GPT-5.5 Have a knowledge Cutoff date of June 2024, Creating Performance Degradation
Resolved 💬 0 comments Opened May 28, 2026 by Croquembouche Closed May 28, 2026
What version of Codex CLI is running?
0.134.0
What subscription do you have?
Pro-Lite
Which model were you using?
GPT-5.5
What platform is your computer?
Linux 6.8.0-40-generic x86_64 x86_64
What terminal emulator and version are you using (if applicable)?
_No response_
Codex doctor report
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"endpoint": "wss://chatgpt.com/backend-api/<redacted>",
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}What issue are you seeing?
CLI shows current model is GPT-5.5 but knowledge cutoff date is June 2024. This is cause performance degradation in code quality and huge increase in token usage
What steps can reproduce the bug?
codex --model gpt-5.5
verify model with /model
prompt: what is your knowledge cutoff date
Response: June 2024
-------------------------------
Token usage have risen significantly. Code output have degraded.
What is the expected behavior?
Expected response should be Dec 1, 2025
Additional information
_No response_