feat: 添加历史话题管理功能，支持获取和记录每个 chat 的历史话题

src/gateway/session.rs

@@ -174,6 +174,11 @@ impl Session {
         self.history.chat_topic(chat_id)
     }
 
+    /// 获取历史所对应的话题 ID（指定 chat）
+    pub fn history_topic(&self, chat_id: &str) -> Option<&str> {
+        self.history.history_topic(chat_id)
+    }
+
     /// 切换话题 - 清除当前历史并加载新话题的历史
     pub fn switch_topic(&mut self, chat_id: &str, topic_id: &str) -> Result<(), AgentError> {
         // 清除当前历史
@@ -201,9 +206,32 @@ impl Session {
     }
 
     pub fn ensure_chat_loaded(&mut self, chat_id: &str) -> Result<(), AgentError> {
+        // 检查历史是否存在且对应正确的话题
+        let current_topic = self.history.chat_topic(chat_id);
+        let stored_topic = self.history.history_topic(chat_id);
+
+        if self.chat_history_exists(chat_id) {
+            // 如果历史已存在，但话题不匹配，需要重新加载
+            if current_topic != stored_topic {
+                tracing::info!(
+                    chat_id = %chat_id,
+                    current_topic = ?current_topic,
+                    stored_topic = ?stored_topic,
+                    "Topic changed, reloading history"
+                );
+                self.reload_chat_history(chat_id)?;
+            }
+            return Ok(());
+        }
+
+        // 历史不存在，正常加载
         self.history.ensure_chat_loaded(chat_id)
     }
 
+    fn chat_history_exists(&self, chat_id: &str) -> bool {
+        self.history.get_history(chat_id).is_some()
+    }
+
     pub fn ensure_agent_prompt_before_user_message(
         &mut self,
         chat_id: &str,

src/gateway/session_history.rs

@@ -26,6 +26,7 @@ pub(crate) struct SessionHistory {
     channel_name: String,
     chat_histories: HashMap<String, Vec<ChatMessage>>,
     chat_topic_ids: HashMap<String, String>, // 每个 chat 的当前 topic
+    history_topic_ids: HashMap<String, String>, // 每个 chat 的历史所对应的话题
     compression_in_flight: HashSet<String>,
     conversations: Arc<dyn ConversationRepository>,
     skill_events: Arc<dyn SkillEventRepository>,
@@ -43,6 +44,7 @@ impl SessionHistory {
             channel_name: channel_name.into(),
             chat_histories: HashMap::new(),
             chat_topic_ids: HashMap::new(),
+            history_topic_ids: HashMap::new(),
             compression_in_flight: HashSet::new(),
             conversations,
             skill_events,
@@ -117,6 +119,15 @@ impl SessionHistory {
 
     pub(crate) fn set_history(&mut self, chat_id: &str, history: Vec<ChatMessage>) {
         self.chat_histories.insert(chat_id.to_string(), history);
+        // 记录历史对应的话题（当前设置的话题）
+        if let Some(topic_id) = self.chat_topic_ids.get(chat_id) {
+            self.history_topic_ids.insert(chat_id.to_string(), topic_id.clone());
+        }
+    }
+
+    /// 获取指定 chat 的历史所对应的话题
+    pub(crate) fn history_topic(&self, chat_id: &str) -> Option<&str> {
+        self.history_topic_ids.get(chat_id).map(|s| s.as_str())
     }
 
     /// 设置指定 chat 的当前 topic
@@ -141,6 +152,7 @@ impl SessionHistory {
     pub(crate) fn remove_history(&mut self, chat_id: &str) {
         self.chat_histories.remove(chat_id);
         self.compression_in_flight.remove(chat_id);
+        self.history_topic_ids.remove(chat_id);
     }
 
     pub(crate) fn clear_chat_history(&mut self, chat_id: &str) -> Result<(), AgentError> {