Support for light-background terminals

[jxy]

Problem

Codex CLI hard-codes colours optimised for dark backgrounds, making prompts, completions and menus almost invisible when the terminal uses a light background. Users must either invert their entire terminal theme, or forego Codex altogether. That clashes with Codex’s goal of “runs in your terminal” and hurts day-to-day usability.

Impact

• Accessibility – developers who rely on light themes for reduced eye-strain or colour-vision requirements cannot read the interface.
• Adoption – teams with enforced light corporate themes (common in financial and healthcare environments) simply skip Codex.
• Consistency – every major TUI framework (ratatui, rich, xterm.js) ships both dark and light palettes. Codex is the outlier.

Proposal

1. Theme selection

   • Add theme = "light" | "dark" in ~/.codex/config.{json,toml} (default to auto-detect via $COLORFGBG, $TERM_PROGRAM_BACKGROUND, or Windows registry).
   • Expose --theme flag for quick overrides.

2. Palette definition

   • Replace hard-coded ANSI names with semantic tokens (e.g. primary, accent, error).
   • Provide two JSON/TOML palettes shipped in the repo; load at startup.

3. Auto-test

   • CI job renders the TUI in both palettes and checks contrast ratios ≥ 4.5 : 1 (WCAG AA).

4. Migration

   • Keep existing colours as the “dark” palette; no breaking changes.

Prior art

• Ink Select component already uses an internal theming object – this can be extended.
• Ratatui examples show palette switching in < 20 LOC; no heavy refactor needed.

Acceptance criteria

• All UI elements (input box, slash-command menu, status bar, onboarding screens) render legibly on a white background.
• codex --theme light works without touching global terminal settings.
• Documentation updated in Configuration section.

Links

• Earlier feature request: Control over color theme in TUI #1618

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Codex already delights on dark screens; adding a light theme would make it universal, accessible and ready for every workflow.

[NightMachinery]

It's unreadable on Solarized Light.

[imajes]

Completely agree; using during the day time can be obnoxious.

[xzbdmw]

The black background and white foreground is hard coded in tui-markdown crate
https://github.com/joshka/tui-markdown/blob/f788f699c75cd3218e073db41b260d7c85194873/tui-markdown/src/lib.rs#L453

[kevincojean]

Agreed; it's very difficult to use Codex.

[rr-]

Here's what it looks on my end – ridiculous

[aurexav]

Here's what it looks on my end – ridiculous

I’m experiencing the same issue, regardless of whether I change to any other light theme.

[rr-]

After rebooting, it worked out by itself (?).
Prior to that, I had to resort to export TERM=dumb – which disabled coloring altogether, along with other capabilities, and would cause bizarre issues after exiting Codex requiring me to restart active shell… but at least made it usable.

[aurexav]

Thanks, I already have a custom CODEX_HOME alias. It’s easy to expand it to:

alias cx='CODEX_HOME=${CODEX_HOME:-$( [ -d .codex ] && echo .codex || echo $HOME/.codex )} TERM=dumb codex'