TopolearnLarge apps hit slow cold starts and oversized bundles; fixing them needs knowledge of the toolchain.
Vite 8 replaced the esbuild + Rollup pair with Rolldown (bundler) and Oxc (parser, transformer, minifier), both written in Rust by the VoidZero team. One toolchain for dev pre-bundling and production means more consistent behaviour and much faster builds. Config moved accordingly: build.rolldownOptions replaces build.rollupOptions (still accepted as a deprecated alias), and the oxc option replaces esbuild.
Chunking: by default, Rolldown creates one chunk per entry and per dynamic import, plus shared chunks. To group modules yourself, use output.codeSplitting.groups, each with a name and a test (regex or function), plus optional size limits like minSize, maxSize and priority. The Rollup-era manualChunks function still works but is deprecated. Splitting vendor code into stable chunks improves cache hit rates across deploys; splitting too much causes request waterfalls.
Dev server performance:
- Audit slow plugins:
vite --debug plugin-transformorvite-plugin-inspect. - Avoid barrel files (
index.tsre-exporting hundreds of modules): every import loads them all. - Use explicit file extensions in imports to reduce resolution work, and
server.warmup.clientFilesto pre-transform frequently used files.
Bundle analysis: rollup-plugin-visualizer or vite-bundle-analyzer, then replace heavy dependencies, lazy-load routes, and check that tree-shaking works (sideEffects: false in packages).
Example
// vite.config.js
import { defineConfig } from "vite";
export default defineConfig({
build: {
rolldownOptions: {
output: {
codeSplitting: {
groups: [
{ name: "react", test: /node_modules[\\/](react|react-dom|scheduler)[\\/]/, priority: 20 },
{ name: "vendor", test: /node_modules/, priority: 10 },
],
},
},
},
},
server: {
warmup: { clientFiles: ["./src/components/Layout.tsx", "./src/routes/*.tsx"] },
},
});
// $ npx vite build
// dist/assets/index-BO0so3wH.js 0.74 kB
// dist/assets/vendor-C0txrztE.js 19.21 kB
// $ npx vite --debug plugin-transform # which plugins are slow?Remember
- Vite 8: Rolldown + Oxc; rolldownOptions and oxc replace rollupOptions and esbuild
codeSplitting.groupscontrols chunks; manualChunks is deprecated- Barrel files and slow plugins are the usual dev bottlenecks
- Analyze bundles before optimizing them
Watch out for
- Splitting every dependency into its own chunk, creating dozens of small requests.