Vite 8 Migration Instructions for LLM

Overview

These instructions guide you through migrating an Nx workspace from Vite 7 to Vite 8. Vite 8 swaps Rollup for Rolldown as its bundler and updates a number of plugin APIs. Work through each section in order and run tests after each change.

Pre-Migration Checklist

1. Identify all Vite-using projects:

   bashCopy

   nx show projects --with-target build
   nx show projects --with-target serve
   

2. Locate all Vite configuration files:

   • Search for vite.config.{ts,js,mts,mjs,cts,cjs}
   • Check project.json files for inline Vite-related options

3. Cypress Component Testing: Cypress >= 15.14.0 supports Vite 8. The nx migrate step bumps Cypress automatically. If you have explicitly pinned Cypress below 15.14.0, upgrade it before bumping Vite.

Migration Steps by Category

1. Rename rollupOptions to rolldownOptions

The nx migrate codemod handles this automatically for vite.config.{ts,js,mts,mjs,cts,cjs} files. If you have rollupOptions declared elsewhere (e.g., in helper modules imported by your config), rename them by hand.

Search Pattern: rollupOptions in any TypeScript/JavaScript file

// ❌ BEFORE (Vite 7)
export default defineConfig({
  build: {
    rollupOptions: {
      external: ['react'],
      output: { manualChunks: { vendor: ['react', 'react-dom'] } },
    },
  },
});

// ✅ AFTER (Vite 8)
export default defineConfig({
  build: {
    rolldownOptions: {
      external: ['react'],
      output: { manualChunks: { vendor: ['react', 'react-dom'] } },
    },
  },
});

Action Items:

• Verify the codemod picked up every config file (rg "rollupOptions" should return zero hits inside vite configs)
• Rename any rollupOptions in helper modules or shared config builders
• Update CI scripts that parse build.rollupOptions (e.g., custom bundle-size assertions)

2. @vitejs/plugin-react v6 (Oxc Replaces Babel)

@vitejs/plugin-react@^6 is required for Vite 8 and uses Oxc instead of Babel for JSX transformation. The plugin's babel option is gone.

// ❌ BEFORE (Vite 7, plugin-react v4)
import react from '@vitejs/plugin-react';

export default defineConfig({
  plugins: [
    react({
      babel: {
        plugins: ['babel-plugin-styled-components'],
      },
    }),
  ],
});

// ✅ AFTER (Vite 8, plugin-react v6)
import react from '@vitejs/plugin-react';

export default defineConfig({
  plugins: [react()],
});

Action Items:

• Remove babel options from react() plugin invocations
• If you depended on a Babel plugin (e.g., styled-components, emotion, relay), find an Oxc-compatible replacement or switch to @vitejs/plugin-react-swc (still Babel-free). There is no drop-in for arbitrary Babel plugins.
• If you cannot drop your Babel plugin, stay on Vite 7 + plugin-react v4 for now (see "Project-Level Vite 7 Pinning")
• Run pnpm install (or your package manager equivalent) so the new plugin-react version resolves

3. Angular + Vitest (vitest-analog path): Add @oxc-project/runtime

Angular projects whose test target uses @nx/vitest:test (the vitest-analog setup wired by @analogjs/vite-plugin-angular) need @oxc-project/runtime declared in the workspace devDependencies.

@analogjs/vite-plugin-angular registers an angularVitestPlugin (active in test mode) whose transform hook matches @angular/* fesm2022 modules that contain async (plus any @angular/cdk file) and calls vite.transformWithOxc(code, id, { target: 'es2016', … }). The downlevel is deliberate: Zone.js relies on monkey-patching promise scheduling for fakeAsync and friends, which it cannot do on native async/await, so the plugin lowers them to a form Zone.js can intercept. With target: 'es2016', oxc emits the helpers as external @oxc-project/runtime/helpers/* imports (oxc's default HelperMode = 'Runtime'). Nothing in the upstream chain (analogjs, @angular/core, vite, rolldown) declares @oxc-project/runtime in a way that's resolvable from the consumer's workspace, so vite:import-analysis fails to resolve those imports unless the dep is added explicitly.

Angular projects whose test target uses @angular/build:unit-test or @nx/angular:unit-test (the vitest-angular path) do not need this dependency — that path doesn't load @analogjs/vite-plugin-angular, sets optimizeDeps.noDiscovery: true, and uses an in-memory test provider, so the downlevel transform that emits the helper imports never runs.

Search Pattern: Projects with test.executor set to @nx/vitest:test that also have @analogjs/vite-plugin-angular in their vite.config.*.

rg '"@nx/vitest:test"' --type json
rg '@analogjs/vite-plugin-angular' --type ts --type js

Action Items:

• For each affected workspace, add @oxc-project/runtime to root devDependencies (the Nx Angular generators do this automatically on the vitest-analog path; check legacy workspaces that pre-date that)
• Run pnpm install (or equivalent)
• Run the project's tests to confirm the helper resolves

4. Type Resolution Under moduleResolution: "node"

Vite 8 ships its types only via conditional exports (it dropped the top-level types field that Vite 7 carried), which TypeScript cannot resolve under moduleResolution: "node". Symptoms include type errors on defineConfig, UserConfig, or plugin return types.

Action Items:

• Update affected tsconfig*.json files: "moduleResolution": "bundler" (recommended) or "node16"/"nodenext"
• If you cannot change moduleResolution, narrow the impact with explicit as any casts at vite imports. The Nx-generated configs already do this in a handful of places.
• Run tsc --noEmit after the change to confirm types resolve cleanly

5. Bundle Validation Scripts

Rolldown produces different chunk and module counts than Rollup for the same input. Custom build validation (e.g., "bundle has exactly N chunks") will need to be re-baselined.

Action Items:

• Identify scripts that assert chunk/module counts or names
• Re-run the build and update expected values
• Prefer asserting on size budgets over exact counts going forward

6. Project-Level Vite 7 Pinning (Custom Babel Plugins)

If a project depends on a Babel plugin that has no Oxc equivalent, pin that project to Vite 7.

// package.json (workspace root)
{
  "devDependencies": {
    "vite": "^7.1.0",
    "@vitejs/plugin-react": "^4.3.0",
  },
}

If only some projects need to stay on 7 while the rest move to 8, use your package manager's overrides feature:

• pnpm: pnpm.overrides in root package.json
• npm/yarn: overrides/resolutions

Action Items:

• Document which projects are pinned to Vite 7 and why
• Track Oxc plugin equivalents so you can unpin later

Post-Migration Validation

1. Run Tests Per Project

nx run-many -t test -p PROJECT_NAME

2. Build All Affected Projects

nx affected -t build

3. Validate Dev Server

nx serve PROJECT_NAME

Open the app and verify HMR still works for changes in source files.

4. Validate CI Pipeline

nx prepush

5. Review Migration Checklist

• All rollupOptions references renamed to rolldownOptions
• @vitejs/plugin-react upgraded to v6 (or pinned to v4 with a documented reason)
• No babel: { ... } options remain in react() calls (or those projects are pinned to Vite 7)
• Angular + vitest-analog projects have @oxc-project/runtime in root devDependencies
• Cypress upgraded by nx migrate (>= 15.14.0 for Vite 8 support)
• tsc --noEmit passes on all affected projects
• Build, test, and dev-server commands all succeed

Common Issues and Solutions

Issue: Cannot find name 'rollupOptions' or build options ignored

Solution: Rename to rolldownOptions. Vite 8 still accepts rollupOptions as a deprecated alias (it copies the value to rolldownOptions and logs a deprecation warning), but mixing both at the same level may cause precedence surprises (rolldownOptions wins).

Issue: Babel plugin no longer applied (e.g., styled-components classNames missing)

Solution: @vitejs/plugin-react@6 removed Babel. Find an Oxc-compatible alternative, switch to @vitejs/plugin-react-swc, or pin to Vite 7 + plugin-react v4.

Issue: Angular + Vitest fails with Failed to resolve import "@oxc-project/runtime/helpers/..."

Solution: Add @oxc-project/runtime to root devDependencies and reinstall. This only affects projects whose test target uses @nx/vitest:test (the vitest-analog setup); projects using @angular/build:unit-test / @nx/angular:unit-test are not affected.

Issue: Type errors on defineConfig, UserConfig, or Plugin imports from vite

Solution: Set moduleResolution: "bundler" in your tsconfig (or nodenext if you need Node-style resolution).

Issue: Cypress CT fails to start under Vite 8

Solution: Confirm cypress >= 15.14.0 is installed (Vite 8 support landed in that release). nx migrate bumps Cypress automatically; if you pinned it lower in package.json, remove the pin and reinstall.

Issue: Bundle-size or chunk-count assertions fail after upgrade

Solution: Rolldown chunks differently than Rollup. Re-baseline expected values.

Files to Review

# Vite config files
find . -name "vite.config.*" -not -path "*/node_modules/*"

# Cypress component testing setup
rg "@nx/(angular|react|next|remix)/plugins/component-testing"

# Babel plugin usage in plugin-react
rg "@vitejs/plugin-react.*babel|babel:\s*\{" --type ts --type js

# Angular projects with Vitest
rg "@angular/build" -l package.json

Guard Rails

DO NOT

• Force tests to pass by removing assertions or replacing them with expect(true).toBe(true)
• Strip react() plugin options without finding an equivalent for what they did
• Roll Cypress back below 15.14.0 after the migrate. Older Cypress fails to start under Vite 8.

Notes for LLM Execution

When executing this migration:

1. Work systematically: Complete one category before moving to the next
2. Test after each change: Build and test affected projects after each step
3. Keep user informed: Report which categories applied and which were skipped
4. Use TodoWrite tool: Track migration progress for visibility
5. Stop and ask if a project depends on a Babel plugin with no Oxc equivalent. Pinning to Vite 7 is a workspace decision.