diff --git a/frontend-web/src/components/workspace/appearance-controls.tsx b/frontend-web/src/components/workspace/appearance-controls.tsx
index 8decbe91..02efa7c8 100644
--- a/frontend-web/src/components/workspace/appearance-controls.tsx
+++ b/frontend-web/src/components/workspace/appearance-controls.tsx
@@ -126,13 +126,21 @@ const LAYOUT_OPTIONS = [
 ];
 
 /**
- * 界面模式（全量 / 简洁）下拉切换。简洁模式下全局顶栏被隐藏，故把外观设置里的
- * 「界面模式」切换也搬到页面级顶栏右上角，图标 + 下拉，与换肤并排。
+ * 界面模式（全量 / 简洁）下拉切换。换肤旁并排，图标 + 下拉：
+ *   - 简洁模式 ChatPage 顶栏（全局顶栏被隐藏）。
+ *   - 全量模式 Header 右上角。
+ * 用户未显式设置过界面模式时（mode === undefined），当前态按调用方所在的实际界面
+ * 兜底——`fallback` 指明这一回退值（Header 传 "full"，ChatPage 传 "compact"）。
  */
-export function LayoutModeSwitcher({ tone }: { tone: AppearanceControlTone }) {
+export function LayoutModeSwitcher({
+  tone,
+  fallback = "compact",
+}: {
+  tone: AppearanceControlTone;
+  fallback?: "full" | "compact";
+}) {
   const [mode, setLayoutMode] = useLayoutMode();
-  // 未显式设置过时简洁模式才会渲染本控件（全量模式有全局顶栏），故当前态按 compact 兜底。
-  const current = mode === "full" ? "full" : "compact";
+  const current = mode ?? fallback;
   const TriggerIcon = current === "full" ? PanelLeftIcon : LayoutIcon;
 
   return (
diff --git a/frontend-web/src/strategy-components/Header.tsx b/frontend-web/src/strategy-components/Header.tsx
index 57d7480e..0bcb8334 100644
--- a/frontend-web/src/strategy-components/Header.tsx
+++ b/frontend-web/src/strategy-components/Header.tsx
@@ -4,7 +4,7 @@ import { useLocation, useNavigate } from "react-router-dom";
 
 import { Button } from "@/components/ui/button";
 import "@/components/page-sdebar.css";
-import { ThemeSwitcher } from "@/components/workspace/appearance-controls";
+import { LayoutModeSwitcher, ThemeSwitcher } from "@/components/workspace/appearance-controls";
 import { NotificationDialog } from "@/components/workspace/notification-dialog";
 import { getStoredAuth, getAccountDisplayName } from "@/core/auth";
 import { isWujieEnv } from "@/core/embed/wujie";
@@ -126,6 +126,11 @@ const Header = ({ collapsed }: HeaderProps) => {
     <>
       <ThemeSwitcher tone={isDark ? "banner-dark" : "banner-light"} />
 
+      <LayoutModeSwitcher
+        tone={isDark ? "banner-dark" : "banner-light"}
+        fallback="full"
+      />
+
       <Button
         type="button"
         variant="ghost"