Streaming

Add "stream": true to the request body and the response becomes text/event-stream: one data: {json} line per event, ending with data: [DONE].

curl https://api.tokrouter.dev/v1/chat/completions \
  -H "Authorization: Bearer $TOKROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.4-mini",
    "messages": [{"role": "user", "content": "Write a four-line poem"}],
    "stream": true
  }'

data: {"id":"...","choices":[{"delta":{"content":"Spring"}}]}

data: {"id":"...","choices":[{"delta":{"content":" sleeps"}}]}

data: [DONE]

With an SDK

Most SDKs handle SSE framing, keep-alive comments and [DONE] for you:

for chunk in client.chat.completions.create(..., stream=True):
    if chunk.choices and chunk.choices[0].delta.content:
        print(chunk.choices[0].delta.content, end="", flush=True)

If you parse SSE yourself

1. Split on \n\n, not on lines — one event can span several network packets
2. Skip comment lines starting with : (keep-alive heartbeats)
3. Close the connection on [DONE]; do not wait for EOF

When not to stream

• You need a complete JSON document (structured output) — streaming only complicates parsing
• The server caches the whole answer and first-token latency does not matter
• Non-chat endpoints such as /v1/systemone do not support streaming; stream has no effect