diff --git a/frontend-web/src/pages/ChatPage.tsx b/frontend-web/src/pages/ChatPage.tsx
index 5df27895..2bec4781 100644
--- a/frontend-web/src/pages/ChatPage.tsx
+++ b/frontend-web/src/pages/ChatPage.tsx
@@ -101,6 +101,11 @@ export default function ChatPage() {
   const router = useRouter();
   const searchParams = useSearchParams();
   const pathname = usePathname();
+  // `chatMode=full` is used by an embedded standard chat. It intentionally
+  // overrides the user's compact-layout preference for this route only, so
+  // the page keeps the full landing composition and its agent/history sidebar.
+  const fullChatMode =
+    searchParams.get("chatMode")?.trim().toLowerCase() === "full";
   const { open: historySidebarOpen, toggleSidebar: toggleHistorySidebar } =
     useSidebar();
   const { t } = useI18n();
@@ -452,7 +457,7 @@ export default function ChatPage() {
   // 主题底图(workspace-chat-bg)不生效。非紧凑（嵌入/standalone）保持原样。
   const layoutMode = effectiveLayoutMode;
   const chromeByPreference =
-    layoutMode === "full"
+    fullChatMode || layoutMode === "full"
       ? true
       : layoutMode === "compact"
         ? false
diff --git a/frontend-web/src/pages/LoginPage.tsx b/frontend-web/src/pages/LoginPage.tsx
index fc7df978..a9bc8fb0 100644
--- a/frontend-web/src/pages/LoginPage.tsx
+++ b/frontend-web/src/pages/LoginPage.tsx
@@ -69,6 +69,7 @@ const DEFAULT_USERNAME = 'guest';
 const IFRAME_LOGIN_SOURCE = 'iframe';
 const DEFAULT_REDIRECT_PATH = '/page/workspace/chats/new';
 const IFRAME_REDIRECT_PATH = '/page/workspace/chats_iframe/new';
+const FULL_CHAT_MODE = 'full';
 
 type LoginStatus = 'loading' | 'success' | 'error';
 
@@ -89,13 +90,28 @@ export default function LoginPage() {
     () => readEmbedParam(searchParams.toString()) === 'on',
     [searchParams],
   );
-  const redirectPath = useMemo(
-    () =>
-      searchParams.get('from') === IFRAME_LOGIN_SOURCE
-        ? IFRAME_REDIRECT_PATH
-        : DEFAULT_REDIRECT_PATH,
+  // External consumers may still send `from=iframe` for the legacy protocol
+  // chat. `chatMode=full` is an explicit escape hatch: always use the regular
+  // full ChatPage instead, which is the route expected by ordinary iframe
+  // nesting and browser deep links.
+  const fullChatRequested = useMemo(
+    () => searchParams.get('chatMode')?.trim().toLowerCase() === FULL_CHAT_MODE,
     [searchParams],
   );
+  const redirectPath = useMemo(
+    () => {
+      // Keep the mode on the destination URL so PageRoutes can retain the
+      // full chat workspace sidebar while hideChrome hides only the global
+      // application chrome.
+      if (fullChatRequested) {
+        return `${DEFAULT_REDIRECT_PATH}?chatMode=${FULL_CHAT_MODE}`;
+      }
+      return searchParams.get('from') === IFRAME_LOGIN_SOURCE
+        ? IFRAME_REDIRECT_PATH
+        : DEFAULT_REDIRECT_PATH;
+    },
+    [fullChatRequested, searchParams],
+  );
   const resolvedUsername = useMemo(() => {
     const raw = username?.trim();
     return raw && raw.length > 0 ? raw : DEFAULT_USERNAME;
diff --git a/frontend-web/src/pages/PageRoutes.tsx b/frontend-web/src/pages/PageRoutes.tsx
index 9616ddb9..146e50af 100644
--- a/frontend-web/src/pages/PageRoutes.tsx
+++ b/frontend-web/src/pages/PageRoutes.tsx
@@ -69,6 +69,19 @@ function PageLayout() {
     () => isHideChromeActive() || readHideChromeParam(location.search) === "on",
     [location.pathname, location.search],
   );
+  // `chatMode=full` is the embed-friendly standard chat view: hide the global
+  // Header/PageSidebar when `hideChrome=1`, but keep WorkspaceSidebar so users
+  // can still pick an agent and access their common agents/history.
+  const fullChatMode = useMemo(() => {
+    const mode = new URLSearchParams(location.search)
+      .get("chatMode")
+      ?.trim()
+      .toLowerCase();
+    return (
+      mode === "full" &&
+      location.pathname.startsWith("/page/workspace/chats/")
+    );
+  }, [location.pathname, location.search]);
   // 「大屏绘制」独立页（/page/strategy/dashboard-agent）本就是「带导航栏 + 侧边栏」的独立页，
   // 但它常被深链「上一步」从去 chrome 的工作区/新标签打开——那里 chromeByPreference 可能为 false
   // （界面模式非全量、或会话级 sidebar 未置位），导致整页没有顶栏/侧栏。故对该路由**强制全局 chrome**
@@ -125,12 +138,17 @@ function PageLayout() {
                 <WorkspaceRoutes
                   pageSidebarCollapsed={collapsed}
                   pageSidebarHidden={!pageSidebarAllowed}
-                  workspaceSidebarHidden={hideChromeActive}
+                  workspaceSidebarHidden={hideChromeActive && !fullChatMode}
                   headerHidden={!pageSidebarAllowed}
-                  compactWorkspaceSidebar={pageSidebarAllowed}
+                  // Full-chat embedding has no global PageSidebar, but it
+                  // still needs the full GeneralQaSidebar (common agents and
+                  // conversation history) inside the workspace.
+                  compactWorkspaceSidebar={pageSidebarAllowed || fullChatMode}
                   compactActionsHidden={hideChromeActive}
                   pageSidebarDark={isDark}
-                  forceWorkspaceSidebarCollapsed={forceCollapsedSidebar}
+                  forceWorkspaceSidebarCollapsed={
+                    forceCollapsedSidebar && !fullChatMode
+                  }
                 />
               }
             />
diff --git a/frontend-web/src/pages/WorkspaceRoutes.tsx b/frontend-web/src/pages/WorkspaceRoutes.tsx
index 778f02fe..6b44be99 100644
--- a/frontend-web/src/pages/WorkspaceRoutes.tsx
+++ b/frontend-web/src/pages/WorkspaceRoutes.tsx
@@ -72,14 +72,6 @@ function NewAgentPageWithKey() {
   return <NewAgentPage key={thread_id} />;
 }
 
-function isInIframe(): boolean {
-  try {
-    return window.self !== window.top;
-  } catch {
-    return true;
-  }
-}
-
 function shouldShowCompactTopActions(pathname: string): boolean {
   return (
     pathname === '/page/workspace/agents' ||
@@ -246,10 +238,13 @@ function NewChatEntryRoute({
     forceWorkspaceSidebarCollapsed: boolean;
   };
 }) {
-  if (isInIframe()) {
-    return <Navigate to="/page/workspace/chats_iframe/new" replace />;
-  }
-
+  // Do not infer the chat experience from window.self !== window.top here.
+  // A generic `/chats/new` deep link must render the same standard chat both
+  // top-level and inside an iframe. The dedicated iframe protocol page remains
+  // available only through its explicit `/chats_iframe/...` route (LoginPage
+  // selects it for `from=iframe`). Otherwise a normal deep link was silently
+  // redirected to IframeChatPage, whose new-thread state intentionally has no
+  // manually selected agent and therefore stopped at "选择 Agent".
   return (
     <WorkspaceLayout {...layoutProps} defaultHistorySidebarOpen>
       <ChatRuntime>