diff --git a/src/components/chat/GlobalChatbox.test.tsx b/src/components/chat/GlobalChatbox.test.tsx
new file mode 100644
index 0000000..235eac9
--- /dev/null
+++ b/src/components/chat/GlobalChatbox.test.tsx
@@ -0,0 +1,124 @@
+import "@testing-library/jest-dom";
+import React from "react";
+import { act, render, screen } from "@testing-library/react";
+
+import { GlobalChatbox } from "./GlobalChatbox";
+
+const createSession = jest.fn();
+let mockCurrentProjectId = "project-1";
+
+jest.mock("@refinedev/core", () => ({
+  useNotification: () => ({ open: jest.fn() }),
+}));
+
+jest.mock("@/lib/chatModels", () => ({
+  fetchAgentModels: jest.fn(() => new Promise(() => {})),
+}));
+
+jest.mock("@/store/projectStore", () => ({
+  useProjectStore: (selector: (state: { currentProjectId: string }) => unknown) =>
+    selector({ currentProjectId: mockCurrentProjectId }),
+}));
+
+jest.mock("./globalChatboxVoice", () => ({
+  useSpeechSynthesis: () => ({
+    speechState: "idle",
+    speakingMessageId: null,
+    speak: jest.fn(),
+    pause: jest.fn(),
+    resume: jest.fn(),
+    stop: jest.fn(),
+    isSupported: true,
+  }),
+  useSpeechRecognition: () => ({
+    isListening: false,
+    start: jest.fn(),
+    stop: jest.fn(),
+    isSupported: true,
+  }),
+}));
+
+jest.mock("./hooks/useAgentToolActions", () => ({
+  useAgentToolActions: () => jest.fn(),
+}));
+
+jest.mock("./hooks/useAgentChatSession", () => ({
+  useAgentChatSession: () => ({
+    messages: [],
+    chatSessions: [],
+    activeSessionId: undefined,
+    isHydrating: false,
+    loadingSessionId: null,
+    isStreaming: false,
+    sessionTitle: "新会话",
+    sendPrompt: jest.fn(),
+    createBranch: jest.fn(),
+    abort: jest.fn(),
+    replyPermission: jest.fn(),
+    replyQuestion: jest.fn(),
+    rejectQuestion: jest.fn(),
+    createSession,
+    renameSession: jest.fn(),
+    removeSession: jest.fn(),
+    switchSession: jest.fn(),
+  }),
+}));
+
+jest.mock("./AgentHeader", () => ({
+  AgentHeader: () => <div>Agent header</div>,
+}));
+
+jest.mock("./AgentHistoryPanel", () => ({
+  AgentHistoryPanel: () => <div>History</div>,
+}));
+
+jest.mock("./AgentWorkspace", () => ({
+  AgentWorkspace: () => <div data-testid="agent-workspace">Workspace</div>,
+}));
+
+jest.mock("./AgentComposer", () => ({
+  AgentComposer: React.forwardRef(function MockAgentComposer() {
+    return <div>Composer</div>;
+  }),
+}));
+
+jest.mock("./GlobalChatboxParts", () => ({
+  Blob: () => null,
+}));
+
+describe("GlobalChatbox lifecycle", () => {
+  beforeEach(() => {
+    jest.useFakeTimers();
+    createSession.mockClear();
+    mockCurrentProjectId = "project-1";
+  });
+
+  afterEach(() => {
+    jest.runOnlyPendingTimers();
+    jest.useRealTimers();
+  });
+
+  it("keeps content mounted and preserves the session across close and reopen", async () => {
+    const { rerender } = render(<GlobalChatbox open onClose={jest.fn()} />);
+
+    act(() => jest.runOnlyPendingTimers());
+    expect(createSession).toHaveBeenCalledTimes(1);
+    expect(screen.getByTestId("agent-workspace")).toBeInTheDocument();
+
+    rerender(<GlobalChatbox open={false} onClose={jest.fn()} />);
+    act(() => jest.advanceTimersByTime(300));
+
+    expect(screen.getByTestId("agent-workspace")).toBeInTheDocument();
+
+    rerender(<GlobalChatbox open onClose={jest.fn()} />);
+    act(() => jest.runOnlyPendingTimers());
+
+    expect(createSession).toHaveBeenCalledTimes(1);
+
+    mockCurrentProjectId = "project-2";
+    rerender(<GlobalChatbox open onClose={jest.fn()} />);
+    act(() => jest.runOnlyPendingTimers());
+
+    expect(createSession).toHaveBeenCalledTimes(2);
+  });
+});
diff --git a/src/components/chat/GlobalChatbox.tsx b/src/components/chat/GlobalChatbox.tsx
index eeaae1c..6c0e51f 100644
--- a/src/components/chat/GlobalChatbox.tsx
+++ b/src/components/chat/GlobalChatbox.tsx
@@ -42,7 +42,7 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
   const isNearBottomRef = useRef(true);
   const streamingScrollFrameRef = useRef<number | null>(null);
   const composerRef = useRef<AgentComposerHandle | null>(null);
-  const hasResetForOpenRef = useRef(false);
+  const initializedProjectIdRef = useRef<string | null | undefined>(undefined);
   const theme = useTheme();
   const { open: openNotification } = useNotification();
   const currentProjectId = useProjectStore((state) => state.currentProjectId);
@@ -154,6 +154,17 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
     isNearBottomRef.current = isNearBottom;
   }, []);
 
+  const resetConversationView = useCallback(() => {
+    composerRef.current?.clear();
+    setIsHistoryOpen(false);
+    window.setTimeout(() => {
+      composerRef.current?.focus();
+      isNearBottomRef.current = true;
+      cancelStreamingScroll();
+      scrollToBottom("auto");
+    }, 0);
+  }, [cancelStreamingScroll, scrollToBottom]);
+
   useEffect(() => {
     if (isStreaming) {
       if (!isNearBottomRef.current) return;
@@ -178,24 +189,18 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
   );
 
   useEffect(() => {
-    if (!open) {
-      hasResetForOpenRef.current = false;
+    if (
+      !open ||
+      isHydrating ||
+      initializedProjectIdRef.current === currentProjectId
+    ) {
       return;
     }
-    if (hasResetForOpenRef.current || isHydrating) return;
-    hasResetForOpenRef.current = true;
 
-    const timer = window.setTimeout(() => {
-      createSession();
-      composerRef.current?.clear();
-      setIsHistoryOpen(false);
-      composerRef.current?.focus();
-      isNearBottomRef.current = true;
-      cancelStreamingScroll();
-      scrollToBottom("auto");
-    }, 0);
-    return () => window.clearTimeout(timer);
-  }, [cancelStreamingScroll, createSession, isHydrating, open, scrollToBottom]);
+    initializedProjectIdRef.current = currentProjectId;
+    createSession();
+    resetConversationView();
+  }, [createSession, currentProjectId, isHydrating, open, resetConversationView]);
 
   const handleSend = useCallback(async (prompt: string) => {
     if (isStreaming || isCheckingAuth) return;
@@ -230,14 +235,8 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
     handleStopSpeech();
     stopListening();
     createSession();
-    composerRef.current?.clear();
-    window.setTimeout(() => {
-      composerRef.current?.focus();
-      isNearBottomRef.current = true;
-      cancelStreamingScroll();
-      scrollToBottom("auto");
-    }, 0);
-  }, [cancelStreamingScroll, createSession, handleStopSpeech, scrollToBottom, stopListening]);
+    resetConversationView();
+  }, [createSession, handleStopSpeech, resetConversationView, stopListening]);
 
   const handleHistoryToggle = useCallback(() => {
     setIsHistoryOpen((prev) => !prev);
@@ -311,6 +310,7 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
       hideBackdrop
       disableScrollLock
       disableEnforceFocus
+      ModalProps={{ keepMounted: true }}
       sx={{
         zIndex: (muiTheme) => muiTheme.zIndex.modal + 100,
         pointerEvents: "none",