Design System Patterns

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name: design-system-patterns model: standard description: Foundational design system architecture — token hierarchies, theming infrastructure, token pipelines, and governance. Use when creating design tokens, implementing theme switching, setting up Style Dictionary, or establishing multi-brand theming. Triggers on design tokens, theme provider, Style Dictionary, token pipeline, multi-brand theming, CSS custom properties architecture.

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Design System Patterns

Foundational architecture for scalable design systems: token hierarchies, theming infrastructure, token pipelines, and governance patterns.

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When to Use

Defining token architecture (primitive → semantic → component layers)

Implementing light/dark/system theme switching with React

Setting up Style Dictionary or Figma-to-code token pipelines

Building multi-brand theming systems

Establishing token naming conventions and governance

Preventing flash of unstyled content (FOUC) in SSR

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Pattern 1: Token Hierarchy

Three-layer token architecture separates raw values from meaning from usage.

/* Layer 1: Primitive tokens — raw values, never used directly in components */
:root {
  --color-blue-500: #3b82f6;
  --color-blue-600: #2563eb;
  --color-gray-50: #fafafa;
  --color-gray-900: #171717;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-4: 1rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
}
/* Layer 2: Semantic tokens — contextual meaning, theme-aware */
:root {
  --text-primary: var(--color-gray-900);
  --text-secondary: var(--color-gray-600);
  --surface-default: white;
  --surface-elevated: var(--color-gray-50);
  --border-default: var(--color-gray-200);
  --interactive-primary: var(--color-blue-500);
  --interactive-primary-hover: var(--color-blue-600);
}
/* Layer 3: Component tokens — specific usage, optional */
:root {
  --button-bg: var(--interactive-primary);
  --button-bg-hover: var(--interactive-primary-hover);
  --button-text: white;
  --button-radius: var(--radius-md);
  --button-padding-x: var(--space-4);
  --button-padding-y: var(--space-2);
}

> Semantic tokens are the most important layer — they enable theming. Component tokens are optional and useful for complex component libraries.

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Pattern 2: Theme Switching with React

Key capabilities: theme (user selection), resolvedTheme (actual light/dark), setTheme, system preference detection, localStorage persistence, DOM attribute application.

type Theme = "light" | "dark" | "system";
export function ThemeProvider({ children, defaultTheme = "system", storageKey = "theme",
  attribute = "data-theme" }: { children: React.ReactNode; defaultTheme?: Theme;
  storageKey?: string; attribute?: "class" | "data-theme" }) {
  const [theme, setThemeState] = useState(() =>
    typeof window === "undefined" ? defaultTheme
      : (localStorage.getItem(storageKey) as Theme) || defaultTheme);
  const [resolvedTheme, setResolvedTheme] = useState<"light" | "dark">("light");
  const getSystem = useCallback(() =>
    matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light" as const, []);
  const apply = useCallback((r: "light" | "dark") => {
    const root = document.documentElement;
    attribute === "class"
      ? (root.classList.remove("light", "dark"), root.classList.add(r))
      : root.setAttribute(attribute, r);
    root.style.colorScheme = r;
    setResolvedTheme(r);
  }, [attribute]);
  useEffect(() => { apply(theme === "system" ? getSystem() : theme); }, [theme, apply, getSystem]);
  useEffect(() => {  // Listen for system preference changes
    if (theme !== "system") return;
    const mq = matchMedia("(prefers-color-scheme: dark)");
    const handler = () => apply(getSystem());
    mq.addEventListener("change", handler);
    return () => mq.removeEventListener("change", handler);
  }, [theme, apply, getSystem]);
  const setTheme = useCallback((t: Theme) => {
    localStorage.setItem(storageKey, t); setThemeState(t);
  }, [storageKey]);
  return 
    {children}
  ;
}

Full implementation with toggleTheme, disableTransitionOnChange, and testing patterns in references/theming-architecture.md.

Preventing FOUC in SSR (Next.js)

Inline script in runs before paint:

const themeScript = (function(){
  var t=localStorage.getItem('theme')||'system';
  var d=t==='dark'||(t==='system'&&matchMedia('(prefers-color-scheme:dark)').matches);
  document.documentElement.setAttribute('data-theme',d?'dark':'light');
  document.documentElement.style.colorScheme=d?'dark':'light';
})();
// In layout.tsx