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fix(ui): use runtime :root color vars in shimmer gradient #434

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fix(ui): use runtime :root color vars in shimmer gradient #434

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3 changes: 2 additions & 1 deletion packages/presentation/ui/src/chat/shimmer.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,8 @@ export function Shimmer({
style={
{
backgroundImage:
'linear-gradient(90deg, transparent 35%, var(--color-background), transparent 65%), linear-gradient(var(--color-muted-foreground), var(--color-muted-foreground))',
// --color-* are @theme-inline-only (no runtime custom properties); use the :root vars.

@pullfrog pullfrog Bot Aug 8, 2026

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This is the only guard against someone reintroducing the bug, so it's worth making it exact — as written it over-generalizes twice. Tailwind's default palette --color-* (--color-white, --color-zinc-500) comes from a non-inline @theme and does exist at runtime, which is precisely what globals.css:68 relies on; and the @theme inline aliases are emitted when a Tailwind-scanned candidate references them (coss-ui's skeleton.tsx:14 uses [background:…var(--color-muted)…] and gets a real custom property). The actual invariant is that a JS inline style string is never scanned, so nothing forces the alias to be emitted.

Technical details 
# Trap comment states the wrong invariant

## Affected sites
- `packages/presentation/ui/src/chat/shimmer.tsx:30` — "`--color-*` are @theme-inline-only
  (no runtime custom properties)" is false for Tailwind's default palette and false for
  `@theme inline` aliases that a scanned candidate references.

## Required outcome
- The comment should name the real rule: Tailwind emits a theme variable only when
  something **it scans** references it via `var()`; a JS inline `style` string is not a
  scanned candidate, so coss-ui's semantic `--color-*` aliases never materialize on
  `:root` for this call site. Keep it to the repo's 1–2 line comment budget.

## Suggested approach
- Apply the inline suggestion, or any wording that distinguishes "not emitted here" from
  "never exists".

## Verification performed
- Compiled `tailwindcss@4.3.3` via its `compile()` API against a minimal repro of
  `packages/vendor/coss-ui/src/styles/globals.css`:
  - no candidates → `--color-muted:` absent from output
  - candidate `bg-muted` → still absent (value inlined into the utility)
  - candidate `[background:var(--color-muted)]` → **present** in `:root`
  - `--color-white:` / `--color-zinc-100:` → present (non-inline default `@theme`)
Suggested change
// --color-* are @theme-inline-only (no runtime custom properties); use the :root vars.
// coss-ui's semantic --color-* aliases are @theme inline and Tailwind never scans a JS
// style string, so they are not emitted to :root — read the underlying vars directly.

'linear-gradient(90deg, transparent 35%, var(--background), transparent 65%), linear-gradient(var(--muted-foreground), var(--muted-foreground))',
backgroundRepeat: 'no-repeat',
} satisfies React.CSSProperties
}
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