> ## 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.

# Doubao Seed 2.1 Turbo

> ByteDance's Doubao-Seed-2.1-Turbo chat model via OpenAI-compatible API. A cost-effective Seed 2.1 variant with a 256K context, deep thinking, and multimodal understanding for scaled production.

Doubao-Seed-2.1-Turbo balances quality and cost, available through Anyfast via an OpenAI-compatible interface. It fully upgrades coding, agent, and multimodal capabilities over the previous generation, and is built for scaled production workloads that need to handle large volumes of online calls reliably — with the same capability surface as Doubao-Seed-2.1-Pro.

## Key capabilities

* **OpenAI-compatible** — Works as a drop-in replacement with the OpenAI SDK
* **256K context window** — Handles project-scale context, with up to 256K tokens of output in a single response
* **Quality/cost balance** — Built for large-scale, standardized production workloads
* **Deep thinking** — Chain-of-thought reasoning, on by default, with adjustable `reasoning_effort`
* **Multimodal understanding** — Text, image, video, and document understanding (audio not supported)
* **Function calling, structured output & context caching** — Robust tool use, JSON output (beta), and prompt caching
* **Streaming** — Real-time token streaming via SSE

## Output specifications

| Property          | Value                        |
| ----------------- | ---------------------------- |
| Input modality    | Text, Image, Video, Document |
| Output modality   | Text                         |
| Context window    | 256K tokens                  |
| Max output tokens | 256K                         |

## Quick example

<CodeGroup>
  ```bash cURL theme={null}
  curl https://www.anyfast.ai/v1/chat/completions \
    -H "Authorization: Bearer YOUR_API_KEY" \
    -H "Content-Type: application/json" \
    -d '{
      "model": "doubao-seed-2.1-turbo",
      "messages": [
        { "role": "user", "content": "Explain quantum entanglement in simple terms." }
      ]
    }'
  ```

  ```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="doubao-seed-2.1-turbo",
      messages=[
          {"role": "user", "content": "Explain quantum entanglement in simple terms."}
      ]
  )

  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="doubao-seed-2.1-turbo",
      messages=[
          {"role": "user", "content": "Write a short poem about the sea."}
      ],
      stream=True
  )

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

## Thinking mode

Doubao-Seed-2.1-Turbo reasons before answering by default. `thinking.type` is `enabled` unless you set it to `disabled` to skip reasoning for lightweight tasks. Use `reasoning_effort` to tune how long the model thinks.

```python Python theme={null}
response = client.chat.completions.create(
    model="doubao-seed-2.1-turbo",
    messages=[
        {"role": "user", "content": "Design a REST API for a blogging platform."}
    ],
    extra_body={
        "thinking": {"type": "enabled"},
        "reasoning_effort": "high"
    }
)

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

`reasoning_effort` controls reasoning length (effective only when thinking is enabled) and accepts `minimal`, `low`, `medium`, and `high`. Default: `high`.

## Parameters

| Parameter          | Type           | Required | Description                                                                             |
| ------------------ | -------------- | -------- | --------------------------------------------------------------------------------------- |
| `model`            | string         | Yes      | Must be `doubao-seed-2.1-turbo`                                                         |
| `messages`         | array          | Yes      | List of `{ role, content }` objects                                                     |
| `thinking`         | object         | No       | `{ "type": "enabled" \| "disabled" }`. Controls deep thinking. Default: `enabled`       |
| `reasoning_effort` | string         | No       | `minimal`, `low`, `medium`, `high`. Effective when thinking is enabled. Default: `high` |
| `max_tokens`       | integer        | No       | Maximum tokens to generate (up to 262144)                                               |
| `temperature`      | float          | No       | `0`–`2`. Controls randomness. Default: `1`                                              |
| `top_p`            | float          | No       | Nucleus sampling threshold. Default: `1`                                                |
| `stream`           | boolean        | No       | Enable SSE streaming. Default: `false`                                                  |
| `tools`            | array          | No       | Function tool definitions for tool use                                                  |
| `response_format`  | object         | No       | `{ "type": "json_object" }` for structured JSON output (beta)                           |
| `stop`             | string / array | No       | Sequences that stop generation                                                          |

<Card title="API Reference" icon="code" href="/api-reference/model-api/bytedance/doubao-seed-2.1-turbo">
  View the interactive API playground for Doubao Seed 2.1 Turbo.
</Card>

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