frontend/src/pages/AssistantChatPage.tsx

@@ -259,6 +259,11 @@ export default function AssistantChatPage() {
   }, [])
 
   const handleNewChat = async () => {
+    // Clear stale state immediately — don't wait for API to return
+    setShowTaskLane(false)
+    setActiveQuestions([])
+    setActiveActions([])
+    setMessages([])
     try {
       const session = await aiSessionsApi.createChatSession({
         intake_type: 'free_text',
@@ -275,11 +280,6 @@ export default function AssistantChatPage() {
       currentChatRef.current = session.session_id
       setChats(prev => [chatItem, ...prev])
       setActiveChatId(session.session_id)
-      setMessages([])
-      // Clear TaskLane from previous session
-      setShowTaskLane(false)
-      setActiveQuestions([])
-      setActiveActions([])
     } catch {
       toast.error('Failed to create chat')
     }
@@ -315,11 +315,14 @@ export default function AssistantChatPage() {
     setMessages(prev => [...prev, { role: 'user', content: userMessage }])
     setLoading(true)
 
+    const sentForChatId = activeChatId
     try {
       const response = await aiSessionsApi.sendChatMessage(activeChatId, {
         message: userMessage,
         upload_ids: completedUploadIds.length > 0 ? completedUploadIds : undefined,
       })
+      // Guard: discard if user switched to a different chat while this was in flight
+      if (currentChatRef.current !== sentForChatId) return
       analytics.aiFeatureUsed({ feature: 'assistant_chat' })
       setMessages(prev => [
         ...prev,
@@ -327,20 +330,20 @@ export default function AssistantChatPage() {
       ])
       setChats(prev =>
         prev.map(c =>
-          c.id === activeChatId
+          c.id === sentForChatId
             ? { ...c, message_count: c.message_count + 2, title: c.message_count === 0 ? userMessage.slice(0, 100) : c.title, updated_at: new Date().toISOString() }
             : c
         )
       )
       // Load branches if fork was created
-      if (response.fork && activeChatId) {
-        branching.loadBranches(activeChatId)
+      if (response.fork && sentForChatId) {
+        branching.loadBranches(sentForChatId)
       }
       // Show task lane if AI sent questions or actions
       const hasQuestions = response.questions && response.questions.length > 0
       const hasActions = response.actions && response.actions.length > 0
       if (hasQuestions || hasActions) {
-        if (activeChatId) clearTaskState(activeChatId)
+        clearTaskState(sentForChatId)
         setActiveQuestions(response.questions || [])
         setActiveActions(response.actions || [])
         setShowTaskLane(true)
@@ -377,19 +380,22 @@ export default function AssistantChatPage() {
     setMessages(prev => [...prev, { role: 'user', content: userMessage }])
     setLoading(true)
 
+    const sentForChatId = activeChatId
     try {
       const response = await aiSessionsApi.sendChatMessage(activeChatId, { message: userMessage })
+      // Guard: discard if user switched to a different chat while this was in flight
+      if (currentChatRef.current !== sentForChatId) return
       setMessages(prev => [
         ...prev,
         { role: 'assistant', content: response.content, suggestedFlows: response.suggested_flows, fork: response.fork, actions: response.actions, questions: response.questions },
       ])
-      if (response.fork && activeChatId) {
-        branching.loadBranches(activeChatId)
+      if (response.fork && sentForChatId) {
+        branching.loadBranches(sentForChatId)
       }
       // Update task lane based on AI response
       const hasQuestions = response.questions && response.questions.length > 0
       const hasActions = response.actions && response.actions.length > 0
-      if (activeChatId) clearTaskState(activeChatId)
+      clearTaskState(sentForChatId)
       if (hasQuestions || hasActions) {
         setActiveQuestions(response.questions || [])
         setActiveActions(response.actions || [])
@@ -430,6 +436,10 @@ export default function AssistantChatPage() {
   }
 
   const handleResumeNew = async (summary: string) => {
+    // Clear stale state immediately — don't wait for API to return
+    setShowTaskLane(false)
+    setActiveQuestions([])
+    setActiveActions([])
     try {
       const resumePrompt = `I'm continuing a previous troubleshooting session. Here's where we left off:\n\n${summary}\n\nPlease review this context and help me continue from where we stopped.`
       const session = await aiSessionsApi.createChatSession({