GPT-5-Codex vs Grok 4 Fast
OpenAI GPT-5-Codex | SpaceXAI Grok 4 Fast | |
|---|---|---|
| Overview | ||
| Company | OpenAI | SpaceXAI |
| Release date | Sep 15 2025 | Sep 19 2025 |
| Access | Proprietary | Proprietary |
| Benchmarks | ||
Nonsense detection BullshitBench v2Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better. | 39% | — |
| Timeline | ||
| Release gap | GPT-5-Codex shipped 4 days before Grok 4 Fast | |
Which is better: GPT-5-Codex or Grok 4 Fast?
GPT-5-Codex and Grok 4 Fast don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. GPT-5-Codex shipped 4 days before Grok 4 Fast, 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 — GPT-5-Codex and Grok 4 Fast don't publish scores on any of the same benchmarks.
Frequently asked questions
GPT-5-Codex was released by OpenAI on Sep 15 2025.
Grok 4 Fast was released by SpaceXAI on Sep 19 2025.
Other comparisons
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