diff --git a/lib/features/discover/models/chat_session.dart b/lib/features/discover/models/chat_session.dart
index 4944c3ac..93e92341 100644
--- a/lib/features/discover/models/chat_session.dart
+++ b/lib/features/discover/models/chat_session.dart
@@ -107,7 +107,7 @@ class ChatSession {
   }
 }
 
-/// 系统会话ID常量（与ChatSessionNotifier中保持一致）
+/// 系统会话ID常量（唯一权威定义，Provider层引用此处）
 class SystemSessionIds {
   static const readlater = 'readlater';
   static const discover = 'discover';
@@ -117,6 +117,7 @@ class SystemSessionIds {
   static const readingReport = 'reading_report';
   static const weather = 'weather';
   static const poetry = 'poetry';
+  static const countdown = 'countdown';
   static const dailyFortune = 'daily_fortune';
   static const solarTerm = 'solar_term';
   static const knowledgeGraph = 'knowledge_graph';
@@ -128,10 +129,24 @@ class SystemSessionIds {
   static const leisure = 'leisure';
 
   static const all = {
-    readlater, discover, footprint, dailyCard, template,
-    readingReport, weather, poetry, dailyFortune, solarTerm,
-    knowledgeGraph, studyPlan, progress, fileTransfer, rssFeed,
-    translate, leisure,
+    readlater,
+    discover,
+    footprint,
+    dailyCard,
+    template,
+    readingReport,
+    weather,
+    poetry,
+    countdown,
+    dailyFortune,
+    solarTerm,
+    knowledgeGraph,
+    studyPlan,
+    progress,
+    fileTransfer,
+    rssFeed,
+    translate,
+    leisure,
   };
 
   static bool isSystem(String id) => all.contains(id);
@@ -163,47 +178,83 @@ extension ChatSessionL10n on ChatSession {
 
   String? _resolveName(TDiscoverBase t) {
     switch (id) {
-      case SystemSessionIds.readlater: return t.sessionReadLater;
-      case SystemSessionIds.discover: return t.sessionInspiration;
-      case SystemSessionIds.footprint: return t.sessionFootprint;
-      case SystemSessionIds.dailyCard: return t.sessionDailyCard;
-      case SystemSessionIds.template: return t.sessionTemplate;
-      case SystemSessionIds.readingReport: return t.sessionReadingReport;
-      case SystemSessionIds.weather: return t.sessionWeather;
-      case SystemSessionIds.poetry: return t.sessionPoetry;
-      case SystemSessionIds.dailyFortune: return t.sessionDailyFortune;
-      case SystemSessionIds.solarTerm: return t.sessionSolarTerm;
-      case SystemSessionIds.knowledgeGraph: return t.sessionKnowledgeGraph;
-      case SystemSessionIds.studyPlan: return t.sessionStudyPlan;
-      case SystemSessionIds.progress: return t.sessionProgress;
-      case SystemSessionIds.fileTransfer: return t.sessionFileTransfer;
-      case SystemSessionIds.rssFeed: return t.sessionRssFeed;
-      case SystemSessionIds.translate: return t.sessionTranslate;
-      case SystemSessionIds.leisure: return t.sessionLeisure;
-      default: return null;
+      case SystemSessionIds.readlater:
+        return t.sessionReadLater;
+      case SystemSessionIds.discover:
+        return t.sessionInspiration;
+      case SystemSessionIds.footprint:
+        return t.sessionFootprint;
+      case SystemSessionIds.dailyCard:
+        return t.sessionDailyCard;
+      case SystemSessionIds.template:
+        return t.sessionTemplate;
+      case SystemSessionIds.readingReport:
+        return t.sessionReadingReport;
+      case SystemSessionIds.weather:
+        return t.sessionWeather;
+      case SystemSessionIds.poetry:
+        return t.sessionPoetry;
+      case SystemSessionIds.dailyFortune:
+        return t.sessionDailyFortune;
+      case SystemSessionIds.solarTerm:
+        return t.sessionSolarTerm;
+      case SystemSessionIds.knowledgeGraph:
+        return t.sessionKnowledgeGraph;
+      case SystemSessionIds.studyPlan:
+        return t.sessionStudyPlan;
+      case SystemSessionIds.progress:
+        return t.sessionProgress;
+      case SystemSessionIds.fileTransfer:
+        return t.sessionFileTransfer;
+      case SystemSessionIds.rssFeed:
+        return t.sessionRssFeed;
+      case SystemSessionIds.translate:
+        return t.sessionTranslate;
+      case SystemSessionIds.leisure:
+        return t.sessionLeisure;
+      default:
+        return null;
     }
   }
 
   String? _resolveDesc(TDiscoverBase t) {
     switch (id) {
-      case SystemSessionIds.readlater: return t.sessionReadLaterDesc;
-      case SystemSessionIds.discover: return t.sessionInspirationDesc;
-      case SystemSessionIds.footprint: return t.sessionFootprintDesc;
-      case SystemSessionIds.dailyCard: return t.sessionDailyCardDesc;
-      case SystemSessionIds.template: return t.sessionTemplateDesc;
-      case SystemSessionIds.readingReport: return t.sessionReadingReportDesc;
-      case SystemSessionIds.weather: return t.sessionWeatherDesc;
-      case SystemSessionIds.poetry: return t.sessionPoetryDesc;
-      case SystemSessionIds.dailyFortune: return t.sessionDailyFortuneDesc;
-      case SystemSessionIds.solarTerm: return t.sessionSolarTermDesc;
-      case SystemSessionIds.knowledgeGraph: return t.sessionKnowledgeGraphDesc;
-      case SystemSessionIds.studyPlan: return t.sessionStudyPlanDesc;
-      case SystemSessionIds.progress: return t.sessionProgressDesc;
-      case SystemSessionIds.fileTransfer: return t.sessionFileTransferDesc;
-      case SystemSessionIds.rssFeed: return t.sessionRssFeedDesc;
-      case SystemSessionIds.translate: return t.sessionTranslateDesc;
-      case SystemSessionIds.leisure: return t.sessionLeisureDesc;
-      default: return null;
+      case SystemSessionIds.readlater:
+        return t.sessionReadLaterDesc;
+      case SystemSessionIds.discover:
+        return t.sessionInspirationDesc;
+      case SystemSessionIds.footprint:
+        return t.sessionFootprintDesc;
+      case SystemSessionIds.dailyCard:
+        return t.sessionDailyCardDesc;
+      case SystemSessionIds.template:
+        return t.sessionTemplateDesc;
+      case SystemSessionIds.readingReport:
+        return t.sessionReadingReportDesc;
+      case SystemSessionIds.weather:
+        return t.sessionWeatherDesc;
+      case SystemSessionIds.poetry:
+        return t.sessionPoetryDesc;
+      case SystemSessionIds.dailyFortune:
+        return t.sessionDailyFortuneDesc;
+      case SystemSessionIds.solarTerm:
+        return t.sessionSolarTermDesc;
+      case SystemSessionIds.knowledgeGraph:
+        return t.sessionKnowledgeGraphDesc;
+      case SystemSessionIds.studyPlan:
+        return t.sessionStudyPlanDesc;
+      case SystemSessionIds.progress:
+        return t.sessionProgressDesc;
+      case SystemSessionIds.fileTransfer:
+        return t.sessionFileTransferDesc;
+      case SystemSessionIds.rssFeed:
+        return t.sessionRssFeedDesc;
+      case SystemSessionIds.translate:
+        return t.sessionTranslateDesc;
+      case SystemSessionIds.leisure:
+        return t.sessionLeisureDesc;
+      default:
+        return null;
     }
   }
 }
diff --git a/lib/features/discover/providers/chat_session_provider.dart b/lib/features/discover/providers/chat_session_provider.dart
index 04ce5049..5e7906f2 100644
--- a/lib/features/discover/providers/chat_session_provider.dart
+++ b/lib/features/discover/providers/chat_session_provider.dart
@@ -110,25 +110,6 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
   static const _sessionsKey = 'chat_sessions_remarks';
   static const _sessionTimeKey = 'chat_sessions_last_time';
 
-  static const kSessionReadlater = 'readlater';
-  static const kSessionDiscover = 'discover';
-  static const kSessionFootprint = 'footprint';
-  static const kSessionDailyCard = 'daily_card';
-  static const kSessionTemplate = 'template';
-  static const kSessionReadingReport = 'reading_report';
-  static const kSessionWeather = 'weather';
-  static const kSessionPoetry = 'poetry';
-  static const kSessionCountdown = 'countdown';
-  static const kSessionDailyFortune = 'daily_fortune';
-  static const kSessionSolarTerm = 'solar_term';
-  static const kSessionKnowledgeGraph = 'knowledge_graph';
-  static const kSessionStudyPlan = 'study_plan';
-  static const kSessionProgress = 'progress';
-  static const kSessionFileTransfer = 'file_transfer';
-  static const kSessionRssFeed = 'rss_feed';
-  static const kSessionTranslate = 'translate';
-  static const kSessionLeisure = 'leisure';
-
   Future<void> _init() async {
     await _buildSessions();
     _loadRemarks();
@@ -141,7 +122,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
 
     final systemSessions = <ChatSession>[
       ChatSession(
-        id: kSessionReadlater,
+        id: SystemSessionIds.readlater,
         type: ChatSessionType.readlater,
         emoji: '📖',
         name: '稍后读',
@@ -153,7 +134,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/readlater-chat',
       ),
       ChatSession(
-        id: kSessionDiscover,
+        id: SystemSessionIds.discover,
         type: ChatSessionType.discover,
         emoji: '🔍',
         name: '灵感',
@@ -164,7 +145,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: 'discover',
       ),
       ChatSession(
-        id: kSessionFootprint,
+        id: SystemSessionIds.footprint,
         type: ChatSessionType.footprint,
         emoji: '👣',
         name: '足迹',
@@ -174,7 +155,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: 'footprint',
       ),
       ChatSession(
-        id: kSessionDailyCard,
+        id: SystemSessionIds.dailyCard,
         type: ChatSessionType.custom,
         emoji: '📅',
         name: '日签卡片',
@@ -184,7 +165,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/daily-card',
       ),
       ChatSession(
-        id: kSessionTemplate,
+        id: SystemSessionIds.template,
         type: ChatSessionType.custom,
         emoji: '🎨',
         name: '壁纸模板',
@@ -194,7 +175,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/template-gallery',
       ),
       ChatSession(
-        id: kSessionReadingReport,
+        id: SystemSessionIds.readingReport,
         type: ChatSessionType.custom,
         emoji: '📊',
         name: '阅读报告',
@@ -204,7 +185,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/reading-report',
       ),
       ChatSession(
-        id: kSessionWeather,
+        id: SystemSessionIds.weather,
         type: ChatSessionType.custom,
         emoji: '🌤️',
         name: '情景诗词',
@@ -214,7 +195,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/weather',
       ),
       ChatSession(
-        id: kSessionPoetry,
+        id: SystemSessionIds.poetry,
         type: ChatSessionType.custom,
         emoji: '📜',
         name: '今日诗词',
@@ -224,7 +205,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/poetry',
       ),
       ChatSession(
-        id: kSessionDailyFortune,
+        id: SystemSessionIds.dailyFortune,
         type: ChatSessionType.custom,
         emoji: '🔮',
         name: '每日运势',
@@ -234,7 +215,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/daily-fortune',
       ),
       ChatSession(
-        id: kSessionSolarTerm,
+        id: SystemSessionIds.solarTerm,
         type: ChatSessionType.custom,
         emoji: '🌿',
         name: '节气日历',
@@ -244,7 +225,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/solar-term',
       ),
       ChatSession(
-        id: kSessionKnowledgeGraph,
+        id: SystemSessionIds.knowledgeGraph,
         type: ChatSessionType.custom,
         emoji: '🕸️',
         name: '知识图谱',
@@ -254,7 +235,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/knowledge-graph',
       ),
       ChatSession(
-        id: kSessionStudyPlan,
+        id: SystemSessionIds.studyPlan,
         type: ChatSessionType.custom,
         emoji: '📚',
         name: '学习计划',
@@ -264,7 +245,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/study-plan',
       ),
       ChatSession(
-        id: kSessionProgress,
+        id: SystemSessionIds.progress,
         type: ChatSessionType.custom,
         emoji: '📊',
         name: '进度',
@@ -274,7 +255,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/progress',
       ),
       ChatSession(
-        id: kSessionFileTransfer,
+        id: SystemSessionIds.fileTransfer,
         type: ChatSessionType.custom,
         emoji: '📁',
         name: '文件传输助手',
@@ -284,7 +265,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/file-transfer',
       ),
       ChatSession(
-        id: kSessionRssFeed,
+        id: SystemSessionIds.rssFeed,
         type: ChatSessionType.custom,
         emoji: '📡',
         name: 'RSS流',
@@ -294,7 +275,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/rss-feed',
       ),
       ChatSession(
-        id: kSessionTranslate,
+        id: SystemSessionIds.translate,
         type: ChatSessionType.custom,
         emoji: '🌐',
         name: '翻译助手',
@@ -305,7 +286,7 @@ class ChatSessionNotifier extends Notifier<ChatSessionState>
         route: '/translate',
       ),
       ChatSession(
-        id: kSessionLeisure,
+        id: SystemSessionIds.leisure,
         type: ChatSessionType.custom,
         emoji: '🌸',
         name: '闲情逸致',