Mistral Mistral Medium 3.5 vs OpenAI GPT-5.5-Pro — side-by-side specs.
Mistral Mistral Medium 3.5 | OpenAI GPT-5.5-Pro | |
|---|---|---|
| Overview | ||
| Company | Mistral | OpenAI |
| Release date | Apr 29 2026 | Apr 23 2026 |
| Model type | — | — |
| Open source | Yes | No |
| Specifications | ||
Parameters | 128B | — |
Context window | 256k | — |
| Benchmarks | ||
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% | — |
Web browsing BrowseCompCan the AI browse the web and track down hard-to-find answers? Higher is better. | — | 90.1% |
Advanced math FrontierMath · Tier 1–3Very hard, research-level math problems. Tiers 1–3 are the (still extremely difficult) lower tiers. Higher is better. | — | 52.4% |
Advanced math FrontierMath · Tier 4Very hard, research-level math problems. Tier 4 is the hardest — close to what professional research mathematicians tackle. Higher is better. | — | 39.6% |
Knowledge work GDPval (win/tie rate)How often the AI's work matches or beats a human expert's on real knowledge-work tasks. Higher is better. | — | 82.3% |
| Timeline | ||
| Release gap | GPT-5.5-Pro shipped 6 days before Mistral Medium 3.5 | |
Mistral Medium 3.5 and GPT-5.5-Pro don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. GPT-5.5-Pro shipped 6 days before Mistral Medium 3.5, so benchmark comparisons should account for the intervening progress.
Mistral Medium 3.5 is an open-source / open-weight model; GPT-5.5-Pro is proprietary.
Direct benchmark comparisons are unavailable — Mistral Medium 3.5 and GPT-5.5-Pro don't publish scores on any of the same benchmarks.