X-Ai/Grok-4-Fast-Reasoning

X-Ai/Grok-4-Fast-Reasoning

Developer	xAI
Release date	December 18, 2025
Family	Grok
Generation	Grok 4
Level
Context window	2M tokens
Max output	2M tokens
Input	Text, image, audio, video
Output	Text
Weights	Closed
Successor	Grok 4.1 Fast (Reasoning)
Website	x.ai
Links	Model card Docs

Part of a series on

Context: 2Mtokens
Released: 10mo ago

Infrastructure

Provider availability

Provider endpoint data will appear after this model's first OpenRouter endpoint sync.

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