VS Code: model picker popover in Codex chat is clipped/hidden when chat view is in sidebar (overflow/z-index)

Summary

In VS Code stable, the model selection popover/menu in the Codex chat view gets clipped/hidden behind other UI when the chat is hosted in the sidebar. If I move the chat view into the Panel (terminal area), the menu renders correctly.

This appears to be a stacking context / overflow clipping issue (popover not promoted to a top-level overlay layer).

Environment

• VS Code: 1.118.1 (user setup)
• Commit: 034f571df509819cc10b0c8129f66ef77a542f0e
• Electron: 39.8.8
• Chromium: 142.0.7444.265
• OS: Windows 11 (Windows_NT x64 10.0.26200)
• Display scaling: 100%

Repro Steps

1. Open VS Code.
2. Open the Codex chat view in the sidebar.
3. Open the model selector dropdown in the Codex chat UI.

Actual

The model picker menu is partially/fully hidden or clipped by other VS Code UI elements (terminal/panel or other views). Closing the terminal doesn’t fix it; it still gets covered/clipped by other elements.

Expected

The dropdown menu should appear above surrounding UI (or flip/relayout) so it is fully visible.

Workaround

Move the Codex chat view into the Panel (same area as the terminal). Then the menu is fully visible.

Notes

Happy to attach a screenshot if you want; it looks like a classic z-index/overflow clipping bug.

If this is ultimately a VS Code overlay/webview issue, please let me know the best upstream repo to file it against.