diff --git a/server/src/nest/collections/collections.service.ts b/server/src/nest/collections/collections.service.ts
index 51f3a0349..200ed40d0 100644
--- a/server/src/nest/collections/collections.service.ts
+++ b/server/src/nest/collections/collections.service.ts
@@ -12,6 +12,7 @@ import {
   trackInsertedInDedupSet,
   type DedupSet,
 } from '../places/places.helpers';
+import { placeMatchStrategies, type PlaceMatchCandidate } from '@trek/shared';
 import type {
   Collection,
   CollectionDetailResponse,
@@ -418,26 +419,48 @@ export class CollectionsService {
   // Dedup (collection-scoped ports of placeService helpers)
   // -------------------------------------------------------------------------
 
+  /**
+   * A third hand-written copy of the place-matching order (alongside
+   * PlacesService.findDuplicatePlace and isPlaceDuplicate), and the one that had
+   * actually drifted live rather than latently: unlike findDuplicatePlace's one
+   * caller, savePlace calls this directly with no isPlaceDuplicate guard in
+   * front, so a named candidate that matched nothing by name fell through to a
+   * coordinate match unconditionally — merging the restaurant and the bar at one
+   * address. It also never read google_place_id/google_ftid/osm_id at all, even
+   * though every collection_places row stores them, so a renamed place with no
+   * matching name or coordinates could be saved again under its old id.
+   *
+   * Now walks the shared strategy list from @trek/shared, same as
+   * PlacesService.findMatchingPlaceId: provider id, then name, then coordinates
+   * and only when there is no name.
+   */
   private findDuplicateCollectionPlace(
     collectionId: number,
-    candidate: { name: string | null | undefined; lat: number | null | undefined; lng: number | null | undefined },
+    candidate: PlaceMatchCandidate,
   ): { id: number; name: string } | null {
-    const normalizedName = candidate.name?.trim().toLowerCase();
-    if (normalizedName) {
-      const dup = this.db.get<{ id: number; name: string }>(`
+    for (const strategy of placeMatchStrategies(candidate)) {
+      let hit: { id: number; name: string } | undefined;
+      if (strategy.by === 'externalId') {
+        hit = this.db.get<{ id: number; name: string }>(`
+      SELECT id, name FROM collection_places
+      WHERE collection_id = ? AND (google_place_id = ? OR google_ftid = ? OR osm_id = ?)
+      ORDER BY id ASC LIMIT 1
+    `, collectionId, strategy.id, strategy.id, strategy.id);
+      } else if (strategy.by === 'name') {
+        hit = this.db.get<{ id: number; name: string }>(`
       SELECT id, name FROM collection_places
       WHERE collection_id = ? AND lower(trim(name)) = ?
       ORDER BY id ASC LIMIT 1
-    `, collectionId, normalizedName);
-      if (dup) return dup;
-    }
-    if (candidate.lat != null && candidate.lng != null) {
-      return this.db.get<{ id: number; name: string }>(`
+    `, collectionId, strategy.name);
+      } else {
+        hit = this.db.get<{ id: number; name: string }>(`
       SELECT id, name FROM collection_places
       WHERE collection_id = ? AND lat IS NOT NULL AND lng IS NOT NULL
         AND abs(lat - ?) <= ? AND abs(lng - ?) <= ?
       ORDER BY id ASC LIMIT 1
-    `, collectionId, candidate.lat, COORD_DEDUP_TOLERANCE, candidate.lng, COORD_DEDUP_TOLERANCE) || null;
+    `, collectionId, strategy.lat, strategy.tolerance, strategy.lng, strategy.tolerance);
+      }
+      if (hit) return hit;
     }
     return null;
   }
@@ -491,7 +514,10 @@ export class CollectionsService {
     this.assertCanEdit(userId, body.collection_id);
 
     if (!body.force) {
-      const dup = this.findDuplicateCollectionPlace(body.collection_id, { name: body.name, lat: body.lat, lng: body.lng });
+      const dup = this.findDuplicateCollectionPlace(body.collection_id, {
+        name: body.name, lat: body.lat, lng: body.lng,
+        google_place_id: body.google_place_id, google_ftid: body.google_ftid, osm_id: body.osm_id,
+      });
       if (dup) return { duplicate: true, duplicateOf: dup };
     }
 
diff --git a/server/tests/unit/nest/collections.service.test.ts b/server/tests/unit/nest/collections.service.test.ts
index ba0abe91c..60309ee88 100644
--- a/server/tests/unit/nest/collections.service.test.ts
+++ b/server/tests/unit/nest/collections.service.test.ts
@@ -179,6 +179,47 @@ describe('saved places + dedup', () => {
     const col = svc.createCollection(a.id, { name: 'Locked' });
     expect(() => svc.savePlace(b.id, { collection_id: col.id, name: 'X' })).toThrow();
   });
+
+  it('COLLECTIONS-SVC-100: a NAMED candidate does not merge into a different place at the same coordinates', () => {
+    // The wrong-city hazard: findDuplicateCollectionPlace used to fall through to
+    // a coordinate match for a named candidate whose name did not match anything,
+    // which would report two distinct places at one address (the restaurant and
+    // the bar) as duplicates of each other.
+    const u = createUser(testDb).user;
+    const col = svc.createCollection(u.id, { name: 'Berlin' });
+    svc.savePlace(u.id, { collection_id: col.id, name: 'Ground Floor Diner', lat: 52.52, lng: 13.405 });
+
+    const result = svc.savePlace(u.id, { collection_id: col.id, name: 'Rooftop Bar', lat: 52.52, lng: 13.405 });
+
+    expect(result.duplicate).toBeFalsy();
+    expect(result.place).toBeDefined();
+  });
+
+  it('COLLECTIONS-SVC-101: a provider id still recognises a renamed place a name/coords search would miss', () => {
+    // google_place_id/google_ftid/osm_id are stored on every collection_places row
+    // but were never read back for dedup, so a renamed place with no matching
+    // name or coordinates could be saved again under its old provider id.
+    const u = createUser(testDb).user;
+    const col = svc.createCollection(u.id, { name: 'Renames' });
+    svc.savePlace(u.id, {
+      collection_id: col.id,
+      name: 'Original Name',
+      lat: 1,
+      lng: 1,
+      google_place_id: 'ChIJ_abc',
+    });
+
+    const result = svc.savePlace(u.id, {
+      collection_id: col.id,
+      name: 'Renamed By User',
+      lat: 2,
+      lng: 2,
+      google_place_id: 'ChIJ_abc',
+    });
+
+    expect(result.duplicate).toBe(true);
+    expect(result.duplicateOf?.name).toBe('Original Name');
+  });
 });
 
 // ── save-from-trip provenance + IDOR ─────────────────────────────────────────