Grok 4 Fast
Grok 4 Fast matches Grok 4 on benchmarks with 40% fewer thinking tokens and a 2M context at $0.20/$0.50 per million tokens.
A unified reasoning/non-reasoning model with 2M context. xAI claims about 98% lower cost to reach Grok 4's benchmark level, from cheaper tokens plus shorter reasoning. Reports GPQA Diamond 85.7% and AIME 2025 92.0%.
- Date
- Friday, 19 September 2025
- Lab
- xAI
- Kind
- model
- Access
- closed API
- Price
- $0.20 in / $0.50 out per 1M tokens (under 128K), Sept 2025
Figures
| Measure | Value | Measured by |
|---|---|---|
| GPQA Diamond | 85.7% | company |
| AIME 2025 | 92.0% | company |
| Thinking tokens vs Grok 4 | -40% on average claimed ~98% cost reduction to reach equal performance | company |
Sources
This record was checked against its sources on 6 October 2026. How we check