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The Model

Terminal apps don’t all get their colors the same way. Understanding this is the key insight behind litmus — and the reason a simple color swatch preview doesn’t cut it.

Why Switching Themes Is Broken

When you change your terminal theme, some apps change with it and some don’t. git diff picks up the new colors immediately. Your neovim colorscheme stays exactly the same. And lazygit might use its own built-in palette or fall back to terminal colors depending on how you configured it.

This is confusing because it’s invisible. You change one config file and expect a uniform result, but the actual outcome depends on a hidden property of each app: where it gets its colors from.

Litmus makes this visible. It models terminal color relationships explicitly, so you can preview exactly what will change — and what won’t — when you switch themes.

Three Roles

Every terminal app falls into one of three roles:

  • Providers — apps that define a complete color palette (terminal emulators like kitty, wezterm)
  • Consumers — apps that inherit colors from their provider (git diff, cargo, bat, ls)
  • Silos — apps that bring their own independent palette (neovim with a colorscheme) (roadmap)

Ecosystems

The provider/consumer relationship creates natural ecosystems. A terminal emulator (provider) plus all the CLI tools running inside it (consumers) form a group where colors flow in one direction: from provider to consumers.

When you preview a theme in litmus, you’re seeing an entire ecosystem. The 13 fixtures represent different consumer apps — git diff, cargo build, bat, ripgrep, ls, and more — all rendered with the same provider palette. This is the core insight: a useful theme preview shows the ecosystem, not just the palette.

Switching between providers (kitty vs wezterm) in litmus shows you that the same theme can look subtly different depending on which terminal you use — because providers sometimes interpret theme definitions differently.

Dual-Mode Apps

Some apps can operate as either a consumer or a silo. lazygit can use terminal ANSI colors (consumer mode) or its own built-in theme (silo mode). jjui behaves similarly.

Litmus will support showing both modes for dual-mode apps in a future version, making it clear what changes when you switch themes and what stays the same.