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HTTP 101 Switching Protocols

The server agrees to switch protocols as requested via the Upgrade header — most commonly upgrading HTTP to a WebSocket connection.

1xx · Informational✗ not retryable — fix the request instead

In AI APIs specifically

Realtime voice/streaming APIs (e.g. OpenAI Realtime) use WebSocket upgrades; a missing 101 means the upgrade was refused.

Fix checklist

  • Verify the Upgrade and Connection headers are sent correctly.
  • Check that proxies/load balancers between you and the API support WebSockets.

Spec: RFC reference

Related status codes

100 Continue

The server received the request headers and the client should proceed to send the body.

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