# fastapi.exceptions.WebSocketRequestValidationError: 400 Bad WebSocket Request

- **ID:** `python/fastapi-websocket-validation-error`
- **Domain:** python
- **Category:** network_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

The WebSocket connection request has invalid parameters or headers.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **** (90% success)
   ```
   Ensure the WebSocket URL includes the correct subprotocols and headers: websocket.connect("ws://...", subprotocols=["chat"])
   ```
2. **** (85% success)
   ```
   Handle the validation error in the endpoint: except WebSocketRequestValidationError as e: await websocket.close(code=1002)
   ```

## Dead Ends

- **** — This can lead to security vulnerabilities or broken connections. (70% fail)
- **** — This breaks the WebSocket functionality entirely. (90% fail)