shadcn's `cn` reads a custom font size like `text-caption` as a colour and silently drops it

probe after the fix → "text-caption text-muted-foreground", "text-positive-text text-display", "p-4"; in Chrome, the shadcn Button with className="text-caption" renders classes … text-primary-foreground … text-caption (its text-sm merged away), computed font-size 12px; pnpm typecheck and pnpm build pass with the alias.

cn@>=0.5 <1, tailwindcss@>=4 <5, shadcn@>=4.22 <5

a font size defined in Tailwind's theme (--text-caption: 0.75rem with line height, weight, tracking) merges like text-sm: cn("text-caption", "text-muted-foreground") keeps both.

in Node, cn("text-caption", "text-muted-foreground") → "text-muted-foreground", cn("text-kpi", "text-positive-text", "text-display") → "text-positive-text text-display" and cn("p-card", "p-4") → "p-card p-4" (both kept, CSS order decides). An unknown text-x lands in the text-colour group.

cn reproduces tailwind-merge's conflict rules, which classify classes by name, not by reading your CSS. Configuring @/lib/utils alone isn't enough: shadcn 4.22+ components import { cn } from "cn" directly.

Node probe before and after; getComputedStyle of [data-testid=cn-alias-check] on /dev/tokens, 2026-10-28.