diff --git a/apps/ai-game-creator-shell/src/view/project-development/useProjectResourceCardPreviews.ts b/apps/ai-game-creator-shell/src/view/project-development/useProjectResourceCardPreviews.ts
index bef0eac06..c0d9301aa 100644
--- a/apps/ai-game-creator-shell/src/view/project-development/useProjectResourceCardPreviews.ts
+++ b/apps/ai-game-creator-shell/src/view/project-development/useProjectResourceCardPreviews.ts
@@ -595,10 +595,48 @@ export function useProjectResourceCardPreviews(input: {
     [touchCachedPreview],
   );
 
+  /**
+   * 把当前登记表里的全部卡片元素补挂到 observer 上。
+   *
+   * 注册（`observePreview`）与 observer 的创建分属不同 effect，两者存在时序窗口：
+   * 在 observer 还没建好时注册的卡只能靠 observer effect 里的一次性补挂兜住，
+   * 一旦那个补挂发生在注册之前、或 observer 之后被重建，卡就会**停留在登记表里
+   * 却从未被观察** —— 它永不触发可见性回调，也就永远停在 `idle`，卡面只剩占位图标。
+   * 所以每次 observer 就绪或重建后都要按登记表重新补挂一遍。
+   */
+  const attachObservedCards = useCallback(() => {
+    const observer = observerRef.current;
+    if (!observer) {
+      return;
+    }
+    for (const element of observedCardsRef.current.keys()) {
+      observer.observe(element);
+    }
+  }, []);
+
+  /**
+   * 创建 observer 时的 root，用来判断它是否变了。
+   *
+   * `null` 有特殊含义：**还没有可用的 root**。注册比本 effect 先跑，所以第一轮这里
+   * 拿到 null 是正常时序，此时不能建 observer。
+   */
+  const observerRootRef = useRef<HTMLElement | null>(null);
+  const [rootEpoch, setRootEpoch] = useState(0);
+
   const observePreview = useCallback(
     (element: HTMLElement, resource: ProjectResource, identity: string) => {
       const binding = { resource, identity };
       observedCardsRef.current.set(element, binding);
+      if (!observerRef.current) {
+        // 卡片一定渲染在资源画本容器内部，所以「有卡片注册」本身就是「root 已就绪」
+        // 的信号。observer 还没建好时用它触发一次重建，避免卡死在未观察状态。
+        // 在测试等没有 IntersectionObserver 的环境里保持静默，不制造多余渲染。
+        const root =
+          input.intersectionRootRef?.current ?? input.canvasRef.current;
+        if (root && window.IntersectionObserver) {
+          setRootEpoch((epoch) => epoch + 1);
+        }
+      }
       observerRef.current?.observe(element);
       return () => {
         observerRef.current?.unobserve(element);
@@ -607,7 +645,7 @@ export function useProjectResourceCardPreviews(input: {
         }
       };
     },
-    [],
+    [input.canvasRef, input.intersectionRootRef],
   );
 
   const failPreview = useCallback(
@@ -755,6 +793,21 @@ export function useProjectResourceCardPreviews(input: {
     if (!IntersectionObserverClass) {
       return undefined;
     }
+    // root 是资源画本容器；它由被观察卡片所在的那棵子树持有。如果这里为 null，
+    // 浏览器会退回按视口判定，而真正裁剪卡片的是画本容器 —— 被祖先裁掉的卡片
+    // 会永远报「不可见」，可见性门禁再也不会放行它们。此时**不建 observer**，
+    // 等卡片注册触发的 `rootEpoch` 让本 effect 重跑再建；期间 `attachObservedCards`
+    // 会把登记表里的卡一次性补挂齐，避免"登记了却没被观察"。
+    const root = input.intersectionRootRef?.current ?? input.canvasRef.current;
+    if (!root) {
+      return undefined;
+    }
+    if (observerRef.current && observerRootRef.current === root) {
+      // root 没变且 observer 已在：只补挂新注册的卡，不做无谓重建。
+      attachObservedCards();
+      return undefined;
+    }
+    observerRef.current?.disconnect();
     const observer = new IntersectionObserverClass(
       (entries) => {
         for (const entry of entries) {
@@ -770,21 +823,30 @@ export function useProjectResourceCardPreviews(input: {
         }
       },
       {
-        root: input.intersectionRootRef?.current ?? input.canvasRef.current,
+        root,
         rootMargin: '160px',
       },
     );
     observerRef.current = observer;
-    for (const element of observedCardsRef.current.keys()) {
-      observer.observe(element);
-    }
+    observerRootRef.current = root;
+    attachObservedCards();
     return () => {
       observer.disconnect();
       if (observerRef.current === observer) {
         observerRef.current = null;
       }
+      if (observerRootRef.current === root) {
+        observerRootRef.current = null;
+      }
     };
-  }, [input.canvasRef, input.intersectionRootRef, requestPreview, scopeKey]);
+  }, [
+    attachObservedCards,
+    input.canvasRef,
+    input.intersectionRootRef,
+    requestPreview,
+    rootEpoch,
+    scopeKey,
+  ]);
 
   return {
     identityByResourceId,
diff --git a/apps/ai-game-creator-shell/tests/useProjectResourceCardPreviews.test.ts b/apps/ai-game-creator-shell/tests/useProjectResourceCardPreviews.test.ts
index 7b20d89f3..adf84f209 100644
--- a/apps/ai-game-creator-shell/tests/useProjectResourceCardPreviews.test.ts
+++ b/apps/ai-game-creator-shell/tests/useProjectResourceCardPreviews.test.ts
@@ -986,4 +986,352 @@ describe('useProjectResourceCardPreviews', () => {
       }
     }
   });
+
+  /**
+   * 可见性门禁的时机契约：observer 必须**等 root 真正就绪**才建，且建好后要把
+   * 登记表里的卡一次性补挂齐。
+   *
+   * 背景：root 是资源画本容器（卡片渲染在它内部）。若在 root 还是 null 时就建 observer，
+   * 浏览器会退回按视口判定，被画本容器裁掉的卡片永远报「不可见」，可见性门禁再也不放行，
+   * 卡片就停在 `idle`、卡面只剩占位图标 —— 真机现场出现的正是「同一屏里 idle 与 loaded 交错」。
+   */
+  describe('可见性门禁的 root 时机契约', () => {
+    type ObserverHarness = {
+      callbacks: IntersectionObserverCallback[];
+      roots: (Element | Document | null)[];
+      observed: Set<Element>;
+      restore: () => void;
+    };
+
+    function installIntersectionObserver(): ObserverHarness {
+      const callbacks: IntersectionObserverCallback[] = [];
+      const roots: (Element | Document | null)[] = [];
+      const observed = new Set<Element>();
+      const original = Object.getOwnPropertyDescriptor(
+        window,
+        'IntersectionObserver',
+      );
+      class TestIntersectionObserver {
+        readonly root = null;
+        readonly rootMargin = '160px';
+        readonly thresholds = [0];
+
+        constructor(
+          callback: IntersectionObserverCallback,
+          options?: IntersectionObserverInit,
+        ) {
+          callbacks.push(callback);
+          roots.push(options?.root ?? null);
+        }
+
+        observe(element: Element) {
+          observed.add(element);
+        }
+
+        unobserve(element: Element) {
+          observed.delete(element);
+        }
+
+        disconnect() {
+          observed.clear();
+        }
+
+        takeRecords() {
+          return [];
+        }
+      }
+      Object.defineProperty(window, 'IntersectionObserver', {
+        configurable: true,
+        writable: true,
+        value: TestIntersectionObserver,
+      });
+      return {
+        callbacks,
+        roots,
+        observed,
+        restore: () => {
+          if (original) {
+            Object.defineProperty(window, 'IntersectionObserver', original);
+          } else {
+            Reflect.deleteProperty(window, 'IntersectionObserver');
+          }
+        },
+      };
+    }
+
+    function fireVisible(harness: ObserverHarness, targets: Iterable<Element>) {
+      act(() => {
+        harness.callbacks.at(-1)!(
+          [...targets].map(
+            (target) =>
+              ({
+                target,
+                isIntersecting: true,
+                intersectionRatio: 1,
+              }) as IntersectionObserverEntry,
+          ),
+          {} as IntersectionObserver,
+        );
+      });
+    }
+
+    it('waits for a real root, then observes and loads the cards', async () => {
+      const art = resource('late-root-art');
+      const invoke = vi.fn(
+        async (_command: string, args?: Record<string, unknown>) =>
+          preview(String(args?.relativePath ?? art.path)),
+      );
+      window.__TAURI__ = { core: { invoke } };
+      // root 在首次渲染时还没有挂上（等价于画本容器尚未就绪）。
+      const canvasRef: { current: HTMLDivElement | null } = { current: null };
+      const harness = installIntersectionObserver();
+
+      try {
+        const { result } = renderHook(() =>
+          useProjectResourceCardPreviews({
+            projectPath: '/tmp/preview-late-root',
+            projectId: 'preview-late-root',
+            mode: 'dependency',
+            resources: [art],
+            canvasRef,
+            // 关掉热预取，逼这张卡只能靠可见性放行。
+            eagerPreviewLimit: 0,
+          }),
+        );
+        const identity = result.current.identityByResourceId.get(art.id)!;
+
+        // root 还没就绪时不得建 observer —— 否则会按视口判定，被容器裁掉的卡永远不可见。
+        expect(harness.callbacks).toHaveLength(0);
+
+        const root = document.createElement('div');
+        const card = document.createElement('div');
+        root.append(card);
+        canvasRef.current = root;
+        let unregister: () => void = () => undefined;
+        act(() => {
+          unregister = result.current.observePreview(card, art, identity);
+        });
+
+        // 注册本身就是「root 已就绪」的信号：observer 必须以真正的 root 建出来。
+        await waitFor(() =>
+          expect(harness.callbacks.length).toBeGreaterThan(0),
+        );
+        expect(harness.roots.at(-1)).toBe(root);
+        expect(harness.observed.has(card)).toBe(true);
+        expect(result.current.previews.get(identity)).toBeUndefined();
+
+        fireVisible(harness, [card]);
+
+        await waitFor(() =>
+          expect(result.current.previews.get(identity)?.status).toBe('loaded'),
+        );
+        unregister();
+      } finally {
+        harness.restore();
+      }
+    });
+
+    it('re-observes cards registered before the observer existed', async () => {
+      const resources = Array.from({ length: 3 }, (_, index) =>
+        resource(`early-register-${index + 1}`),
+      );
+      const invoke = vi.fn(
+        async (_command: string, args?: Record<string, unknown>) =>
+          preview(String(args?.relativePath ?? '')),
+      );
+      window.__TAURI__ = { core: { invoke } };
+      const canvasRef: { current: HTMLDivElement | null } = { current: null };
+      const harness = installIntersectionObserver();
+
+      try {
+        const { result } = renderHook(() =>
+          useProjectResourceCardPreviews({
+            projectPath: '/tmp/preview-early-register',
+            projectId: 'preview-early-register',
+            mode: 'dependency',
+            resources,
+            canvasRef,
+            eagerPreviewLimit: 0,
+          }),
+        );
+
+        const root = document.createElement('div');
+        canvasRef.current = root;
+        const elements = resources.map(() => document.createElement('div'));
+        act(() => {
+          resources.forEach((item, index) => {
+            result.current.observePreview(
+              elements[index]!,
+              item,
+              result.current.identityByResourceId.get(item.id)!,
+            );
+          });
+        });
+
+        // 登记与建 observer 的先后顺序无关：建好之后登记表里的每一张都必须被挂上。
+        await waitFor(() =>
+          expect(harness.observed.size).toBe(elements.length),
+        );
+        for (const element of elements) {
+          expect(harness.observed.has(element)).toBe(true);
+        }
+
+        fireVisible(harness, elements);
+
+        await waitFor(() => {
+          for (const item of resources) {
+            const identity = result.current.identityByResourceId.get(item.id)!;
+            expect(result.current.previews.get(identity)?.status).toBe(
+              'loaded',
+            );
+          }
+        });
+      } finally {
+        harness.restore();
+      }
+    });
+  });
+
+  it('does not leave a visible card idle when it is outside the eager window', async () => {
+    // 真机现场：同一屏里 idle 与 loaded 交错，idle 的那批从未入队。
+    // 热预取只覆盖前 12 张，其余全部依赖可见性门禁 —— 所以这里必须证明
+    // 「注册进 observer 的卡，在回调报可见后会真的进入队列」，而不是停在 idle。
+    const resources = Array.from({ length: 20 }, (_, index) =>
+      resource(`visibility-${index + 1}`),
+    );
+    const invoke = vi.fn(
+      async (_command: string, args?: Record<string, unknown>) =>
+        preview(String(args?.relativePath ?? '')),
+    );
+    window.__TAURI__ = { core: { invoke } };
+    const canvasRef = { current: document.createElement('div') };
+
+    const callbacks: IntersectionObserverCallback[] = [];
+    const roots: (Element | Document | null)[] = [];
+    const observed = new Set<Element>();
+    const originalIntersectionObserver = Object.getOwnPropertyDescriptor(
+      window,
+      'IntersectionObserver',
+    );
+    class TestIntersectionObserver {
+      readonly root = null;
+      readonly rootMargin = '160px';
+      readonly thresholds = [0];
+
+      constructor(
+        callback: IntersectionObserverCallback,
+        options?: IntersectionObserverInit,
+      ) {
+        callbacks.push(callback);
+        roots.push(options?.root ?? null);
+      }
+
+      observe(element: Element) {
+        observed.add(element);
+      }
+
+      unobserve(element: Element) {
+        observed.delete(element);
+      }
+
+      disconnect() {
+        observed.clear();
+      }
+
+      takeRecords() {
+        return [];
+      }
+    }
+    Object.defineProperty(window, 'IntersectionObserver', {
+      configurable: true,
+      writable: true,
+      value: TestIntersectionObserver,
+    });
+
+    try {
+      const { result } = renderHook(() =>
+        useProjectResourceCardPreviews({
+          projectPath: '/tmp/preview-visibility',
+          projectId: 'preview-visibility',
+          mode: 'dependency',
+          resources,
+          canvasRef,
+          // 热预取只覆盖前 12 张：第 13 张起完全依赖可见性门禁。
+          eagerPreviewLimit: 12,
+        }),
+      );
+
+      // 模拟卡片挂载后的注册：按计划顺序，前 12 张已进热预取窗口，
+      // 从第 13 张起是「只能靠可见性放行」的那批。
+      const unregister: Array<() => void> = [];
+      act(() => {
+        for (const item of resources.slice(12)) {
+          const element = document.createElement('div');
+          const identity = result.current.identityByResourceId.get(item.id)!;
+          unregister.push(
+            result.current.observePreview(element, item, identity),
+          );
+        }
+      });
+
+      // 注册的每个元素都必须真的进了 observer：漏 observe 的卡永远不会被放行。
+      expect(observed.size).toBe(unregister.length);
+      expect(roots.at(-1)).toBe(canvasRef.current);
+
+      await waitFor(() =>
+        expect(
+          result.current.previews.get(
+            result.current.identityByResourceId.get(resources[0]!.id)!,
+          )?.status,
+        ).toBe('loaded'),
+      );
+
+      // 报可见之前，未进热预取窗口的卡应仍是「从未请求」。
+      const registerOrder: Array<[ProjectResource, string]> = resources
+        .slice(12)
+        .map((item) => [
+          item,
+          result.current.identityByResourceId.get(item.id)!,
+        ]);
+      for (const [, identity] of registerOrder) {
+        expect(result.current.previews.get(identity)?.status).toBeUndefined();
+      }
+
+      act(() => {
+        callbacks.at(-1)!(
+          [...observed].map(
+            (target) =>
+              ({
+                target,
+                isIntersecting: true,
+                intersectionRatio: 1,
+              }) as IntersectionObserverEntry,
+          ),
+          {} as IntersectionObserver,
+        );
+      });
+
+      await waitFor(() => {
+        for (const [, identity] of registerOrder) {
+          expect(result.current.previews.get(identity)?.status).toBe('loaded');
+        }
+      });
+      // 契约：可见卡不得停在 idle —— 每张注册过的卡都要落成 loaded。
+      expect(
+        registerOrder.filter(
+          ([, identity]) => result.current.previews.get(identity) === undefined,
+        ),
+      ).toEqual([]);
+    } finally {
+      if (originalIntersectionObserver) {
+        Object.defineProperty(
+          window,
+          'IntersectionObserver',
+          originalIntersectionObserver,
+        );
+      } else {
+        Reflect.deleteProperty(window, 'IntersectionObserver');
+      }
+    }
+  });
 });