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    xAI: Grok 4.1 Fast

    x-ai/grok-4.1-fast

    Created Nov 19, 20252,000,000 context
    $0/M input tokens$0/M output tokens

    Grok 4.1 Fast is xAI's best agentic tool calling model that shines in real-world use cases like customer support and deep research. 2M context window.

    Reasoning can be enabled/disabled using the reasoning enabled parameter in the API. Learn more in our docs

    Sample code and API for Grok 4.1 Fast

    OpenRouter normalizes requests and responses across providers for you.

    OpenRouter supports reasoning-enabled models that can show their step-by-step thinking process. Use the reasoning parameter in your request to enable reasoning, and access the reasoning_details array in the response to see the model's internal reasoning before the final answer. When continuing a conversation, preserve the complete reasoning_details when passing messages back to the model so it can continue reasoning from where it left off. Learn more about reasoning tokens.

    In the examples below, the OpenRouter-specific headers are optional. Setting them allows your app to appear on the OpenRouter leaderboards.

    Using third-party SDKs

    For information about using third-party SDKs and frameworks with OpenRouter, please see our frameworks documentation.

    See the Request docs for all possible fields, and Parameters for explanations of specific sampling parameters.