diff --git a/‎packages/vite/src/node/__tests__/config.spec.ts‎
Lines changed: 20 additions & 0 deletions b/‎packages/vite/src/node/__tests__/config.spec.ts‎
Lines changed: 20 additions & 0 deletions
diff --git a/‎packages/vite/src/node/build.ts‎
Lines changed: 3 additions & 0 deletions b/‎packages/vite/src/node/build.ts‎
Lines changed: 3 additions & 0 deletions
@@ -669,6 +669,26 @@ describe('mergeConfig', () => {
     ).toBe('browser')
   })
 
+  test('resolved build options keep rollupOptions as a live proxy of rolldownOptions', async () => {
+    const config = await resolveConfig({}, 'serve')
+
+    for (const build of [
+      config.build,
+      config.environments.client.build,
+      config.environments.ssr.build,
+    ]) {
+      // Reassigning `rolldownOptions` must be reflected through the `rollupOptions` getter.
+      const newOptions = { treeshake: false }
+      build.rolldownOptions = newOptions
+      expect(build.rollupOptions).toBe(newOptions)
+
+      // Assigning through `rollupOptions` must update `rolldownOptions` too.
+      const newerOptions = { treeshake: true }
+      build.rollupOptions = newerOptions
+      expect(build.rolldownOptions).toBe(newerOptions)
+    }
+  })
+
   test('syncs `server.hmr.*` to `server.ws.*`', () => {
     const baseConfig = defineConfig({
       server: {
 
@@ -505,6 +505,9 @@ export function resolveBuildEnvironmentOptions(
               ...merged.modulePreload,
             },
   }
+  // The object spread above evaluates the `rollupOptions` getter set up on
+  // `merged` and copies it as a plain data property.
+  setupRollupOptionCompat(resolved, 'build')
 
   return resolved
 }
Original file line number	Diff line number	Diff line change
`@@ -505,6 +505,9 @@ export function resolveBuildEnvironmentOptions(`
`505`	`505`	`...merged.modulePreload,`
`506`	`506`	`},`
`507`	`507`	`}`
	`508`	+ // The object spread above evaluates the `rollupOptions` getter set up on
	`509`	+ // `merged` and copies it as a plain data property.
	`510`	`+ setupRollupOptionCompat(resolved, 'build')`
`508`	`511`
`509`	`512`	`return resolved`
`510`	`513`	`}`