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

# Claude Sonnet 4.6 Thinking

> Anthropic's Claude Sonnet 4.6 with extended thinking enabled. Enhanced reasoning with the latest Sonnet's speed and capability.

Claude Sonnet 4.6 Thinking is the extended thinking variant of Claude Sonnet 4.6, available through Anyfast via an OpenAI-compatible interface. It combines Sonnet 4.6's excellent balance of speed and capability with step-by-step internal reasoning enabled by default, delivering improved accuracy on complex tasks while maintaining fast response times.

## Key capabilities

* **OpenAI-compatible** — Works as a drop-in replacement with the OpenAI SDK
* **Extended thinking** — Step-by-step internal reasoning enabled by default
* **Latest Sonnet** — Built on the newest Sonnet architecture for top-tier performance
* **Enhanced reasoning** — Improved accuracy on complex, multi-step tasks
* **Long context** — Handles large documents and multi-turn conversations
* **Streaming** — Supports real-time token streaming via SSE

## Quick example

<CodeGroup>
  ```bash cURL theme={null}
  curl https://www.anyfast.ai/v1/messages \
    -H "Authorization: Bearer YOUR_API_KEY" \
    -H "Content-Type: application/json" \
    -d '{
      "model": "claude-sonnet-4-6-thinking",
      "messages": [
        { "role": "user", "content": "Solve step by step: If a train travels 120 km in 2 hours, then slows down and travels 80 km in 3 hours, what is the average speed for the entire trip?" }
      ]
    }'
  ```

  ```python Python theme={null}
  from openai import OpenAI

  client = OpenAI(
      api_key="YOUR_API_KEY",
      base_url="https://www.anyfast.ai/v1"
  )

  response = client.chat.completions.create(
      model="claude-sonnet-4-6-thinking",
      messages=[
          {"role": "user", "content": "Solve step by step: If a train travels 120 km in 2 hours, then slows down and travels 80 km in 3 hours, what is the average speed for the entire trip?"}
      ]
  )

  print(response.choices[0].message.content)
  ```

  ```python Streaming theme={null}
  from openai import OpenAI

  client = OpenAI(
      api_key="YOUR_API_KEY",
      base_url="https://www.anyfast.ai/v1"
  )

  stream = client.chat.completions.create(
      model="claude-sonnet-4-6-thinking",
      messages=[
          {"role": "user", "content": "Write a proof that there are infinitely many prime numbers."}
      ],
      stream=True
  )

  for chunk in stream:
      print(chunk.choices[0].delta.content or "", end="")
  ```
</CodeGroup>

## Parameters

| Parameter     | Type           | Required | Description                                |
| ------------- | -------------- | -------- | ------------------------------------------ |
| `model`       | string         | Yes      | Must be `claude-sonnet-4-6-thinking`       |
| `messages`    | array          | Yes      | List of `{ role, content }` objects        |
| `max_tokens`  | integer        | No       | Maximum tokens to generate                 |
| `temperature` | float          | No       | `0`–`2`. Controls randomness. Default: `1` |
| `stream`      | boolean        | No       | Enable SSE streaming. Default: `false`     |
| `top_p`       | float          | No       | Nucleus sampling threshold. Default: `1`   |
| `stop`        | string / array | No       | Sequences that stop generation             |

<Card title="API Reference" icon="code" href="/api-reference/model-api/anthropic/claude-sonnet-4-6-thinking">
  View the interactive API playground for Claude Sonnet 4.6 Thinking.
</Card>

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