Stream tokens back in real time over standard Server-Sent Events (SSE).

Endpoint: POST /v1/chat/completions
Required Payload Field: "stream": true

Event Stream Protocol #

Each chunk is returned as a UTF-8 text block prefixed with data: :

http

HTTP/1.1 200 OK
Content-Type: text/event-stream
Cache-Control: no-cache
Connection: keep-alive

data: {"id":"chatcmpl_1","object":"chat.completion.chunk","created":1790355262,"model":"gpt-4o","choices":[{"index":0,"delta":{"role":"assistant","content":""},"finish_reason":null}]}

data: {"id":"chatcmpl_1","object":"chat.completion.chunk","created":1790355262,"model":"gpt-4o","choices":[{"index":0,"delta":{"content":"Hello"},"finish_reason":null}]}

data: {"id":"chatcmpl_1","object":"chat.completion.chunk","created":1790355262,"model":"gpt-4o","choices":[{"index":0,"delta":{"content":" World!"},"finish_reason":null}]}

data: {"id":"chatcmpl_1","object":"chat.completion.chunk","created":1790355262,"model":"gpt-4o","choices":[{"index":0,"delta":{},"finish_reason":"stop"}]}

data: [DONE]

Next Steps #

Embeddings spec: Embeddings API
Telemetry reference: Provider Attempts API

Streaming (SSE) API

Event Stream Protocol #

Next Steps #