Markdown preview tab becomes unresponsive after Codex edits the file

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

26.707.72221

What subscription do you have?

Pro

What platform is your computer?

Darwin 25.5.0 arm64 arm

What issue are you seeing?

When a Markdown file is open in rendered/rich-text preview and Codex edits the file, that preview tab becomes unresponsive. Clicking the tab's close button does nothing. The tab remains stuck until I switch to a different Codex task and then switch back, after which the tab can be closed normally. The rest of the app remains responsive enough to switch tasks.

What steps can reproduce the bug?

1. Open a Markdown file in the Codex Desktop file viewer.
2. Switch the file to rendered/rich-text preview.
3. Ask Codex in the current task to edit that Markdown file.
4. After Codex applies the edit, click the preview tab's close button.
5. Observe that nothing happens and the tab cannot be closed.
6. Switch to a different Codex task, then switch back to the original task.
7. Click the tab's close button again; it now closes normally.

What is the expected behavior?

The Markdown preview tab's controls should remain responsive after Codex edits the underlying file. Clicking the close button should immediately close the tab without requiring a task switch.

Additional information

Workaround: switch to a different Codex task and then back to refresh the tab state.

This is distinct from #32571: the problem is not the preview switching to source/diff mode or losing scroll position. The tab's close action itself stops responding after the edit.