Documentation 2026-08-19 18:02 UTC to 2026-08-20 15:02 UTC

2 2 

3> For the complete documentation index, see [llms.txt](/llms.txt). Markdown versions of documentation pages are available by appending `.md` to the page URL.3> For the complete documentation index, see [llms.txt](/llms.txt). Markdown versions of documentation pages are available by appending `.md` to the page URL.

4 4 

5The Responses API supports a WebSocket mode for long-running, tool-call-heavy workflows. Beyond lowering latency, `stream_id` lets one persistent connection to `/v1/responses` run parallel conversations and fork an existing conversation onto a new stream. Continue each turn by sending only new input items plus `previous_response_id`.5The Responses API supports a WebSocket mode for long-running, tool-call-heavy workflows. Beyond lowering latency, `stream_id` enables WebSocket multiplexing: one persistent connection to `/v1/responses` can run parallel conversations and fork an existing conversation onto a new stream. Continue each turn by sending only new input items plus `previous_response_id`.

6 

7This pattern is WebSocket multiplexing: multiple logical response lanes over one persistent connection.

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9WebSocket mode is compatible with both Zero Data Retention (ZDR) and `store=false`.7WebSocket mode is compatible with both Zero Data Retention (ZDR) and `store=false`.

10 8 

326}324}

327```325```

328 326 

327`invalid_stream_id`

328 

329```json

330{

331 "type": "error",

332 "status": 400,

333 "error": {

334 "type": "invalid_request_error",

335 "code": "invalid_stream_id",

336 "message": "The 'stream_id' field must be a non-empty string with at most 256 characters and may only contain letters, numbers, underscores, hyphens, and periods.",

337 "param": "stream_id"

338 }

339}

340```

341 

329`websocket_stream_limit_reached`342`websocket_stream_limit_reached`

330 343 

331```json344```json