Html to component

html-to-component

Convert HTML (a whole page, a pasted section, or a fetched URL) into Next.js + Tailwind + shadcn/ui that looks production-grade and fits the project's existing structure. It does two jobs in order: first it lifts the design's tokens into the theme (colors in oklch, fonts, radius, shadows, spacing, gradients) so everything downstream is token-based; then it turns the markup into components without creating duplicates — the headline being no duplicate Header, no second Avatar, no third Card.

The hard part isn't generating JSX from HTML — current models do that well. The hard parts are: (a) not hardcoding the raw #3B82F6/14px/box-shadow the HTML is full of, but routing them through a real theme; and (b) not re-emitting the same header/card/avatar inline on every section. So this skill is built around a theme-first, then dedup-first discipline.

This is a builder skill. It assumes the project is already scaffolded (nextjs-bootstrap) — it builds into that structure. It does not scaffold.

The two core problems this skill solves

1. Raw values everywhere. HTML/CSS hands you literal hex, px, rgba shadows, inline styles, or baked-in Tailwind arbitrary values (bg-[#3B82F6], text-[14px]). Shipped as-is, the redesign never survives and shadcn components stay unthemed. The fix: extract the recurring values as tokens and write them where a shadcn app stores its theme — globals.css (colors in oklch) and layout.tsx (fonts) — then style components with bg-primary/rounded-lg/shadow-card, never the raw value.
2. Designs repeat. The same header sits on five sections, avatars and cards are everywhere. A naive markup→code pass re-emits each inline and the codebase fills with duplicates. The fix: treat MODULE_REGISTRY.md as a dedup ledger and the shared/feature trees as the source of truth — before writing any component, check whether it already exists; reuse it, extend it, or only then create it, and put reusable ones in components/shared/ so the next section reuses them. Read references/dedup-protocol.md; it's the heart of phase 2.

Prerequisites & resolution

1. Resolve the project dir. Read .claude/workspace.json (repo root) → frontend entry = <proj>. Else find a frontend-* folder (e.g. frontend-shoply/), a plain frontend/, or a src/app/ with shadcn (globals.css + components/ui/). If there's no scaffolded Next.js + shadcn project, stop and point at nextjs-bootstrap — this skill builds into an existing structure, it doesn't create one.
2. Read the contract files (required): ARCHITECTURE.md (conventions) and MODULE_REGISTRY.md (the dedup ledger — every existing shared component, hook, util). You cannot dedup against a ledger you haven't read.
3. Resolve the HTML input. In priority order: an explicit path the user gave → a pasted HTML block in the message → a URL (fetch it) → scan _docs/designs/ (the project's design drop-folder) and use/confirm the relevant file. If the HTML links external CSS (<link rel="stylesheet">) or fonts, read those files too — the styling lives there. See references/reading-html.md.
4. Determine the package manager (pnpm/npm/yarn from the lockfile) for shadcn/build commands below.

Decide the scope (which phases to run)

• A whole page / a fresh design, or the project still has the stock shadcn theme → run Phase 1 (theme) then Phase 2 (components).
• A single section/snippet on an already-themed project → Phase 2 is the focus, but still scan the snippet for new tokens (a brand color or font not yet in the theme). Don't hardcode them — append them to the theme (a light Phase 1 pass) and then reference them. Surface to the user when you add a token.
• The user explicitly asks for only theming or only a component → do just that phase. Stay in scope.

State which phases you'll run before you start, so the user can redirect.

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Phase 1 — Theme (tokens → globals.css + layout.tsx)

Skip or trim per the scope decision above. Paths are relative to <proj>.

1. Extract the tokens from the HTML. Pull every recurring color, font-family, font-size/line-height, font-weight, radius, shadow, spacing step, gradient, and background image out of the <style> blocks, linked CSS, inline style= attributes, and any baked-in Tailwind classes. Run scripts/extract_tokens.py <file> to get a frequency-sorted inventory fast, then read it with judgment — recurring values are tokens; one-offs belong to a component, not the theme. See references/reading-html.md ("Extracting design tokens").
2. Normalize into a token map. Group into: colors (→ shadcn roles), typography (families + the size/line-height/weight scale), radius, shadows, spacing, gradients, background images. Map the design's colors onto shadcn's semantic roles rather than inventing names (so every shadcn component is themed for free). See references/theme-tokens.md.
3. Convert every color to oklch. Collect the values into {role: "#hex"} and run python scripts/hex_to_oklch.py --json colors.json. Use the output verbatim — shadcn/Tailwind v4 store theme colors as oklch; never paste raw hex into theme variables.
4. Rewrite globals.css — light AND dark. Update the :root (light), .dark (dark), and @theme inline blocks — re-value the roles, don't rename them. shadcn themes are dual-mode: if the HTML defines a dark variant (.dark/[data-theme="dark"] block, prefers-color-scheme: dark media query, or dark: Tailwind variants) capture that palette into .dark; if it's single-mode, fill the given mode and derive the other (don't leave stale shadcn defaults) and say you derived it. Set --radius, add --shadow-*, gradient tokens, and any custom type-scale entries. references/theme-tokens.md has the exact block shapes and the dark-derivation rules.
5. Wire fonts in layout.tsx. Google families via next/font/google, custom/brand files via next/font/local (drop files under src/app/fonts/). Each font exposes a CSS variable; add them to <html className> and bind them in @theme (--font-sans, --font-display, …). Never <link> tags or @import url(). See references/fonts.md.
6. Apply the rest as tokens. Radius, shadows, gradients, background images → tokens/utilities so components reference rounded-lg, shadow-card, bg-[image:var(--gradient-brand)], never raw values.
7. Update the contract files. In ARCHITECTURE.md, make the theme concrete (fonts used, palette source = this HTML, oklch). In MODULE_REGISTRY.md, log the theming decision.

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Phase 2 — Components (the dedup-first build)

Paths relative to <proj>. Conventions come from ARCHITECTURE.md + the references below; project docs win on project-specifics.

1. Map the structure before coding. Read the HTML top-down. Semantic tags (<header>, <nav>, <main>, <section>, <footer>, <aside>) and class names (hero, card, navbar, avatar) are your decomposition map and dedup hints — the HTML analog of Figma layer names. List the discrete pieces. For a big page, outline the sections first, then drill into each. See references/reading-html.md.
2. Classify each candidate piece reusable-generic vs feature-specific using references/shared-taxonomy.md. A block that is a header/navbar/hero/carousel/chart/sidebar/avatar/logo/banner is almost always a shared component.
3. Run the dedup protocol for every candidate (references/dedup-protocol.md): check MODULE_REGISTRY.md → grep components/shared, components/ui, features/*/components → decide reuse / extend / create. Never create something the ledger already lists. If a feature-local component is now needed by a second feature, move it to shared (don't copy). The protocol covers non-component reusables too — utils, hooks, types, constants get the same search (lib, hooks, src/types, src/constants) and the same placement-by-dependency rule, so design-time code lands where frontend-module-builder expects it.
4. Fill primitive gaps via shadcn, not by hand. If a piece is really a primitive the project lacks (carousel, avatar, chart, tabs, accordion, sidebar, …), add it with <pm> dlx shadcn@latest add <name> into components/ui/ and compose it — never hand-author or re-skin a primitive.
5. Build each new component — mobile-first and token-based. Tailwind utility classes only (no separate CSS files; no inline style={{}} for things Tailwind covers); reference theme tokens (bg-primary, text-muted-foreground, rounded-lg, shadow-card, font-display) instead of the raw hex/px in the source HTML — never a hardcoded color when a token exists. Author mobile-first: base classes target small screens, layer up with md:/lg: prefixes; honor the source's @media queries via breakpoints, and infer the mobile layout when the markup is desktop-only. Any header/navbar/sidebar collapses on mobile into a hamburger that opens a shadcn Sheet. Match spacing, gap, radius, border, shadow, line-height faithfully — through the token system, responsively (don't pin desktop px). TypeScript props; cva for variant-bearing components. Reusable → components/shared/<group>/; domain-specific → features/<name>/components/. See references/building-components.md.
6. Assets & icons. For <img>/background images in the HTML: copy local asset files into public/ (or the feature) and use next/image; for remote src URLs, download into public/ rather than hotlinking. Icons come from the single registry file components/shared/icons.tsx (lucide-react first, react-icons for gaps, custom currentColor SVGs last) — map source icon fonts/inline <svg>s to lucide equivalents and import from the registry, never from the icon library directly. See references/building-components.md ("Assets", "Icons").
7. Animation. Default to Tailwind/CSS transitions and shadcn's built-in motion; reach for framer-motion (motion/react) only for orchestrated/gesture/scroll-linked motion. Translate CSS transition/@keyframes/animation in the source to the equivalent. See references/animation.md.
8. Compose & register. Assemble the pieces into the screen via a feature template/ if it's a full screen; keep page.tsx thin. Register every new shared component in MODULE_REGISTRY.md (name, path, what it wraps, purpose) — an unregistered shared component is a future duplicate.
9. Verify. <pm> run build (typecheck + lint) and a quick read-through against the source HTML. Report: theme changes (if Phase 1 ran), components created vs reused, where each landed, primitives added, registry rows added.

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What to read when

• references/reading-html.md — how to read the input (file / pasted / URL / _docs/designs), resolve linked CSS & fonts, parse structure for decomposition, and extract design tokens from plain CSS, inline styles, and baked-in Tailwind. Read before Phase 1 step 1 and Phase 2 step 1.
• references/theme-tokens.md — shadcn role table, color→role mapping, the exact Tailwind v4 :root / .dark / @theme inline block shapes, and radius/shadow/gradient/bg-image tokens. Read during Phase 1 steps 2–6.
• references/fonts.md — next/font/google and next/font/local patterns, exposing & binding CSS variables, handling the families the HTML uses. Read during Phase 1 step 5.
• references/dedup-protocol.md — the reuse/extend/create decision and the exact search order. Read before creating any component. This is the skill's reason to exist.
• references/shared-taxonomy.md — reusable-shared vs feature-specific, the canonical shared list (header, navbar, hero, small-hero, carousel, charts, sidebar, avatar, logo, banner …) and which components/shared/ subfolder each lands in. Read during Phase 2 step 2.
• references/building-components.md — Tailwind-token styling rules, cva, server vs client, props/typing, faithful spacing/shadow/radius via tokens, assets/next/image, accessibility. Read before Phase 2 step 5.
• references/animation.md — Tailwind/CSS vs framer-motion decision and patterns; translating CSS animation from the source. Read before Phase 2 step 7 (only if the design animates).
• scripts/extract_tokens.py — scans an HTML/CSS file and prints a frequency-sorted inventory of colors, font-families, font-sizes, radii, shadows, gradients. Run it first in Phase 1.
• scripts/hex_to_oklch.py — hex/rgb → oklch() converter (single, many, or --json batch). Use it for every color.

Non-negotiables (why this skill exists)

• Colors are oklch, tokens not raw values. Recurring colors become shadcn role tokens in globals.css, converted with the script. A component shipping bg-[#3B82F6] or text-[14px] when a token exists defeats the theme and the next redesign. Always use the token — translate raw HTML values to bg-primary/text-sm/rounded-xl/shadow-card, never a hardcoded color.
• Mobile-first responsive, with a real mobile nav. Every component is authored mobile-first (base = small screen, md:/lg: layer up), never desktop-pinned to the mockup's fixed width. Any header/navbar/sidebar collapses on mobile into a hamburger that opens a shadcn Sheet — not links silently hidden with no affordance.
• Check the registry before you create — every time. The MODULE_REGISTRY.md ledger + a grep of shared/ui/features is mandatory per candidate component. Re-creating something that exists is the exact failure this skill prevents. Reuse > extend > create.
• One home per component, by dependency. Generic/reusable → components/shared/<group>/. Depends on one feature's domain → features/<name>/components/. A reusable component buried in a feature folder is a bug; so is a domain component in shared. When a feature-local piece is needed by a second feature, it moves to shared and gets registered — never copied. The same placement-by-dependency applies to non-components: utils → lib/, hooks → hooks/, multi-feature types → src/types/, multi-feature constants → src/constants/.
• shadcn primitives are composed, never duplicated. Need a carousel/avatar/chart/tabs/sidebar? shadcn add it and wrap it. Hand-writing a primitive shadcn ships, or forking a styled sibling of Button/Select, is a regression. When the design's primitive looks different, edit its cva variants in place (see references/building-components.md "The design's variants live in ui/") — that's the sanctioned path.
• Don't restructure shadcn's theme — re-value it. Keep the role names and the :root/.dark/@theme inline shape; swap values and add tokens. Fonts go through next/font, never <link>/@import.
• Always produce both light and dark. shadcn's theme is dual-mode. Capture the design's dark palette when it has one; derive it when it doesn't. Every role in :root must also exist in .dark — a missing role is an unthemed component in dark mode. Leaving stock shadcn dark defaults under a custom light theme is the failure to avoid.
• Reusable shared components get registered immediately. A new Header/Avatar/Carousel in components/shared/ that isn't in MODULE_REGISTRY.md is invisible to the next run and will be rebuilt.
• Faithful, but production-grade. Honor the design's spacing, gaps, radii, borders, shadows, gradients, line-heights — through tokens, responsively (mobile-first, not desktop-pinned). Semantic markup, alt text, focus states. The output should look like a senior engineer built it, not like converted markup.
• Stay in your lane. Build into the existing structure. Don't scaffold (that's nextjs-bootstrap). When the source is Figma, use figma-to-component instead.