diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1fe7703b..17e51a6e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@
 
 - Added an explicit regional GRB building operator that fetches the approved Kempen scope in 28 resumable municipality partitions and follows every OGC API pagination link.
 - Assigned boundary-crossing GRB features to exactly one partition using maximum municipality intersection, with deterministic NIS-code tie breaking and one retained source identity.
+- Added a covered-by-member fast path so ordinary interior buildings avoid the regional boundary-owner scan while true border cases retain the exact overlap rule.
 - Added streaming artifact copy and batch-wise partition indexing through `DatasetService` and `VectorFeatureService`, avoiding one giant multipart parse while preserving one normal regional dataset for existing map and PostGIS selection flows.
 - Added truncation guards, source/checksum manifests, immutable observation dates, duplicate-source rejection and focused service/operator tests.
 - Kept the provider endpoint contract unchanged and retained explicit operator-only fetching; no source request runs during application startup or interactive map use.
diff --git a/backend/tests/test_sprint190_regional_grb_buildings.py b/backend/tests/test_sprint190_regional_grb_buildings.py
index a281699e..2b5ed95d 100644
--- a/backend/tests/test_sprint190_regional_grb_buildings.py
+++ b/backend/tests/test_sprint190_regional_grb_buildings.py
@@ -84,6 +84,41 @@ def test_partition_assignment_is_deterministic_and_has_no_cross_member_duplicate
     assert alpha_features[1]["properties"]["partition_assignment"] == "maximum_boundary_intersection"
 
 
+def test_interior_buildings_skip_regional_owner_scan(monkeypatch) -> None:
+    operator = load_operator()
+    scopes = importlib.import_module("geographic_scopes")
+    member = scopes.ScopeMember("Alpha", "10001")
+    boundary = Polygon([(0, 0), (1, 0), (1, 1), (0, 1)])
+    scope = scopes.GeographicScope(
+        key="single",
+        display_name="Single",
+        project_name="Single",
+        project_region="Single",
+        area_name="Single boundary",
+        authority_name="Test",
+        authority_url="https://example.test",
+        scope_type="municipality",
+        limitation_message="Test.",
+        members=(member,),
+    )
+    monkeypatch.setattr(
+        operator,
+        "assign_owner_nis",
+        lambda *_args, **_kwargs: (_ for _ in ()).throw(AssertionError("interior feature used slow owner scan")),
+    )
+
+    features, _ = operator.build_partition_features(
+        [({"type": "FeatureCollection", "features": [feature("GBG.inside", Polygon([(0.1, 0.1), (0.2, 0.1), (0.2, 0.2), (0.1, 0.2)]))]}, "https://example.test/grb")],
+        member=member,
+        members=[(member, boundary)],
+        regional_boundary=boundary,
+        scope=scope,
+        max_features=10,
+    )
+
+    assert [item["id"] for item in features] == ["GBG.inside"]
+
+
 def test_combined_artifact_streams_partitions_and_rejects_duplicate_source_ids(tmp_path: Path) -> None:
     operator = load_operator()
     scope = importlib.import_module("geographic_scopes").KEMPEN_TRANSPORT_REGION_SCOPE
diff --git a/scripts/provision_regional_grb_buildings.py b/scripts/provision_regional_grb_buildings.py
index 813345fa..19240f57 100644
--- a/scripts/provision_regional_grb_buildings.py
+++ b/scripts/provision_regional_grb_buildings.py
@@ -230,6 +230,7 @@ def build_partition_features(
     assigned_elsewhere_count = 0
     outside_scope_count = 0
     clipped_to_scope_count = 0
+    member_boundary = next(boundary for candidate, boundary in members if candidate.nis_code == member.nis_code)
 
     for payload, source_url in pages:
         source_urls.append(source_url)
@@ -247,7 +248,11 @@ def build_partition_features(
             if source_geometry is None or not source_geometry.intersects(regional_boundary):
                 outside_scope_count += 1
                 continue
-            owner_nis = assign_owner_nis(source_geometry, members)
+            owner_nis = (
+                member.nis_code
+                if member_boundary.covers(source_geometry)
+                else assign_owner_nis(source_geometry, members)
+            )
             if owner_nis != member.nis_code:
                 assigned_elsewhere_count += 1
                 continue