diff --git a/src/App.tsx b/src/App.tsx
index 0d1f1df..15562c6 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -31,10 +31,11 @@ function App() {
   const [authReady, setAuthReady] = useState(false);
 
   useEffect(() => {
-    initializeTheme();
+    const cleanupTheme = initializeTheme();
     void restoreSession().finally(() => {
       setAuthReady(true);
     });
+    return cleanupTheme;
   }, [initializeTheme, restoreSession]);
 
   useEffect(() => {
diff --git a/src/components/layout/MainLayout.tsx b/src/components/layout/MainLayout.tsx
index 0481d97..b132e6d 100644
--- a/src/components/layout/MainLayout.tsx
+++ b/src/components/layout/MainLayout.tsx
@@ -1,4 +1,12 @@
-import { ReactNode, SVGProps, useCallback, useEffect, useLayoutEffect, useRef, useState } from 'react';
+import {
+  ReactNode,
+  SVGProps,
+  useCallback,
+  useEffect,
+  useLayoutEffect,
+  useRef,
+  useState,
+} from 'react';
 import { NavLink, Outlet } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
 import { Button } from '@/components/ui/Button';
@@ -14,10 +22,16 @@ import {
   IconScrollText,
   IconSettings,
   IconShield,
-  IconSlidersHorizontal
+  IconSlidersHorizontal,
 } from '@/components/ui/icons';
 import { INLINE_LOGO_JPEG } from '@/assets/logoInline';
-import { useAuthStore, useConfigStore, useLanguageStore, useNotificationStore, useThemeStore } from '@/stores';
+import {
+  useAuthStore,
+  useConfigStore,
+  useLanguageStore,
+  useNotificationStore,
+  useThemeStore,
+} from '@/stores';
 import { configApi, versionApi } from '@/services/api';
 
 const sidebarIcons: Record<string, ReactNode> = {
@@ -30,7 +44,7 @@ const sidebarIcons: Record<string, ReactNode> = {
   usage: <IconChartLine size={18} />,
   config: <IconSettings size={18} />,
   logs: <IconScrollText size={18} />,
-  system: <IconInfo size={18} />
+  system: <IconInfo size={18} />,
 };
 
 // Header action icons - smaller size for header buttons
@@ -44,7 +58,7 @@ const headerIconProps: SVGProps<SVGSVGElement> = {
   strokeLinecap: 'round',
   strokeLinejoin: 'round',
   'aria-hidden': 'true',
-  focusable: 'false'
+  focusable: 'false',
 };
 
 const headerIcons = {
@@ -97,19 +111,38 @@ const headerIcons = {
       <path d="m19.07 4.93-1.41 1.41" />
     </svg>
   ),
-	  moon: (
-	    <svg {...headerIconProps}>
-	      <path d="M12 3a6 6 0 0 0 9 9 9 9 0 1 1-9-9z" />
-	    </svg>
-	  ),
-	  logout: (
-	    <svg {...headerIconProps}>
-	      <path d="M9 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h4" />
-	      <path d="m16 17 5-5-5-5" />
-	      <path d="M21 12H9" />
-	    </svg>
-	  )
-	};
+  moon: (
+    <svg {...headerIconProps}>
+      <path d="M12 3a6 6 0 0 0 9 9 9 9 0 1 1-9-9z" />
+    </svg>
+  ),
+  autoTheme: (
+    <svg {...headerIconProps}>
+      <defs>
+        <clipPath id="mainLayoutAutoThemeSunLeftHalf">
+          <rect x="0" y="0" width="12" height="24" />
+        </clipPath>
+      </defs>
+      <circle cx="12" cy="12" r="4" />
+      <circle cx="12" cy="12" r="4" clipPath="url(#mainLayoutAutoThemeSunLeftHalf)" fill="currentColor" />
+      <path d="M12 2v2" />
+      <path d="M12 20v2" />
+      <path d="M4.93 4.93l1.41 1.41" />
+      <path d="M17.66 17.66l1.41 1.41" />
+      <path d="M2 12h2" />
+      <path d="M20 12h2" />
+      <path d="M6.34 17.66l-1.41 1.41" />
+      <path d="M19.07 4.93l-1.41 1.41" />
+    </svg>
+  ),
+  logout: (
+    <svg {...headerIconProps}>
+      <path d="M9 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h4" />
+      <path d="m16 17 5-5-5-5" />
+      <path d="M21 12H9" />
+    </svg>
+  ),
+};
 
 const parseVersionSegments = (version?: string | null) => {
   if (!version) return null;
@@ -153,7 +186,7 @@ export function MainLayout() {
   const updateConfigValue = useConfigStore((state) => state.updateConfigValue);
 
   const theme = useThemeStore((state) => state.theme);
-  const toggleTheme = useThemeStore((state) => state.toggleTheme);
+  const cycleTheme = useThemeStore((state) => state.cycleTheme);
   const toggleLanguage = useLanguageStore((state) => state.toggleLanguage);
 
   const [sidebarOpen, setSidebarOpen] = useState(false);
@@ -187,7 +220,9 @@ export function MainLayout() {
     updateHeaderHeight();
 
     const resizeObserver =
-      typeof ResizeObserver !== 'undefined' && headerRef.current ? new ResizeObserver(updateHeaderHeight) : null;
+      typeof ResizeObserver !== 'undefined' && headerRef.current
+        ? new ResizeObserver(updateHeaderHeight)
+        : null;
     if (resizeObserver && headerRef.current) {
       resizeObserver.observe(headerRef.current);
     }
@@ -320,8 +355,10 @@ export function MainLayout() {
     { path: '/oauth', label: t('nav.oauth', { defaultValue: 'OAuth' }), icon: sidebarIcons.oauth },
     { path: '/usage', label: t('nav.usage_stats'), icon: sidebarIcons.usage },
     { path: '/config', label: t('nav.config_management'), icon: sidebarIcons.config },
-    ...(config?.loggingToFile ? [{ path: '/logs', label: t('nav.logs'), icon: sidebarIcons.logs }] : []),
-    { path: '/system', label: t('nav.system_info'), icon: sidebarIcons.system }
+    ...(config?.loggingToFile
+      ? [{ path: '/logs', label: t('nav.logs'), icon: sidebarIcons.logs }]
+      : []),
+    { path: '/system', label: t('nav.system_info'), icon: sidebarIcons.system },
   ];
 
   const handleRefreshAll = async () => {
@@ -370,7 +407,11 @@ export function MainLayout() {
           <button
             className="sidebar-toggle-header"
             onClick={() => setSidebarCollapsed((prev) => !prev)}
-            title={sidebarCollapsed ? t('sidebar.expand', { defaultValue: '展开' }) : t('sidebar.collapse', { defaultValue: '收起' })}
+            title={
+              sidebarCollapsed
+                ? t('sidebar.expand', { defaultValue: '展开' })
+                : t('sidebar.collapse', { defaultValue: '收起' })
+            }
           >
             {sidebarCollapsed ? headerIcons.chevronRight : headerIcons.chevronLeft}
           </button>
@@ -400,20 +441,40 @@ export function MainLayout() {
           </div>
 
           <div className="header-actions">
-            <Button className="mobile-menu-btn" variant="ghost" size="sm" onClick={() => setSidebarOpen((prev) => !prev)}>
+            <Button
+              className="mobile-menu-btn"
+              variant="ghost"
+              size="sm"
+              onClick={() => setSidebarOpen((prev) => !prev)}
+            >
               {headerIcons.menu}
             </Button>
-            <Button variant="ghost" size="sm" onClick={handleRefreshAll} title={t('header.refresh_all')}>
+            <Button
+              variant="ghost"
+              size="sm"
+              onClick={handleRefreshAll}
+              title={t('header.refresh_all')}
+            >
               {headerIcons.refresh}
             </Button>
-            <Button variant="ghost" size="sm" onClick={handleVersionCheck} loading={checkingVersion} title={t('system_info.version_check_button')}>
+            <Button
+              variant="ghost"
+              size="sm"
+              onClick={handleVersionCheck}
+              loading={checkingVersion}
+              title={t('system_info.version_check_button')}
+            >
               {headerIcons.update}
             </Button>
             <Button variant="ghost" size="sm" onClick={toggleLanguage} title={t('language.switch')}>
               {headerIcons.language}
             </Button>
-            <Button variant="ghost" size="sm" onClick={toggleTheme} title={t('theme.switch')}>
-              {theme === 'dark' ? headerIcons.sun : headerIcons.moon}
+            <Button variant="ghost" size="sm" onClick={cycleTheme} title={t('theme.switch')}>
+              {theme === 'auto'
+                ? headerIcons.autoTheme
+                : theme === 'dark'
+                  ? headerIcons.moon
+                  : headerIcons.sun}
             </Button>
             <Button variant="ghost" size="sm" onClick={logout} title={t('header.logout')}>
               {headerIcons.logout}
@@ -423,7 +484,9 @@ export function MainLayout() {
       </header>
 
       <div className="main-body">
-        <aside className={`sidebar ${sidebarOpen ? 'open' : ''} ${sidebarCollapsed ? 'collapsed' : ''}`}>
+        <aside
+          className={`sidebar ${sidebarOpen ? 'open' : ''} ${sidebarCollapsed ? 'collapsed' : ''}`}
+        >
           <div className="nav-section">
             {navItems.map((item) => (
               <NavLink
@@ -454,7 +517,9 @@ export function MainLayout() {
             </span>
             <span>
               {t('footer.build_date')}:{' '}
-              {serverBuildDate ? new Date(serverBuildDate).toLocaleString(i18n.language) : t('system_info.version_unknown')}
+              {serverBuildDate
+                ? new Date(serverBuildDate).toLocaleString(i18n.language)
+                : t('system_info.version_unknown')}
             </span>
           </footer>
         </div>
diff --git a/src/pages/AuthFilesPage.tsx b/src/pages/AuthFilesPage.tsx
index 5508321..232aee1 100644
--- a/src/pages/AuthFilesPage.tsx
+++ b/src/pages/AuthFilesPage.tsx
@@ -17,6 +17,7 @@ import styles from './AuthFilesPage.module.scss';
 
 type ThemeColors = { bg: string; text: string; border?: string };
 type TypeColorSet = { light: ThemeColors; dark?: ThemeColors };
+type ResolvedTheme = 'light' | 'dark';
 
 // 标签类型颜色配置（对齐重构前 styles.css 的 file-type-badge 颜色）
 const TYPE_COLORS: Record<string, TypeColorSet> = {
@@ -129,7 +130,7 @@ export function AuthFilesPage() {
   const { t } = useTranslation();
   const { showNotification } = useNotificationStore();
   const connectionStatus = useAuthStore((state) => state.connectionStatus);
-  const theme = useThemeStore((state) => state.theme);
+  const resolvedTheme: ResolvedTheme = useThemeStore((state) => state.resolvedTheme);
 
   const [files, setFiles] = useState<AuthFileItem[]>([]);
   const [loading, setLoading] = useState(true);
@@ -488,7 +489,7 @@ export function AuthFilesPage() {
   // 获取类型颜色
   const getTypeColor = (type: string): ThemeColors => {
     const set = TYPE_COLORS[type] || TYPE_COLORS.unknown;
-    return theme === 'dark' && set.dark ? set.dark : set.light;
+    return resolvedTheme === 'dark' && set.dark ? set.dark : set.light;
   };
 
   // OAuth 排除相关方法
@@ -547,7 +548,7 @@ export function AuthFilesPage() {
       {existingTypes.map((type) => {
         const isActive = filter === type;
         const color = type === 'all' ? { bg: 'var(--bg-tertiary)', text: 'var(--text-primary)' } : getTypeColor(type);
-        const activeTextColor = theme === 'dark' ? '#111827' : '#fff';
+        const activeTextColor = resolvedTheme === 'dark' ? '#111827' : '#fff';
         return (
           <button
             key={type}
diff --git a/src/pages/ConfigPage.tsx b/src/pages/ConfigPage.tsx
index 7af93ea..58d597b 100644
--- a/src/pages/ConfigPage.tsx
+++ b/src/pages/ConfigPage.tsx
@@ -16,7 +16,7 @@ export function ConfigPage() {
   const { t } = useTranslation();
   const { showNotification } = useNotificationStore();
   const connectionStatus = useAuthStore((state) => state.connectionStatus);
-  const theme = useThemeStore((state) => state.theme);
+  const resolvedTheme = useThemeStore((state) => state.resolvedTheme);
 
   const [content, setContent] = useState('');
   const [loading, setLoading] = useState(true);
@@ -289,7 +289,7 @@ export function ConfigPage() {
               value={content}
               onChange={handleChange}
               extensions={extensions}
-              theme={theme === 'dark' ? 'dark' : 'light'}
+              theme={resolvedTheme}
               editable={!disableControls && !loading}
               placeholder={t('config_management.editor_placeholder')}
               height="100%"
diff --git a/src/pages/UsagePage.tsx b/src/pages/UsagePage.tsx
index f5f1be3..2c0c729 100644
--- a/src/pages/UsagePage.tsx
+++ b/src/pages/UsagePage.tsx
@@ -64,8 +64,8 @@ interface UsagePayload {
 export function UsagePage() {
   const { t } = useTranslation();
   const isMobile = useMediaQuery('(max-width: 768px)');
-  const theme = useThemeStore((state) => state.theme);
-  const isDark = theme === 'dark';
+  const resolvedTheme = useThemeStore((state) => state.resolvedTheme);
+  const isDark = resolvedTheme === 'dark';
 
   const [usage, setUsage] = useState<UsagePayload | null>(null);
   const [loading, setLoading] = useState(true);
diff --git a/src/stores/useThemeStore.ts b/src/stores/useThemeStore.ts
index 31a3849..65088ce 100644
--- a/src/stores/useThemeStore.ts
+++ b/src/stores/useThemeStore.ts
@@ -8,63 +8,79 @@ import { persist } from 'zustand/middleware';
 import type { Theme } from '@/types';
 import { STORAGE_KEY_THEME } from '@/utils/constants';
 
+type ResolvedTheme = 'light' | 'dark';
+
 interface ThemeState {
   theme: Theme;
+  resolvedTheme: ResolvedTheme;
   setTheme: (theme: Theme) => void;
-  toggleTheme: () => void;
-  initializeTheme: () => void;
+  cycleTheme: () => void;
+  initializeTheme: () => () => void;
 }
 
+const getSystemTheme = (): ResolvedTheme => {
+  if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) {
+    return 'dark';
+  }
+  return 'light';
+};
+
+const applyTheme = (resolved: ResolvedTheme) => {
+  if (resolved === 'dark') {
+    document.documentElement.setAttribute('data-theme', 'dark');
+  } else {
+    document.documentElement.removeAttribute('data-theme');
+  }
+};
+
 export const useThemeStore = create<ThemeState>()(
   persist(
     (set, get) => ({
-      theme: 'light',
+      theme: 'auto',
+      resolvedTheme: 'light',
 
       setTheme: (theme) => {
-        // 应用主题到 DOM
-        if (theme === 'dark') {
-          document.documentElement.setAttribute('data-theme', 'dark');
-        } else {
-          document.documentElement.removeAttribute('data-theme');
-        }
-
-        set({ theme });
+        const resolved: ResolvedTheme = theme === 'auto' ? getSystemTheme() : theme;
+        applyTheme(resolved);
+        set({ theme, resolvedTheme: resolved });
       },
 
-      toggleTheme: () => {
+      cycleTheme: () => {
         const { theme, setTheme } = get();
-        const newTheme: Theme = theme === 'light' ? 'dark' : 'light';
-        setTheme(newTheme);
+        const order: Theme[] = ['light', 'dark', 'auto'];
+        const currentIndex = order.indexOf(theme);
+        const nextTheme = order[(currentIndex + 1) % order.length];
+        setTheme(nextTheme);
       },
 
       initializeTheme: () => {
         const { theme, setTheme } = get();
 
-        // 检查系统偏好
-        if (
-          !localStorage.getItem(STORAGE_KEY_THEME) &&
-          window.matchMedia &&
-          window.matchMedia('(prefers-color-scheme: dark)').matches
-        ) {
-          setTheme('dark');
-          return;
-        }
-
         // 应用已保存的主题
         setTheme(theme);
 
-        // 监听系统主题变化（仅在用户未手动设置时）
-        if (window.matchMedia) {
-          window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', (e) => {
-            if (!localStorage.getItem(STORAGE_KEY_THEME)) {
-              setTheme(e.matches ? 'dark' : 'light');
-            }
-          });
+        // 监听系统主题变化（仅在 auto 模式下生效）
+        if (!window.matchMedia) {
+          return () => {};
         }
-      }
+
+        const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
+        const listener = () => {
+          const { theme: currentTheme } = get();
+          if (currentTheme === 'auto') {
+            const resolved = getSystemTheme();
+            applyTheme(resolved);
+            set({ resolvedTheme: resolved });
+          }
+        };
+
+        mediaQuery.addEventListener('change', listener);
+
+        return () => mediaQuery.removeEventListener('change', listener);
+      },
     }),
     {
-      name: STORAGE_KEY_THEME
+      name: STORAGE_KEY_THEME,
     }
   )
 );
diff --git a/src/types/common.ts b/src/types/common.ts
index fa3e7a3..c41d23b 100644
--- a/src/types/common.ts
+++ b/src/types/common.ts
@@ -2,7 +2,7 @@
  * 通用类型定义
  */
 
-export type Theme = 'light' | 'dark';
+export type Theme = 'light' | 'dark' | 'auto';
 
 export type Language = 'zh-CN' | 'en';