Option to disable diff background highlight

[aurexav]

What variant of Codex are you using?

cli

What feature would you like to see?

After #12581

I can't read. I don't like the background highlight.

@fcoury

Additional information

No response

[aurexav]

Screen.Recording.2026-02-25.at.15.36.14.mov

Every theme is unreadable

[etraut-openai]

Which terminal emulator are you using? Which platform?

[aurexav]

Which terminal emulator are you using? Which terminal emulator?

Ghostty, I also tested in Zed. All my tokyo-night* terminal themes are not happy with this.

[aurexav]

BTW, I use TERM=dumb due to #2020. Even if this is fixed I will not use it as I dislike the black input box.

But anyway, I would like to suggest that an option to disable this feature be available.

[teneko]

I can confirm that I cannot read anything anymore.

The green is too green and the red is too red. Every time I open this terminal, my retinas file a formal complaint. 😅

I use mintty 3.8.1.

Fortunately, mintty can actually change colors (they call it a "theme"). I switched the theme from “mintty” to “html” and finally: the text becomes readable again.

Edit: now ordered lists and code blocks become unreadable 😆 but sadly the "html" theme is the only theme among the others that don't let my eyes bleed.

I think I need to switch back to 0.104.0 for the current time.

[ignatremizov]

+1 from my side. My eyes, they burn. The current add/remove diff line backgrounds are too strong for all themes due to being hardcoded in codex-rs/tui/src/diff_render.rs.

Suggested implementation path/spec:

1. Add a user-facing diff background mode under [tui]:

   • diff_background = "auto" | "off" | "theme" | "custom"
   • default: auto (preserve current behavior)

2. Behavior by mode:

   • auto: current hardcoded palette (no behavior change)
   • off: no add/remove line background, keep only fg/gutter/sign styling
   • theme: derive add/remove backgrounds from theme scopes if available
   • custom: use explicit user-provided colors

3. .tmTheme scope mapping for theme mode:

   • additions: markup.inserted, fallback diff.inserted
   • removals: markup.deleted, fallback diff.deleted
   • use scope background if present; fallback to auto for missing scope/background

4. custom mode config keys (optional, with fallback to auto):

   • diff_add_bg, diff_del_bg
   • accept hex #RRGGBB (and optionally named/indexed later)

5. Renderer integration:

   • Thread a DiffBackgroundConfig into style_line_bg_for/add_line_bg/del_line_bg
   • keep existing color-level quantization (truecolor/256/16) after resolving target RGB

6. Nice-to-have follow-up:

   • optional separate control for gutter background (or derive from line bg)
   • include a preview row in /theme so users can verify theme/custom/off quickly.

This would cover both camps: users who want backgrounds disabled and users who want subtle, theme-matched diff backgrounds instead of hardcoded bright red/green.

[wenGravitas]

+1 colour blind here and makes it awful to use, please add an option to turn it off.

[ignatremizov]

I implemented in ignatremizov#1 but cannot open a PR here