Model page
GPT-5.3-Codex
The most capable agentic coding model to date. Optimized for agentic coding tasks in Codex or similar environments. 400K context, 128K max output. Reasoning off by default.
Key dates
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ChatGPT
GPT‑4o retirement (ChatGPT)
OpenAI is retiring GPT‑4o inside ChatGPT on February 13, 2026. This does not automatically imply API removal.