🐛(backend) acknowledge unknown LiveKit webhook events instead of 422

Around 0.76% of incoming LiveKit webhooks were being flagged as
unprocessable and returned a 422, even though LiveKit was sending
legitimate data — just with event types we do not handle. This
inflated error metrics and made real webhook issues harder to spot.

Return a 200 for these webhooks instead. When a new, unhandled
event type shows up, log a warning so we can decide whether it is
worth adding explicit handling.

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to
 
 ### Fixed
 
+- 🐛(backend) acknowledge unknown LiveKit webhook events instead of 422
 - 🔒️(backend) enforce display name setting on rename API
 
 ## [1.31.0] - 2026-09-08

src/backend/core/services/livekit_events.py

@@ -52,12 +52,6 @@ class InvalidPayloadError(LiveKitWebhookError):
     status_code = 400
 
 
-class UnsupportedEventTypeError(LiveKitWebhookError):
-    """Unsupported event type."""
-
-    status_code = 422
-
-
 class ActionFailedError(LiveKitWebhookError):
     """Webhook action fails to process or complete."""
 
@@ -74,6 +68,7 @@ class LiveKitWebhookEventType(Enum):
     # Participant events
     PARTICIPANT_JOINED = "participant_joined"
     PARTICIPANT_LEFT = "participant_left"
+    PARTICIPANT_CONNECTION_ABORTED = "participant_connection_aborted"
 
     # Track events
     TRACK_PUBLISHED = "track_published"
@@ -153,10 +148,13 @@ class LiveKitEventsService:
 
         try:
             webhook_type = LiveKitWebhookEventType(data.event)
-        except ValueError as e:
-            raise UnsupportedEventTypeError(
-                f"Unknown webhook type: {data.event}"
-            ) from e
+        except ValueError:
+            logger.warning(
+                "Ignoring unknown LiveKit webhook event type '%s' for room '%s'",
+                data.event,
+                room_name,
+            )
+            return
 
         # Handle according to received webhook type
         handler = self._webhook_handlers.get(webhook_type.value)

src/backend/core/tests/rooms/test_api_rooms_webhook.py

@@ -94,7 +94,7 @@ def test_invalid_payload(client, auth_token, mock_livekit_config):
 
 
 def test_unknown_event_type(client, mock_livekit_config):
-    """Should return 422 for unknown event type."""
+    """Should acknowledge (200) an unknown event type rather than reject it."""
     event_data = json.dumps({"event": "unknown_event_type"})
 
     # Generate auth token for this specific payload
@@ -112,10 +112,8 @@ def test_unknown_event_type(client, mock_livekit_config):
         HTTP_AUTHORIZATION=auth_token,
     )
 
-    assert response.status_code == 422
-    assert response.json() == {
-        "status": "error",
-    }
+    assert response.status_code == 200
+    assert response.json() == {"status": "success"}
 
 
 @mock.patch.object(LiveKitEventsService, "_handle_room_finished")

src/backend/core/tests/services/test_livekit_events.py

@@ -16,7 +16,6 @@ from core.services.livekit_events import (
     AuthenticationError,
     InvalidPayloadError,
     LiveKitEventsService,
-    UnsupportedEventTypeError,
     api,
 )
 from core.services.lobby import LobbyService
@@ -665,22 +664,27 @@ def test_receive_missing_auth(service):
 
 
 @mock.patch.object(api.WebhookReceiver, "receive")
-def test_receive_unsupported_event(mock_receive, service):
-    """Should raise LiveKitWebhookError for unsupported events."""
+def test_receive_unknown_event_is_acknowledged(mock_receive, service, caplog):
+    """Unknown event types are logged and ignored, not rejected.
+
+    LiveKit adds event types over time and does not retry 4xx responses, so
+    raising here would silently drop the event.
+    """
     mock_request = mock.MagicMock()
     mock_request.headers = {"Authorization": "test_token"}
     mock_request.body = b"{}"
 
-    # Mock returned data with unsupported event type
     mock_data = mock.MagicMock()
     mock_data.room.name = str(uuid.uuid4())
-    mock_data.event = "unsupported_event"
+    mock_data.event = "some_future_event"
     mock_receive.return_value = mock_data
 
-    with pytest.raises(
-        UnsupportedEventTypeError, match="Unknown webhook type: unsupported_event"
-    ):
-        service.receive(mock_request)
+    with caplog.at_level("WARNING", logger="core.services.livekit_events"):
+        service.receive(mock_request)  # must not raise
+
+    assert "Ignoring unknown LiveKit webhook event type 'some_future_event'" in (
+        caplog.text
+    )
 
 
 @mock.patch.object(api.WebhookReceiver, "receive")