fix: 同步前置 subAgentViewRef/subAgentStackRef,消除子智能体视图间歇性丢消息

根因: subAgentViewRef.current 在 setSubAgentStack updater 内部更新,updater 在 React render 阶段才执行,不是同步的。从 enterSubAgentView() 返回到 React render 之间存在竞态窗口,WebSocket 消息读到过时的 ref 被错误路由到主视图并丢弃。

修复: ref 赋值从 updater 内部移到 setSubAgentStack 之前同步执行。新增 subAgentStackRef 供 exit/navigate 在空依赖闭包中读取最新栈计算新栈顶。selectTopic/selectChannel/selectSession 清空栈时也同步设置 ref。updater 变纯函数,StrictMode 双调用无副作用。

Plan: fix-subagent-view-ref-race

web/src/hooks/useChat.ts

@@ -181,6 +181,9 @@ export function useChat(): UseChatReturn {
 
   // Ref to track subAgentView and schedulerView for use in callbacks
   const subAgentViewRef = useRef<SubAgentView | null>(null)
+  // 同步追踪 subAgentStack，供 exit/navigate 在回调中读取最新栈计算新栈顶
+  // ref 必须在事件处理器返回前同步更新，避免 WebSocket 消息路由竞态
+  const subAgentStackRef = useRef<SubAgentView[]>([])
   const schedulerViewRef = useRef<SchedulerJobView | null>(null)
   const topicsRef = useRef<Topic[]>([])
   const selectedTopicRef = useRef<string | null>(null)
@@ -1007,6 +1010,8 @@ export function useChat(): UseChatReturn {
   const selectTopic = useCallback((topicId: string) => {
     setSelectedTopic(topicId)
     setMessages([])
+    subAgentViewRef.current = null
+    subAgentStackRef.current = []
     setSubAgentStack([])
   }, [])
 
@@ -1053,6 +1058,8 @@ export function useChat(): UseChatReturn {
     setTopics([])
     setSelectedTopic(null)
     setMessages([])
+    subAgentViewRef.current = null
+    subAgentStackRef.current = []
     setSubAgentStack([])
     setIsLoading(true)
   }, [selectedChannel])
@@ -1063,6 +1070,8 @@ export function useChat(): UseChatReturn {
     setTopics([])
     setSelectedTopic(null)
     setMessages([])
+    subAgentViewRef.current = null
+    subAgentStackRef.current = []
     setSubAgentStack([])
     setIsLoading(true)
   }, [selectedSessionId])
@@ -1075,11 +1084,15 @@ export function useChat(): UseChatReturn {
     }
   }, [sessionId])
 
-  // Keep refs in sync with state
+  // Keep refs in sync with state (兜底，确保 ref 与 state 最终一致)
   useEffect(() => {
     subAgentViewRef.current = subAgentView
   }, [subAgentView])
 
+  useEffect(() => {
+    subAgentStackRef.current = subAgentStack
+  }, [subAgentStack])
+
   useEffect(() => {
     schedulerViewRef.current = schedulerView
   }, [schedulerView])
@@ -1100,12 +1113,12 @@ export function useChat(): UseChatReturn {
       status: 'loading',
       messages: [],
     }
-    setSubAgentStack((prev) => {
-      const newStack = [...prev, newView]
-      // Sync ref immediately so WebSocket response routing works correctly
-      subAgentViewRef.current = newView
-      return newStack
-    })
+    // 同步设置 ref，消除竞态窗口：updater 在 React render 阶段才执行，
+    // 期间 WebSocket 消息会读到过时的 ref。ref 必须在事件处理器返回前同步更新。
+    subAgentViewRef.current = newView
+    subAgentStackRef.current = [...subAgentStackRef.current, newView]
+    // updater 变纯函数，不再有副作用
+    setSubAgentStack((prev) => [...prev, newView])
     return {
       type: 'load_task_messages',
       task_id: taskId,
@@ -1113,42 +1126,45 @@ export function useChat(): UseChatReturn {
   }, [])
 
   const exitSubAgentView = useCallback((): Command | null => {
-    let command: Command | null = null
-    setSubAgentStack((prev) => {
-      if (prev.length <= 1) {
-        subAgentViewRef.current = null
-        return []
-      }
-      const newStack = prev.slice(0, -1)
-      const newTop = newStack[newStack.length - 1]
-      subAgentViewRef.current = newTop
-      // 清空目标层 messages + status 置 loading，并准备重新拉取命令
-      const clearedStack = [...newStack]
-      clearedStack[clearedStack.length - 1] = { ...newTop, messages: [], status: 'loading' }
-      command = { type: 'load_task_messages', task_id: newTop.taskId }
-      return clearedStack
-    })
-    return command
+    // 从 ref 读取最新栈（useCallback 依赖为空，闭包中的 subAgentStack 是旧值）
+    const current = subAgentStackRef.current
+    if (current.length <= 1) {
+      subAgentViewRef.current = null
+      subAgentStackRef.current = []
+      setSubAgentStack([])
+      return null
+    }
+    const newStack = current.slice(0, -1)
+    const newTop = newStack[newStack.length - 1]
+    // 同步设置 ref，消除竞态窗口
+    subAgentViewRef.current = newTop
+    // 清空目标层 messages + status 置 loading，准备重新拉取
+    const clearedStack = [...newStack]
+    clearedStack[clearedStack.length - 1] = { ...newTop, messages: [], status: 'loading' }
+    subAgentStackRef.current = clearedStack
+    setSubAgentStack(clearedStack)
+    return { type: 'load_task_messages', task_id: newTop.taskId }
   }, [])
 
   const navigateToSubAgentLevel = useCallback((index: number): Command | null => {
-    let command: Command | null = null
-    setSubAgentStack((prev) => {
-      if (index < 0) {
-        // -1 means go back to main session (clear all)
-        subAgentViewRef.current = null
-        return []
-      }
-      if (index >= prev.length) return prev
-      const newStack = prev.slice(0, index + 1)
-      const newTop = newStack[newStack.length - 1]
-      subAgentViewRef.current = newTop
-      const clearedStack = [...newStack]
-      clearedStack[clearedStack.length - 1] = { ...newTop, messages: [], status: 'loading' }
-      command = { type: 'load_task_messages', task_id: newTop.taskId }
-      return clearedStack
-    })
-    return command
+    const current = subAgentStackRef.current
+    if (index < 0) {
+      // -1 means go back to main session (clear all)
+      subAgentViewRef.current = null
+      subAgentStackRef.current = []
+      setSubAgentStack([])
+      return null
+    }
+    if (index >= current.length) return null
+    const newStack = current.slice(0, index + 1)
+    const newTop = newStack[newStack.length - 1]
+    // 同步设置 ref，消除竞态窗口
+    subAgentViewRef.current = newTop
+    const clearedStack = [...newStack]
+    clearedStack[clearedStack.length - 1] = { ...newTop, messages: [], status: 'loading' }
+    subAgentStackRef.current = clearedStack
+    setSubAgentStack(clearedStack)
+    return { type: 'load_task_messages', task_id: newTop.taskId }
   }, [])
 
   // 记忆方法