Claude Instant 1.2 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. Claude Instant 1.2 shipped 833 days before GPT-5.1-Codex-Max, 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 — Claude Instant 1.2 and GPT-5.1-Codex-Max don't publish scores on any of the same benchmarks.