vite-impl-optimization
Installation
SKILL.md
vite-impl-optimization
Quick Reference
Why Pre-Bundling Exists
Vite pre-bundles dependencies on first dev server start for two reasons:
| Reason | Problem | Solution |
|---|---|---|
| CJS/UMD to ESM conversion | Dev server serves native ESM only; most npm packages ship CJS/UMD | Pre-bundler converts to ESM with smart import analysis |
| HTTP request reduction | ESM deps with many internal modules cause hundreds of requests (e.g., lodash-es = 600+ modules) | Pre-bundler collapses into a single module |
CRITICAL: Pre-bundling applies ONLY in development mode. Production builds use Rolldown (v8) or Rollup (v5-v7) natively.