build: align Vite 8 bundler config

.agents/skills/migrate-to-vinext/SKILL.md

@@ -94,6 +94,8 @@ Add `"type": "module"` to package.json. Rename any CJS config files:
 
 See [references/config-examples.md](references/config-examples.md) for config variants per router and deployment target.
 
+If the project already has custom Vite config, prefer Vite 8-native keys when editing it: `oxc`, `optimizeDeps.rolldownOptions`, and `build.rolldownOptions`. Older `esbuild` and `build.rollupOptions` settings still work for now but are migration targets.
+
 **Pages Router (minimal):**
 
 ```ts

.agents/skills/migrate-to-vinext/references/config-examples.md

@@ -1,5 +1,7 @@
 # Vite Config Examples
 
+These examples stay minimal on purpose. If you add custom build tuning on Vite 8, prefer `oxc`, `optimizeDeps.rolldownOptions`, and `build.rolldownOptions` / `worker.rolldownOptions` over older `esbuild` and `build.rollupOptions` settings.
+
 ## Pages Router — Local Development
 
 No Cloudflare, no deployment. Simplest possible config.

.agents/skills/migrate-to-vinext/references/troubleshooting.md

@@ -12,6 +12,20 @@
 | RSC environment crash on dev start            | Native Node module (sharp, satori) loaded in RSC env | vinext auto-stubs these in production; in dev, ensure these are only imported in server code behind dynamic `import()` |
 | `ASSETS binding not found`                    | wrangler.jsonc missing assets config                 | Add `"assets": { "not_found_handling": "none" }` to wrangler.jsonc                                                     |
 
+## Vite 8 Migration Notes
+
+- **Symptom:** deprecation warnings for `esbuild`, `optimizeDeps.esbuildOptions`, or `build.rollupOptions`.
+  **Cause:** Vite 8 now defaults to Oxc and Rolldown.
+  **Fix:** Prefer `oxc`, `optimizeDeps.rolldownOptions`, and `build.rolldownOptions` / `worker.rolldownOptions` in custom Vite config.
+
+- **Symptom:** a package only breaks on Vite 8 with a bad `default` import from CommonJS.
+  **Cause:** Vite 8 made CommonJS default import handling more consistent.
+  **Fix:** Fix the import or package if possible. As a temporary workaround, set `legacy.inconsistentCjsInterop: true`.
+
+- **Symptom:** older browsers stop working after migration.
+  **Cause:** Vite 8 raised the default `build.target` browser baseline.
+  **Fix:** Set `build.target` explicitly in `vite.config.*` if you need older browser support.
+
 ## ESM Conversion Issues
 
 When adding `"type": "module"`, any `.js` file using `module.exports` or `require()` will break. Common files that need renaming to `.cjs`:

AGENTS.md

@@ -355,6 +355,16 @@ The RSC entry's `default` export is the request handler. The plugin calls it for
 
 You **must** use `createBuilder()` + `builder.buildApp()` for production builds, not `build()` directly. Calling `build()` from the Vite JS API doesn't trigger the RSC plugin's multi-environment build pipeline. `buildApp()` runs the 5-step RSC/SSR/client build sequence in the correct order.
 
+### Vite 8 Defaults
+
+This repo currently resolves `vite` to `@voidzero-dev/vite-plus-core`, which bundles Vite 8. Keep that in mind when touching Vite config or plugin integration code:
+
+- Prefer `oxc` over `esbuild` for new JavaScript transform config
+- Prefer `optimizeDeps.rolldownOptions` over `optimizeDeps.esbuildOptions`
+- Prefer `build.rolldownOptions` / `worker.rolldownOptions` over adding new `*.rollupOptions` config
+- When touching existing `build.rollupOptions` or `manualChunks`, preserve Vite 7 compatibility but treat them as migration targets, not patterns to copy forward
+- If something breaks only on Vite 8, check the newer `build.target` baseline and stricter CommonJS default import behavior first
+
 ### Virtual Module Resolution Quirks
 
 - **Build-time root prefix:** Vite prefixes virtual module IDs with the project root path when resolving SSR build entries. The `resolveId` hook must handle both `virtual:vinext-server-entry` and `<root>/virtual:vinext-server-entry`.

README.md

@@ -99,6 +99,8 @@ This will:
 
 The migration is non-destructive -- your existing Next.js setup continues to work alongside vinext. It does not modify `next.config`, `tsconfig.json`, or any source files, and it does not remove Next.js dependencies.
 
+vinext supports both Vite 7 and Vite 8. If you bring custom Vite config or plugins from an older setup, note that Vite 8 now defaults to Rolldown, Oxc, Lightning CSS, and a newer browser baseline. Prefer `oxc`, `optimizeDeps.rolldownOptions`, and `build.rolldownOptions` over older `esbuild` and `build.rollupOptions` knobs, and override `build.target` if you still need older browsers. If a dependency only breaks on Vite 8 because of stricter CommonJS default import handling, fix the import or use `legacy.inconsistentCjsInterop: true` as a temporary escape hatch. See the [Vite 8 migration guide](https://vite.dev/guide/migration).
+
 ```bash
 npm run dev:vinext    # Start the vinext dev server (port 3001)
 npm run dev           # Still runs Next.js as before
@@ -696,7 +698,7 @@ Or add it to your `package.json` as a file dependency:
 }
 ```
 
-vinext has peer dependencies on `react ^19.2.4`, `react-dom ^19.2.4`, and `vite ^7.0.0`. Then replace `next` with `vinext` in your scripts and run as normal.
+vinext has peer dependencies on `react ^19.2.4`, `react-dom ^19.2.4`, and `vite ^7.0.0 || ^8.0.0`. Then replace `next` with `vinext` in your scripts and run as normal.
 
 ## Contributing
 

packages/vinext/package.json

@@ -76,7 +76,7 @@
   "peerDependencies": {
     "@mdx-js/rollup": "^3.0.0",
     "@vitejs/plugin-react": "^5.1.4 || ^6.0.0",
-    "@vitejs/plugin-rsc": "^0.5.19",
+    "@vitejs/plugin-rsc": "^0.5.21",
     "react": ">=19.2.0",
     "react-dom": ">=19.2.0",
     "react-server-dom-webpack": "^19.2.4",

packages/vinext/src/cli.ts

@@ -13,7 +13,7 @@
  * needed for most Next.js apps.
  */
 
-import vinext, { clientOutputConfig, clientTreeshakeConfig } from "./index.js";
+import vinext, { clientTreeshakeConfig, getClientOutputConfigForVite } from "./index.js";
 import { printBuildReport } from "./build/report.js";
 import { runPrerender } from "./build/run-prerender.js";
 import path from "node:path";
@@ -358,6 +358,12 @@ async function buildApp() {
   applyViteConfigCompatibility(process.cwd());
 
   const vite = await loadVite();
+  const viteMajorVersion = Number.parseInt(vite.version, 10) || 7;
+
+  const withBuildBundlerOptions = (bundlerOptions: Record<string, unknown>) =>
+    viteMajorVersion >= 8
+      ? { rolldownOptions: bundlerOptions }
+      : { rollupOptions: bundlerOptions };
 
   console.log(`\n  vinext build  (Vite ${getViteVersion()})\n`);
 
@@ -445,11 +451,11 @@ async function buildApp() {
           outDir: "dist/server",
           emptyOutDir: false, // preserve RSC artefacts from buildApp()
           ssr: "virtual:vinext-server-entry",
-          rollupOptions: {
+          ...withBuildBundlerOptions({
             output: {
               entryFileNames: "entry.js",
             },
-          },
+          }),
         },
       });
     }
@@ -465,11 +471,11 @@ async function buildApp() {
             outDir: "dist/client",
             manifest: true,
             ssrManifest: true,
-            rollupOptions: {
+            ...withBuildBundlerOptions({
               input: "virtual:vinext-client-entry",
-              output: clientOutputConfig,
+              output: getClientOutputConfigForVite(viteMajorVersion),
               treeshake: clientTreeshakeConfig,
-            },
+            }),
           },
         },
         logger,
@@ -483,11 +489,11 @@ async function buildApp() {
           build: {
             outDir: "dist/server",
             ssr: "virtual:vinext-server-entry",
-            rollupOptions: {
+            ...withBuildBundlerOptions({
               output: {
                 entryFileNames: "entry.js",
               },
-            },
+            }),
           },
         },
         logger,

packages/vinext/src/index.ts

@@ -540,6 +540,17 @@ const clientOutputConfig = {
   experimentalMinChunkSize: 10_000,
 };
 
+const clientCodeSplittingConfig = {
+  minSize: 10_000,
+  groups: [
+    {
+      name(moduleId: string) {
+        return clientManualChunks(moduleId) ?? null;
+      },
+    },
+  ],
+};
+
 /**
  * Rollup treeshake configuration for production client builds.
  *
@@ -570,6 +581,36 @@ const clientTreeshakeConfig = {
   moduleSideEffects: "no-external" as const,
 };
 
+type VinextBuildConfig = NonNullable<UserConfig["build"]>;
+type VinextBuildBundlerOptions = NonNullable<VinextBuildConfig["rolldownOptions"]>;
+type VinextBuildConfigWithLegacy = VinextBuildConfig & {
+  rollupOptions?: VinextBuildBundlerOptions;
+};
+
+function getBuildBundlerOptions(
+  build: UserConfig["build"] | undefined,
+): VinextBuildBundlerOptions | undefined {
+  const buildConfig = build as VinextBuildConfigWithLegacy | undefined;
+  return buildConfig?.rolldownOptions ?? buildConfig?.rollupOptions;
+}
+
+function withBuildBundlerOptions(
+  viteMajorVersion: number,
+  bundlerOptions: VinextBuildBundlerOptions,
+): Partial<VinextBuildConfigWithLegacy> {
+  return viteMajorVersion >= 8
+    ? { rolldownOptions: bundlerOptions }
+    : { rollupOptions: bundlerOptions };
+}
+
+function getClientOutputConfigForVite(viteMajorVersion: number) {
+  return viteMajorVersion >= 8
+    ? {
+        codeSplitting: clientCodeSplittingConfig,
+      }
+    : clientOutputConfig;
+}
+
 type BuildManifestChunk = {
   file: string;
   isEntry?: boolean;
@@ -1766,15 +1807,15 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
           // Disable Vite's default HTML serving - we handle all routing
           appType: "custom",
           build: {
-            rollupOptions: {
+            ...withBuildBundlerOptions(viteMajorVersion, {
               // Suppress "Module level directives cause errors when bundled"
               // warnings for "use client" / "use server" directives. Our shims
               // and third-party libraries legitimately use these directives;
               // they are handled by the RSC plugin and are harmless in the
               // final bundle. We preserve any user-supplied onwarn so custom
               // warning handling is not lost.
               onwarn: (() => {
-                const userOnwarn = config.build?.rollupOptions?.onwarn;
+                const userOnwarn = getBuildBundlerOptions(config.build)?.onwarn;
                 return (warning, defaultHandler) => {
                   if (
                     warning.code === "MODULE_LEVEL_DIRECTIVE" &&
@@ -1817,8 +1858,10 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
               // Router). For multi-environment builds (App Router, Cloudflare),
               // manualChunks is set per-environment on the client env below
               // to avoid leaking into RSC/SSR environments.
-              ...(!isSSR && !isMultiEnv ? { output: clientOutputConfig } : {}),
-            },
+              ...(!isSSR && !isMultiEnv
+                ? { output: getClientOutputConfigForVite(viteMajorVersion) }
+                : {}),
+            }),
           },
           // Let OPTIONS requests pass through Vite's CORS middleware to our
           // route handlers so they can set the Allow header and run user-defined
@@ -1959,9 +2002,9 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
               },
               build: {
                 outDir: options.rscOutDir ?? "dist/server",
-                rollupOptions: {
+                ...withBuildBundlerOptions(viteMajorVersion, {
                   input: { index: VIRTUAL_RSC_ENTRY },
-                },
+                }),
               },
             },
             ssr: {
@@ -1984,9 +2027,9 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
               },
               build: {
                 outDir: options.ssrOutDir ?? "dist/server/ssr",
-                rollupOptions: {
+                ...withBuildBundlerOptions(viteMajorVersion, {
                   input: { index: VIRTUAL_APP_SSR_ENTRY },
-                },
+                }),
               },
             },
             client: {
@@ -2035,11 +2078,11 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
                 // on every page — defeating code-splitting for React.lazy() and
                 // next/dynamic boundaries.
                 ...(hasCloudflarePlugin ? { manifest: true } : {}),
-                rollupOptions: {
+                ...withBuildBundlerOptions(viteMajorVersion, {
                   input: { index: VIRTUAL_APP_BROWSER_ENTRY },
-                  output: clientOutputConfig,
+                  output: getClientOutputConfigForVite(viteMajorVersion),
                   treeshake: clientTreeshakeConfig,
-                },
+                }),
               },
             },
           };
@@ -2054,11 +2097,11 @@ export default function vinext(options: VinextOptions = {}): PluginOption[] {
               build: {
                 manifest: true,
                 ssrManifest: true,
-                rollupOptions: {
+                ...withBuildBundlerOptions(viteMajorVersion, {
                   input: { index: VIRTUAL_CLIENT_ENTRY },
-                  output: clientOutputConfig,
+                  output: getClientOutputConfigForVite(viteMajorVersion),
                   treeshake: clientTreeshakeConfig,
-                },
+                }),
               },
             },
           };
@@ -4504,7 +4547,13 @@ export type {
 export type { NextConfig } from "./config/next-config.js";
 
 // Exported for CLI and testing
-export { clientManualChunks, clientOutputConfig, clientTreeshakeConfig, computeLazyChunks };
+export {
+  clientManualChunks,
+  clientOutputConfig,
+  clientTreeshakeConfig,
+  computeLazyChunks,
+  getClientOutputConfigForVite,
+};
 export { augmentSsrManifestFromBundle as _augmentSsrManifestFromBundle };
 export { resolvePostcssStringPlugins as _resolvePostcssStringPlugins };
 export { _postcssCache };