GPT 5.5 Pro is only in chat/API, not Codex.
From https://openai.com/index/introducing-gpt-5-5/
In Codex, GPT‑5.5 is available for Plus, Pro, Business, Enterprise, Edu, and Go plans with a 400K context window.
alt Hacker News
From https://openai.com/index/introducing-gpt-5-5/
In Codex, GPT‑5.5 is available for Plus, Pro, Business, Enterprise, Edu, and Go plans with a 400K context window.