diff --git a/apps/ai-game-creator-shell/src/styles.css b/apps/ai-game-creator-shell/src/styles.css
index 05f24f2c9..af78f75d4 100644
--- a/apps/ai-game-creator-shell/src/styles.css
+++ b/apps/ai-game-creator-shell/src/styles.css
@@ -12861,7 +12861,13 @@ button.design-workspace-tree__entry:hover,
   right: 0;
   bottom: 0;
   left: 0;
-  z-index: 240;
+  /*
+   * 必须低于二级浮层：这里点「运行配置」打开的是既有 `.settings-overlay`
+   * （z-index 220），插件面板 `.agc-plugin-panel-overlay` 为 230。
+   * 设置浮层若压在最上层，二级弹窗就会盖在它下面；210 仍高于工作台内容
+   * 与启动器（200），同时让运行配置 / 插件面板正常叠在其上。
+   */
+  z-index: 210;
   display: grid;
   padding: 20px;
   background: rgb(65 43 34 / 42%);
diff --git a/apps/ai-game-creator-shell/tests/windowChromeOverlayContract.test.ts b/apps/ai-game-creator-shell/tests/windowChromeOverlayContract.test.ts
index b9bbb16d9..2369c472c 100644
--- a/apps/ai-game-creator-shell/tests/windowChromeOverlayContract.test.ts
+++ b/apps/ai-game-creator-shell/tests/windowChromeOverlayContract.test.ts
@@ -50,4 +50,19 @@ describe('窗口标题栏与全屏弹层的层叠约定', () => {
       `${selector} 必须声明 top: var(--window-chrome-height)`,
     ).toBe('var(--window-chrome-height)');
   });
+
+  it('从「对话设置」打开的二级弹窗叠在设置浮层之上', () => {
+    const zIndexOf = (selector: string) => {
+      const raw = declarationsForSelector(css, selector).get('z-index');
+      expect(raw, `${selector} 必须声明 z-index`).toBeDefined();
+      return Number(raw);
+    };
+    const settingsZIndex = zIndexOf('.project-chat-settings-backdrop');
+    const runtimeConfigZIndex = zIndexOf('.settings-overlay');
+    const pluginPanelZIndex = zIndexOf('.agc-plugin-panel-overlay');
+    // 对话设置里点「运行配置」会就地打开 `.settings-overlay`，插件面板又从
+    // 运行配置里打开；三层必须严格递增，否则后开的会盖在上一层下面。
+    expect(runtimeConfigZIndex).toBeGreaterThan(settingsZIndex);
+    expect(pluginPanelZIndex).toBeGreaterThan(runtimeConfigZIndex);
+  });
 });