Context window is still 258k
Resolved 💬 2 comments Opened Apr 24, 2026 by beyond0573 Closed Apr 24, 2026
💡 Likely answer: A maintainer (github-actions[bot], contributor)
responded on this thread — see the highlighted reply below.
What version of the Codex App are you using (From “About Codex” dialog)?
26.422.21637 (2056)
What subscription do you have?
Pro
What platform is your computer?
_No response_
What issue are you seeing?
I’m on ChatGPT Pro and using the latest Codex app version 26.422.21637.
GPT-5.5 is available in Codex, but the context window still shows ~258K tokens instead of the announced 400K context window.
I’ve tried updating the app and starting a new thread. Could you check whether 400K context for GPT-5.5 in Codex has rolled out to my account/workspace?
What steps can reproduce the bug?
- update app to latest version : 26.422.21637
- create a new thread and chat with agent
What is the expected behavior?
_No response_
Additional information
_No response_
2 Comments
Potential duplicates detected. Please review them and close your issue if it is a duplicate.
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The 400K context window includes space for 272K of input + 128K of output. The 258K value is somewhat less than the full 272K to guarantee that compaction is possible. These are the same default values that have been in place for gpt 5.4, gpt 5.3-codex and gpt 5.2.