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 1M tokens for complex agent workflows.
ReasoningFile InputVision (Image)Tool UseImplicit Caching
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 |
|---|
| 500K | 1.5s | 71tps | $2/M | $6/M | Read: $0.3/M Write: — | $5/K + input costs | +3 |  | 07/08/2026 | |||
| 256K | 0.4s | 231tps | $1/M | $2/M | Read: $0.2/M Write: — | $5/K + input costs | +2 | | 05/20/2026 | |||
| 1M | 0.7s | 137tps | $1.25/M | $2.50/M | Read: $0.2/M Write: — | $5/K + input costs | +3 |  | 04/30/2026 | |||
| 2M | 0.3s | 127tps | $1.25/M | $2.50/M | Read: $0.2/M Write: — | $5/K + input costs | +2 | | 03/10/2026 | |||
| 2M | 0.5s | 187tps | $1.25/M | $2.50/M | Read: $0.2/M Write: — | $5/K + input costs | +3 | | 03/10/2026 | |||
| 1M | 0.3s | 179tps | $0.20/M | $0.50/M | Read:$0.05/M Write:— | — | +1 | | 11/19/2025 |