Is Grok 4 Fast available on FastMetal?

Not at the moment. Grok 4.6, from the same lab, is available on the FastMetal API today.

What is the context window of Grok 4 Fast?

2,000,000 tokens, shared between the prompt and the response.

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xAI

x-ai/grok-4-fast

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Grok 4 Fast

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](http://x.ai/news/grok-4-fast). Reasoning can be enabled/disabled using the `reasoning` `enabled` parameter in the API.

9/19/2025

2,000,000 tokens

Specifications

Modalities

Input

text

image

Output

text

Supported Parameters

include_reasoning

logprobs

max_tokens

reasoning

response_format

seed

structured_outputs

temperature

tool_choice

tools

top_logprobs

top_p

Max Output Tokens

30,000

Data policy

Prompt retention: Unknown — we could not confirm
Training: Unknown — not declared

"Unknown" does not mean "safe". It means we could not confirm it.

Whether a provider trains on prompts is a declared value from our terms with them. Retention is determined from the upstream listing for every host this model can reach. Neither is guessed.

Frequently asked questions

Is Grok 4 Fast available on FastMetal?: Not at the moment. Grok 4.6, from the same lab, is available on the FastMetal API today.
What is the context window of Grok 4 Fast?: 2,000,000 tokens, shared between the prompt and the response.

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