Tabbed environment/sources popover overlaps adjacent Codex pane in split view

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

26.527.60818(3437)

What subscription do you have?

Plus

What platform is your computer?

Darwin 25.5.0 arm64 arm

What issue are you seeing?

| When split-pane is opened | When split-pane is closed |
|----|----|
| <img width="2352" height="1371" alt="Image" src="https://github.com/user-attachments/assets/279d51bc-ec1b-425a-9911-f309d3d3865c" /> | <img width="2352" height="1371" alt="Image" src="https://github.com/user-attachments/assets/d60bfc6a-01f2-4487-a3ba-9a99507f3456" /> |

When Codex invokes a sub-agent and the side panel is open, clicking the popover tab with the “Environment” and “Sources” tabs — the To-Do icon — causes the main screen UI to shift to the right. Up to this point, this appears to be the expected behavior.

However, the same layout shift is also applied to side panels that do not have this popover tab, which creates an empty blank area on the right side of the screen.

This issue does not occur when I open the side chat manually. It only happens when Codex opens a side chat for a sub-agent.

What steps can reproduce the bug?

1. Open any chat in any project.
2. Tell codex to open any sub-agent.
3. Display side panel of sub-agent.
4. Open 'environment & source' tab.

What is the expected behavior?

Opening the Environment/Sources popover should only affect the main panel where that popover exists.

Side panel layout should not shift and it should not reserve any empty space on the right side.

In particular, when Codex opens a side chat for a sub-agent, the layout state of the main Codex panel and the sub-agent side chat should remain independent. The sub-agent side chat should render normally without inheriting the popover-related right-side offset from the main panel.

Additional information

Nothing. Thanks for making cool app!