Token Architecture

Skill: token-architecture

Load this skill when the primary task is designing or auditing a token system — the architecture that governs how tokens are named, derived, and organized. Do not load this skill for routine surface work where seeding a token block is sufficient; the seed token block in frontend-engineering step 2 covers that case. Load token-architecture when:

• The product needs a token system designed from scratch
• An existing token system has hardcoded value drift and needs an audit
• A new semantic alias layer is being added (e.g., adding a dark-theme override)
• Multi-platform distribution requires DTCG-compatible source generation

Three-tier architecture

The one-way dependency rule governs the entire system:

Primitive  →  Semantic  →  Component

• Primitives are raw values: #5e6ad2, 16px, 1.5. They have no meaning beyond their value. They are defined once at the top of the CSS file (or in the design tool) and referenced only by the semantic layer. Component tokens must not reference primitives directly — only semantics.
• Semantics are role assignments: --ds-color-primary points to a primitive. Semantics carry the design intent. When the brand changes, only the semantic layer's pointer changes; component tokens remain stable.
• Components are usage tokens scoped to a specific component: --btn-bg: var(--ds-color-primary). They reference semantics, never primitives.

Violation to refuse: a component token that reads var(--primitive-color-indigo-500) directly. This is a one-way dependency violation — if the primitive moves, every component that references it must be updated rather than only the semantic pointer.

Naming conventions

The --ds- namespace prefix is required for all system tokens. It signals "design system" and prevents collisions with author-defined custom properties or third-party libraries.

Semantic naming rules

The naming rule: a token name encodes role, never implementation. --ds-color-primary survives a rebrand to a different hue. --color-blue-500 does not.

Scale derivation

Derive spacing, typography, and radius scales from a single organizing ratio. Three ratios cover most design needs:

Spacing scale (minor third, 4px base)

--ds-space-1:  4px          (base)
--ds-space-2:  8px          (base × 1.25 → round to 8)
--ds-space-3:  12px
--ds-space-4:  16px
--ds-space-5:  24px         (major jump — section separation)
--ds-space-6:  32px
--ds-space-7:  48px
--ds-space-8:  64px

Typography scale (major third)

--ds-text-sm:   0.75rem     (12px)
--ds-text-base: 0.875rem    (14px)
--ds-text-lg:   1rem        (16px)
--ds-text-xl:   1.125rem    (18px)
--ds-text-2xl:  1.25rem     (20px)
--ds-text-3xl:  1.5rem      (24px)

Derive line-height from the scale ratio — not from a fixed pixel value. A unitless multiplier (1.25, 1.5, 1.75) scales with the font size and avoids WCAG 1.4.12 (Text Spacing) violations.

Radius scale

--ds-radius-sm:   4px       (chips, badges, small controls)
--ds-radius-md:   8px       (buttons, cards)
--ds-radius-lg:   12px      (modals, sheets, large containers)
--ds-radius-full: 9999px    (pills)

Semantic alias layer

The semantic layer maps roles to primitives. A complete minimum viable set:

Light/dark theme switching

Declare the semantic layer inside :root for light mode. Override inside @media (prefers-color-scheme: dark) for automatic system-preference switching, and/or inside [data-theme="dark"] for an explicit user toggle:

:root {
  --ds-color-surface: #ffffff;
  --ds-color-primary: #5e6ad2;
  /* ... all semantic tokens ... */
}

@media (prefers-color-scheme: dark) {
  :root {
    --ds-color-surface: #0d0d0d;
    --ds-color-primary: #8b93e8;
    /* ... dark overrides only ... */
  }
}

[data-theme="dark"] {
  --ds-color-surface: #0d0d0d;
  --ds-color-primary: #8b93e8;
  /* identical to the media query block — both must be kept in sync */
}

The [data-theme] attribute toggle and the prefers-color-scheme query are independent — a user who has set data-theme="dark" expects the dark theme regardless of system preference. Both must be maintained.

Component token pattern

Component tokens scope semantic tokens to a component's internal anatomy. They are the only layer allowed to reference semantics (never primitives).

Button token example — three-tier chain:

/* Tier 1: Primitive (defined once, never referenced by components) */
:root {
  --primitive-color-indigo-500: #5e6ad2;
  --primitive-color-indigo-700: #4338ca;
  --primitive-color-white: #ffffff;
}

/* Tier 2: Semantic (roles, not values) */
:root {
  --ds-color-primary: var(--primitive-color-indigo-500);
  --ds-color-primary-hover: var(--primitive-color-indigo-700);
  --ds-color-on-primary: var(--primitive-color-white);
}

/* Tier 3: Component (anatomy, references semantics only) */
.btn {
  --btn-bg:           var(--ds-color-primary);
  --btn-bg-hover:     var(--ds-color-primary-hover);
  --btn-text:         var(--ds-color-on-primary);
  --btn-radius:       var(--ds-radius-md);
  --btn-padding-x:    var(--ds-space-4);
  --btn-padding-y:    var(--ds-space-2);

  background-color: var(--btn-bg);
  color:            var(--btn-text);
  border-radius:    var(--btn-radius);
  padding:          var(--btn-padding-y) var(--btn-padding-x);
}

.btn:hover,
.btn:focus-visible {
  background-color: var(--btn-bg-hover);
}

The chain: .btn reads --btn-bg; --btn-bg reads --ds-color-primary; --ds-color-primary reads --primitive-color-indigo-500. When the brand changes --primitive-color-indigo-500 to a new hue, .btn picks it up automatically through the chain.

DTCG export

The Design Tokens Community Group (DTCG) format is the correct structure for multi-platform distribution (producing iOS/Android values from the same source, or supplying a design tool with a token JSON it understands).

DTCG token format — each token uses $type, $value, and optionally $description:

{
  "color": {
    "primary": {
      "$type": "color",
      "$value": "#5e6ad2",
      "$description": "Brand primary — interactive elements and focus indicators"
    },
    "surface": {
      "$type": "color",
      "$value": "#ffffff",
      "$description": "Primary surface background"
    }
  },
  "spacing": {
    "4": {
      "$type": "dimension",
      "$value": "16px",
      "$description": "Base unit × 4 — standard internal padding"
    }
  }
}

When to produce DTCG output: when the token system feeds a build pipeline that generates platform-specific token files (CSS custom properties, Swift UIColor, Android XML, Figma variables). For a web-only project that consumes tokens directly as CSS custom properties, DTCG export is optional.

Token audit

To detect token drift — hardcoded values in CSS that should be tokens — run:

grep -E "#[0-9a-fA-F]{3,6}|rgba?\(|hsl\(|[0-9]+px" <file.css>

The output should return only the :root / primitive-definition block. Any hardcoded colour or spacing value outside that block is a violation.

Triage priority:

1. Hardcoded colour values in component or semantic files — these break theming and must be migrated to tokens.
2. Magic pixel values for spacing (margin: 13px) — migrate to the scale.
3. Hardcoded font sizes — migrate to the type scale.
4. Hardcoded z-index numbers — migrate to a named z-index scale.

Governance checklist

A token architecture encodes organizational decisions. Before finalizing:

• Who owns the primitive layer? Changes here affect every component through the chain. Primitives should change only with explicit stakeholder sign-off.
• Who owns the semantic layer? A new semantic role (e.g. a new status color) should require review from both design and engineering.
• Are component tokens scoped to the component that owns them? Shared component tokens across unrelated components are a coupling smell.
• Is the DTCG export needed? If multi-platform, a build step that produces platform tokens from the DTCG source is part of the governance contract.
• Is the dark-theme override kept in sync with the light-theme semantic layer? Every new semantic token added to light mode must have a corresponding dark override (or an explicit decision that it inherits the light value).

Output rendering

Lead with the useful outcome or next action. Use warm, non-blaming language and everyday words. Define an unfamiliar term in a few plain words before naming it; keep proper names and exact technical terms intact. During tool work, do not narrate routine calls. Send an update only for safety, a blocker, a needed decision, a material scope change, a long wait, or an active host requirement. When requesting input, ask only for what is needed now. Ask dependent questions one at a time; otherwise group related questions. Offer no more than three clear choices when choices help. Shape the answer to the facts: one fact needs one sentence; related facts use prose; separate items use bullets; real sequences use numbered steps. For prose artifacts, use descriptive headings, short resumable sections, one fact per sentence, and no repeated summary. Emphasize at most one load-bearing point per section. Group long inventories instead of truncating them. Make the result stand alone. Do needed arithmetic, give real dates or times, and say what a file or link establishes instead of making the reader inspect it. For code and comments, prefer obvious structure and names. Comment on intent, constraints, or trade-offs that the code cannot state clearly. Use a table, tree, flow, or other visual only when it makes a relationship materially easier to understand. Report the current state, not the path taken. Omit dead ends, resolved trade-offs, hedges, and advice the user did not request. When editing maintained prose, consolidate repeated rules and navigation before adding another caveat. Silence and brevity never reduce the work, checks, or requested coverage. Preserve depth, evidence, constraints, warnings, code, diffs, errors, and exact names, paths, and counts. Keep verification compact: pass or fail, count, and runtime. Name a suite when it failed or when the name changes what the reader should do. Before sending, check that the reader can act without counting, converting, opening a file, or asking what a line means.

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