diff --git a/frontend/components/auth/login-button.tsx b/frontend/components/auth/login-button.tsx
index 3b80b60a..c090036e 100644
--- a/frontend/components/auth/login-button.tsx
+++ b/frontend/components/auth/login-button.tsx
@@ -3,6 +3,7 @@
  */
 "use client";
 
+import React from "react";
 import { useAuth } from "@/contexts/auth-context";
 import { Button } from "@/components/ui/button";
 import {
@@ -40,11 +41,22 @@ function GoogleIcon({ className }: { className?: string }) {
 
 export function LoginButton() {
   const { user, isLoading, isAuthenticated, login, logout } = useAuth();
+  const [loggingOut, setLoggingOut] = React.useState(false);
 
-  if (isLoading) {
+  const handleLogout = async () => {
+    setLoggingOut(true);
+    try {
+      await logout();
+    } finally {
+      setLoggingOut(false);
+    }
+  };
+
+  if (isLoading || loggingOut) {
     return (
       <Button variant="outline" size="sm" disabled>
         <div className="w-4 h-4 border-2 border-gray-300 border-t-gray-600 rounded-full animate-spin" />
+        {loggingOut && <span className="ml-2 hidden sm:inline">登出中...</span>}
       </Button>
     );
   }
@@ -84,7 +96,7 @@ export function LoginButton() {
             雲端同步已啟用
           </DropdownMenuItem>
           <DropdownMenuSeparator />
-          <DropdownMenuItem onClick={logout} className="text-red-600">
+          <DropdownMenuItem onClick={handleLogout} className="text-red-600">
             <LogOut className="w-4 h-4 mr-2" />
             登出
           </DropdownMenuItem>
diff --git a/frontend/contexts/auth-context.tsx b/frontend/contexts/auth-context.tsx
index 3bced31d..88f8cdd2 100644
--- a/frontend/contexts/auth-context.tsx
+++ b/frontend/contexts/auth-context.tsx
@@ -5,6 +5,9 @@
 "use client";
 
 import React, { createContext, useContext, useState, useEffect, useCallback, ReactNode } from "react";
+import { clearApiSettings, saveApiSettingsAsync } from "@/lib/storage";
+import { clearAllReports, saveReport } from "@/lib/reports-db";
+import { getCloudSettings, getCloudReports } from "@/lib/user-api";
 
 // User interface
 export interface User {
@@ -21,8 +24,8 @@ interface AuthContextType {
   isLoading: boolean;
   isAuthenticated: boolean;
   login: () => void;
-  logout: () => void;
-  setAuthFromCallback: (token: string) => void;
+  logout: () => Promise<void>;
+  setAuthFromCallback: (token: string) => Promise<void>;
 }
 
 // Create context
@@ -107,6 +110,37 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     initAuth();
   }, [parseToken, isTokenExpired]);
 
+  // Auto-clear local data when unauthenticated user leaves the page
+  useEffect(() => {
+    if (typeof window === "undefined") return;
+
+    const handleBeforeUnload = () => {
+      // Only clear data if user is not authenticated
+      const currentToken = localStorage.getItem(TOKEN_KEY);
+      if (!currentToken) {
+        // Clear API settings (synchronous)
+        clearApiSettings();
+        
+        // Clear reports - use synchronous approach for beforeunload
+        // IndexedDB operations are async, but we can at least attempt it
+        clearAllReports().catch(() => {
+          // Ignore errors during unload
+        });
+        
+        console.log("Cleared local data for unauthenticated user on page leave");
+      }
+    };
+
+    // Use both beforeunload and pagehide for better browser compatibility
+    window.addEventListener("beforeunload", handleBeforeUnload);
+    window.addEventListener("pagehide", handleBeforeUnload);
+
+    return () => {
+      window.removeEventListener("beforeunload", handleBeforeUnload);
+      window.removeEventListener("pagehide", handleBeforeUnload);
+    };
+  }, []); // No dependencies - we check localStorage directly
+
   // Login - redirect to Google OAuth
   const login = useCallback(() => {
     if (!googleClientId) {
@@ -131,22 +165,70 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     window.location.href = `https://accounts.google.com/o/oauth2/v2/auth?${params.toString()}`;
   }, [googleClientId]);
 
-  // Logout
-  const logout = useCallback(() => {
+  // Logout - clear auth and all local data
+  const logout = useCallback(async () => {
+    // Clear auth token
     localStorage.removeItem(TOKEN_KEY);
     setToken(null);
     setUser(null);
+    
+    // Clear all local data
+    clearApiSettings();
+    await clearAllReports();
+    
+    console.log("Logged out and cleared all local data");
+  }, []);
+
+  // Restore cloud data to local storage
+  const restoreCloudData = useCallback(async (authToken: string) => {
+    try {
+      // Temporarily set token for API calls
+      localStorage.setItem(TOKEN_KEY, authToken);
+      
+      // Fetch and restore cloud settings
+      const cloudSettings = await getCloudSettings();
+      if (cloudSettings) {
+        await saveApiSettingsAsync(cloudSettings);
+        console.log("Restored API settings from cloud");
+      }
+      
+      // Fetch and restore cloud reports
+      const cloudReports = await getCloudReports();
+      if (cloudReports && cloudReports.length > 0) {
+        // Clear existing local reports first
+        await clearAllReports();
+        
+        // Save each cloud report to local IndexedDB
+        for (const report of cloudReports) {
+          await saveReport(
+            report.ticker,
+            report.market_type,
+            report.analysis_date,
+            report.result,
+            (report as any).task_id
+          );
+        }
+        console.log(`Restored ${cloudReports.length} reports from cloud`);
+      }
+    } catch (error) {
+      console.error("Failed to restore cloud data:", error);
+    }
   }, []);
 
   // Set auth from callback (after OAuth redirect)
-  const setAuthFromCallback = useCallback((newToken: string) => {
+  const setAuthFromCallback = useCallback(async (newToken: string) => {
     const userData = parseToken(newToken);
     if (userData) {
+      // First restore cloud data, then set the auth state
+      await restoreCloudData(newToken);
+      
       localStorage.setItem(TOKEN_KEY, newToken);
       setToken(newToken);
       setUser(userData);
+      
+      console.log("Login complete, cloud data restored");
     }
-  }, [parseToken]);
+  }, [parseToken, restoreCloudData]);
 
   const value: AuthContextType = {
     user,
diff --git a/frontend/lib/reports-db.ts b/frontend/lib/reports-db.ts
index d508276a..7e3cee67 100644
--- a/frontend/lib/reports-db.ts
+++ b/frontend/lib/reports-db.ts
@@ -3,18 +3,18 @@
  * Uses Dexie.js for a cleaner API
  */
 
-import Dexie, { type Table } from 'dexie';
-import type { AnalysisResponse } from './types';
+import Dexie, { type Table } from "dexie";
+import type { AnalysisResponse } from "./types";
 
 // Saved report interface
 export interface SavedReport {
-  id?: number;                              // Auto-generated primary key
-  ticker: string;                           // Stock ticker symbol
-  market_type: "us" | "twse" | "tpex";      // Market type
-  analysis_date: string;                    // Analysis date (YYYY-MM-DD)
-  saved_at: Date;                           // Save timestamp
-  task_id?: string;                         // Original task ID
-  result: AnalysisResponse;                 // Full analysis result
+  id?: number; // Auto-generated primary key
+  ticker: string; // Stock ticker symbol
+  market_type: "us" | "twse" | "tpex"; // Market type
+  analysis_date: string; // Analysis date (YYYY-MM-DD)
+  saved_at: Date; // Save timestamp
+  task_id?: string; // Original task ID
+  result: AnalysisResponse; // Full analysis result
 }
 
 // Database class extending Dexie
@@ -22,10 +22,10 @@ class ReportsDatabase extends Dexie {
   reports!: Table<SavedReport>;
 
   constructor() {
-    super('TradingAgentsReports');
+    super("TradingAgentsReports");
     this.version(1).stores({
       // Define indexes: ++id = auto-increment, others are indexed fields
-      reports: '++id, ticker, market_type, analysis_date, saved_at'
+      reports: "++id, ticker, market_type, analysis_date, saved_at",
     });
   }
 }
@@ -51,7 +51,7 @@ export async function saveReport(
     task_id,
     result,
   };
-  
+
   return await db.reports.add(report);
 }
 
@@ -62,26 +62,25 @@ export async function getReportsByMarketType(
   market_type: "us" | "twse" | "tpex"
 ): Promise<SavedReport[]> {
   return await db.reports
-    .where('market_type')
+    .where("market_type")
     .equals(market_type)
     .reverse()
-    .sortBy('saved_at');
+    .sortBy("saved_at");
 }
 
 /**
  * Get all saved reports, sorted by saved_at descending
  */
 export async function getAllReports(): Promise<SavedReport[]> {
-  return await db.reports
-    .orderBy('saved_at')
-    .reverse()
-    .toArray();
+  return await db.reports.orderBy("saved_at").reverse().toArray();
 }
 
 /**
  * Get a single report by ID
  */
-export async function getReportById(id: number): Promise<SavedReport | undefined> {
+export async function getReportById(
+  id: number
+): Promise<SavedReport | undefined> {
   return await db.reports.get(id);
 }
 
@@ -108,11 +107,11 @@ export async function getReportCountByMarketType(): Promise<{
   tpex: number;
 }> {
   const [us, twse, tpex] = await Promise.all([
-    db.reports.where('market_type').equals('us').count(),
-    db.reports.where('market_type').equals('twse').count(),
-    db.reports.where('market_type').equals('tpex').count(),
+    db.reports.where("market_type").equals("us").count(),
+    db.reports.where("market_type").equals("twse").count(),
+    db.reports.where("market_type").equals("tpex").count(),
   ]);
-  
+
   return { us, twse, tpex };
 }
 
@@ -124,11 +123,18 @@ export async function checkDuplicateReport(
   analysis_date: string
 ): Promise<SavedReport | undefined> {
   return await db.reports
-    .where('ticker')
+    .where("ticker")
     .equals(ticker)
-    .and(report => report.analysis_date === analysis_date)
+    .and((report) => report.analysis_date === analysis_date)
     .first();
 }
 
+/**
+ * Clear all reports from the database (for logout)
+ */
+export async function clearAllReports(): Promise<void> {
+  await db.reports.clear();
+}
+
 // Export the db instance for advanced usage
 export { db };