Skip to content

Grok 4 Fast Reasoning

Grok 4 Fast Reasoning is the speed-optimized reasoning variant of xAI's Grok 4 Fast. It combines chain-of-thought reasoning with faster inference than the full Grok 4, within a context window of 2M tokens.

ReasoningTool UseImplicit Cachingtiered-costVision (Image)File InputWeb Search
index.ts
import { streamText } from 'ai'


const result = streamText({
  model: 'xai/grok-4-fast-reasoning',
  prompt: 'Why is the sky blue?'
})
OverviewPlaygroundAboutProvidersThroughputLatencyUptimeStatusSimilarFAQ

Playground

Try out Grok 4 Fast Reasoning by xAI. Usage is billed to your team at API rates. Free users (those who haven't made a payment) get $5 of credits every 30 days.