Devstral Small and GPT-5.1-Codex-Max don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Devstral Small shipped 182 days before GPT-5.1-Codex-Max, so benchmark comparisons should account for the intervening progress.

Devstral Small is open weight, while GPT-5.1-Codex-Max is proprietary.

Direct benchmark comparisons are unavailable — Devstral Small and GPT-5.1-Codex-Max don't publish scores on any of the same benchmarks.