Design System Patterns

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

---

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

  
    
  
  {children}

---

Pattern 3: Multi-Brand Theming

Layer brand tokens on top of semantic tokens for white-label products:

[data-brand="corporate"] {
  --brand-primary: #0066cc;
  --brand-primary-hover: #0052a3;
  --brand-font-heading: "Helvetica Neue", sans-serif;
  --brand-radius: 0.25rem;
}

[data-brand="startup"] {
  --brand-primary: #7c3aed;
  --brand-primary-hover: #6d28d9;
  --brand-font-heading: "Poppins", sans-serif;
  --brand-radius: 1rem;
}

/* Map brand tokens into semantic tokens */
:root {
  --interactive-primary: var(--brand-primary);
  --interactive-primary-hover: var(--brand-primary-hover);
}

---

Pattern 4: Style Dictionary Pipeline

Multi-platform token generation from a single JSON source:

// style-dictionary.config.js — generates CSS, iOS Swift, and Android XML
module.exports = {
  source: ["tokens/**/*.json"],
  platforms: {
    css: {
      transformGroup: "css", buildPath: "dist/css/",
      files: [{ destination: "variables.css", format: "css/variables",
        options: { outputReferences: true } }],
    },
    ios: {
      transformGroup: "ios-swift", buildPath: "dist/ios/",
      files: [{ destination: "DesignTokens.swift", format: "ios-swift/class.swift",
        className: "DesignTokens" }],
    },
    android: {
      transformGroup: "android", buildPath: "dist/android/",
      files: [{ destination: "colors.xml", format: "android/colors",
        filter: { attributes: { category: "color" } } }],
    },
  },
};

See references/design-tokens.md for token category definitions, custom transforms, and platform-specific output examples.

---

Pattern 5: Accessibility Tokens

@media (prefers-reduced-motion: reduce) {
  :root {
    --duration-fast: 0ms;
    --duration-normal: 0ms;
    --duration-slow: 0ms;
  }
}

@media (prefers-contrast: high) {
  :root {
    --text-primary: #000000;
    --surface-default: #ffffff;
    --border-default: #000000;
    --interactive-primary: #0000ee;
  }
}

@media (forced-colors: active) {
  .button { border: 2px solid currentColor; }
  .card { border: 1px solid CanvasText; }
}

---

Token Naming Conventions

Format: [category]-[property]-[variant]-[state] (e.g. color-border-input-focus)

1. kebab-case — text-primary not textPrimary
2. Semantic names — danger not red
3. State suffixes — -hover, -focus, -active, -disabled
4. Scale indicators — spacing-4, font-size-lg

---

Token Governance

Change management: Propose → Review (design + eng) → Test (all platforms/themes) → Deprecate (with migration path) → Remove (after deprecation period).

{
  "color.primary": {
    "value": "{color.primitive.blue.500}",
    "deprecated": true,
    "deprecatedMessage": "Use semantic.accent.default instead",
    "replacedBy": "semantic.accent.default"
  }
}

---

Best Practices

1. Name tokens by purpose — semantic names, not visual descriptions
2. Maintain the hierarchy — primitives → semantic → component
3. Version tokens — treat token changes as API changes with semver
4. Test all theme combinations — every theme must work with every component
5. Automate the pipeline — CI/CD for Figma-to-code synchronization
6. Provide migration paths — deprecate gradually with clear alternatives
7. Validate contrast — automated WCAG AA/AAA checks on token pairs

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Common Pitfalls

• Token sprawl — too many tokens without clear hierarchy
• Inconsistent naming — mixing camelCase and kebab-case
• Hardcoded values — using raw hex/rem instead of token references
• Circular references — tokens referencing each other in loops
• Platform gaps — tokens defined for web but missing for mobile
• Missing dark mode — semantic tokens that don't adapt to themes

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Related Skills

• design-system-components — CVA variant patterns and Surface primitives
• distinctive-design-systems — Aesthetic documentation and visual identity
• theme-factory — Pre-built theme palettes for artifacts

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References

• references/design-tokens.md — Complete token category definitions
• references/theming-architecture.md — Detailed theming implementation
• references/component-architecture.md — Compound, polymorphic, and headless patterns