User-prompt turn background doesn't adapt to light terminal themes (renders near-black even on light backgrounds)

Summary

Claude Code styles user-prompt turns with a filled background block to distinguish them from assistant output — useful behaviour. However the block is rendered with a near-black background and light text regardless of terminal theme, so on light terminals it appears as a stark dark box against the otherwise-light window. It reads fine but looks visually inverted against the rest of the UI.

Expected on a light theme: user turn background in a light grey (e.g. #e6e6e6 / #eaeaea), with dark text — mirror of the dark-mode behaviour.

Reproduce

1. Use any light terminal theme (GitHub Light Default, Catppuccin Latte, Gruvbox Light Hard — all exhibit this).
2. Run claude and send a message.
3. Scroll back — your user turn sits inside a near-black rectangle while the rest of the conversation is on the light background.

Screenshot behaviour: the window, title bar, assistant text, and all surrounding UI render on a light background. Only the user-prompt block is inverted.

Why — likely root cause

Claude Code probably renders user turns either via:

• ANSI reverse-video (SGR 7), which swaps the terminal's current foreground and background — on a light terminal this produces dark fg on light bg which would look right, but the observed behaviour is the opposite, so probably not this; or
• A hardcoded dark colour (via RGB escapes or a fixed ANSI index) for the background, assuming the user is always on a dark theme.

Either way, the styling doesn't consult the detected background colour or adapt.

Suggested fixes

1. Detect light vs. dark background at startup (OSC 11 query, COLORFGBG, or terminal capability query) and pick an appropriate user-turn background accordingly — light grey on light themes, dark grey on dark themes.
2. Use SGR 7 (reverse video) for the user-turn block — the terminal handles the inversion correctly against whatever colours are active.
3. Use a semantically-neutral approach: draw user-turn text in the terminal's default colours with a thin border / prefix indicator rather than a filled background block.
4. Expose a config option (userTurnBackground / userTurnStyle) so users can override while a proper fix is designed.

Related

Companion issue #49839 covers the related problem of Claude Code's dim/secondary text being unreadable on light themes because it uses ANSI bright-black. These two are separate render paths but share the same root cause — assumptions about background colour that hold on dark themes and fail on light ones.

Environment

• Claude Code 2.1.112
• Ghostty 1.2.3 (Wayland, --gtk-single-instance=true)
• KDE Plasma 6.4.5 with Breeze Light global theme
• Themes tested: GitHub Light Default, Catppuccin Latte, TokyoNight Day, Gruvbox Light Hard, Rose Pine Dawn — all show the same dark user-turn block on their light backgrounds.