diff --git a/frontend/src/stores/gallerySelection.js b/frontend/src/stores/gallerySelection.js
index 881dbcf..daf31a0 100644
--- a/frontend/src/stores/gallerySelection.js
+++ b/frontend/src/stores/gallerySelection.js
@@ -51,7 +51,7 @@ export const useGallerySelectionStore = defineStore('gallerySelection', () => {
       body: { image_ids: order.value, tag_id: tagId, source }
     })
     await refresh()
-    window.__fcToast?.({
+    globalThis.window?.__fcToast?.({
       text: `Added to ${body.added_count} image(s)`, type: 'success'
     })
     return body
@@ -62,7 +62,7 @@ export const useGallerySelectionStore = defineStore('gallerySelection', () => {
       body: { image_ids: order.value, tag_id: tagId }
     })
     await refresh()
-    window.__fcToast?.({
+    globalThis.window?.__fcToast?.({
       text: `Removed from ${body.removed_count} image(s)`, type: 'success'
     })
     return body
diff --git a/tests/test_api_bulk_tags.py b/tests/test_api_bulk_tags.py
index 86027b5..1917734 100644
--- a/tests/test_api_bulk_tags.py
+++ b/tests/test_api_bulk_tags.py
@@ -22,10 +22,11 @@ async def _mk_tag(client, name, kind="general"):
 
 
 @pytest.mark.asyncio
-async def test_common_tags_route(client):
+async def test_common_tags_rejects_empty_list(client):
+    # Spec guard: image_ids must be a non-empty list (the frontend never
+    # calls this with an empty selection).
     resp = await client.post("/api/images/common-tags", json={"image_ids": []})
-    assert resp.status_code == 200
-    assert (await resp.get_json())["tags"] == []
+    assert resp.status_code == 400
 
 
 @pytest.mark.asyncio
@@ -34,6 +35,16 @@ async def test_common_tags_requires_list(client):
     assert resp.status_code == 400
 
 
+@pytest.mark.asyncio
+async def test_common_tags_ok_shape(client):
+    # Unknown image ids are valid input; result is just an empty tag list.
+    resp = await client.post(
+        "/api/images/common-tags", json={"image_ids": [999999]}
+    )
+    assert resp.status_code == 200
+    assert (await resp.get_json())["tags"] == []
+
+
 @pytest.mark.asyncio
 async def test_bulk_add_route_happy(client):
     tag = await _mk_tag(client, "RouteAdd")