Model Fallbacks

The models parameter lets you automatically try other models if the primary model’s providers are down, rate-limited, or refuse to reply due to content moderation.

How It Works

Provide an array of model IDs in priority order. If the first model returns an error, OpenRouter will automatically try the next model in the list.

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import { OpenRouter } from '@openrouter/sdk';
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const openRouter = new OpenRouter({
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  apiKey: '<OPENROUTER_API_KEY>',
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});
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const completion = await openRouter.chat.send({
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  models: ['~anthropic/claude-sonnet-latest', 'gryphe/mythomax-l2-13b'],
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  messages: [
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    {
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      role: 'user',
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      content: 'What is the meaning of life?',
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    },
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  ],
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});
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console.log(completion.choices[0].message.content);

Fallback Behavior

If the model you selected returns an error, OpenRouter will try to use the fallback model instead. If the fallback model is down or returns an error, OpenRouter will return that error.

By default, any error can trigger the use of a fallback model, including:

• Context length validation errors
• Moderation flags for filtered models
• Rate-limiting
• Downtime

Pricing

Requests are priced using the model that was ultimately used, which will be returned in the model attribute of the response body.

Using with OpenAI SDK

To use the models array with the OpenAI SDK, include it in the extra_body parameter. In the example below, ~openai/gpt-latest will be tried first, and the models array will be tried in order as fallbacks.

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from openai import OpenAI
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openai_client = OpenAI(
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  base_url="https://openrouter.ai/api/v1",
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  api_key={{API_KEY_REF}},
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)
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completion = openai_client.chat.completions.create(
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    model="~openai/gpt-latest",
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    extra_body={
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        "models": ["~anthropic/claude-sonnet-latest", "gryphe/mythomax-l2-13b"],
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    },
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    messages=[
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        {
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            "role": "user",
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            "content": "What is the meaning of life?"
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        }
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    ]
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)
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print(completion.choices[0].message.content)