diff --git a/lib/main.dart b/lib/main.dart
index fab8546..0582d60 100644
--- a/lib/main.dart
+++ b/lib/main.dart
@@ -9,6 +9,7 @@ import 'utils/theme/app_theme.dart';
 import 'utils/app_router.dart';
 import 'utils/user_prefs.dart';
 import 'utils/sync/auto_backup_service.dart';
+import 'utils/sync/server_sync_service.dart';
 import 'utils/usage_stats_service.dart';
 import 'providers/app_provider.dart';
 import 'package:flutter/widget_previews.dart';
@@ -18,7 +19,7 @@ void main() async {
   await UserPrefs.init();
   final appProvider = AppProvider();
   runApp(MyApp(appProvider: appProvider));
-  unawaited(appProvider.initDatabase().then((_) => appProvider.initMainTabIndex()));
+  unawaited(_validateSyncOnStartup().then((_) => appProvider.initDatabase().then((_) => appProvider.initMainTabIndex())));
   unawaited(_initAutoBackup());
   unawaited(_initUsageStats());
 }
@@ -42,6 +43,34 @@ Future<void> _initUsageStats() async {
   }
 }
 
+/// 启动时校验同步激活码：有效则继续，过期/失效则下载数据并关闭同步
+Future<void> _validateSyncOnStartup() async {
+  try {
+    final prefs = UserPrefs();
+    if (!prefs.syncEnabled || prefs.syncServerUrl.isEmpty || prefs.syncActivationCode.isEmpty) {
+      return; // 未开启同步，跳过
+    }
+
+    debugPrint('[Startup] 校验同步激活码...');
+    final result = await ServerSyncService.instance.checkActivation();
+
+    if (result != null && result['valid'] == true) {
+      // 激活码有效，更新有效期信息
+      await prefs.setSyncExpiresAt(result['expires_at'] ?? '');
+      await prefs.setSyncIsPermanent(result['is_permanent'] == true);
+      debugPrint('[Startup] 激活码有效，继续同步模式');
+    } else {
+      // 激活码无效/过期，下载服务端数据并关闭同步
+      debugPrint('[Startup] 激活码失效: ${result?['error'] ?? '未知'}，关闭同步并下载数据');
+      await ServerSyncService.instance.downloadToLocal();
+      await prefs.setSyncEnabled(false);
+      debugPrint('[Startup] 已切换到本地模式');
+    }
+  } catch (e) {
+    debugPrint('[Startup] 激活码校验异常: $e');
+  }
+}
+
 class MyApp extends StatefulWidget {
   final AppProvider appProvider;
   const MyApp({super.key, required this.appProvider});
diff --git a/lib/pages/note/note_form_page.dart b/lib/pages/note/note_form_page.dart
index 581d1f3..f13deab 100644
--- a/lib/pages/note/note_form_page.dart
+++ b/lib/pages/note/note_form_page.dart
@@ -549,14 +549,19 @@ class _NoteFormPageState extends State<NoteFormPage> {
   }
 
   /// 显示添加标签对话框
-  void _showAddTagDialog() {
+  Future<void> _showAddTagDialog() async {
     final controller = TextEditingController();
 
-    // 获取所有已有标签（从所有笔记中收集）
+    // 从 tags 表获取已有标签（sync 模式下走服务端 API）
     final provider = context.read<AppProvider>();
-    final allTags = _getAllExistingTags(provider);
+    final tagRows = await provider.getTags('note_tag');
+    final allTags = tagRows.map((t) => t['name'] as String).toSet();
+    // 也从当前笔记内容中收集
+    for (final note in provider.notes) {
+      allTags.addAll(note.tags);
+    }
     // 过滤掉已添加的标签
-    final availableTags = allTags.where((tag) => !_tags.contains(tag)).toList();
+    final availableTags = allTags.where((tag) => !_tags.contains(tag)).toList()..sort();
 
     showDialog(
       context: context,
@@ -713,14 +718,6 @@ class _NoteFormPageState extends State<NoteFormPage> {
   }
 
   /// 获取所有已有标签（从所有笔记中收集）
-  List<String> _getAllExistingTags(AppProvider provider) {
-    final allTags = <String>{};
-    for (final note in provider.notes) {
-      allTags.addAll(note.tags);
-    }
-    return allTags.toList()..sort();
-  }
-
   /// 添加标签
   void _addTag(String tag) {
     final trimmed = tag.trim();
diff --git a/lib/pages/sync/server_sync_page.dart b/lib/pages/sync/server_sync_page.dart
index 1a95c0a..81180ea 100644
--- a/lib/pages/sync/server_sync_page.dart
+++ b/lib/pages/sync/server_sync_page.dart
@@ -48,7 +48,10 @@ class _ServerSyncPageState extends State<ServerSyncPage> {
     _isActivated = url.isNotEmpty && code.isNotEmpty;
     _syncEnabled = _isActivated && _prefs.syncEnabled;
     _updateExpiresText();
-    if (_isActivated) _startStatusPolling();
+    if (_isActivated) {
+      _startStatusPolling();
+      _checkStatus(); // 立即向服务端验证
+    }
   }
 
   void _updateExpiresText() {
diff --git a/lib/providers/app_provider.dart b/lib/providers/app_provider.dart
index d2159c3..2d470b7 100644
--- a/lib/providers/app_provider.dart
+++ b/lib/providers/app_provider.dart
@@ -582,19 +582,34 @@ class AppProvider extends ChangeNotifier {
   // ========== 标签管理方法 ==========
 
   Future<List<Map<String, dynamic>>> getTags(String type) async {
+    if (_useRemote) {
+      return await ServerDataService.instance.getTags(type.isEmpty ? null : type);
+    }
     return await _tagDao.getTagsByType(type);
   }
 
   Future<String> addTag(String name, String type) async {
     final id = await _tagDao.addTag(name, type);
+    if (_useRemote) {
+      await ServerDataService.instance.saveTag(name, type);
+    }
     await _reloadByTagType(type);
     return id;
   }
 
   Future<bool> renameTag(String tagId, String newName, String type) async {
+    final tag = await _tagDao.getTagById(tagId);
+    final oldName = tag?['name'] as String?;
     final result = await _tagDao.renameTag(tagId, newName);
     if (result) {
-      await _reloadByTagType(type);
+      if (_useRemote) {
+        if (oldName != null) {
+          await ServerDataService.instance.deleteTagByName(oldName, type);
+        }
+        await ServerDataService.instance.saveTag(newName, type);
+        await _pushAffectedByType(type); // 先推到服务端
+      }
+      await _reloadByTagType(type); // 再从服务端拉最新
     }
     return result;
   }
@@ -602,15 +617,38 @@ class AppProvider extends ChangeNotifier {
   Future<void> deleteTag(String tagId, String type,
       {String? replacementName}) async {
     await _tagDao.deleteTag(tagId, replacementName: replacementName);
-    await _reloadByTagType(type);
+    if (_useRemote) {
+      await ServerDataService.instance.deleteTag(tagId);
+      if (replacementName != null) {
+        await ServerDataService.instance.saveTag(replacementName, type);
+      }
+      await _pushAffectedByType(type); // 先推到服务端
+    }
+    await _reloadByTagType(type); // 再从服务端拉最新
   }
 
   /// 仅删除标签本身，不级联影响已有条目
   Future<void> deleteTagOnly(String tagId, String type) async {
     await _tagDao.deleteTagOnly(tagId);
+    if (_useRemote) {
+      await ServerDataService.instance.deleteTag(tagId);
+    }
     await _reloadByTagType(type);
   }
 
+  /// 把某类型的所有条目推送到服务端（标签级联后调用）
+  Future<void> _pushAffectedByType(String type) async {
+    final server = ServerDataService.instance;
+    switch (type) {
+      case 'movie_genre':
+        for (final m in _movies) { await server.saveMovie(m); }
+      case 'book_genre':
+        for (final b in _books) { await server.saveBook(b); }
+      case 'note_tag':
+        for (final n in _notes) { await server.saveNote(n); }
+    }
+  }
+
   /// 从影视/书籍/笔记数据中解析标签，同步到 tags 表
   Future<int> syncTagsFromData() async {
     final db = await DatabaseHelper.instance.database;
diff --git a/lib/utils/sync/server_data_service.dart b/lib/utils/sync/server_data_service.dart
index e9b7ae7..19ef300 100644
--- a/lib/utils/sync/server_data_service.dart
+++ b/lib/utils/sync/server_data_service.dart
@@ -257,6 +257,11 @@ class ServerDataService {
     return data != null;
   }
 
+  Future<bool> deleteTagByName(String name, String type) async {
+    final data = await _post('/api/data/tag/delete_by_name', {'name': name, 'type': type});
+    return data != null;
+  }
+
   // ─── 图片 ────────────────────────────────────────────────────
 
   /// 是否激活（AppProvider 也会用这个检查）