FeaturesRouters

Auto Router

Automatically select the best model for your prompt

The Auto Router (openrouter/auto) automatically selects the best model for your prompt, powered by NotDiamond.

Overview

Instead of manually choosing a model, let OpenRouter’s intelligent routing system analyze your prompt and select the optimal model from a curated set of high-quality options. The router considers factors like prompt complexity, task type, and model capabilities.

Usage

Set your model to openrouter/auto:

1import { OpenRouter } from '@openrouter/sdk';
2
3const openRouter = new OpenRouter({
4  apiKey: '<OPENROUTER_API_KEY>',
5});
6
7const completion = await openRouter.chat.send({
8  model: 'openrouter/auto',
9  messages: [
10    {
11      role: 'user',
12      content: 'Explain quantum entanglement in simple terms',
13    },
14  ],
15});
16
17console.log(completion.choices[0].message.content);
18// Check which model was selected
19console.log('Model used:', completion.model);

Response

The response includes the model field showing which model was actually used:

1{
2  "id": "gen-...",
3  "model": "anthropic/claude-sonnet-4.5",  // The model that was selected
4  "choices": [
5    {
6      "message": {
7        "role": "assistant",
8        "content": "..."
9      }
10    }
11  ],
12  "usage": {
13    "prompt_tokens": 15,
14    "completion_tokens": 150,
15    "total_tokens": 165
16  }
17}

How It Works

  1. Prompt Analysis: Your prompt is analyzed by NotDiamond’s routing system
  2. Model Selection: The optimal model is selected based on the task requirements
  3. Request Forwarding: Your request is forwarded to the selected model
  4. Response Tracking: The response includes metadata showing which model was used

Supported Models

The Auto Router selects from a curated set of high-quality models including:

Model slugs change as new versions are released. The examples below are current as of December 4, 2025. Check the models page for the latest available models.

  • Claude Sonnet 4.5 (anthropic/claude-sonnet-4.5)
  • Claude Opus 4.5 (anthropic/claude-opus-4.5)
  • GPT-5.1 (openai/gpt-5.1)
  • Gemini 3 Pro (google/gemini-3-pro-preview)
  • DeepSeek 3.2 (deepseek/deepseek-v3.2)
  • And other top-performing models

The exact model pool may be updated as new models become available.

Pricing

You pay the standard rate for whichever model is selected. There is no additional fee for using the Auto Router.

Use Cases

  • General-purpose applications: When you don’t know what types of prompts users will send
  • Cost optimization: Let the router choose efficient models for simpler tasks
  • Quality optimization: Ensure complex prompts get routed to capable models
  • Experimentation: Discover which models work best for your use case

Limitations

  • The router requires messages format (not prompt)
  • Streaming is supported
  • All standard OpenRouter features (tool calling, etc.) work with the selected model