bundle-analyze

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• SKILL.md

SKILL.md (first lines)

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# Bundle Analyze

Bundle size rules enforced on 18 production projects. The 100KB gzip rule per component chunk exists because it maps directly to a ~300ms FCP regression on median mobile.

---

## 100KB Rule

Any dynamically-imported component chunk must be under 100KB gzip. (BLOCKING)

Measure with:
```bash
# Vite
npx vite build --mode production
# Output includes per-chunk sizes

# Next.js
ANALYZE=true next build
# Requires @next/bundle-analyzer
```

---

## Vite manualChunks Configuration

```typescript
// vite.config.ts
import { defineConfig } from 'vite'
import react from '@vitejs/plugin-react'

export default defineConfig({
  plugins: [react()],
  build: {
    rollupOptions: {
      output: {
        manualChunks: (id) => {
          // Vendor chunk: React ecosystem
          if (id.includes('node_modules/react') ||
              id.includes('node_modules/react-dom') ||
              id.includes('node_modules/scheduler')) {
            return 'react-vendor'
          }

          // Routing chunk
          if (id.includes('node_modules/react-router') ||
              id.includes('node_modules/@remix-run')) {
            return 'router'
          }

          // UI library chunk (keep separate — large)
          if (id.includes('node_modules/@radix-ui') ||
              id.includes('node_modules/lucide-react')) {
            return 'ui'
          }

          // Data/validation chunk
          if (id.includes('node_modules/zod') ||
              id.includes('node_modules/@tanstack')) {
            return 'data'
          }

          // Charts (often 200-400KB — must be lazy)
          if (id.includes('node_modules/recharts') ||
              id.includes('node_modules/chart.js') ||
              id.includes('node_modules/d3')) {
            return 'charts'
          }

          // Date handling (use date-fns tree-shaking, not moment)
          if (id.includes('node_modules/date-fns')) {
            return 'dates'
          }
        },
      },
    },
    // Warn if chunk exceeds 150KB gzip (will fail CI at 200KB)
    chunkSizeWarningLimit: 150,
  },
})
```

---

## Next.js Dynamic Imports

```typescript
// components/HeavyChart.tsx — loaded only when visible
import dynamic from 'next/dynamic'

// Basic lazy load with spinner fallback
const HeavyChart = dynamic(() => import('./HeavyChartImpl'), {
  loading: () => <div className="h-64 animate-pulse rounded-lg bg-gray-100" />,
  ssr: false,  // charts often use window — disable SSR
})

// Named export pattern
const DataTable = dynamic(
  () => import('./DataTable').then(mod => mod.DataTable),
  { loading: () => <TableSkeleton /> }
)

// Conditional import — only load on client after interaction
export function DashboardPage() {
  const [showChart, setShowChart] = useState(false)
  return (
    <div>
      <button onClick={() => setShowChart(true)}>Show Analytics</button>
      {showChart && <HeavyChart />}
    </div>
  )
}
```

Rule: Any component over 50KB must be dynamically imported. (BLOCKING for Next.js)

---

From Nadav011/apex-skills, MIT.

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