Clarification: Does LangSmith Cloud Support WebSockets in Production Deployments?

LangSmith Product Help
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Body:
Hi, I have a question regarding WebSocket support on the LangSmith Cloud deployment platform:

Scenario:

  • I have built an application using LangGraph, FastAPI, and uvicorn.

  • My app exposes a WebSocket endpoint for streaming messages, and I connect to it from a React frontend using the WebSocket protocol.

  • Everything works perfectly in my local development environment:

    • Backend is started with uvicorn

    • React frontend connects to ws://localhost/...

    • WebSocket connection is stable and messaging works as expected.

Deployment steps taken:

  • I deployed my backend to LangSmith Cloud and updated my langgraph.json as follows:

    json

    {
    "graph_id": "dynamic_tone_agent/dynamictoneagent.py",
    "entrypoint": "dynamic_tone_agent.server:app",
    "type": "fastapi",
    "python_version": "3.11",
    "dependencies": {
    "file": "requirements.txt"
    }
    }

  • After deployment, I updated my React frontend to connect to the WebSocket using the provided API URL from LangSmith Cloud, changing https:// to wss://.

  • When running the frontend with the deployed backend URL, the WebSocket fails to connect. In the console, I consistently see “WebSocket Disconnected” errors and the connection closes immediately.

Question:

  • Does LangSmith Cloud currently allow production WebSocket connections for deployed FastAPI apps?

  • Are there any special configuration requirements or known infrastructure limitations that might cause the connection to be dropped or blocked after deployment?

  • Is there any official example or guidance for deploying and exposing WebSocket endpoints on LangSmith Cloud that work with React or other browser clients?