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?'})More models by xAI
| Model |
|---|
| 1M | 1.4s | 70tps | $1.25/M | $2.50/M | Read: $0.2/M Write: — | $5/K + input costs | — |  | 04/30/2026 | ||||
| 2M | 3.4s | 1274tps | $1.25/M | $2.50/M | Read: $0.2/M Write: — | $5/K + input costs | — | | 03/09/2026 | ||||
| 2M | 0.7s | 50tps | $0.20/M | $0.50/M | Read: $0.05/M Write: — | $5/K + input costs | — | | 09/19/2025 | ||||
| 256K | 0.4s | 87tps | $0.20/M | $1.50/M | Read:$0.02/M Write:— | — | — | | 08/28/2025 | ||||
| 2M | 0.2s | 193tps | $0.20/M | $0.50/M | Read: $0.05/M Write: — | $5/K + input costs | — |  | 07/09/2025 | ||||
| 131K | 0.3s | 114tps | $0.30/M | $0.50/M | Read:$0.07/M Write:— | — | — | | 02/17/2025 |