# Streaming

> Server-sent events in both formats — the event shapes differ, and mixing them up reads as silence.

_Source: https://aiprimetech.io/docs/api-reference/streaming/ · Home > Docs > API reference_

Set `stream` to true and the response becomes `text/event-stream`. Both endpoints stream, but they emit **different event shapes**.


## Anthropic format

```bash
curl -N https://aiprimetech.io/v1/messages \
  -H "x-api-key: $CLAUDEAPIKEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{"model":"claude-sonnet-4-6","max_tokens":512,"stream":true,
       "messages":[{"role":"user","content":"Count to five"}]}'
```

```json
event: message_start
data: {"type":"message_start","message":{"id":"msg_...","usage":{"input_tokens":9}}}

event: content_block_delta
data: {"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":"One"}}

event: message_delta
data: {"type":"message_delta","delta":{"stop_reason":"end_turn"},"usage":{"output_tokens":14}}

event: message_stop
data: {"type":"message_stop"}
```

Text arrives in `content_block_delta` events at `delta.text`. Final output token counts arrive in `message_delta`, not `message_start`.


## OpenAI format

```json
data: {"choices":[{"delta":{"content":"One"},"index":0}]}

data: {"choices":[{"delta":{},"finish_reason":"stop","index":0}]}

data: [DONE]
```

Text arrives at `choices[0].delta.content`, and the stream ends with a literal `data: [DONE]` sentinel that is not JSON.

> This mismatch produces an empty response with no error: a client parsing `choices[].delta.content` against a Messages stream finds nothing, every time, and reports success. If streaming appears to work but returns nothing, check which shape you are parsing.


## Python, Anthropic SDK

```python
from anthropic import Anthropic

client = Anthropic(api_key="sk-your-key", base_url="https://aiprimetech.io")

with client.messages.stream(
    model="claude-sonnet-4-6",
    max_tokens=512,
    messages=[{"role": "user", "content": "Count to five"}],
) as stream:
    for text in stream.text_stream:
        print(text, end="", flush=True)
```


## Operational notes

- Use `curl -N` when testing by hand, or curl buffers the whole stream and it looks like nothing is happening.
- Disable proxy buffering in front of your own app (`proxy_buffering off` in nginx) or clients see the reply arrive in one lump at the end.
- A dropped connection mid-stream still bills the tokens already generated.
- Streaming does not change the price — only when the bytes arrive.

- [Messages API](https://aiprimetech.io/docs/api-reference/messages/) — Non-streaming reference
- [Errors](https://aiprimetech.io/docs/api-reference/errors/) — Failures mid-stream
- [Troubleshooting](https://aiprimetech.io/docs/guides/troubleshooting/) — Empty responses


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_ClaudeAPIKey.dev is an independently operated, Anthropic-compatible API gateway. Not affiliated with Anthropic._