diff --git a/lib/services/node_cache.dart b/lib/services/node_cache.dart
index 39a0207..9a29be3 100644
--- a/lib/services/node_cache.dart
+++ b/lib/services/node_cache.dart
@@ -30,7 +30,9 @@ class NodeCache {
           id: node.id,
           coord: node.coord,
           tags: mergedTags,
-          isConstrained: node.isConstrained, // Preserve constraint information
+          // Once a node is known to be constrained, keep it that way - see
+          // NodeSpatialCache.addOrUpdateNodes for the full explanation.
+          isConstrained: existing.isConstrained || node.isConstrained,
         );
       } else {
         _nodes[node.id] = node;
diff --git a/lib/services/node_spatial_cache.dart b/lib/services/node_spatial_cache.dart
index 35d9044..1360e90 100644
--- a/lib/services/node_spatial_cache.dart
+++ b/lib/services/node_spatial_cache.dart
@@ -58,7 +58,13 @@ class NodeSpatialCache {
           id: node.id,
           coord: node.coord,
           tags: mergedTags,
-          isConstrained: node.isConstrained,
+          // Once a node is known to be constrained (part of a way/relation),
+          // keep treating it as constrained. Callers that build a fresh
+          // OsmNode for cache updates (e.g. after an edit upload succeeds)
+          // don't have way/relation data and default to false, so blindly
+          // taking the incoming value would "unconstrain" the node until
+          // the next Overpass fetch.
+          isConstrained: existing.isConstrained || node.isConstrained,
         );
       } else {
         _nodes[node.id] = node;
diff --git a/test/services/node_spatial_cache_test.dart b/test/services/node_spatial_cache_test.dart
new file mode 100644
index 0000000..1b7122c
--- /dev/null
+++ b/test/services/node_spatial_cache_test.dart
@@ -0,0 +1,65 @@
+import 'package:deflockapp/models/osm_node.dart';
+import 'package:deflockapp/services/node_spatial_cache.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:latlong2/latlong.dart';
+
+void main() {
+  group('NodeSpatialCache constrained flag', () {
+    setUp(() {
+      // NodeSpatialCache is a singleton - start each test from a clean slate.
+      NodeSpatialCache().clear();
+    });
+
+    test('stays constrained after an update that omits the flag', () {
+      final cache = NodeSpatialCache();
+      const nodeId = 123;
+
+      cache.addOrUpdateNodes([
+        OsmNode(
+          id: nodeId,
+          coord: const LatLng(0, 0),
+          tags: const {},
+          isConstrained: true,
+        ),
+      ]);
+
+      // Simulate what happens after an edit upload succeeds: a brand-new
+      // OsmNode is built from upload data, which has no way/relation
+      // information and so defaults isConstrained to false.
+      cache.addOrUpdateNodes([
+        OsmNode(
+          id: nodeId,
+          coord: const LatLng(1, 1),
+          tags: const {'amenity': 'surveillance'},
+        ),
+      ]);
+
+      final updated = cache.getNodeById(nodeId);
+      expect(updated, isNotNull);
+      expect(updated!.isConstrained, isTrue);
+      // Non-constraint fields should still be updated as normal.
+      expect(updated.coord, const LatLng(1, 1));
+      expect(updated.tags['amenity'], 'surveillance');
+    });
+
+    test('becomes constrained if a later update says it is', () {
+      final cache = NodeSpatialCache();
+      const nodeId = 456;
+
+      cache.addOrUpdateNodes([
+        OsmNode(id: nodeId, coord: const LatLng(0, 0), tags: const {}),
+      ]);
+
+      cache.addOrUpdateNodes([
+        OsmNode(
+          id: nodeId,
+          coord: const LatLng(0, 0),
+          tags: const {},
+          isConstrained: true,
+        ),
+      ]);
+
+      expect(cache.getNodeById(nodeId)!.isConstrained, isTrue);
+    });
+  });
+}