OpenBMB/ChatDev · error · HTTPException

Failed to download session

Error message

Failed to download session

What it means

The catch-all handler in download_session: any exception other than ValidationError, ResourceNotFoundError, or HTTPException is logged as 'Unexpected error during session download' and returned as HTTP 500 'Failed to download session'.

Source

Thrown at server/routes/sessions.py:83

                zip_path.unlink()

        return FileResponse(
            path=zip_path,
            filename=f"{dir_name}.zip",
            media_type="application/zip",
            headers={"Content-Disposition": f"attachment; filename={dir_name}.zip"},
            background=BackgroundTask(cleanup_zip),
        )
    except ValidationError as exc:
        raise HTTPException(status_code=400, detail=str(exc))
    except ResourceNotFoundError:
        raise HTTPException(status_code=404, detail="Session directory not found")
    except HTTPException:
        raise
    except Exception as exc:
        logger = get_server_logger()
        logger.log_exception(exc, f"Unexpected error during session download: {session_id}")
        raise HTTPException(status_code=500, detail="Failed to download session")

View on GitHub (pinned to 4fb2db0ea9)

Solutions

1. Inspect the server log 'Unexpected error during session download' for the actual traceback
2. Verify /tmp is writable and has space for the temp zip
3. Check ulimits/file descriptors if streaming large sessions
4. Retry once transient IO issues are ruled out; report with logs if persistent

assert os.access(tempfile.gettempdir(), os.W_OK), 'temp dir not writable'
assert shutil.disk_usage(tempfile.gettempdir()).free > MIN_FREE_BYTES

except HTTPError as e:
    if e.response.status_code == 500 and 'Failed to download session' in e.response.text:
        if looks_transient(env_check()): retry_with_backoff(download, attempts=3)
        else: collect_server_logs_and_report()

When it happens

Trigger: GET download failing outside validation/zip steps: errors streaming the file response, temp file creation failure, background task setup errors, or unexpected IO problems.

Common situations: Temp directory not writable, disk exhaustion, file handle limits, or issues streaming large archives; often environmental rather than a code bug.

Related errors

• Failed to start workflow: {exc}
• Failed to run workflow: {exc}
• Failed to create zip archive
• Design file not found: {config_path}
• YAML root must be a mapping

AI-assisted analysis of OpenBMB/ChatDev@4fb2db0ea9 (2026-08-27). Data as JSON: /api/errors/746c9a4bde0a4f0a. Report an issue: GitHub.