diff --git a/src/components/chat/GlobalChatbox.tsx b/src/components/chat/GlobalChatbox.tsx
index 010405a..c49a49e 100644
--- a/src/components/chat/GlobalChatbox.tsx
+++ b/src/components/chat/GlobalChatbox.tsx
@@ -9,6 +9,7 @@ import React, {
 import { Box, Drawer, alpha, useTheme } from "@mui/material";
 
 import type { AgentModel } from "@/lib/chatStream";
+import { useProjectStore } from "@/store/projectStore";
 import { AgentComposer } from "./AgentComposer";
 import { AgentHeader } from "./AgentHeader";
 import { AgentHistoryPanel } from "./AgentHistoryPanel";
@@ -32,6 +33,7 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
   const bottomRef = useRef<HTMLDivElement>(null);
   const inputRef = useRef<HTMLInputElement | null>(null);
   const theme = useTheme();
+  const currentProjectId = useProjectStore((state) => state.currentProjectId);
 
   const {
     speechState,
@@ -74,6 +76,7 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
     removeSession,
     switchSession,
   } = useAgentChatSession({
+    projectId: currentProjectId,
     onToolCall: handleToolCall,
     onBeforeSend: stopListening,
     getModel: () => selectedModel,
diff --git a/src/components/chat/chatStorage.test.ts b/src/components/chat/chatStorage.test.ts
index e602d3b..4b3f2b7 100644
--- a/src/components/chat/chatStorage.test.ts
+++ b/src/components/chat/chatStorage.test.ts
@@ -42,6 +42,39 @@ describe("chatStorage backend-only persistence", () => {
     expect(loaded.title).toBe("已存在会话");
   });
 
+  it("loads the active remote session from the current project's storage key", async () => {
+    window.localStorage.setItem(
+      "tjwater_agent_active_session_id_v2:project-a",
+      "chat-project-a",
+    );
+    window.localStorage.setItem(
+      "tjwater_agent_active_session_id_v2:project-b",
+      "chat-project-b",
+    );
+
+    apiFetch.mockImplementation(async (url: string) => {
+      if (url.endsWith("/api/v1/agent/chat/session/chat-project-b")) {
+        return {
+          ok: true,
+          json: async () => ({
+            id: "chat-project-b",
+            title: "项目 B 会话",
+            is_title_manually_edited: false,
+            session_id: "chat-project-b",
+            messages: [],
+            branch_groups: [],
+          }),
+        } as Response;
+      }
+      throw new Error(`Unexpected request ${url}`);
+    });
+
+    const loaded = await loadActiveChatState("project-b");
+
+    expect(loaded.storageSessionId).toBe("chat-project-b");
+    expect(loaded.title).toBe("项目 B 会话");
+  });
+
   it("creates a backend conversation when saving the first non-empty state", async () => {
     apiFetch.mockImplementation(async (url: string, init?: RequestInit) => {
       if (url.endsWith("/api/v1/agent/chat/session")) {
@@ -67,26 +100,29 @@ describe("chatStorage backend-only persistence", () => {
       throw new Error(`Unexpected request ${url}`);
     });
 
-    const savedSessionId = await saveActiveChatState({
-      storageSessionId: undefined,
-      title: "新对话",
-      isTitleManuallyEdited: false,
-      messages: [
-        {
-          id: "message-2",
-          role: "user",
-          content: "第一条消息",
-          branchRootId: "message-2",
-        },
-      ],
-      sessionId: undefined,
-      branchGroups: [],
-    });
+    const savedSessionId = await saveActiveChatState(
+      {
+        storageSessionId: undefined,
+        title: "新对话",
+        isTitleManuallyEdited: false,
+        messages: [
+          {
+            id: "message-2",
+            role: "user",
+            content: "第一条消息",
+            branchRootId: "message-2",
+          },
+        ],
+        sessionId: undefined,
+        branchGroups: [],
+      },
+      "project-a",
+    );
 
     expect(savedSessionId).toBe("chat-new-1");
-    expect(window.localStorage.getItem("tjwater_agent_active_session_id_v2")).toBe(
-      "chat-new-1",
-    );
+    expect(
+      window.localStorage.getItem("tjwater_agent_active_session_id_v2:project-a"),
+    ).toBe("chat-new-1");
   });
 
   it("does not persist a blank new session before there is chat content", async () => {
diff --git a/src/components/chat/chatStorage.ts b/src/components/chat/chatStorage.ts
index dd2a974..ca1a9de 100644
--- a/src/components/chat/chatStorage.ts
+++ b/src/components/chat/chatStorage.ts
@@ -60,19 +60,32 @@ const toMillis = (value: string | number | undefined) =>
 
 const normalizeTitle = (value?: string) => value?.trim() || "新对话";
 
-const getStoredActiveSessionId = () => {
+const getActiveSessionStorageKey = (projectId?: string | null) => {
+  const normalizedProjectId = projectId?.trim();
+  return normalizedProjectId
+    ? `${ACTIVE_SESSION_STORAGE_KEY}:${encodeURIComponent(normalizedProjectId)}`
+    : ACTIVE_SESSION_STORAGE_KEY;
+};
+
+const getStoredActiveSessionId = (projectId?: string | null) => {
   if (typeof window === "undefined") return undefined;
-  const stored = window.localStorage.getItem(ACTIVE_SESSION_STORAGE_KEY)?.trim();
+  const stored = window.localStorage
+    .getItem(getActiveSessionStorageKey(projectId))
+    ?.trim();
   return stored || undefined;
 };
 
-const setStoredActiveSessionId = (sessionId?: string) => {
+const setStoredActiveSessionId = (
+  sessionId?: string,
+  projectId?: string | null,
+) => {
   if (typeof window === "undefined") return;
+  const storageKey = getActiveSessionStorageKey(projectId);
   if (sessionId) {
-    window.localStorage.setItem(ACTIVE_SESSION_STORAGE_KEY, sessionId);
+    window.localStorage.setItem(storageKey, sessionId);
     return;
   }
-  window.localStorage.removeItem(ACTIVE_SESSION_STORAGE_KEY);
+  window.localStorage.removeItem(storageKey);
 };
 
 const fetchRemoteChatSessions = async (): Promise<ChatSessionSummary[]> => {
@@ -233,16 +246,18 @@ const deleteRemoteChatSession = async (sessionId: string) => {
   }
 };
 
-export const loadActiveChatState = async (): Promise<LoadedChatState> => {
+export const loadActiveChatState = async (
+  projectId?: string | null,
+): Promise<LoadedChatState> => {
   if (typeof window === "undefined") return emptyLoadedChatState();
 
-  const activeSessionId = getStoredActiveSessionId();
+  const activeSessionId = getStoredActiveSessionId(projectId);
   if (activeSessionId) {
     const activeSession = await fetchRemoteChatSession(activeSessionId);
     if (activeSession.storageSessionId) {
       return activeSession;
     }
-    setStoredActiveSessionId(undefined);
+    setStoredActiveSessionId(undefined, projectId);
   }
 
   const sessions = await fetchRemoteChatSessions();
@@ -250,17 +265,18 @@ export const loadActiveChatState = async (): Promise<LoadedChatState> => {
   if (!latestSession) {
     return emptyLoadedChatState();
   }
-  setStoredActiveSessionId(latestSession.id);
+  setStoredActiveSessionId(latestSession.id, projectId);
   return await fetchRemoteChatSession(latestSession.id);
 };
 
 export const saveActiveChatState = async (
   state: LoadedChatState,
+  projectId?: string | null,
 ): Promise<string | undefined> => {
   if (typeof window === "undefined") return state.storageSessionId;
 
   if (!hasChatContent(state)) {
-    setStoredActiveSessionId(undefined);
+    setStoredActiveSessionId(undefined, projectId);
     return undefined;
   }
 
@@ -274,7 +290,7 @@ export const saveActiveChatState = async (
     storageSessionId: remoteSessionId,
     sessionId: remoteSessionId,
   });
-  setStoredActiveSessionId(savedSessionId);
+  setStoredActiveSessionId(savedSessionId, projectId);
   return savedSessionId;
 };
 
@@ -301,10 +317,12 @@ export const updateChatSessionTitle = async (
   );
 };
 
-export const createEmptyChatSession = async (): Promise<LoadedChatState> => {
+export const createEmptyChatSession = async (
+  projectId?: string | null,
+): Promise<LoadedChatState> => {
   if (typeof window === "undefined") return emptyLoadedChatState();
 
-  setStoredActiveSessionId(undefined);
+  setStoredActiveSessionId(undefined, projectId);
   return {
     ...emptyLoadedChatState(),
     title: "新对话",
@@ -313,23 +331,25 @@ export const createEmptyChatSession = async (): Promise<LoadedChatState> => {
 
 export const loadChatSessionById = async (
   sessionId: string,
+  projectId?: string | null,
 ): Promise<LoadedChatState> => {
   if (typeof window === "undefined") return emptyLoadedChatState();
 
   const loaded = await fetchRemoteChatSession(sessionId);
   if (loaded.storageSessionId) {
-    setStoredActiveSessionId(sessionId);
+    setStoredActiveSessionId(sessionId, projectId);
   }
   return loaded;
 };
 
 export const deleteChatSession = async (
   sessionId: string,
+  projectId?: string | null,
 ): Promise<string | undefined> => {
   if (typeof window === "undefined") return undefined;
 
   await deleteRemoteChatSession(sessionId);
   const nextActiveSession = (await listChatSessions())[0];
-  setStoredActiveSessionId(nextActiveSession?.id);
+  setStoredActiveSessionId(nextActiveSession?.id, projectId);
   return nextActiveSession?.id;
 };
diff --git a/src/components/chat/hooks/useAgentChatSession.test.tsx b/src/components/chat/hooks/useAgentChatSession.test.tsx
index 79163da..063ed60 100644
--- a/src/components/chat/hooks/useAgentChatSession.test.tsx
+++ b/src/components/chat/hooks/useAgentChatSession.test.tsx
@@ -53,6 +53,7 @@ describe("useAgentChatSession", () => {
 
     const { result } = renderHook(() =>
       useAgentChatSession({
+        projectId: "project-1",
         onToolCall: jest.fn(),
       }),
     );
@@ -83,6 +84,7 @@ describe("useAgentChatSession", () => {
 
     const { result } = renderHook(() =>
       useAgentChatSession({
+        projectId: "project-1",
         onToolCall: jest.fn(),
       }),
     );
@@ -127,6 +129,7 @@ describe("useAgentChatSession", () => {
 
     const { result } = renderHook(() =>
       useAgentChatSession({
+        projectId: "project-1",
         onToolCall: jest.fn(),
       }),
     );
diff --git a/src/components/chat/hooks/useAgentChatSession.ts b/src/components/chat/hooks/useAgentChatSession.ts
index 883c349..221ea6b 100644
--- a/src/components/chat/hooks/useAgentChatSession.ts
+++ b/src/components/chat/hooks/useAgentChatSession.ts
@@ -28,6 +28,7 @@ import {
 } from "../chatStorage";
 
 type UseAgentChatSessionOptions = {
+  projectId?: string | null;
   onToolCall: (
     event: StreamEvent & { type: "tool_call" },
     options: {
@@ -145,6 +146,7 @@ const messagesEqual = (left: Message[], right: Message[]) =>
   JSON.stringify(left) === JSON.stringify(right);
 
 export const useAgentChatSession = ({
+  projectId,
   onToolCall,
   onBeforeSend,
   getModel,
@@ -190,9 +192,37 @@ export const useAgentChatSession = ({
     let cancelled = false;
 
     const hydrate = async () => {
+      setIsHydrating(true);
+      hydrationCompletedRef.current = false;
+
+      if (!projectId) {
+        storageSessionIdRef.current = undefined;
+        sessionIdRef.current = undefined;
+        lastPersistedStateKeyRef.current = createPersistedStateKey({
+          storageSessionId: undefined,
+          title: undefined,
+          isTitleManuallyEdited: false,
+          messages: [],
+          sessionId: undefined,
+          branchGroups: [],
+        });
+        hydrationCompletedRef.current = true;
+        hydrationNonceRef.current += 1;
+        titleUpdateNonceRef.current += 1;
+        setBranchTransition(null);
+        setMessages([]);
+        setSessionTitle(undefined);
+        setIsSessionTitleManuallyEdited(false);
+        setSessionId(undefined);
+        setBranchGroups([]);
+        setChatSessions([]);
+        setIsHydrating(false);
+        return;
+      }
+
       try {
         const [loadedState, sessions] = await Promise.all([
-          loadActiveChatState(),
+          loadActiveChatState(projectId),
           listChatSessions(),
         ]);
         if (cancelled) return;
@@ -224,10 +254,10 @@ export const useAgentChatSession = ({
     return () => {
       cancelled = true;
     };
-  }, []);
+  }, [projectId]);
 
   useEffect(() => {
-    if (isHydrating || !hydrationCompletedRef.current) return;
+    if (!projectId || isHydrating || !hydrationCompletedRef.current) return;
 
     const currentHydrationNonce = hydrationNonceRef.current;
     const persistTimer = window.setTimeout(() => {
@@ -244,7 +274,7 @@ export const useAgentChatSession = ({
         return;
       }
 
-      void saveActiveChatState(state)
+      void saveActiveChatState(state, projectId)
         .then((storageSessionId) => {
           if (hydrationNonceRef.current !== currentHydrationNonce) return;
           storageSessionIdRef.current = storageSessionId;
@@ -266,7 +296,7 @@ export const useAgentChatSession = ({
     return () => {
       window.clearTimeout(persistTimer);
     };
-  }, [branchGroups, isHydrating, isSessionTitleManuallyEdited, messages, sessionId, sessionTitle]);
+  }, [branchGroups, isHydrating, isSessionTitleManuallyEdited, messages, projectId, sessionId, sessionTitle]);
 
   useEffect(() => {
     setBranchGroups((prev) => {
@@ -578,7 +608,7 @@ export const useAgentChatSession = ({
       setIsHydrating(true);
       try {
         const [nextState, sessions] = await Promise.all([
-          loadChatSessionById(nextStorageSessionId),
+          loadChatSessionById(nextStorageSessionId, projectId),
           listChatSessions(),
         ]);
 
@@ -600,7 +630,7 @@ export const useAgentChatSession = ({
         setIsHydrating(false);
       }
     },
-    [isHydrating, isStreaming],
+    [isHydrating, isStreaming, projectId],
   );
 
   const removeSession = useCallback(
@@ -608,7 +638,10 @@ export const useAgentChatSession = ({
       if (isHydrating || isStreaming) return;
 
       try {
-        const nextActiveSessionId = await deleteChatSession(targetStorageSessionId);
+        const nextActiveSessionId = await deleteChatSession(
+          targetStorageSessionId,
+          projectId,
+        );
         const sessions = await listChatSessions();
         setChatSessions(sessions);
 
@@ -640,7 +673,7 @@ export const useAgentChatSession = ({
 
         setIsHydrating(true);
         const [nextState, sessionsAfterDelete] = await Promise.all([
-          loadChatSessionById(nextActiveSessionId),
+          loadChatSessionById(nextActiveSessionId, projectId),
           listChatSessions(),
         ]);
         hydrationNonceRef.current += 1;
@@ -661,7 +694,7 @@ export const useAgentChatSession = ({
         setIsHydrating(false);
       }
     },
-    [isHydrating, isStreaming],
+    [isHydrating, isStreaming, projectId],
   );
 
   const sendPrompt = useCallback(