1m context window gone after Gpt 5.5 Release.
Resolved 💬 12 comments Opened Apr 23, 2026 by Zakisb Closed Apr 23, 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)?
26.422.20832
What subscription do you have?
Pro plan
What platform is your computer?
Mac os
What issue are you seeing?
I've enable 1m context window via codex config since the release of GPT 5.4 and it was working exceptionally well. today Codex announces GPT 5.5 stating it supports 1m Context window but weirdly thought it's gone in the codex app.
<img width="884" height="227" alt="Image" src="https://github.com/user-attachments/assets/8e8048b6-e1b4-494f-982f-063f5f1cffba" />
What steps can reproduce the bug?
Just launch the codex app and enable 1m context window in config.toml file
What is the expected behavior?
Having 1m context window automatically enabled
Additional information
here's my current config.toml file
model = "gpt-5.5"
model_reasoning_effort = "xhigh"
model_context_window = 1000000
model_auto_compact_token_limit = 900000
personality = "pragmatic"
12 Comments
Potential duplicates detected. Please review them and close your issue if it is a duplicate.
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cli v0.124.0 has this issue too
I read the release page https://openai.com/index/introducing-gpt-5-5/ it says
Which 400K context window is fine for me, and it can keep good proformance. However, 258K is not 400K.
Could Codex fix this ASAP?
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.
gpt 5.5 supports 1M context window. Please reopen issue
Sorry, but why did you closed the issue, if the main problem is that 1m tokens context is gone?
<img width="1088" height="286" alt="Image" src="https://github.com/user-attachments/assets/fa6d9031-c470-4980-a118-8d92759daf99" />
Wtf why is this closed? Is this OpenAI stance now no 1M context? Then why use this vs Claude were 1M is the default?
why is this closed? this is clear regression
only see 258k in the codex app... is it 400k or 1M? very unclear
Why is this closed? Mayor regression with no announcement. Wasting everyones time. Must we just guess what's gonna happen?
Let's continue the discussion in #19464.