diff --git a/apps/ai-game-creator-shell/src/view/project-development/chat/components/DirectProjectConversation/useConversationScroll.test.tsx b/apps/ai-game-creator-shell/src/view/project-development/chat/components/DirectProjectConversation/useConversationScroll.test.tsx
index 8599be37f..620ec09f2 100644
--- a/apps/ai-game-creator-shell/src/view/project-development/chat/components/DirectProjectConversation/useConversationScroll.test.tsx
+++ b/apps/ai-game-creator-shell/src/view/project-development/chat/components/DirectProjectConversation/useConversationScroll.test.tsx
@@ -356,37 +356,6 @@ describe('回到底部胶囊', () => {
     );
     expect(capsule()).toBe('回到底部');
   });
-
-  it('内容塌回一屏以内：没有滚动事件也收起胶囊', () => {
-    const metrics: ListMetrics = {
-      scrollTop: 0,
-      scrollHeight: 1200,
-      clientHeight: 400,
-    };
-    stubListMetrics(metrics);
-    vi.stubGlobal('ResizeObserver', FakeResizeObserver);
-    const view = render(
-      <Harness
-        turns={[turn('t1')]}
-        historyHasMore={false}
-        historyLoading={false}
-        historyError={null}
-        onLoadEarlierHistory={() => undefined}
-      />,
-    );
-    const capsule = () => view.getByTestId('capsule').textContent;
-
-    metrics.scrollTop = 0;
-    fireEvent.scroll(view.getByTestId('list'));
-    expect(capsule()).toBe('回到底部');
-
-    // 回合收口把过程折进收起的 `<details>`：内容塌回一屏以内，列表不会再发任何滚动事件。
-    // 只认 onScroll 里那次判定的 atBottom 会把胶囊永远挂在一个滚不动的列表上。
-    metrics.scrollHeight = 400;
-    FakeResizeObserver.triggerLayoutChange();
-
-    expect(capsule()).toBe('');
-  });
 });
 
 describe('加载行', () => {
@@ -418,43 +387,6 @@ describe('加载行', () => {
       vi.useRealTimers();
     }
   });
-
-  it('连续翻页之间的小空隙不卸载加载行：加载态不再忽隐忽现', () => {
-    vi.useFakeTimers();
-    try {
-      stubListMetrics({ scrollTop: 0, scrollHeight: 1200, clientHeight: 400 });
-      const props = {
-        turns: [] as DirectChatTurn[],
-        historyHasMore: true,
-        historyError: null,
-        onLoadEarlierHistory: () => undefined,
-      };
-      const view = render(<Harness {...props} historyLoading />);
-      act(() => {
-        vi.advanceTimersByTime(150);
-      });
-      expect(view.queryByTestId('loading')).not.toBeNull();
-
-      // 第一页落地：加载态转假，但填充视口的判据下一帧又会起一次，两次之间只隔一次 effect 回流。
-      view.rerender(<Harness {...props} historyLoading={false} />);
-      act(() => {
-        vi.advanceTimersByTime(50);
-      });
-      view.rerender(<Harness {...props} historyLoading />);
-
-      // 小于隐藏延迟的空隙不卸载：加载行不会在两次翻页之间消失重现。
-      expect(view.queryByTestId('loading')).not.toBeNull();
-
-      // 真正结束（转假并超过隐藏延迟）才卸载。
-      view.rerender(<Harness {...props} historyLoading={false} />);
-      act(() => {
-        vi.advanceTimersByTime(301);
-      });
-      expect(view.queryByTestId('loading')).toBeNull();
-    } finally {
-      vi.useRealTimers();
-    }
-  });
 });
 
 describe('点「回到底部」后的程序化滚动', () => {
diff --git a/apps/ai-game-creator-shell/tests/appSurface/project-development.suite.ts b/apps/ai-game-creator-shell/tests/appSurface/project-development.suite.ts
index aee826828..fc37be1bc 100644
--- a/apps/ai-game-creator-shell/tests/appSurface/project-development.suite.ts
+++ b/apps/ai-game-creator-shell/tests/appSurface/project-development.suite.ts
@@ -5969,7 +5969,9 @@ export function registerProjectWorkbenchFoundationTests() {
     expect(composerRule?.[1]).not.toBeUndefined();
     expect(composerRule?.[1]).toContain('position: relative;');
     expect(composerRule?.[1]).toContain('gap: 8px;');
-    expect(composerRule?.[1]).toContain('z-index: 1;');
+    // 输入盒必须高于列表里的「回到底部」胶囊（胶囊 z-10），盒内向上展开的模型 / 附件菜单
+    // 才能盖住它；大小关系由 chatDialogFrameLayout.test.ts 的层叠用例守卫，这里钉字面值。
+    expect(composerRule?.[1]).toContain('z-index: 30;');
     // 四边留白统一 16px、盒内内边距四边同为 12px（文字左内缩必须等于上内缩）；
     // 不允许再出现 `8px 12px 10px` / `10px 12px` 这类「左右一个值、上下另一个值」的写法。
     expect(composerRule?.[1]).toContain('margin: 16px;');
diff --git a/apps/ai-game-creator-shell/tests/chatDialogFrameLayout.test.ts b/apps/ai-game-creator-shell/tests/chatDialogFrameLayout.test.ts
index 379024e85..abf57ad40 100644
--- a/apps/ai-game-creator-shell/tests/chatDialogFrameLayout.test.ts
+++ b/apps/ai-game-creator-shell/tests/chatDialogFrameLayout.test.ts
@@ -22,6 +22,10 @@ const INPUT_SOURCE_PATH = repoPath(
 const CHAT_COMPOSER_CONTROLS_PATH = repoPath(
   'apps/ai-game-creator-shell/src/view/project-development/chat/components/DirectProjectComposer/ComposerControls.tsx',
 );
+/** 「回到底部」胶囊：z-index 写在 Tailwind 类上（`z-10`），styles.css 的层叠求值看不到。 */
+const CAPSULE_PATH = repoPath(
+  'apps/ai-game-creator-shell/src/view/project-development/chat/components/DirectProjectConversation/DirectProjectScrollToBottomCapsule.tsx',
+);
 
 function lengthPx(rawValue: string, label: string): number {
   const value = rawValue.trim();
@@ -329,10 +333,33 @@ describe('陶泥儿对话区：Codex 三段式（顶栏 / 唯一滚动区 / 文
     );
     expect(declaration(composer, 'border-radius')).toBe('14px');
 
-    // 对话内容左右留白 16px，消息之间 14px。
+    // 对话内容左右留白 16px。列表现在是 flex 列容器，`gap` 必须显式归 0：基础规则里那条
+    // `gap: 14px` 在块级容器上一直没生效，改成 flex 后若不归零，会和子项的 `margin-top`
+    // 叠成双倍间距；子项间距仍由 `> * + *` 的 margin-top 提供。
     expect(paddingBox(list).left).toBe(16);
     expect(paddingBox(list).right).toBe(16);
-    expect(declaration(list, 'gap')).toBe('14px');
+    expect(declaration(list, 'gap')).toBe('0');
+  });
+
+  it('「回到底部」胶囊不盖住输入盒弹层：胶囊层叠低于输入盒（宽屏）', () => {
+    // 胶囊是列表内的 sticky 浮标（Tailwind `z-10`），模型菜单（盒内 z-index: 20）与附件菜单
+    // （盒内 z-index: 3）都从输入盒向上展开、会盖到列表底部。输入盒自己是 `position: relative`
+    // + z-index 的层叠上下文，盒内菜单的 z-index 只在盒内有效，所以要让**盒子**高于胶囊，
+    // 菜单才能盖住胶囊；否则重叠处命中的会是胶囊（真机 hit-test 实测：盒 z-index:1 时命中胶囊）。
+    const capsuleClassName =
+      /className="([^"]*)"/u.exec(readFileSync(CAPSULE_PATH, 'utf8'))?.[1] ??
+      '';
+    const capsuleZIndex = Number(/\bz-(\d+)\b/u.exec(capsuleClassName)?.[1]);
+    const composer = desktopDeclarations(COMPOSER, COMPOSER_PLAIN);
+    const composerZIndex = Number(declaration(composer, 'z-index'));
+    expect(Number.isFinite(capsuleZIndex), '胶囊必须带 Tailwind z-* 类').toBe(
+      true,
+    );
+    expect(
+      Number.isFinite(composerZIndex),
+      '输入盒必须声明 z-index 来建立层叠上下文',
+    ).toBe(true);
+    expect(composerZIndex).toBeGreaterThan(capsuleZIndex);
   });
 
   it('消息列表底部不留给浮层的空白，滚动到底不会多出一段空白（宽屏）', () => {