Govern an existing DESIGN.md during UI work. Enforce token-backed colors, typography, spacing, and radius when the file exists; steps aside when it does not. Use for token-affecting edits and seven subcommands, four backed by the canonical CLI — audit, diff, export, spec, migrate, init, and extension drift checks. CLI-backed operations stop with exact remediation when the canonical validator is unavailable or invalid.
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name
design-system
description
Govern an existing DESIGN.md during UI work. Enforce token-backed colors, typography, spacing, and radius when the file exists; steps aside when it does not. Use for token-affecting edits and seven subcommands, four backed by the canonical CLI — audit, diff, export, spec, migrate, init, and extension drift checks. CLI-backed operations stop with exact remediation when the canonical validator is unavailable or invalid.
when_to_use
When the user asks to change colors, typography, spacing, corner radius, shadows, component styles, layout, or any visual aspect of the UI. When creating new components or pages. When editing existing UI files. When the user changes the theme or references visual tokens in an existing DESIGN.md. Full redesigns / new visual direction → /award-design. When linting, diffing, exporting, porting, or initializing a DESIGN.md file. When DESIGN.md uses extension namespaces (motion, shadows, etc.) — run `audit-extensions` to validate them against the globals.css `@theme` mirror. Keywords — audit, check, lint, diff, export, spec, migrate, init, audit-extensions, DESIGN.md, tokens, extended tokens. For empty directories, run `/scaffold` first (then `/award-design` for a DESIGN.md) before invoking this skill.
Two modes for governing a project's visual identity:
Auto-activate — when editing UI files (components, pages, layouts, styles, DESIGN.md, tailwind.config.*) and a DESIGN.md is present, the skill reads it first and enforces token-only sourcing for colors, typography, spacing, and corner radius. No DESIGN.md? It stays out of the way — a one-line pointer to /award-design, no enforcement, no block on the edit.
Subcommands — /design-system <verb> [path] exposes the full DESIGN.md lifecycle, built on the canonical @google/design.md CLI.
Subcommand routing
Parse the first positional invocation argument. If it matches a verb below, load the referenced file and follow its workflow. Otherwise proceed with the token-enforcement workflow at the end of this document.
First token
Mode
Reference
audit (aliases: check, lint)
Lint + fix proposals, human-readable report
references/subcommand-audit.md
diff
Regression check between versions (git-aware)
references/subcommand-diff.md
export
Tokens → Tailwind theme or W3C DTCG tokens.json
references/subcommand-export.md
spec
Emit the canonical spec from the installed CLI
references/subcommand-spec.md
migrate
Port legacy Stitch 9-section DESIGN.md → Google standard
references/subcommand-migrate.md
init
Scaffold a minimal valid DESIGN.md (fallback from /award-design)
Token enforcement — see the default workflow at the end
(this file)
Source of truth
When a DESIGN.md exists at the project root, read it before writing any UI code: every color, font, spacing value, corner radius, and component style comes from this file — the YAML frontmatter tokens (normative values) or the prose explaining when and why to apply them.
No DESIGN.md? Step aside. The default governance mode neither requires nor creates one. It never blocks an edit for lack of a DESIGN.md and never invents a design direction — that is /award-design's job (it forces a universe, writes the DESIGN.md up front, then builds the frontend under it). So:
Building or editing UI with no file → proceed. For a designed build, point to /award-design, which authors the DESIGN.md up front and builds the frontend under it.
A bare token scaffold is needed now and /award-design is unavailable → /design-system init [archetype] is a minimal fallback, not the primary path.
Phrase the pointer as an optional handoff, never as a prerequisite: "Design System imposes no prerequisite here; use /award-design if you want it to define and build the new visual direction." Do not say the user must create DESIGN.md before editing.
If a legacy Stitch-format DESIGN.md is detected (9 numbered sections, ## Agent Prompt Guide heading, no YAML frontmatter): suggest /design-system migrate <path> to port it before proceeding.
The standard
DESIGN.md is Google's open format for describing a design system to coding agents. Canonical source: github.com/google-labs-code/design.md. A file has two layers:
DESIGN.md is written for both agents and humans. These principles govern every section:
Tokens are normative, prose is context. YAML values are what agents render. Prose tells them when and why. Both are required — prose without values is a mood board; values without prose is a spreadsheet.
Descriptive over technical. Write "whisper-soft shadow" alongside the exact value. Translate CSS into spatial language — rounded-full → "pill-shaped".
Every value has a role.#5e5d59 alone is meaningless; Olive Gray (#5e5d59): secondary body text — warm medium-dark gray is actionable.
Name tokens semantically.primary, tertiary, button-primary-hover — not blue-500, shadow-sm.
Show the personality in Overview. Section 1 sets the tone; every later section should feel written by the same person.
Exact values are non-negotiable. Every color, dimension, component property is a concrete token.
Rules
Colors, fonts, spacing, corner radius come only from DESIGN.md YAML tokens
Map tokens to CSS custom properties in the global stylesheet
Map tokens to tailwind.config.ts theme.extend — or generate via /design-system export tailwind
Never use arbitrary Tailwind values (text-[13px], bg-[#abc]) when a token exists
Never introduce values absent from DESIGN.md — use the closest token and flag to the user
Extended tokens — values outside the canonical 5 namespaces (motion, shadows, aspectRatios, heights, containers, breakpoints, zIndex, borderWidths, opacity, scrollTriggers) live as top-level YAML namespaces, are validated by convention via /design-system audit-extensions, and are mirrored to globals.css@theme. Upstream accepts unknown component properties with a warning, but this skill deliberately forbids using them to bind extension semantics because exporters and consumers do not share a contract for those keys. Reference extensions in prose instead (for example, {motion.duration-reveal-slow}). See references/extended-tokens.md
Dark mode: the Google spec has no dedicated mode concept. Use semantic tokens in a single DESIGN.md (e.g., surface, on-surface, inverse-surface, inverse-on-surface) and let the framework's CSS custom properties map each semantic name to the right value per mode. The Google-published atmospheric-glass example follows this pattern — one file, both modes via semantic naming. Avoid dual-file setups (DESIGN.md + DESIGN.dark.md) unless the brand truly diverges between modes
Shared brand across projects: same DESIGN.md, framework-specific implementation. Distribution patterns — pick one and document it in the applicable project instructions (AGENTS.md, CLAUDE.md, or equivalent):
Monorepo — packages/brand/DESIGN.md consumed by all apps; single PR for cross-cutting changes
Git submodule — canonical brand repo included as submodule; atomic updates via submodule bump
Published package — @org/design-tokens on npm with DESIGN.md + build outputs; versioned, works cross-repo
Copy + periodic /design-system diff — copies in each repo; periodic diff against the canonical catches drift; simplest tooling, highest drift risk
Monorepo: the spec and this skill assume a single root DESIGN.md per project. For monorepos with per-package brand variations, keep each package's DESIGN.md at the package root and pass the intended file explicitly (/design-system audit packages/web/DESIGN.md)
Post-edit invariant — after any DESIGN.md mutation (token update during the enforcement flow, migrate, init, or manual edit via this skill), run /design-system audit <path> and surface findings. A mutation that leaves errors behind is not done
Duplicate section headings are a spec error — reject the file
Unknown section headings are preserved. Unknown component properties receive an upstream warning and fail this skill's portability convention; broken-ref applies only when a token reference does not resolve. Top-level keys resembling schema typos emit unknown-key warnings
CLI validator
The canonical @google/design.md CLI powers audit, diff, export, and spec. Install it once with npm install --global --ignore-scripts @google/design.md, then verify designmd --version.
Agent operations use the bundled wrappers, which resolve one designmd binary from PATH, preflight its version, and validate operation output before reporting success. They never inspect project package manifests, invoke a package manager, or download at runtime.
The current CLI exposes eleven rules: broken-ref (error), missing-primary, contrast-ratio, orphaned-tokens, token-summary, missing-sections, missing-typography, section-order, unknown-key, token-like-ignored, and omitted-rules. Full semantics and severities: references/cli-reference.md.
For any non-ok wrapper status, surface remediation and rerun, then stop. A manual structural read is not an equivalent lint, diff, export, or spec result.
Framework behavior
Detect framework from config files (astro.config.*, next.config.*, etc.), then follow project instructions (AGENTS.md, CLAUDE.md, or equivalent) for implementation specifics (component library, font loading, file structure).
Default workflow — token enforcement
When no subcommand is matched — either activated from its description during a UI edit, or invoked directly to discuss enforcement — follow this workflow.
When there is no DESIGN.md
The default governance mode does not author a design file from scratch. When the user explicitly wants a DESIGN.md, it is born one of two ways:
/award-design authors it (preferred) — it forces a universe and writes the full DESIGN.md up front, then builds the frontend under it. design-system governs the result from there.
/design-system init [archetype] — a minimal token scaffold, only when /award-design is unavailable and a bare file is needed now.
Either way, once the file exists, the change flow below applies. Atmosphere scores (Density, Variance, Motion) live in Overview prose, not YAML.
How award-design's universe maps to DESIGN.md:
award-design output
DESIGN.md section
YAML tokens
Archetype + atmosphere (Density/Variance/Motion) + signature moment + photography direction + copy register
1. Overview (prose)
—
Color palette + photography colour guidance
2. Colors
colors:
Typography + kinetic typography intent
3. Typography
typography:
Spacing, grid, scroll choreography, responsive system
Extension namespaces (ext: rows above) live as top-level YAML per references/extended-tokens.md. Components bind only to the eight canonical property tokens — extension tokens are referenced in prose, never as components: keys.
Once the file exists (authored or scaffolded), wire it into the project:
Audit — run /design-system audit <path> (post-edit invariant). Fix errors before proceeding.
Wire into the framework: /design-system export tailwind → merge the result into tailwind.config.ts theme.extend (v3) or globals.css@theme block (v4); set up CSS custom properties in the global stylesheet.
Validate the mirror — /design-system audit-extensions <path> confirms every extension token in the YAML has its CSS custom property and every prose reference resolves. Run after every export.
When UI/UX changes are requested
Any visual change — colors, typography, spacing, radius, shadows, component styles, layout, responsive behavior — follows this flow.
Check whether the change affects tokens. New value, modified value, or altered visual system → DESIGN.md first. Pure layout bugs, alt text, content reordering → code only.
Update DESIGN.md first.
Open DESIGN.md, locate the affected YAML tokens and prose sections
Update values, semantic names, reference paths
Cascade — if the primary color changes, update every components: entry referencing it
Sync Do's and Don'ts if the change contradicts an existing guardrail
Audit — /design-system audit <path> to verify no broken references or contrast regressions (post-edit invariant).
Propagate to code:
Re-export Tailwind theme (/design-system export tailwind) or update theme.extend by hand
Update CSS custom properties in the global stylesheet
Update components using raw values — components referencing tokens by name pick up the new value automatically
Shared brand — if the DESIGN.md is shared across projects, propagate to all, then step 4 in each.
Examples of token-affecting changes:
"Change CTA color" → colors.* + Colors prose + every components: entry referencing the old color
A fundamental visual change (new archetype, different atmosphere, complete restyle) is a new design, not a token update. Recommend or hand off to /award-design when the user wants that designed build — it writes a fresh DESIGN.md and builds under it. If /award-design is unavailable or not selected, design-system steps aside and does not block the edit. Any existing DESIGN.md is replaced whole, never patched in place.
Gotchas
Unknown component properties are not portable. The upstream parser accepts them with a warning, but downstream exporters and agents only share the eight canonical properties (backgroundColor, textColor, typography, rounded, padding, size, height, width). Treat an extension key such as shadow as a skill-level failure even when upstream lint does not. Reference extension tokens in prose and mirror them to CSS instead.
Duplicate ## section heading breaks spec parsing silently. Two ## Colors sections (from a botched re-architect) cause the parser to read only the first; YAML in the second is dropped without warning. Each of the 8 sections must appear exactly once. Fix: prescan for heading duplicates; fail hard with the duplicated name.
export tailwind emits Tailwind v3 configuration JSON. Semantic token names are preserved and valid, but Tailwind v4 projects use CSS-first @theme declarations instead of theme.extend. Translate the exported entries into the global stylesheet and regenerate that mirror after DESIGN.md changes; do not paste the JSON into a v4 stylesheet.
Multiple DESIGN.md files make the target ambiguous. A monorepo may contain both ./DESIGN.md and files such as packages/*/DESIGN.md. Fix: when multiple candidates are detected, ask which one to govern. Never silently pick the root.
