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✨ ui-modernizer

One prompt. Modern UI.

A Claude Code Skill that turns your tired React / Vue / Svelte + Tailwind UI into a 2026 SaaS product. Linear · Vercel · Stripe · shadcn — pick a vibe, get the look.

"modernize this UI"

🚀 Install in 10 seconds

npx ui-modernizer

That's it. The Skill is now available in any project you open with Claude Code.

Then in Claude Code, in any React/Vue/Svelte + Tailwind project:

modernize this UI

Claude takes it from there.

🎯 What you get

Pick a vibe:

modernize this UI like Linear      # ultra-tight, mono-ish, soft purples (dark-first)
modernize this UI like Vercel      # monochrome, brutalist, hero gradients
modernize this UI like Stripe      # trust + precision, layered gradients, premium
modernize this UI like shadcn      # semantic CSS vars, the de-facto modern default
modernize this UI like Notion      # warm, calm, generous whitespace
modernize this UI like Raycast     # dark, dense, command-bar energy
modernize this UI like Apple       # premium pills, soft shadows, glass

Or bring your own profile — point at any local Markdown file matching the spec:

modernize this UI using ./design/our-brand.md

See Pluggable style profiles and the profile format spec.

🧱 Want shadcn primitives? Just ask.

modernize this UI and use shadcn components

ui-modernizer scans your project for hand-rolled <button> / <input> / <span class="badge-shape"> / card patterns, runs npx shadcn@latest add ... for what it needs, then rewrites them to <Button> / <Input> / <Badge> / <Card> — preserving every event handler, ref, and aria-* along the way.

Read references/component-substitution.md for the full workflow and safety rules.

🛡️ Safe by design

ui-modernizer only touches your visual layer:

• ✅ className string contents
• ✅ Layout wrapper <div>s (additive only)
• ✅ globals.css, tailwind.config
• ❌ Event handlers
• ❌ State, effects, fetches, server actions
• ❌ Props or component signatures
• ❌ Anything that could break your app

Every run is:

1. Planned — you see exactly what it'll change, before it changes.
2. Backed up — full copy of every modified file in .ui-modernizer-backup/<timestamp>/.
3. Diffed — a report.md with file-by-file +/- counts.
4. Reversible — one command:

npx ui-modernizer rollback

⚙️ How it works

┌──────────┐   ┌──────────┐   ┌──────────┐
│ DETECT   │ → │ PLAN     │ → │ BACKUP   │
│ stack    │   │ files    │   │ originals│
└──────────┘   └──────────┘   └──────────┘
                                    ↓
┌──────────┐   ┌──────────┐   ┌──────────┐
│ DONE ✨  │ ← │ REPORT   │ ← │ APPLY    │
│          │   │ .md      │   │ rules    │
└──────────┘   └──────────┘   └──────────┘

Knowledge is split into Markdown files that Claude reads on demand — so you can:

• Fork the skill, edit references/style-references/<your-brand>.md, get a custom modernizer for your design system.
• Audit every rule the AI applies, in plain English, in references/tailwind-modernization.md.

📦 Supported stacks

🧪 Try it on the included demo

git clone https://github.com/Rosalina7515/ui-modernizer
cd ui-modernizer/examples/before && npm install && npm run dev
# → http://localhost:3000  (looks dated on purpose)

cd ../after && npm install && npm run dev
# → http://localhost:3001  (what ui-modernizer produces)

🗺️ Roadmap

Released

• v0.1 — MVP: React + Next.js + Tailwind v3, 10 modernization rules, backup/rollback
• v0.2 — Tailwind v4 support + custom brand color detection
• v0.3 — Vue 3 (Nuxt / Vite) + Svelte 5 (SvelteKit / Vite) support
• v0.4 — Pluggable style profiles (7 built-in + bring-your-own Markdown)
• v0.5 — Component substitution (auto-install shadcn primitives)
• v0.6 — Visual regression checks (diff DOM + computed styles before/after)
• v0.7 — AST safety net (@babel/parser for JSX/TSX; tightened scanners for Vue/Svelte)
• v0.8 — .ui-modernizer.json config + --dry-run mode
• v0.9 — Polish: UMD-NNN error codes, unified JSON output, Vitest tests, "did you mean?" suggestions
• v1.0 — Stable API contract (SemVer commitment), governance docs, health-check, 41-test suite

Upcoming

• v1.1 — Tests & stability hardening (90%+ coverage)
• v1.2 — Docs site polish (interactive playground, profile gallery)
• v1.3 — AI reverse generation — "create a settings page like Linear"
• v1.4 — A11y audit + auto-fix
• v1.5 — Performance audit (images, fonts, hydration)
• v1.6 — VS Code + JetBrains plugins
• v1.7 — Figma → code
• v1.8 — More design systems (Material 3, Fluent, Carbon, Ant)
• v1.9 — React Native + Expo (via NativeWind)
• v2.0 — Full plugin system (ESLint-style ecosystem)

Full reasoning, strategic notes, and explicit non-goals → ROADMAP.md.

🤝 Contributing

ui-modernizer is mostly prompt + Markdown rules. Adding a new aesthetic is one PR:

1. Copy references/style-references/notion.md as a starting template.
2. Edit the frontmatter (name must match your filename) and fill in ## Tokens, ## Patterns, ## Don'ts.
3. Validate locally: node scripts/validate-profile.mjs references/style-references/<your>.md — must exit 0.
4. Open a PR. CI re-runs the validator on every push.

Read the profile format spec before you start. It's short.

Running tests

npm install
npm test

(Uses Vitest — npm test runs once, npm run test:watch watches.)

❓ FAQ

Does it call an external API? No. It runs entirely inside your local Claude Code. Your code never leaves your machine.

Will it change my business logic? By design, no. Hard rules in SKILL.md forbid it, and every run produces an auditable diff.

What if I hate the result? npx ui-modernizer rollback — every modified file is restored from a timestamped backup.

Does it work without Tailwind? Not in MVP. CSS Modules and styled-components are on the roadmap (v0.4+).

Why "Skill" and not a CLI? The visual judgement here needs an LLM. A CLI would be doing dumb regex replaces; the Skill leverages Claude's design taste while keeping side effects (backups, diffs, rollback) deterministic.

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