● Covered by 1 source · 1 reportLow impact1 negative
Codex App Users Report 404 Errors During GPT 5.4 xhigh Sessions
Key points
- Codex App users encounter 404 errors in GPT 5.4 xhigh sessions.
- The error occurs during agent thinking and continuation phases.
- GPT 5.5 xhigh sessions are not experiencing the same issue.
- The problem appeared after steering to spin up a sub-agent.
Codex App Experiences 404 Errors
Users of the Codex App, specifically those running GPT 5.4 xhigh sessions, are reporting "unexpected status 404 Not Found" errors. The error message indicates an issue with the URL "https://chatgpt.com/backend-api/codex/responses" and a "cf-ray" identifier.
Impact on User Sessions
The error causes sessions to stop after multiple retries, typically occurring when the agent attempts to think and continue its process. While sending a message and receiving an update works, subsequent agent actions trigger the 404 error, interrupting the workflow. One user noted the issue appeared shortly after steering the session to spin up a sub-agent.
Version-Specific Issue
The problem appears to be isolated to the GPT 5.4 xhigh version of the Codex App (version 26.611.61753). Users running GPT 5.5 xhigh sessions have not reported similar issues, suggesting a version-specific bug or incompatibility.
User Expectations and Workarounds
Users expect sessions to run without interruption and suggest more error-resistant retry mechanisms, such as exponential back-off. Although the session initially stops, sending a 'Continue' command can sometimes allow the session to proceed, though the error may reoccur.
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Primary sources
GitHub cmc_internal/api GitHub github/collect GitHub _view_fragments/issues GitHub openai/codex GitHub user-attachments/assets GitHub 28756/codexReporting from
Users of the Codex App are experiencing "404 Not Found" errors during long-running GPT 5.4 xhigh sessions, leading to session interruptions. This issue specifically affects the GPT 5.4 xhigh version, while GPT 5.5 xhigh sessions appear unaffected.