diff --git a/src/builders/rollup/config.ts b/src/builders/rollup/config.ts
index 2ee9a60b..bd331537 100644
--- a/src/builders/rollup/config.ts
+++ b/src/builders/rollup/config.ts
@@ -155,7 +155,16 @@ export function getRollupOptions(ctx: BuildContext): RollupOptions {
 
       ctx.options.rollup.preserveDynamicImports && {
         name: "unbuild=preserve-dynamic-imports",
-        renderDynamicImport(): { left: string; right: string } {
+        renderDynamicImport({
+          targetModuleId,
+          targetChunk,
+        }: {
+          targetModuleId?: string | null;
+          targetChunk?: unknown;
+        }): { left: string; right: string } | null {
+          if (targetModuleId || targetChunk) {
+            return null;
+          }
           return { left: "import(", right: ")" };
         },
       },
diff --git a/test/rollup.test.ts b/test/rollup.test.ts
new file mode 100644
index 00000000..cc6da8af
--- /dev/null
+++ b/test/rollup.test.ts
@@ -0,0 +1,63 @@
+import { describe, it, expect } from "vitest";
+import { getRollupOptions } from "../src/builders/rollup/config";
+import type { BuildContext } from "../src/types";
+
+describe("preserveDynamicImports", () => {
+  it("preserves external dynamic imports but delegates internal chunks to Rollup", () => {
+    const ctx = {
+      options: {
+        rootDir: "/root",
+        entries: [],
+        alias: {},
+        replace: {},
+        rollup: {
+          replace: false,
+          alias: false,
+          resolve: false,
+          json: false,
+          esbuild: false,
+          commonjs: false,
+          preserveDynamicImports: true,
+          cjsBridge: false,
+          dts: {},
+        },
+      },
+      pkg: {},
+      buildEntries: [],
+      usedImports: new Set(),
+      warnings: new Set(),
+      hooks: {} as any,
+    } as unknown as BuildContext;
+
+    const rollupOptions = getRollupOptions(ctx);
+    const plugin = rollupOptions.plugins?.find(
+      (p: any) => p && p.name === "unbuild=preserve-dynamic-imports",
+    ) as any;
+
+    expect(plugin).toBeDefined();
+
+    // External import (targetModuleId is null) should be preserved as import(...)
+    expect(
+      plugin.renderDynamicImport({
+        targetModuleId: null,
+        targetChunk: null,
+      }),
+    ).toEqual({ left: "import(", right: ")" });
+
+    // Internal chunk by targetModuleId should return null so Rollup emits appropriate loader (e.g. require in CJS)
+    expect(
+      plugin.renderDynamicImport({
+        targetModuleId: "/root/src/plugin.ts",
+        targetChunk: null,
+      }),
+    ).toBeNull();
+
+    // Internal chunk by targetChunk should also return null
+    expect(
+      plugin.renderDynamicImport({
+        targetModuleId: null,
+        targetChunk: { fileName: "chunks/plugin.cjs" },
+      }),
+    ).toBeNull();
+  });
+});