Streaming

Server-sent events, unbuffered end to end, with pre-stream failures surfaced as real HTTP errors.

Set "stream": true on POST /v1/chat/completions. The response is server-sent events, unbuffered end to end, terminated by data: [DONE].

bash

curl -N https://onerouter.network/v1/chat/completions \
  -H "Authorization: Bearer $ONEROUTER_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "meta-llama/llama-3.3-70b-instruct",
    "messages": [{"role":"user","content":"ping"}],
    "stream": true,
    "stream_options": {"include_usage": true}
  }'

Buffering is disabled at every layer that could introduce it, so tokens reach you as the upstream produces them rather than in bursts.

A pre-stream failure is a real HTTP error#

OneRouter pulls the first chunk before returning the response. That one detail decides how your client sees a failure:

When it fails	What your client sees
Before the first chunk	A normal HTTP status and an error envelope
After the first chunk	`200 OK`, then a terminal error chunk, then `[DONE]`

Without that first pull, every failure would arrive as 200 OK with the error buried inside the event stream — which most SDK error handlers never look at.

Cost arrives in the final chunk#

A stream's headers are written before the first token, so the charge cannot be known when they are sent. Send stream_options.include_usage and the last chunk before [DONE] carries it:

json

{"usage":{"prompt_tokens":18,"completion_tokens":242,"total_tokens":260,
          "cost":0.000417}}

On a stream, x-onerouter-balance-usd is the balance before the request

It is a head-of-response header, so it cannot include a charge that has not happened yet. Non-streaming responses carry the settled figures in x-onerouter-cost-usd and x-onerouter-balance-usd instead.

Aborting#

Close the connection and OneRouter aborts the upstream with it, immediately. You are charged for the tokens generated before the abort, not for the completion you did not wait for. The usage record is marked usage_source: estimated_on_abort — an estimate, flagged as one, rather than a precise-looking number nobody can verify.

Running out mid-stream#

If the balance reaches zero while tokens are flowing, the stream ends with an OpenAI-shaped error chunk whose code is insufficient_credit, followed by [DONE] and a clean close. Never a silent truncation: a stream that just stops is indistinguishable from a network fault, and your retry logic cannot tell those apart.

Retries#

Before the first content byte, OneRouter retries another upstream automatically. After it, the route is committed — see Failover for why that boundary exists and what it costs you.