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Specifications
Context window
1M128k

These models have no shared benchmark scores.

Overview
CompanyAnthropicOpenAI
Release dateJun 9 2026Feb 12 2026
AccessClosedClosed
Model detailsView modelView model

Frequently asked questions

Claude Mythos 5 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. GPT-5.3-Codex-Spark shipped 117 days before Claude Mythos 5, so benchmark comparisons should account for the intervening progress.

Context windows are 1M (Claude Mythos 5) vs 128k (GPT-5.3-Codex-Spark).

Direct benchmark comparisons are unavailable — Claude Mythos 5 and GPT-5.3-Codex-Spark don't publish scores on any of the same benchmarks.