> ## 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 Haiku 4.5 Thinking

> Anthropic's Claude Haiku 4.5 with extended thinking enabled. Fast reasoning for math, coding, and analysis at low cost.

Claude Haiku 4.5 Thinking is the extended thinking variant of Claude Haiku 4.5, available through Anyfast via an OpenAI-compatible interface. It combines Haiku's speed and cost-efficiency with step-by-step internal reasoning, delivering improved accuracy on complex tasks while remaining significantly faster and cheaper than larger thinking models.

## Key capabilities

* **OpenAI-compatible** — Works as a drop-in replacement with the OpenAI SDK
* **Extended thinking** — Step-by-step internal reasoning enabled by default
* **Fast + affordable** — Thinking capability at Haiku-level speed and cost
* **Streaming** — Supports real-time token streaming via SSE
* **Strong reasoning** — Improved accuracy on math, logic, and multi-step problems

## 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-haiku-4-5-20251001-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-haiku-4-5-20251001-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-haiku-4-5-20251001-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-haiku-4-5-20251001-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-haiku-4-5-20251001-thinking">
  View the interactive API playground for Claude Haiku 4.5 Thinking.
</Card>

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