diff --git a/frontend-web/src/App.tsx b/frontend-web/src/App.tsx
index 277f3974..e2c8695c 100644
--- a/frontend-web/src/App.tsx
+++ b/frontend-web/src/App.tsx
@@ -7,6 +7,7 @@ import { QueryClientProvider } from "@/components/query-client-provider";
 import { AuthSyncWatcher } from "@/core/auth/sync";
 import { I18nProvider } from "@/core/i18n/context";
 import { detectLocale } from "@/core/i18n/locale";
+import { resolveForcedThemeForPath } from "@/core/page-layout/chats-iframe-route";
 import { ChatProvider } from "@/contexts/ChatContext";
 import { ThemeProvider } from "@/contexts/ThemeContext";
 
@@ -29,7 +30,7 @@ import { NotFoundPage } from "./pages/NotFoundPage";
 function AppProviders({ children }: { children: React.ReactNode }) {
   const locale = useMemo(() => detectLocale(), []);
   const location = useLocation();
-  const forcedTheme = location.pathname === "/landing" ? "light" : undefined;
+  const forcedTheme = resolveForcedThemeForPath(location.pathname);
 
   return (
     <NextThemesProvider
diff --git a/frontend-web/src/core/page-layout/chats-iframe-route.test.mjs b/frontend-web/src/core/page-layout/chats-iframe-route.test.mjs
new file mode 100644
index 00000000..eefe33b2
--- /dev/null
+++ b/frontend-web/src/core/page-layout/chats-iframe-route.test.mjs
@@ -0,0 +1,33 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  isChatsIframeWorkspacePath,
+  resolveForcedThemeForPath,
+} from "./chats-iframe-route.ts";
+
+test("matches only workspace chats_iframe routes", () => {
+  assert.equal(
+    isChatsIframeWorkspacePath("/page/workspace/chats_iframe/new"),
+    true,
+  );
+  assert.equal(
+    isChatsIframeWorkspacePath("/page/workspace/chats_iframe/thread-123"),
+    true,
+  );
+  assert.equal(isChatsIframeWorkspacePath("/page/workspace/chats/new"), false);
+  assert.equal(isChatsIframeWorkspacePath("/landing"), false);
+});
+
+test("forces light theme for landing and chats_iframe routes only", () => {
+  assert.equal(resolveForcedThemeForPath("/landing"), "light");
+  assert.equal(
+    resolveForcedThemeForPath("/page/workspace/chats_iframe/new"),
+    "light",
+  );
+  assert.equal(
+    resolveForcedThemeForPath("/page/workspace/chats_iframe/thread-123"),
+    "light",
+  );
+  assert.equal(resolveForcedThemeForPath("/page/workspace/chats/new"), undefined);
+});
diff --git a/frontend-web/src/core/page-layout/chats-iframe-route.ts b/frontend-web/src/core/page-layout/chats-iframe-route.ts
new file mode 100644
index 00000000..30c6ba78
--- /dev/null
+++ b/frontend-web/src/core/page-layout/chats-iframe-route.ts
@@ -0,0 +1,16 @@
+export function isChatsIframeWorkspacePath(pathname: string): boolean {
+  return (
+    pathname === "/page/workspace/chats_iframe/new" ||
+    pathname.startsWith("/page/workspace/chats_iframe/")
+  );
+}
+
+export function resolveForcedThemeForPath(
+  pathname: string,
+): "light" | undefined {
+  if (pathname === "/landing" || isChatsIframeWorkspacePath(pathname)) {
+    return "light";
+  }
+
+  return undefined;
+}
diff --git a/frontend-web/src/pages/PageRoutes.tsx b/frontend-web/src/pages/PageRoutes.tsx
index 96400566..1e9b0e43 100644
--- a/frontend-web/src/pages/PageRoutes.tsx
+++ b/frontend-web/src/pages/PageRoutes.tsx
@@ -3,8 +3,10 @@ import { Navigate, Route, Routes } from "react-router-dom";
 
 import { PageSidebar } from "@/components/page-sidebar";
 import { PageSidebarDark } from "@/components/page-sidebar-dark";
+import { isChatsIframeWorkspacePath } from "@/core/page-layout/chats-iframe-route";
 import { readSidebarEnabled } from "@/core/page-layout/sidebar-enabled";
 import { useTheme } from "@/contexts/ThemeContext";
+import { useLocation } from "react-router-dom";
 
 import WorkspaceRoutes from "./WorkspaceRoutes";
 import StrategyRoutes from "./StrategyRoutes";
@@ -16,17 +18,20 @@ import NotebookRoutes from "./NotebookRoutes";
 function PageLayout() {
   const [collapsed, setCollapsed] = useState(false);
   const sidebarEnabled = useMemo(() => readSidebarEnabled(), []);
+  const location = useLocation();
   const { theme } = useTheme();
   const isDark = theme === "dark";
+  const pageSidebarAllowed =
+    sidebarEnabled && !isChatsIframeWorkspacePath(location.pathname);
 
   // h-full(100%)而非 h-screen(100vh):配合 globals.css 的 html/body/#root height:100%
   // 高度链,根布局跟随容器高度。全屏下 100% 解析到视口,与 h-screen 等价;无界等嵌套
   // 下容器不占满整屏时,高度才能正确收缩而非锁死整屏。
   return (
     <div className="h-full flex flex-col bg-muted/20">
-      {sidebarEnabled && <Header collapsed={collapsed} />}
+      {pageSidebarAllowed && <Header collapsed={collapsed} />}
       <div className="flex flex-1 overflow-hidden">
-        {sidebarEnabled && (
+        {pageSidebarAllowed && (
           isDark ? (
             <PageSidebarDark
               collapsed={collapsed}
@@ -41,7 +46,7 @@ function PageLayout() {
         )}
         <main
           className={`flex-1 overflow-hidden ${
-            !sidebarEnabled
+            !pageSidebarAllowed
               ? ""
               : isDark
                 // 深色 sidebar：展开 118px（10 + 98 + 10 gap），收起 = 0 sidebar 完全消失，
@@ -59,9 +64,9 @@ function PageLayout() {
               element={
                 <WorkspaceRoutes
                   pageSidebarCollapsed={collapsed}
-                  pageSidebarHidden={!sidebarEnabled}
-                  headerHidden={!sidebarEnabled}
-                  compactWorkspaceSidebar={sidebarEnabled}
+                  pageSidebarHidden={!pageSidebarAllowed}
+                  headerHidden={!pageSidebarAllowed}
+                  compactWorkspaceSidebar={pageSidebarAllowed}
                   pageSidebarDark={isDark}
                 />
               }
diff --git a/frontend-web/src/pages/WorkspaceRoutes.tsx b/frontend-web/src/pages/WorkspaceRoutes.tsx
index 462b5d5b..bb7df093 100644
--- a/frontend-web/src/pages/WorkspaceRoutes.tsx
+++ b/frontend-web/src/pages/WorkspaceRoutes.tsx
@@ -67,6 +67,7 @@ export function WorkspaceLayout({
   children,
   pageSidebarCollapsed,
   pageSidebarHidden = false,
+  workspaceSidebarHidden = false,
   headerHidden = false,
   compactWorkspaceSidebar = false,
   wrapperOverflowHidden = false,
@@ -76,6 +77,7 @@ export function WorkspaceLayout({
   children: ReactNode;
   pageSidebarCollapsed: boolean;
   pageSidebarHidden?: boolean;
+  workspaceSidebarHidden?: boolean;
   headerHidden?: boolean;
   compactWorkspaceSidebar?: boolean;
   wrapperOverflowHidden?: boolean;
@@ -109,7 +111,9 @@ export function WorkspaceLayout({
       data-page-sidebar-collapsed={pageSidebarCollapsed}
       defaultOpen
     >
-      <WorkspaceSidebar compactChrome={compactWorkspaceSidebar} />
+      {!workspaceSidebarHidden && (
+        <WorkspaceSidebar compactChrome={compactWorkspaceSidebar} />
+      )}
       <SidebarInset
         className={cn('min-w-0', insetOverflowHidden && 'overflow-hidden')}
       >
@@ -205,7 +209,11 @@ export default function WorkspaceRoutes({
         <Route
           path="chats_iframe/new"
           element={
-            <WorkspaceLayout {...layoutProps}>
+            <WorkspaceLayout
+              {...layoutProps}
+              pageSidebarHidden
+              workspaceSidebarHidden
+            >
               <ChatRuntime>
                 <IframeChatPage />
               </ChatRuntime>
@@ -217,6 +225,8 @@ export default function WorkspaceRoutes({
           element={
             <WorkspaceLayout
               {...layoutProps}
+              pageSidebarHidden
+              workspaceSidebarHidden
               wrapperOverflowHidden
               insetOverflowHidden
             >