GPT-5.6 rollout appears to break existing GPT-5.5 projects (authentication/model migration issue)

What version of the Codex App are you using (From “About Codex” dialog)?

0.144.6

What subscription do you have?

Plus

What platform is your computer?

Windows11 Home version 25H2 (OS Build 26200.8875)

What issue are you seeing?

Summary

After the GPT-5.6 rollout, existing projects that were originally created and used with GPT-5.5 can no longer be used reliably.

The issue seems related to project/session migration rather than the repository itself.

Environment

• OS: Windows 11
• Codex: Latest version
• Account: ChatGPT Plus/Pro (replace with your plan)
• Repository: Existing project created before GPT-5.6 rollout

What steps can reproduce the bug?

Steps to Reproduce

1. Open an existing project that was previously using GPT-5.5.
2. Try to continue working on the project after the GPT-5.6 rollout.
3. Observe authentication/model behavior.

What is the expected behavior?

Actual Behavior

• GPT-5.6 models disappeared from the model list (previously available).
• Existing project cannot continue normally.
• Authentication repeatedly fails with:

Your access token could not be refreshed because your refresh token was revoked.
Please log out and sign in again.

Logging out and signing back in does not permanently resolve the issue.

The problem appears only after the GPT-5.6 rollout and affects projects that were already in progress.

Expected Behavior

Existing GPT-5.5 projects should continue to function normally after GPT-5.6 is released.

Model migration should not invalidate existing project sessions or require recreating projects.

Additional information

Additional Notes

There appear to be multiple reports related to GPT-5.6 rollout, including:

• Existing project/task migration issues
• GPT-5.6 models disappearing from Codex
• Authentication/session failures
• Refresh token revoked errors

These issues may be related to project metadata or session migration performed during the GPT-5.6 rollout.