backend/app/celery_signals.py

@@ -69,7 +69,15 @@ def _queue_for(task) -> str:
         return "ml"
     if name.startswith("backend.app.tasks.thumbnail."):
         return "thumbnail"
-    if name.startswith("backend.app.tasks.download."):
+    if name.startswith((
+        "backend.app.tasks.download.",
+        # External file-host fetches share the download lane (celery_app
+        # routes external.* → download). Mirror it here or TaskRun.queue
+        # lies 'default' for them, so per-queue dashboard filters and the
+        # per-queue threshold override miss them — the same gap the
+        # 2026-06-02 audit fixed for backup/admin/library_audit.
+        "backend.app.tasks.external.",
+    )):
         return "download"
     if name.startswith("backend.app.tasks.scan."):
         return "scan"

tests/test_celery_routing.py

@@ -18,3 +18,21 @@ def test_long_one_shots_route_to_maintenance_long():
 def test_quick_maintenance_stays_on_maintenance():
     routes = celery.conf.task_routes
     assert routes["backend.app.tasks.maintenance.*"]["queue"] == "maintenance"
+
+
+def test_queue_for_mirrors_external_to_download():
+    """celery_signals._queue_for is a hand-maintained mirror of task_routes
+    that stamps TaskRun.queue. external.* routes to the download lane, so the
+    mirror must agree — else TaskRun.queue lies 'default' for external fetches
+    and per-queue dashboard filters / threshold overrides miss them
+    (operator-flagged 2026-06-17)."""
+    from backend.app.celery_signals import _queue_for
+
+    class _T:
+        name = "backend.app.tasks.external.fetch_external_link"
+
+    assert _queue_for(_T()) == "download"
+    assert (
+        celery.conf.task_routes["backend.app.tasks.external.*"]["queue"]
+        == "download"
+    )