langflow-ai/langflow · error · HTTPException

Project MCP Server disconnected, error: {e}

Error message

Project MCP Server disconnected, error: {e}

What it means

Error "Project MCP Server disconnected, error: {e}" thrown in langflow-ai/langflow.

Source

Thrown at src/backend/base/langflow/api/v1/mcp_projects.py:472

async def _handle_project_sse_messages(
    project_id: UUID,
    request: Request,
    current_user: User,
):
    """Handle POST messages for a project-specific MCP server using SSE transport."""
    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)
    req_vars_token = current_request_variables_ctx.set(variables or None)

    try:
        sse = get_project_sse(project_id)
        await sse.handle_post_message(request.scope, request.receive, request._send)  # noqa: SLF001
    except BrokenResourceError as e:
        await logger.ainfo("Project MCP Server disconnected for project %s", project_id)
        raise HTTPException(status_code=404, detail=f"Project MCP Server disconnected, error: {e}") from e
    finally:
        current_user_ctx.reset(user_token)
        current_project_ctx.reset(project_token)
        current_request_variables_ctx.reset(req_vars_token)


@router.post(
    "/{project_id}",
    dependencies=[Depends(raise_error_if_astra_cloud_env)],
    include_in_schema=False,
)
@router.post(
    "/{project_id}/",
    dependencies=[Depends(raise_error_if_astra_cloud_env)],
    include_in_schema=False,
)
async def handle_project_messages(
    project_id: UUID,

View on GitHub (pinned to 976ec789d2)

Solutions

1. Reconnect the MCP client; check that the project's MCP server process is still running and review its logs.

When it happens

Trigger: Occurs when the project MCP server connection drops with an error during an active session.

Common situations: See trigger scenarios.

AI-assisted analysis of langflow-ai/langflow@976ec789d2 (2026-08-14). Data as JSON: /api/errors/7f5aa63fbbda15d9. Report an issue: GitHub.