Client or integration
Codex App
Area
Authentication / entitlement / model catalog
Summary
After upgrading OpenCodex from 2.35.0 to 2.36.0, a ChatGPT Plus account can no longer use the GPT-5.6 family in Codex.
Downgrading the same OpenCodex installation back to 2.35.0 immediately restores GPT-5.6 availability for the same Plus account.
Affected models:
gpt-5.6-sol
gpt-5.6-terra
gpt-5.6-luna
This looks like a 2.36.0 regression in the entitlement/catalog synchronization path rather than an actual account entitlement change, because the result is reproducible across the version boundary with the same account.
Reproduction
- Sign in to Codex with a ChatGPT Plus account that can use GPT-5.6 under OpenCodex 2.35.0.
- Confirm GPT-5.6 models are available/usable.
- Upgrade OpenCodex to 2.36.0.
- Restart/reload Codex so the model catalog is refreshed.
- Observe that the GPT-5.6 family is no longer usable / the model picker changes.
- Downgrade OpenCodex back to 2.35.0:
npm install -g @bitkyc08/opencodex@2.35.0
- Restart Codex.
- GPT-5.6 availability returns for the same Plus account.
Controlled A/B result
| OpenCodex version |
ChatGPT plan |
GPT-5.6 |
| 2.35.0 |
Plus |
Works |
| 2.36.0 |
Plus |
Does not work |
| 2.35.0 (downgrade) |
Plus |
Works again |
Version
Regression observed in 2.36.0. Control version: 2.35.0.
Operating system
macOS 26.6.2
Provider and model
OpenAI Codex login / ChatGPT Plus:
gpt-5.6-sol
gpt-5.6-terra
gpt-5.6-luna
Suspected area
2.36.0 includes changes around requesting/reconciling the upstream entitlement roster using the real Codex client version. The clean 2.35 → 2.36 → 2.35 A/B suggests that the refreshed entitlement/catalog logic may be producing a false negative for an entitled Plus account.
Related issue #2886 reports a similar false-negative catalog projection on an earlier version, but this report specifically captures a 2.36.0 regression where 2.35.0 works for the same account and downgrading restores GPT-5.6.
Expected behavior
An entitled ChatGPT Plus account that can use GPT-5.6 on 2.35.0 should retain the same GPT-5.6 models after upgrading to 2.36.0. A missing/stale/incorrect entitlement roster should not incorrectly remove or reject models the account is actually entitled to use.
Checks
Client or integration
Codex App
Area
Authentication / entitlement / model catalog
Summary
After upgrading OpenCodex from 2.35.0 to 2.36.0, a ChatGPT Plus account can no longer use the GPT-5.6 family in Codex.
Downgrading the same OpenCodex installation back to 2.35.0 immediately restores GPT-5.6 availability for the same Plus account.
Affected models:
gpt-5.6-solgpt-5.6-terragpt-5.6-lunaThis looks like a 2.36.0 regression in the entitlement/catalog synchronization path rather than an actual account entitlement change, because the result is reproducible across the version boundary with the same account.
Reproduction
Controlled A/B result
Version
Regression observed in 2.36.0. Control version: 2.35.0.
Operating system
macOS 26.6.2
Provider and model
OpenAI Codex login / ChatGPT Plus:
gpt-5.6-solgpt-5.6-terragpt-5.6-lunaSuspected area
2.36.0 includes changes around requesting/reconciling the upstream entitlement roster using the real Codex client version. The clean 2.35 → 2.36 → 2.35 A/B suggests that the refreshed entitlement/catalog logic may be producing a false negative for an entitled Plus account.
Related issue #2886 reports a similar false-negative catalog projection on an earlier version, but this report specifically captures a 2.36.0 regression where 2.35.0 works for the same account and downgrading restores GPT-5.6.
Expected behavior
An entitled ChatGPT Plus account that can use GPT-5.6 on 2.35.0 should retain the same GPT-5.6 models after upgrading to 2.36.0. A missing/stale/incorrect entitlement roster should not incorrectly remove or reject models the account is actually entitled to use.
Checks