Observe Async Chat Stream Events

Observe an asynchronous chat stream via Server-Sent Events.

This endpoint provides a Server-Sent Events stream that delivers chat completion events in real-time. The events follow the same format as synchronous chat streaming responses.

Stream Lifecycle:

1. Stream initiated via POST /v1/messages/async
2. Events begin flowing when processing starts
3. Stream automatically closes when message completes
4. Stream can be cancelled via POST /v1/messages/async/{message_id}/cancel

Notes:

• Stream remains active until message completion or cancellation
• Events are delivered in chronological order
• Connection will automatically close when stream ends
• Use appropriate SSE client libraries for robust event handling