langflow-ai/langflow · error · HTTPException

Internal server error in project MCP transport

Error message

Internal server error in project MCP transport

What it means

Error "Internal server error in project MCP transport" thrown in langflow-ai/langflow.

Source

Thrown at src/backend/base/langflow/api/v1/mcp_projects.py:530

) -> Response:
    """Common handler for project-specific Streamable HTTP requests."""
    # Lazily initialize the project's Streamable HTTP manager
    # to pick up new projects as they are created.
    project_server = get_project_mcp_server(project_id)
    await project_server.ensure_session_manager_running()

    user_token = current_user_ctx.set(current_user)
    project_token = current_project_ctx.set(project_id)
    variables = extract_global_variables_from_headers(request.headers, include_auth_headers=True)
    request_vars_token = current_request_variables_ctx.set(variables or None)

    try:
        await project_server.session_manager.handle_request(request.scope, request.receive, request._send)  # noqa: SLF001
    except HTTPException:
        raise
    except Exception as exc:
        await logger.aexception(f"Error handling Streamable HTTP request for project {project_id}: {exc!s}")
        raise HTTPException(status_code=500, detail="Internal server error in project MCP transport") from exc
    finally:
        current_request_variables_ctx.reset(request_vars_token)
        current_project_ctx.reset(project_token)
        current_user_ctx.reset(user_token)

    return ResponseNoOp(status_code=200)


streamable_http_route_config = {
    "methods": ["GET", "POST", "DELETE"],
    "response_class": ResponseNoOp,
    "include_in_schema": False,
}


@router.api_route("/{project_id}/streamable", **streamable_http_route_config)
@router.api_route("/{project_id}/streamable/", **streamable_http_route_config)
async def handle_project_streamable_http(

View on GitHub (pinned to 976ec789d2)

Solutions

1. Check server logs for the transport error and retry; restart the MCP server if it is stuck.

When it happens

Trigger: Occurs when an unexpected internal error is raised inside the project MCP transport handler.

Common situations: See trigger scenarios.

Understand the failure class

• HTTP status errors: handling 4xx and 5xx responses — how to handle 4xx and 5xx responses properly.

AI-assisted analysis of langflow-ai/langflow@976ec789d2 (2026-08-14). Data as JSON: /api/errors/6d9fa3a3e12ccc70. Report an issue: GitHub.