties={"Foo": None})
         assert subject.is_pset_empty(pset) is True
+
+
+class TestEditingAnOverriddenUnitPropertyRoundTrips(NewFile):
+    def test_run(self):
+        # Project default is mm, but this property is authored directly in m.
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcProject")
+        length_mm = ifcopenshell.api.unit.add_si_unit(ifc, unit_type="LENGTHUNIT", prefix="MILLI")
+        ifcopenshell.api.unit.assign_unit(ifc, units=[length_mm])
+        length_m = ifcopenshell.api.unit.add_si_unit(ifc, unit_type="LENGTHUNIT")
+
+        element = ifc.createIfcWall()
+        pset = ifcopenshell.api.pset.add_pset(ifc, product=element, name="Pset_Test")
+        prop = ifc.createIfcPropertySingleValue(
+            Name="Foo", NominalValue=ifc.createIfcLengthMeasure(2.5), Unit=length_m
+        )
+        pset.HasProperties = [prop]
+
+        obj = bpy.data.objects.new("Wall", None)
+        tool.Ifc.link(element, obj)
+        blender_props = obj.PsetProperties
+        subject.import_pset_from_existing(pset, blender_props, None)
+
+        metadata = blender_props.properties["Foo"].metadata
+        assert metadata.unit_symbol == "m"
+        assert metadata.float_value == 2.5  # raw stored value, not rescaled to the project's mm
+
+        # Simulate a user edit in the property editor.
+        metadata.float_value = 3.5
+
+        # Simulate what EditPset.execute() does: collect the raw value straight
+        # off the metadata and write it back, with no rescaling step.
+        properties = {"Foo": metadata.get_value()}
+        ifcopenshell.api.pset.edit_pset(ifc, pset=pset, properties=properties)
+
+        assert prop.NominalValue.wrappedValue == 3.5  # not rescaled to 3500mm
+        assert prop.Unit == length_m  # override preserved
+
+
+class TestImportingATemplatedQuantityRespectsItsOwnUnitOverride(NewFile):
+    def test_run(self):
+        # Regression test: import_pset_from_template's Q_ branch used to
+        # unconditionally re-template existing quantities, which shadowed
+        # their own Unit override with the project default -- edit mode
+        # showed "m" while the read-only panel correctly showed "mm".
+        # Project default is m, but this quantity is authored directly in mm.
+        ifc = ifcopenshell.file()
+        tool.Ifc.set(ifc)
+        ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcProject")
+        length_m = ifcopenshell.api.unit.add_si_unit(ifc, unit_type="LENGTHUNIT")
+        ifcopenshell.api.unit.assign_unit(ifc, units=[length_m])
+        length_mm = ifcopenshell.api.unit.add_si_unit(ifc, unit_type="LENGTHUNIT", prefix="MILLI")
+
+        element = ifc.createIfcBeam()
+        qto = ifcopenshell.api.pset.add_qto(ifc, product=element, name="Qto_Test")
+        quantity = ifc.createIfcQuantityLength(Name="Foo", Unit=length_mm, LengthValue=2500.0)
+        qto.Quantities = [quantity]
+
+        pset_template = ifc.createIfcPropertySetTemplate(
+            Name="Qto_Test",
+            TemplateType="PSET_TYPEDRIVENOVERRIDE",
+            ApplicableEntity="IfcBeam",
+            HasPropertyTemplates=[ifc.createIfcSimplePropertyTemplate(Name="Foo", TemplateType="Q_LENGTH")],
+        )
+
+        obj = bpy.data.objects.new("Beam", None)
+        tool.Ifc.link(element, obj)
+        blender_props = obj.PsetProperties
+        # Mirrors core/pset.py's enable_pset_editing: template pass, then existing-data pass.
+        subject.import_pset_from_template(pset_template, qto, blender_props)
+        subject.import_pset_from_existing(qto, blender_props, pset_template)
+
+        assert len(blender_props.properties) == 1  # not duplicated by the template pass
+        metadata = blender_props.properties["Foo"].metadata
+        assert metadata.unit_symbol == "mm"  # the quantity's own override, not the project default "m"
+        assert metadata.float_value == 2500.0  # raw stored value, not rescaled