# Streaming

> Receive tokens as they are generated with server-sent events, in every API format.


Set `stream: true`. The response is `text/event-stream`. Events are sent one by one, without buffering.

```bash test
curl -N https://api.notholy.com/v1/chat/completions \
  -H "Authorization: Bearer $NOTHOLY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "notholy-specter", "stream": true, "stream_options": {"include_usage": true}, "messages": [{"role": "user", "content": "Define XSS."}]}'
```

```python test
import os
from openai import OpenAI

client = OpenAI(base_url="https://api.notholy.com/v1", api_key=os.environ["NOTHOLY_API_KEY"])

stream = client.chat.completions.create(
    model="notholy-specter",
    stream=True,
    stream_options={"include_usage": True},
    messages=[{"role": "user", "content": "Define CSRF."}],
)
for chunk in stream:
    if chunk.choices and chunk.choices[0].delta.content:
        print(chunk.choices[0].delta.content, end="")
    if chunk.usage:
        print("\n", chunk.usage.total_tokens, "tokens")
```

```js test
import OpenAI from 'openai';

const client = new OpenAI({ baseURL: 'https://api.notholy.com/v1', apiKey: process.env.NOTHOLY_API_KEY });

const stream = await client.chat.completions.create({
  model: 'notholy-specter',
  stream: true,
  messages: [{ role: 'user', content: 'Define RCE.' }],
});
for await (const chunk of stream) process.stdout.write(chunk.choices[0]?.delta?.content ?? '');
console.log();
```

## What to expect

- Chat completions and text completions end with `data: [DONE]`. The chunk before it always carries `usage`, with or without `include_usage`.
- Responses ends with `response.completed` (or `response.incomplete` at the output limit). Messages ends with `message_delta` and `message_stop`. Neither sends `[DONE]`.
- Long pauses get keep-alive comments (OpenAI formats) or `ping` events (Messages).
- If the stream breaks, you pay only for the tokens that were generated before the break.
- Errors found before the stream starts (key, credits, limits) come back as a normal JSON error with its HTTP status. A failure after the stream starts arrives as an error event in the same format: `data: {"error": ...}`, `response.failed` or an `error` event.

## Next

- [Errors](/en/guides/errors)