Mistral Medium 3.5vsGPT-5-Codex
Mistral Medium 3.5 | GPT-5-Codex | |
|---|---|---|
| Specifications | ||
Parameters | 128B | — |
Context window | 256k | — |
| 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% |
Coding SWE-Bench VerifiedReal coding tasks pulled from open-source projects — the AI has to find and fix actual bugs. A human-checked version of the original SWE-Bench. Higher is better. | 77.6% | — |
Community preference (code) Arena Elo (Code)Like the text arena, but people vote on which AI writes better code. The votes become a chess-style Elo rating on arena.ai. Higher is better. | 1267 | — |
| Overview | ||
| Company | Mistral | OpenAI |
| Release date | Apr 29 2026 | Sep 15 2025 |
| Access | Open Weight | Proprietary |
Which is better: Mistral Medium 3.5 or GPT-5-Codex?
Mistral Medium 3.5 and GPT-5-Codex don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. GPT-5-Codex shipped 226 days before Mistral Medium 3.5, so benchmark comparisons should account for the intervening progress.
Mistral Medium 3.5 is open weight, while GPT-5-Codex is proprietary.
Direct benchmark comparisons are unavailable — Mistral Medium 3.5 and GPT-5-Codex don't publish scores on any of the same benchmarks.
Frequently asked questions
Mistral Medium 3.5 was released by Mistral on Apr 29 2026.
GPT-5-Codex was released by OpenAI on Sep 15 2025.
Mistral Medium 3.5 is an open weight model released by Mistral. GPT-5-Codex is a proprietary model released by OpenAI.
Other comparisons
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