[Codex Cloud] Automatic code review does not trigger on GitHub native stacked PR pushes

What issue are you seeing?

Codex Cloud automatic code review does not start for a GitHub native stacked pull request when the review trigger is set to For every push.

In a private repository:

• The pull request is open and ready for review; it is not a draft.
• Codex Cloud is enabled for the repository.
• Personal Auto review is enabled.
• The review trigger was changed from Smart detect (Experimental) to For every push before reproducing.
• A new commit was pushed after changing the trigger.
• Codex did not react with 👀 or 👍, create a review task, or post a review automatically.
• Adding the exact comment @codex review immediately triggered 👀 and completed a review successfully.

The successful manual review indicates that the GitHub connector can access the repository and pull request and that review capacity was available. The failure appears isolated to automatic event matching or ingestion for the stacked pull request.

What steps can reproduce the bug?

1. Connect a GitHub repository to Codex Cloud and enable code review for it.
2. Enable personal Auto review.
3. Set Review trigger to For every push.
4. Create a GitHub native stack containing at least two non-draft pull requests.
5. Push a new commit to a pull request in the stack.
6. Observe that Codex does not acknowledge or start an automatic review.
7. Comment @codex review on the same pull request.
8. Observe that Codex acknowledges the comment and completes the manual review.

What is the expected behavior?

With Auto review enabled and the trigger set to For every push, Codex should automatically start a review after each qualifying push to a non-draft stacked pull request. GitHub's stack metadata should not prevent the pull request event from matching the configured trigger.

Additional information

Observed on 2026-09-04.

GitHub native stacked pull requests are in public preview and add a stack object to pull_request webhook payloads:

https://docs.github.com/en/pull-requests/get-started/about-stacked-prs

I searched the existing Codex issue tracker and did not find a report specific to GitHub native stacked pull requests. A broader potentially related report is #13701, but that issue concerns intermittent PR triggers generally rather than a reproducible stacked-PR event mismatch:

https://github.com/openai/codex/issues/13701

Start by tracing GitHub pull_request webhook ingestion and the automatic review trigger matching for the “For every push” setting. Compare the stacked pull request push event, including its stack metadata, with the successful @codex review path. Done means qualifying pushes to non-draft stacked pull requests acknowledge and start automatic reviews without requiring a comment.