diff --git a/backend/app/api/tags.py b/backend/app/api/tags.py
index fbe746f..d477ea9 100644
--- a/backend/app/api/tags.py
+++ b/backend/app/api/tags.py
@@ -56,6 +56,8 @@ async def autocomplete():
 @tags_bp.route("/tags/directory", methods=["GET"])
 async def directory():
     kind = request.args.get("kind") or None
+    if kind is not None and _coerce_kind(kind) is None:
+        return jsonify({"error": f"invalid kind {kind!r}"}), 400
     q = request.args.get("q") or None
     cursor = request.args.get("cursor") or None
     try:
diff --git a/frontend/src/views/TagsView.vue b/frontend/src/views/TagsView.vue
index 8381763..a1ce81f 100644
--- a/frontend/src/views/TagsView.vue
+++ b/frontend/src/views/TagsView.vue
@@ -51,7 +51,10 @@ import { useTagDirectoryStore } from '../stores/tagDirectory.js'
 import TagCard from '../components/discovery/TagCard.vue'
 import MergeConfirmDialog from '../components/discovery/MergeConfirmDialog.vue'
 
-const KINDS = ['artist', 'character', 'copyright', 'general', 'series', 'meta']
+// Must stay a subset of the backend TagKind enum (artist, character,
+// fandom, general, series, archive, post, meta, rating). 'fandom' is this
+// model's copyright/franchise concept (characters link via fandom_id).
+const KINDS = ['artist', 'character', 'fandom', 'general', 'series', 'meta']
 const store = useTagDirectoryStore()
 const router = useRouter()
 
diff --git a/tests/test_api_tags_directory.py b/tests/test_api_tags_directory.py
index de9c01e..1865482 100644
--- a/tests/test_api_tags_directory.py
+++ b/tests/test_api_tags_directory.py
@@ -28,3 +28,22 @@ async def test_directory_endpoint(client, db):
 async def test_directory_bad_limit(client):
     resp = await client.get("/api/tags/directory?limit=nan")
     assert resp.status_code == 400
+
+
+@pytest.mark.asyncio
+async def test_directory_invalid_kind_is_400_not_500(client):
+    # 'copyright' is not a TagKind member; the route must reject it
+    # cleanly (400) instead of letting the enum cast 500.
+    resp = await client.get("/api/tags/directory?kind=copyright")
+    assert resp.status_code == 400
+
+
+@pytest.mark.asyncio
+async def test_directory_valid_kind_ok(client, db):
+    db.add(Tag(name="a_fandom", kind=TagKind.fandom))
+    await db.flush()
+    await db.commit()
+    resp = await client.get("/api/tags/directory?kind=fandom&limit=10")
+    assert resp.status_code == 200
+    body = await resp.get_json()
+    assert any(c["name"] == "a_fandom" for c in body["cards"])