diff --git a/packages/stage/src/StageRender.ts b/packages/stage/src/StageRender.ts
index 92fa06e5..9b24abad 100644
--- a/packages/stage/src/StageRender.ts
+++ b/packages/stage/src/StageRender.ts
@@ -194,7 +194,10 @@ export default class StageRender extends EventEmitter {
   }
 
   public postTmagicRuntimeReady() {
-    this.contentWindow = this.iframe?.contentWindow as RuntimeWindow;
+    this.contentWindow = (this.iframe?.contentWindow as RuntimeWindow | null) ?? null;
+
+    // iframe 尚未就绪时 contentWindow 为空，等 load 后再注入 magic
+    if (!this.contentWindow) return;
 
     this.contentWindow.magic = this.getMagicApi();
 
diff --git a/packages/stage/tests/unit/StageRender.spec.ts b/packages/stage/tests/unit/StageRender.spec.ts
index 722702ee..2a31e4bd 100644
--- a/packages/stage/tests/unit/StageRender.spec.ts
+++ b/packages/stage/tests/unit/StageRender.spec.ts
@@ -154,6 +154,24 @@ describe('StageRender - NATIVE', () => {
     renderer.destroy();
   });
 
+  test('contentWindow 未就绪时 mount 不抛错，就绪后注入 magic', async () => {
+    const host = globalThis.document.createElement('div');
+    globalThis.document.body.appendChild(host);
+    const renderer = new StageRender({ renderType: RenderType.IFRAME, runtimeUrl: '' });
+    await expect(renderer.mount(host)).resolves.toBeUndefined();
+    expect(renderer.contentWindow).toBeNull();
+
+    const postMessage = vi.fn();
+    Object.defineProperty(renderer.iframe!, 'contentWindow', {
+      configurable: true,
+      value: { postMessage, document: globalThis.document },
+    });
+    renderer.postTmagicRuntimeReady();
+    expect(postMessage).toHaveBeenCalledWith({ tmagicRuntimeReady: true }, '*');
+    expect(renderer.contentWindow?.magic).toBeDefined();
+    renderer.destroy();
+  });
+
   test('IFRAME getElementsFromPoint 考虑 iframe 偏移', async () => {
     const host = globalThis.document.createElement('div');
     globalThis.document.body.appendChild(host);