OpenAI GPT-5-Codex vs xAI Grok Code Fast 1 — side-by-side specs.
OpenAI GPT-5-Codex | xAI Grok Code Fast 1 | |
|---|---|---|
| Overview | ||
| Company | OpenAI | xAI |
| Release date | Sep 15 2025 | Aug 28 2025 |
| Model type | — | — |
| Open source | No | No |
| Specifications | ||
Parameters | — | — |
Context window | — | — |
| Benchmarks | ||
Science reasoning GPQA Diamond | — | — |
Software engineering SWE-Bench Verified | — | — |
Multimodal understanding MMMU | — | — |
| Timeline | ||
| Release gap | Grok Code Fast 1 shipped 18 days before GPT-5-Codex | |
GPT-5-Codex and Grok Code Fast 1 do not have directly comparable benchmark scores published on GPQA Diamond, SWE-Bench Verified, or MMMU. Grok Code Fast 1 shipped 18 days before GPT-5-Codex, so benchmark comparisons should account for the intervening progress.
Published specifications for these two models are limited — see each model page for the latest details.
Direct benchmark comparisons are unavailable — at least one of these models has not published scores on GPQA Diamond, SWE-Bench Verified, or MMMU.