Claude Instant 1.2 and GPT-5.3-Codex-Spark don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Claude Instant 1.2 shipped 918 days before GPT-5.3-Codex-Spark, 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-5.3-Codex-Spark don't publish scores on any of the same benchmarks.