GPT-5.3-Codex-Spark and Grok 4 Heavy don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Grok 4 Heavy shipped 218 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 — GPT-5.3-Codex-Spark and Grok 4 Heavy don't publish scores on any of the same benchmarks.