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Grok 4.1 Fast Reasoning

xai/grok-4.1-fast-reasoning

Grok 4.1 Fast is xAI's best tool-calling model with a 2M context window. It reasons and completes agentic tasks accurately and rapidly, excelling at complex real-world use cases such as customer support and finance. To optimize for maximal intelligence use this variant. Otherwise, use the non-reasoning version.

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