System theme makes dialogs/overlays look black on light terminals

[akronb]

Description

Since #8467 introduced background transparency, dialog backgrounds have been rendering incorrectly. The dimmer appears to be rendering against a black buffer rather than the terminal background, breaking contrast on light themes.

Plugins

No response

OpenCode version

1.1.63

Steps to reproduce

1. Use a light terminal theme
2. Set opencode theme to system
3. Open any dialog in app to see a problem

Screenshot and/or share link

That's a light theme!

Operating System

macOS 15.7.3

Terminal

Ghostty 1.2.3

[github-actions]

This issue might be a duplicate of an existing issue. Please check:

• System theme broken with light color schemes #12184: System theme broken with light color schemes (exact same issue with the same reproduction steps and root cause from PR fix(tui): respect terminal transparency in system theme #8467)

[kommander]

That seems to be only an overlay color issue. I don't know if that overlay color is actually in the theme and if that is a regression. Should be a simple fix.

[ckyever]

Hi, I'd like to take this on

Looks like the dialog overlay isn't using anything from the theme just a hardcoded black (per my screenshot), so was thinking of replacing this with theme.backgroundPanel and some transparency so it handles both light/dark themes

[akronb]

@kommander the overlay is semi-transparent, as it’s supposed to be, but combining a semi-transparent color with a transparent background is creating a solid color

Sorry for the imagery, but it’s the easiest way for me to explain it since I’m not very technical in this area

After merging #13239, the rendering for the system theme looks like this

When we open a dialog, everything looks okay with the parts that have a solid background

But when opentui combines the semi-transparent overlay background with a transparent background, we somehow end up with a solid black background

[ckyever]

Nice diagrams, definitely seems like there is a strange interaction between the transparent opencode bg and overlay bg. I think as long as we ensure the overlay matches the appropriate darkness of the theme we should be good

Something like this:

Produces this for both themes: