Gemma 3 and GPT-5-Codex-Mini don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Gemma 3 shipped 241 days before GPT-5-Codex-Mini, so benchmark comparisons should account for the intervening progress.

Gemma 3 is open weight, while GPT-5-Codex-Mini is proprietary.

Direct benchmark comparisons are unavailable — Gemma 3 and GPT-5-Codex-Mini don't publish scores on any of the same benchmarks.