> ## Documentation Index
> Fetch the complete documentation index at: https://docs.unifically.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Claude Sonnet 5.5

> Anthropic's Claude Sonnet 5.5 language model. See supported inputs, parameters, pricing, response fields, and API examples.

Claude Sonnet 5.5 is Anthropic's Sonnet model from the Claude 5.5 family, released September 28, 2026, for everyday coding, bug fixing, and document, slide, and spreadsheet work. It takes text and image input, outputs text, and carries a 1M token context window with up to 128k output tokens. It uses adaptive thinking steered by effort, which defaults to `high`; to keep up-front thinking off, use the `between_tools` setting.

## Model

```
anthropic/claude-sonnet-5-5
```

| | |
| - | - |
| **Provider** | Anthropic |
| **Name** | Claude Sonnet 5.5 |

## Supported Endpoints

All three API formats are supported:

* [Chat Completions](/api-reference/v1-chat-completions) — `POST /v1/chat/completions`
* [Responses](/api-reference/v1-responses) — `POST /v1/responses`
* [Messages](/api-reference/v1-messages) — `POST /v1/messages`

## Example

```bash theme={null}
curl -X POST https://api.unifically.com/v1/messages \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "anthropic/claude-sonnet-5-5",
    "max_tokens": 4096,
    "messages": [
      {"role": "user", "content": "Design a distributed job queue with exactly-once semantics."}
    ]
  }'
```

<Note>
  **Volume discounts** are available for almost all models. Reach out at [contact@unifically.com](mailto:contact@unifically.com) to discuss custom pricing.
</Note>