extract-design

Extract DESIGN.md from HTML

HARD GATE — Do NOT write DESIGN.md without Puppeteer dual-pass extraction. Tokens from static HTML (Cheerio, regex, string scanning) are invalid — they miss cascade, custom properties, and Tailwind resolution.

HARD GATE — Do NOT claim certainty where evidence is thin. Low-confidence color roles, component classifications, and prose assertions MUST be flagged with <!-- AGENT NOTE: uncertain — validate during grill-me. Evidence: [what was observed] -->.

HARD GATE — Do NOT ship DESIGN.md without running npx @google/design.md lint. Unvalidated output is unverified output. If lint is unavailable (offline), flag prominently in terminal and in DESIGN.md prose.

Quick Start

# First run — extract from HTML prototype
node extract-design/scripts/extract.js --source ./prototype.html

# From a published URL
node extract-design/scripts/extract.js --source https://my-prototype.example.com

# With a custom name
node extract-design/scripts/extract.js --source ./proto.html --name "My Design System"

# Update — re-extract from new HTML, diff against existing
node extract-design/scripts/extract.js --source ./proto-v2.html

# Lint-only — validate existing DESIGN.md without re-extraction
node extract-design/scripts/extract.js --lint-only

Flow

1. Launch Puppeteer — dual-pass (light + dark) with retry + timeout. CI flags: --headless=new --no-sandbox --disable-gpu --disable-dbus --use-gl=angle --use-angle=swiftshader.
2. Collect styles — page.evaluate() collects computed styles from every element. Returns raw JSON to Node.js. Browser = sensor; Node = brain.
3. Classify tokens — modular pipeline: colors (Material 3 roles), typography (scale detection), spacing (tolerance GCD), rounded (clustering), components (visual signature + pseudo-state variants).
4. Generate prose — AI heuristics produce all 8 DESIGN.md sections. Overview and Do's/Don'ts flagged with agent notes.
5. Write + validate — serialize to specs/tech-architecture/DESIGN_LATEST.md, run npx @google/design.md lint, report to terminal.
6. Handoff — writes handoff.next_skill: grill-me to specs/state.yaml with uncertain decisions context.

Inputs

Parameter	Required	Description
--source <file|url>	First run: yes. Update: optional	HTML prototype path or URL
--name <string>	No	Design system name (defaults to <title> or directory name)
--lint-only	No	Validate existing DESIGN.md without re-extraction

Output

• specs/tech-architecture/DESIGN_LATEST.md — replaces DESIGN_PLAN_LATEST.md as the canonical design artifact
• Terminal summary: token counts, component count, lint result, uncertain decisions
• Structured JSON log to stderr: extraction events, timing, counts
• specs/state.yaml → handoff.next_skill: grill-me with context

Error Tiers

Tier	Condition	Response
Fatal	No Chrome, page load timeout after retries	Exit non-zero, suggest fixes
Degraded	Zero colors, zero typography, SPA shell	Write DESIGN.md with degradation warning
Warned	Lint errors, uncertain decisions	Write DESIGN.md, flag in terminal, hand off to grill-me

Dependencies

• Puppeteer (Chrome binary) — wrapped behind BrowserExtractor interface for testability
• @google/design.md (soft, via npx) — wrapped behind DesignValidator interface. Warns and skips if offline.

verify

node extract-design/tests/test-extraction.js

See REFERENCE.md for extraction algorithms and heuristics.

---

Extract Design — Reference

Extraction Algorithms

Color Classification

1. Collect unique computed background-color, color, border-color from every DOM element.
2. Count frequency and context (text vs. bg vs. border vs. button).
3. Classify using Material 3 roles: surface = largest-area bg, on-surface = most-used text, tertiary = highest-saturation on CTAs, error = reddish.
4. Surface container levels: luminance-ordered. Hard-cap at 3 unless data supports 5.
5. Low-confidence → <!-- AGENT NOTE --> in Colors prose.

Typography Classification

1. Collect unique (fontFamily, fontSize, fontWeight, lineHeight, letterSpacing) tuples.
2. Cluster by fontSize (±2px) → type scale.
3. Detect heading hierarchy from HTML tag + computed size.
4. Name levels: display-lg, headline-lg/md/sm, title-lg, body-lg/md/sm, label-lg/md/sm.
5. Parse <link> and @font-face; warn if computed font differs from declared.

Spacing Classification

1. Collect unique padding, margin, gap values. Filter: ignore values < 3 occurrences.
2. Compute tolerance-based GCD (0.5px tolerance).
3. Declare base unit. Detect half-step if gcd/2 values present ≥3 times.
4. Map: unit×1 → sm, ×2 → md, ×4 → lg, ×8 → xl.

Rounded Classification

1. Collect unique border-radius values. Cluster (1px tolerance).
2. Name: none (0), sm (smallest), md (median), lg (large), xl (largest), full (9999px).

Component Detection

• Button: w<300px, h<64px, bg+radius set, short text. cursor:pointer is bonus.
• Card: bg+radius+padding set, larger area.
• Input: <input> or <textarea> tag.
• Pseudo-state variants: force :hover, :active, :focus for high-confidence components.

Prose Generation

Generates all 8 DESIGN.md sections. Overview and Do's/Don'ts flagged with <!-- AGENT NOTE: Generated from visual analysis. Grill-me should validate. -->.

Material 3 Token Conventions

Colors: primary, on-primary, secondary, tertiary, error, surface, on-surface, surface-container-*, outline, background, on-background. Typography: display-lg/md/sm, headline-lg/md/sm, title-lg/md/sm, body-lg/md/sm, label-lg/md/sm. Rounded: none, xs, sm, md, lg, xl, full.

CI Compatibility

Chrome flags: --headless=new --no-sandbox --disable-gpu --disable-dbus --use-gl=angle --use-angle=swiftshader

Defensive Code

Retry with backoff (3 attempts, 1s/2s/4s), Timeout (30s page load, 10s pseudo-state), Graceful degradation (Tier 2 on empty extraction).

Known Risks

• DESIGN.md spec is alpha. Skill pins to current spec.
• Puppeteer is heavy (~300MB Chrome). Document requirement clearly.
• Prose quality depends on AI heuristics. grill-me is the validation gate.