v26.323.20928 regression: VS Code extension conversation panel becomes opaque black on macOS

What version of the IDE extension are you using?

26.323.20928

What subscription do you have?

ChatGPT Plus

Which IDE are you using?

VS Code 1.111.0

What platform is your computer?

Darwin 25.4.0 arm64 arm (macOS 26.4)

What issue are you seeing?

In v26.323.20928, the extension's inner conversation webview/body becomes an opaque solid black surface on macOS. The surrounding VS Code sidebar/workbench chrome can still be translucent or transparent, so the Codex panel looks visually broken and very ugly.

This is a visual regression compared with the previous version. I rolled back to the previous version as a workaround.

The issue seems to be in how the extension handles its internal background/surface layers in the webview. It is especially obvious in setups that use VS Code transparency/vibrancy/custom CSS, but the core regression is that the inner Codex panel is forced into an opaque dark background instead of preserving the previous visual behavior.

What steps can reproduce the bug?

1. Install the VS Code extension version 26.323.20928 on macOS.
2. Open the Codex sidebar and open any conversation/thread.
3. Use a VS Code setup where the surrounding sidebar/workbench is translucent or transparent.
4. Observe that the outer VS Code shell remains translucent/transparent, but the inner Codex conversation panel renders as a solid black block.
5. Roll back to the previous extension version and compare: the old version does not show the same opaque black panel.

What is the expected behavior?

The inner Codex conversation surface should not force an opaque black background. It should preserve the previous appearance and avoid rendering an obviously mismatched black panel inside the VS Code sidebar.

Additional information

• Regression observed specifically in v26.323.20928.
• Current workaround is to roll back to the previous version.
• From a UX perspective this is a severe visual regression: the extension looks broken even when it is otherwise functional.
• I can provide a screenshot if needed.