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    xAI: Grok 4 Fast

    x-ai/grok-4-fast

    Created Sep 19, 20252,000,000 context
    Starting at $0.20/M input tokensStarting at $0.50/M output tokens

    Grok 4 Fast is xAI's latest multimodal model with SOTA cost-efficiency and a 2M token context window. It comes in two flavors: non-reasoning and reasoning. Read more about the model on xAI's news post. Reasoning can be enabled using the reasoning enabled parameter in the API. Learn more in our docs

    Prompts and completions on Grok 4 Fast Free may be used by xAI or OpenRouter to improve future models.

    Sample code and API for Grok 4 Fast

    OpenRouter normalizes requests and responses across providers for you.

    OpenRouter provides an OpenAI-compatible completion API to 400+ models & providers that you can call directly, or using the OpenAI SDK. Additionally, some third-party SDKs are available.

    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.