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Validate design system tokens for WCAG AA/AAA contrast. Compute color token contrast, focus ring validation (WCAG 2.4.13), motion tokens, and spacing for touch targets across frameworks.
基于 SOC 职业分类
Use for web accessibility work in HTML, JSX, CSS, ARIA, keyboard, forms, contrast, modals, live regions, headings, links, tables, or WCAG review; starts accessibility-lead first and uses tool_search if subagent tools are lazy-loaded.
Developer tools accessibility router for Python, wxPython, desktop accessibility APIs, NVDA add-ons, scanner tooling, CI tooling, and accessibility developer experience.
Document accessibility router for Word, Excel, PowerPoint, PDF, EPUB, Office remediation, PDF remediation, and accessible generated documents.
GitHub workflow accessibility router for PR review, issues, Actions, releases, projects, security alerts, notifications, repository management, and accessible contributor workflows.
Markdown accessibility router for docs, README files, headings, links, tables, alt text, diagrams, generated docs, and publication-ready accessible markdown.
Compute web accessibility scores (0-100, A-F grades) with severity scoring, confidence levels, and remediation tracking across audits.
| name | design-system |
| description | Validate design system tokens for WCAG AA/AAA contrast. Compute color token contrast, focus ring validation (WCAG 2.4.13), motion tokens, and spacing for touch targets across frameworks. |
This skill provides reference data for design token contrast validation, focus ring compliance, and spacing audits. Used by design-system-auditor.agent.md.
For each channel C in [0, 255]:
c = C / 255
c_lin = c / 12.92 if c <= 0.04045
c_lin = ((c + 0.055) / 1.055)^2.4 otherwise
L = 0.2126 * R_lin + 0.7152 * G_lin + 0.0722 * B_lin
ratio = (L_lighter + 0.05) / (L_darker + 0.05)
function relativeLuminance(hex) {
const c = hex.replace('#', '').match(/.{2}/g)
.map(h => parseInt(h, 16) / 255)
.map(c => c <= 0.04045 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4));
return 0.2126 * c[0] + 0.7152 * c[1] + 0.0722 * c[2];
}
function contrastRatio(hex1, hex2) {
const L1 = relativeLuminance(hex1);
const L2 = relativeLuminance(hex2);
const lighter = Math.max(L1, L2);
const darker = Math.min(L1, L2);
return (lighter + 0.05) / (darker + 0.05);
}
// Example
contrastRatio('#6B7280', '#FFFFFF'); // 5.74:1 - PASSES AA (was a common misconception)
contrastRatio('#9CA3AF', '#FFFFFF'); // 2.85:1 - FAILS AA
Many design systems store colors as HSL triplets (e.g., shadcn/ui, Radix):
function hslToHex(h, s, l) {
s /= 100; l /= 100;
const a = s * Math.min(l, 1 - l);
const f = n => {
const k = (n + h / 30) % 12;
return l - a * Math.max(Math.min(k - 3, 9 - k, 1), -1);
};
return '#' + [f(0), f(8), f(4)]
.map(x => Math.round(x * 255).toString(16).padStart(2, '0'))
.join('');
}
// shadcn/ui: --muted-foreground: 215.4 16.3% 46.9%
hslToHex(215.4, 16.3, 46.9); // -> approximately #6B7280
| Use Case | AA | AAA | Notes |
|---|---|---|---|
| Normal text (< 18pt / < 14pt bold) | 4.5:1 | 7:1 | Most body text |
| Large text (>= 18pt / >= 14pt bold) | 3:1 | 4.5:1 | Headings, display text |
| UI components (borders, icons) | 3:1 | - | Input borders, icon buttons |
| Focus indicators (WCAG 2.4.13, 2.2) | 3:1 | - | Against adjacent colors |
| Placeholder text | 4.5:1 | - | Counts as normal text |
| Disabled state | Exempt | Exempt | Documented exemption |
| Logo / brand | Exempt | Exempt | No requirement |
| Decorative content | Exempt | Exempt | Must be marked decorative |
// tailwind.config.js / tailwind.config.ts
module.exports = {
theme: {
// Base colors (Tailwind default palette)
colors: {
// All color scales: slate, gray, zinc, neutral, stone, red, orange, amber,
// yellow, lime, green, emerald, teal, cyan, sky, blue, indigo, violet,
// purple, fuchsia, pink, rose
// Each scale: 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 950
},
extend: {
colors: {
// Custom semantic colors - CHECK ALL PAIRS
brand: { primary: '#...', secondary: '#...' },
background: '#...',
foreground: '#...',
muted: '#...',
'muted-foreground': '#...',
accent: '#...',
'accent-foreground': '#...',
destructive: '#...',
'destructive-foreground': '#...',
card: '#...',
'card-foreground': '#...',
popover: '#...',
'popover-foreground': '#...',
border: '#...', // UI component - check 3:1 against background
input: '#...', // UI component - check 3:1 against background
ring: '#...', // Focus ring - check 3:1 against background
primary: '#...',
'primary-foreground': '#...',
secondary: '#...',
'secondary-foreground': '#...',
},
ringColor: { DEFAULT: '...' }, // Focus state
ringWidth: { DEFAULT: '2px' }, // Must be >= 2px for WCAG 2.4.13
}
}
}
/* globals.css - HSL triplets without hsl() wrapper */
:root {
--background: 0 0% 100%;
--foreground: 222.2 84% 4.9%;
--card: 0 0% 100%;
--card-foreground: 222.2 84% 4.9%;
--popover: 0 0% 100%;
--popover-foreground: 222.2 84% 4.9%;
--primary: 222.2 47.4% 11.2%;
--primary-foreground: 210 40% 98%;
--secondary: 210 40% 96.1%;
--secondary-foreground: 222.2 47.4% 11.2%;
--muted: 210 40% 96.1%;
--muted-foreground: 215.4 16.3% 46.9%; /* HIGH RISK - check on --background */
--accent: 210 40% 96.1%;
--accent-foreground: 222.2 47.4% 11.2%;
--destructive: 0 84.2% 60.2%; /* HIGH RISK - red on white */
--destructive-foreground: 210 40% 98%;
--border: 214.3 31.8% 91.4%; /* UI component - check 3:1 */
--input: 214.3 31.8% 91.4%; /* UI component - check 3:1 */
--ring: 222.2 84% 4.9%; /* Focus ring - check 3:1 */
}
.dark {
--background: 222.2 84% 4.9%;
--foreground: 210 40% 98%;
/* ... all dark mode variants */
}
// Token paths in createTheme()
palette: {
primary: {
main: '#1976d2', // text-on-white: 4.56:1
light: '#42a5f5', // text-on-white: 2.86:1 (do not use as text color)
dark: '#1565c0', // text-on-white: 5.91:1
contrastText: '#fff', // check on main
},
secondary: {
main: '#9c27b0', // text-on-white: 4.56:1 (barely)
light: '#ba68c8', // text-on-white: 2.55:1
dark: '#7b1fa2',
contrastText: '#fff',
},
error: {
main: '#d32f2f', // text-on-white: 5.08:1
light: '#ef5350', // text-on-white: 3.04:1
},
warning: {
main: '#ed6c02', // text-on-white: 2.94:1 COMMON FAILURE
light: '#ff9800', // text-on-white: 2.02:1
dark: '#e65100', // text-on-white: 3.84:1 (still fails!)
contrastText: 'rgba(0, 0, 0, 0.87)', // check on warning.main
},
info: {
main: '#0288d1', // text-on-white: 4.54:1 (barely)
light: '#03a9f4', // text-on-white: 2.88:1
},
success: {
main: '#2e7d32', // text-on-white: 7.24:1
light: '#4caf50', // text-on-white: 2.52:1
},
text: {
primary: 'rgba(0,0,0,0.87)', // -> ~#212121: 16.07:1 on white
secondary: 'rgba(0,0,0,0.6)', // -> ~#666: 5.74:1 on white
disabled: 'rgba(0,0,0,0.38)', // -> ~#9E9E9E: 2.34:1 (exempt when disabled)
},
background: { paper: '#fff', default: '#fafafa' },
action: {
active: 'rgba(0,0,0,0.54)', // ~4.48:1 for small icons
disabled: 'rgba(0,0,0,0.26)', // exempt when disabled
}
}
// Token paths in extendTheme()
const theme = extendTheme({
colors: {
// Direct palette values
brand: { 50: '#f5f3ff', 500: '#7C3AED', 600: '#6D28D9', 700: '#5B21B6', 900: '#2E1065' },
gray: { 50: '#F9FAFB', 100: '#F3F4F6', 200: '#E5E7EB', 300: '#D1D5DB',
400: '#9CA3AF', // text-on-white: 2.85:1
500: '#6B7280', // text-on-white: 4.48:1 (near-miss)
600: '#4B5563', // text-on-white: 7.44:1
700: '#374151', 800: '#1F2937', 900: '#111827' },
},
semanticTokens: {
colors: {
'chakra-body-text': { default: 'gray.800', _dark: 'whiteAlpha.900' },
'chakra-body-bg': { default: 'white', _dark: 'gray.800' },
'chakra-placeholder-color': { default: 'gray.400', _dark: 'whiteAlpha.400' },
// gray.400 on white = 2.85:1 - placeholder fails AA
}
},
components: {
Button: {
variants: {
solid: (props) => ({
bg: `${props.colorScheme}.500`, // check colorScheme.500 on white
color: 'white', // white on colorScheme.500 - check 3:1
}),
ghost: (props) => ({
color: `${props.colorScheme}.600`, // text-on-white variant
}),
}
}
}
});
{
"color": {
"text": {
"primary": { "$value": "#111827", "$type": "color" },
"secondary": { "$value": "#6B7280", "$type": "color" }, // 4.48:1 on white
"muted": { "$value": "#9CA3AF", "$type": "color" }, // 2.85:1 on white
"inverse": { "$value": "#FFFFFF", "$type": "color" },
"on-primary": { "$value": "#FFFFFF", "$type": "color" }
},
"background": {
"default": { "$value": "#FFFFFF", "$type": "color" },
"subtle": { "$value": "#F9FAFB", "$type": "color" },
"primary": { "$value": "#1D4ED8", "$type": "color" }
},
"status": {
"error": { "$value": "#DC2626", "$type": "color" },
"warning": { "$value": "#D97706", "$type": "color" }, // 3:1 on white for normal text
"success": { "$value": "#16A34A", "$type": "color" },
"info": { "$value": "#2563EB", "$type": "color" }
},
"border": {
"default": { "$value": "#D1D5DB", "$type": "color" }, // 1.44:1 on white UI component
"focus": { "$value": "#2563EB", "$type": "color" } // focus ring
}
}
}
| Token pair | Common value | Ratio on white | Status | Notes |
|---|---|---|---|---|
MUI warning.main | #ed6c02 | 2.94:1 | FAIL | Orange on white - always fails |
MUI warning.light | #ff9800 | 2.02:1 | FAIL | Light orange - critical failure |
Tailwind amber-400 | #FBBF24 | 1.73:1 | FAIL | Never use amber-400 as text |
Tailwind yellow-400 | #FACC15 | 1.60:1 | FAIL | Yellow always fails on white |
| gray-400 (Tailwind) | #9CA3AF | 2.85:1 | FAIL | Common placeholder color |
| gray-500 (Tailwind) | #6B7280 | 4.48:1 | FAIL | Near-miss - very common |
Chakra gray.400 | #9CA3AF | 2.85:1 | FAIL | Chakra placeholder default |
MUI text.disabled | rgba(0,0,0,0.38) | ~2.34:1 | (exempt) | Disabled = exempt per WCAG |
MUI action.active | rgba(0,0,0,0.54) | ~4.48:1 | FAIL | Icon color on white |
shadcn --muted-foreground | hsl(215.4 16.3% 46.9%) | ~4.48:1 | FAIL | Default shadcn theme |
shadcn --destructive | hsl(0 84.2% 60.2%) | ~3.13:1 | FAIL | Red badge on white |
Style Dictionary text.secondary | #6B7280 | 4.48:1 | FAIL | Ubiquitous - always check |
| Failing token | Replacement | New ratio | Notes |
|---|---|---|---|
#9CA3AF (gray-400) | #6B7280 (gray-500) | 4.48:1 | Still near-miss; use #595959 for safety |
#6B7280 (gray-500) | #4B5563 (gray-600) | 7.44:1 | Safest option |
#ed6c02 (MUI warning) | #b45309 (amber-700) | 4.57:1 | Minimum pass |
#ff9800 (MUI warning.light) | #b45309 (amber-700) | 4.57:1 | |
#FBBF24 (amber-400) | #92400e (amber-800) | 8.80:1 | Use as background, not text |
#FACC15 (yellow-400) | #713f12 (yellow-900) | 12.04:1 | Use as background, not text |
hsl(0 84.2% 60.2%) (shadcn destructive) | #b91c1c (red-700) | 5.56:1 |
npm install --save-dev @storybook/addon-a11y
// .storybook/main.js
module.exports = {
addons: ['@storybook/addon-a11y'],
};
// .storybook/preview.js - global configuration
export const parameters = {
a11y: {
config: {
rules: [
{ id: 'color-contrast', enabled: true },
{ id: 'button-name', enabled: true },
{ id: 'image-alt', enabled: true },
{ id: 'focus-visible', enabled: true }, // Requires axe-core 4.4+
{ id: 'target-size', enabled: true }, // WCAG 2.5.5 / 2.5.8
],
},
// Disable for specific stories (use sparingly)
disable: false,
},
};
// Per-story override
export const MyStory = {
parameters: {
a11y: {
config: {
rules: [{ id: 'color-contrast', enabled: false }], // Document WHY
}
}
}
};
# Install storybook test runner
npm install --save-dev @storybook/test-runner
# package.json scripts
{
"scripts": {
"storybook:test": "test-storybook",
"storybook:test:a11y": "test-storybook --ci"
}
}
# Run in CI
npx storybook dev --port 6006 &
npx wait-on tcp:6006
npx test-storybook --ci
WCAG 2.4.13 Focus Appearance (Level AAA in WCAG 2.2) - exceeds the 2.4.7 Focus Visible (AA) baseline, but recommended as best practice:
/* Minimum WCAG 2.4.13 compliant focus ring */
:focus-visible {
outline: 2px solid #0054B3; /* >= 2px width */
outline-offset: 2px; /* Separates from component edge */
/* #0054B3 on #FFF = 8.28:1 -> passes 3:1 for UI components */
}
/* Dark mode variant */
@media (prefers-color-scheme: dark) {
:focus-visible {
outline-color: #7CAFFF; /* lighter blue on dark background */
/* #7CAFFF on #1E1E1E = 5.74:1 */
}
}
/* VIOLATION patterns to detect */
:focus { outline: none; } /* Hard fail */
:focus { outline: 0; } /* Hard fail */
:focus-visible { box-shadow: none; outline: none; } /* Hard fail */
button:focus { outline: none; } /* Hard fail */
*:focus { outline-color: transparent; } /* Hard fail */
| Check | Requirement | Tool |
|---|---|---|
outline-width >= 2px | WCAG 2.4.13 area requirement | CSS audit |
| Focus color contrast >= 3:1 | Against adjacent background | Contrast calculator |
| Focus state differs from unfocused | Visible change required | Visual inspection |
No outline: none without replacement | N/A | grep / CSS audit |
| Present in both light and dark modes | Consistent | Visual inspection |
# Find all token files in a project
find . -type f \( \
-name "tokens.json" \
-o -name "design-tokens.json" \
-o -name "colors.json" \
-o -name "variables.css" \
-o -name "tokens.css" \
-o -name "_variables.scss" \
-o -name "theme.ts" \
-o -name "theme.js" \
-o -name "tailwind.config.*" \
\) \
-not -path "*/node_modules/*" \
-not -path "*/.next/*" \
-not -path "*/dist/*"
# PowerShell equivalent
Get-ChildItem -Recurse -File -Include tokens.json,design-tokens.json,colors.json,`
variables.css,tokens.css,_variables.scss,theme.ts,theme.js,tailwind.config.js,tailwind.config.ts `
| Where-Object { $_.FullName -notmatch 'node_modules|\.next|dist' }
| Finding | Severity |
|---|---|
| Text token below 3:1 | Critical |
| Text token 3:1-4.49:1 (normal text) | Error |
| Text token 4.5:1-6.99:1, AAA target | Warning |
| UI component token below 3:1 | Error |
| Focus ring missing completely | Critical |
| Focus ring below 2px | Error |
| Focus ring contrast below 3:1 | Error |
| Touch target token below 24 x 24px (WCAG 2.5.8) | Error |
| Touch target token below 44 x 44px (WCAG 2.5.5) | Warning |
No prefers-reduced-motion reset | Warning |
| Placeholder color below 4.5:1 | Error |
| Disabled token below 3:1 | Info (documented exemption, note for transparency) |