OpenBMB/ChatDev · error · HTTPException

Artifact stream not available

Error message

Artifact stream not available

What it means

The session exists but session.artifact_queue is None, meaning no artifact event stream was ever attached to it. The helper returns 404 because there is nothing to poll or stream from this session.

Solutions

  1. Establish the websocket connection for the session first so the artifact queue is created
  2. Run a workflow that produces artifacts before polling
  3. Reconnect the session if the queue was torn down after disconnect
  4. Confirm you're using the same server instance that owns the session
Defensive patterns

Strategy: validation

Validate before calling

# only poll after the session reports a websocket connection / artifacts exist
if not session_has_artifacts(session_id):
    return  # skip polling

Try / catch

if resp.status_code == 404 and resp.json()['detail'] == 'Artifact stream not available':
    connect_websocket(session_id)  # initialize the queue, then retry

Prevention

When it happens

Trigger: Calling artifact endpoints on a session whose websocket connection never initialized the artifact queue, or after the queue was torn down at session close.

Common situations: Polling artifact events on a session that completed without ever connecting a websocket client, or after the session's streaming lifecycle ended.

Related errors

AI-assisted analysis of OpenBMB/ChatDev@4fb2db0ea9 (2026-08-27). Data as JSON: /api/errors/c5cfbba84ae4fc5a. Report an issue: GitHub.

Appendix: source

Thrown at server/routes/artifacts.py:31

MAX_FILE_SIZE = 20 * 1024 * 1024  # 20 MB


def _split_csv(value: Optional[str]) -> Optional[List[str]]:
    if not value:
        return None
    parts = [part.strip() for part in value.split(",")]
    filtered = [part for part in parts if part]
    return filtered or None


def _get_session_and_queue(session_id: str):
    manager = get_websocket_manager()
    session = manager.session_store.get_session(session_id)
    if not session:
        raise HTTPException(status_code=404, detail="Session not found")
    queue = session.artifact_queue
    if queue is None:
        raise HTTPException(status_code=404, detail="Artifact stream not available")
    return manager, queue


@router.get("/api/sessions/{session_id}/artifact-events")
async def poll_artifact_events(
    session_id: str,
    wait_seconds: float = Query(25.0, ge=0.0, le=60.0),
    after: Optional[int] = Query(None, ge=0),
    include_mime: Optional[str] = Query(None),
    include_ext: Optional[str] = Query(None),
    max_size: Optional[int] = Query(None, gt=0),
    limit: int = Query(25, ge=1, le=100),
):
    manager, queue = _get_session_and_queue(session_id)
    include_mime_list = _split_csv(include_mime)
    include_ext_list = _split_csv(include_ext)

    events, next_cursor, timed_out = await asyncio.to_thread(

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