fix: 修复话题描述更新逻辑的竞态条件和语义错误，前端自动刷新描述

- topic_description.rs: LLM 返回空字符串时返回 Err 而非 Ok("")，防止空值写回 DB 触发循环生成
- processor.rs: 添加 Arc<Mutex<HashSet>> 生成中守卫防止重复触发，改用 DB 中真正第一条用户消息生成描述
- useChat.ts: assistant_response 时检测当前话题描述为空则递增刷新信号
- App.tsx: 监听刷新信号，500ms 防抖后自动发送 list_topics 获取新描述

src/gateway/processor.rs

@@ -1,4 +1,5 @@
-use std::sync::Arc;
+use std::collections::HashSet;
+use std::sync::{Arc, Mutex};
 
 use tokio::sync::Semaphore;
 
@@ -35,6 +36,7 @@ pub struct InboundProcessor {
     provider_config: LLMProviderConfig,
     command_router: Arc<CommandRouter>,
     cancel_manager: CancelManager,
+    description_generation_in_flight: Arc<Mutex<HashSet<String>>>,
 }
 
 impl InboundProcessor {
@@ -120,6 +122,7 @@ impl InboundProcessor {
             provider_config,
             command_router: Arc::new(command_router),
             cancel_manager,
+            description_generation_in_flight: Arc::new(Mutex::new(HashSet::new())),
         }
     }
 
@@ -285,20 +288,48 @@ impl InboundProcessor {
                     }
                 }
 
-                // 异步生成 topic 描述（仅第一条消息后触发一次）
+                // 异步生成 topic 描述（仅当描述为空且没有正在进行的生成任务时触发）
                 if let Some(ref topic_id) = current_topic {
                     let store = self.session_manager.store();
                     if let Ok(Some(topic)) = store.get_topic(topic_id) {
                         if topic.description.is_none() || topic.description.as_ref().map(|d| d.is_empty()).unwrap_or(true) {
+                            // 检查并设置"生成中"守卫，防止竞态条件导致重复生成
+                            let should_generate = {
+                                let mut in_flight = self.description_generation_in_flight.lock().unwrap();
+                                if in_flight.contains(topic_id) {
+                                    false
+                                } else {
+                                    in_flight.insert(topic_id.clone());
+                                    true
+                                }
+                            };
+
+                            if should_generate {
                                 let provider_config = self.provider_config.clone();
                                 let topic_id_clone = topic_id.clone();
-                            let first_message = inbound.content.clone();
                                 let store_clone = store.clone();
+                                let in_flight = self.description_generation_in_flight.clone();
 
                                 tokio::spawn(async move {
+                                    // 从 DB 查询该 topic 的第一条用户消息作为描述生成的依据
+                                    let first_user_message = store_clone
+                                        .load_messages_for_topic(&topic_id_clone)
+                                        .ok()
+                                        .and_then(|msgs| msgs.into_iter().find(|m| m.role == "user"))
+                                        .map(|m| m.content);
+
+                                    let message_content = match first_user_message {
+                                        Some(content) => content,
+                                        None => {
+                                            tracing::warn!(topic_id = %topic_id_clone, "No user message found for topic, skipping description generation");
+                                            in_flight.lock().unwrap().remove(&topic_id_clone);
+                                            return;
+                                        }
+                                    };
+
                                     let runtime_config: ProviderRuntimeConfig = provider_config.into();
                                     if let Ok(provider) = create_provider(runtime_config) {
-                                    match generate_topic_description(provider.as_ref(), &first_message).await {
+                                        match generate_topic_description(provider.as_ref(), &message_content).await {
                                             Ok(description) => {
                                                 if let Err(e) = store_clone.update_topic_description(&topic_id_clone, &description) {
                                                     tracing::error!(error = %e, topic_id = %topic_id_clone, "Failed to update topic description");
@@ -311,11 +342,14 @@ impl InboundProcessor {
                                             }
                                         }
                                     }
+                                    // 无论成功失败，释放生成守卫
+                                    in_flight.lock().unwrap().remove(&topic_id_clone);
                                 });
                             }
                         }
                     }
                 }
+            }
             Err(error) => {
                 tracing::error!(error = %error, "Failed to handle message");
                 let mut metadata = inbound.forwarded_metadata.clone();

src/topic_description.rs

@@ -17,11 +17,15 @@ pub async fn generate_topic_description(
     };
 
     let response = provider.chat(request).await?;
-    let description = response.content.trim();
+    let description = response.content.trim().to_string();
+
+    if description.is_empty() {
+        return Err("LLM returned empty description".into());
+    }
 
     if description.len() > 50 {
         Ok(description.chars().take(50).collect())
     } else {
-        Ok(description.to_string())
+        Ok(description)
     }
 }

web/src/App.tsx

@@ -60,6 +60,7 @@ function App() {
     deleteTopic,
     requestSessionList,
     requestTopicList,
+    topicRefreshTrigger,
     enterSubAgentView,
     exitSubAgentView,
     handleStop,
@@ -125,6 +126,21 @@ function App() {
     }
   }, [sessionId, status, handleCommand, sendMessage, requestTopicList])
 
+  // 话题描述异步生成后自动刷新话题列表
+  useEffect(() => {
+    if (topicRefreshTrigger === 0) return
+    if (status !== 'connected') return
+    const topicCmd = requestTopicList()
+    if (!topicCmd) return
+
+    const timer = setTimeout(() => {
+      handleCommand(topicCmd)
+      sendMessage({ type: 'command', payload: JSON.stringify(topicCmd) })
+    }, 500)
+
+    return () => clearTimeout(timer)
+  }, [topicRefreshTrigger])
+
   // Topics 加载后，自动选择第一个并通知后端切换，以便加载历史消息
   useEffect(() => {
     if (topics.length === 0 || status !== 'connected') {

web/src/hooks/useChat.ts

@@ -68,6 +68,7 @@ interface UseChatReturn {
   // 初始化方法
   requestSessionList: () => Command
   requestTopicList: () => Command | null
+  topicRefreshTrigger: number
   requestChannelList: () => Command
   selectChannel: (channelId: string) => void
   selectSession: (sessionId: string) => void
@@ -118,6 +119,7 @@ export function useChat(): UseChatReturn {
   const [connectionId, setConnectionId] = useState<string | null>(null)
   const [topics, setTopics] = useState<Topic[]>([])
   const [selectedTopic, setSelectedTopic] = useState<string | null>(null)
+  const [topicRefreshTrigger, setTopicRefreshTrigger] = useState(0)
   const [sessions, setSessions] = useState<SessionSummary[]>([])
   const [selectedSessionId, setSelectedSessionId] = useState<string | null>(null)
   const [subAgentView, setSubAgentView] = useState<SubAgentView | null>(null)
@@ -137,6 +139,8 @@ export function useChat(): UseChatReturn {
   // Ref to track subAgentView and schedulerView for use in callbacks
   const subAgentViewRef = useRef<SubAgentView | null>(null)
   const schedulerViewRef = useRef<SchedulerJobView | null>(null)
+  const topicsRef = useRef<Topic[]>([])
+  const selectedTopicRef = useRef<string | null>(null)
 
   const isConnected = useMemo(() => connectionId !== null, [connectionId])
   const selectedSession = useMemo(
@@ -401,6 +405,12 @@ export function useChat(): UseChatReturn {
           },
         ])
         setIsLoading(false)
+
+        // 当前话题无描述时，可能刚触发了异步生成，标记需要刷新
+        const currentTopic = topicsRef.current.find(t => t.id === selectedTopicRef.current)
+        if (currentTopic && !currentTopic.description) {
+          setTopicRefreshTrigger(n => n + 1)
+        }
         break
       }
 
@@ -617,6 +627,14 @@ export function useChat(): UseChatReturn {
     schedulerViewRef.current = schedulerView
   }, [schedulerView])
 
+  useEffect(() => {
+    topicsRef.current = topics
+  }, [topics])
+
+  useEffect(() => {
+    selectedTopicRef.current = selectedTopic
+  }, [selectedTopic])
+
   const enterSubAgentView = useCallback((taskId: string, description: string): Command => {
     const newView: SubAgentView = {
       taskId,
@@ -714,6 +732,7 @@ export function useChat(): UseChatReturn {
     deleteTopic,
     requestSessionList,
     requestTopicList,
+    topicRefreshTrigger,
     requestChannelList,
     selectChannel,
     selectSession,