Fix pink header in chromatic light palettes (mix alpha in oklab, not oklch)#284
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Translucent theme tokens were derived with `color-mix(in oklch, <color>, transparent)`. Mixing with `transparent` in a polar space drops the result hue to `none`, which renders as hue 0 (red): the chroma survives, so any palette whose canvas/ink/primary isn't pure gray got a pink-tinted header (--surface-scrim), hover, and selection. The default palette escaped only because its anchors are chroma-0. Mix translucency in oklab (rectangular — carries the hue through) instead. Opaque color->canvas mixes stay oklch. Covers --surface-scrim, --state-hover/active, --surface-recessed/raised/destructive/selected and their borders in theme.css, plus the scrollbar thumbs in app.css. Add a theme.test.ts guard that fails if `color-mix(in oklch, ..., transparent)` is reintroduced, so future palettes stay correct by construction. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Problem
In Light mode, the Nord and Dracula palettes (and any non-gray palette) rendered the app header (
bg-surface-scrim) with a pink/warm tint that didn't match the cool body. Every new palette hit this, so it was a systematic derivation bug rather than a per-theme mistake.Root cause
Translucent tokens were derived with
color-mix(in oklch, <color>, transparent). Mixing a color withtransparentin a polar space drops the result hue tonone, which renders as hue 0 (red) while the chroma survives. Chromium computes, for Nord's canvas:Composited over the canvas that's
[243,237,240](pink). The default palette escaped only because its anchors areoklch(1 0 0)— chroma exactly 0, so there's no hue to lose.Fix
Mix translucency in
oklab(rectangular — carries the hue through). Verified:color-mix(in oklab, #eceff4 92%, transparent)over canvas →[236,239,245], matching the cool body. Opaque color→canvas mixes correctly stayoklch.Touched (light + dark):
--surface-scrim,--state-hover/active,--surface-recessed/raised/destructive/destructive-border/selected/selected-borderintheme.css, plus the scrollbar thumbs inapp.css.This is the systematic fix: palettes only set opaque anchors and never touch these derived tokens, so every current and future palette is correct by construction.
Tests
theme.test.tsto acceptoklabfor the translucent tokens.color-mix(in oklch, …, transparent)is reintroduced.pnpm exec turbo run test --filter=@bb/app -- theme.test.ts→ 17 passed.Notes
Out of scope:
apps/landing/src/styles.csshas the same pattern (~24 spots), but it's the marketing site — not palette-driven, and mostly dark box-shadows where the hue shift is imperceptible. Worth a follow-up sweep for full consistency.🤖 Generated with Claude Code