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Grok 4.1 Fast Reasoning

Grok 4.1 Fast Reasoning is xAI's reasoning-enabled Grok 4.1 Fast model optimized for agentic operations. It combines structured chain-of-thought reasoning with speed-optimized inference and a context window of 2M tokens for complex agent workflows.

ReasoningTool UseImplicit Cachingtiered-costVision (Image)File InputWeb Search
index.ts
import { streamText } from 'ai'
const result = streamText({
model: 'xai/grok-4.1-fast-reasoning',
prompt: 'Why is the sky blue?'
})