Reuse preview sanitizer across client page bundles

packages/block-editor/test/preview-html.test.ts

@@ -11,3 +11,15 @@ test("preview sanitization preserves email layout and editor markers but removes
   expect(result).not.toMatch(/onerror|javascript:|<script|<iframe/);
   window.close();
 });
+
+test("separately bundled preview modules reuse one realm sanitizer", async () => {
+  const { window } = new JSDOM("");
+  const doc = window.document as unknown as Document;
+  builderPreviewHTML("<p>First page</p>", doc);
+  const key = Symbol.for("wrnexus.block-editor.preview-sanitizer");
+  const first = (window as any)[key];
+  const secondModule = await import("../src/preview-html.ts?second-page");
+  expect(String(secondModule.builderPreviewHTML("<p>Second page</p>", doc))).toContain("Second page");
+  expect((window as any)[key]).toBe(first);
+  window.close();
+});