Addendum to GPT-5 system card: GPT-5-Codex

September 15, 2025

This addendum to the GPT-5 system card shares a new model: GPT-5-Codex, a version of GPT-5 further optimized for agentic coding in Codex. GPT-5-Codex adjusts its thinking effort more dynamically based on task complexity, responding quickly to simple conversational queries or small tasks, while independently working for longer on more complex tasks.

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