diff --git a/packages/presentation/ui/src/chat/shimmer.tsx b/packages/presentation/ui/src/chat/shimmer.tsx
index 52bb5cbd..20bcd492 100644
--- a/packages/presentation/ui/src/chat/shimmer.tsx
+++ b/packages/presentation/ui/src/chat/shimmer.tsx
@@ -27,7 +27,9 @@ 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))',
+            // 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
       }