Edit preview diff has poor contrast on muted terminal themes

Description

The edit preview (the inline diff shown when Claude Code proposes a file edit) has poor contrast with muted/dark terminal color schemes. Specifically, the green background for added lines combined with white text makes the content very hard to read — the text blends into the background.

This happens on NixOS running Claude Code inside tmux via WezTerm (SSH session). The same config on Arch Linux did not have this issue.

Screenshot

<img width="1085" height="649" alt="Image" src="https://github.com/user-attachments/assets/01103b13-8723-4206-a41c-2e40d91ffc9a" />

Steps to reproduce

1. Use a terminal with a muted dark color scheme (e.g., Everforest Dark in WezTerm)
2. Run Claude Code inside tmux
3. Have Claude Code propose a file edit
4. Observe the edit preview diff — the added lines (green background + white text) blend together

Terminal environment

TERM=tmux-256color
COLORTERM=truecolor

WezTerm config (color scheme):

config.color_scheme = "Everforest Dark (Gogh)"
config.front_end = "WebGpu"

tmux config (color/terminal settings):

set -g default-terminal "tmux-256color"
set -ag terminal-features ",xterm-256color:RGB,alacritty:RGB,wezterm:RGB,xterm-kitty:RGB,foot:RGB"
set -ag terminal-overrides ",xterm-256color:RGB,wezterm:RGB"

Expected behavior

The diff preview should have sufficient contrast between text and background across a range of common terminal themes, not just high-contrast ones.

Possible solutions

• Use the terminal's default foreground color (or black) on colored backgrounds instead of white
• Use ANSI color combinations with better guaranteed contrast
• Respect the terminal's own diff/highlight colors

Environment

• Claude Code v2.1.81
• Terminal: WezTerm (SSH into NixOS)
• Multiplexer: tmux
• Color scheme: Everforest Dark (Gogh)
• OS: NixOS