wip(handoff): start issue cleanup plan sections 1 and 2

Co-Authored-By: Codex <noreply@openai.com>

frontend/src/pages/AssistantChatPage.tsx

@@ -267,6 +267,15 @@ export default function AssistantChatPage() {
   // path: post-claim the chat surface had no messages and the senior
   // landed on a blank pane).
   const loadedChatIdsRef = useRef<Set<string>>(new Set())
+  const guardCurrentChat = useCallback((expectedChatId: string, source: string) => {
+    if (currentChatRef.current === expectedChatId) return true
+    console.warn('[AssistantChat] Discarded stale async result', {
+      source,
+      expectedChatId,
+      currentChatId: currentChatRef.current,
+    })
+    return false
+  }, [])
 
   // Persist active chat ID to sessionStorage
   useEffect(() => {
@@ -612,7 +621,7 @@ export default function AssistantChatPage() {
     }
     window.addEventListener(PILOT_INLINE_SCRIPT_EVENT, handler as EventListener)
     return () => window.removeEventListener(PILOT_INLINE_SCRIPT_EVENT, handler as EventListener)
-  }, [activeFix])
+  }, [activeFix, activeChatId])
 
   const loadChats = async () => {
     try {
@@ -684,7 +693,7 @@ export default function AssistantChatPage() {
     try {
       const list = await sessionFactsApi.list(chatId)
       // Guard: discard stale fetch if the user switched chats mid-flight.
-      if (currentChatRef.current !== chatId) return
+      if (!guardCurrentChat(chatId, 'refreshFacts')) return
       setFacts(list)
       // Auto-open the task lane when the session has facts so the engineer
       // can see them — without this, a session with only facts (no open
@@ -699,7 +708,7 @@ export default function AssistantChatPage() {
       // Best-effort — facts are accessory state. Surfacing a toast on every
       // refetch failure would be noisy; the empty state explains the absence.
     }
-  }, [])
+  }, [guardCurrentChat])
 
   // Phase 3 — active suggested fix + resolution-note preview.
   // Declared BEFORE refreshSessionDerived / handleAddNote so the useCallback
@@ -707,7 +716,7 @@ export default function AssistantChatPage() {
   const refreshActiveFix = useCallback(async (chatId: string) => {
     try {
       const fix = await sessionSuggestedFixesApi.getActive(chatId)
-      if (currentChatRef.current !== chatId) return
+      if (!guardCurrentChat(chatId, 'refreshActiveFix')) return
       setActiveFix((prev) => {
         // If the active fix changed (AI emitted a new SUGGEST_FIX that
         // superseded the prior), close the script panel so the engineer
@@ -719,7 +728,7 @@ export default function AssistantChatPage() {
       // No-fix-yet (404) is normalized to null inside the client. Genuine
       // failures stay silent — accessory state, not load-bearing.
     }
-  }, [])
+  }, [guardCurrentChat])
 
   // Kind-aware preview fetch: Resolve hits /resolution-note/preview,
   // Escalate hits /escalation-package/preview. They're cached separately
@@ -733,7 +742,7 @@ export default function AssistantChatPage() {
       const p = effectiveKind === 'resolve'
         ? await sessionSuggestedFixesApi.getResolutionNotePreview(chatId)
         : await sessionSuggestedFixesApi.getEscalationPackagePreview(chatId)
-      if (currentChatRef.current !== chatId) return
+      if (!guardCurrentChat(chatId, 'refreshPreview')) return
       setPreviewData(p)
     } catch (err: unknown) {
       const status = (err as { response?: { status?: number } })?.response?.status
@@ -745,7 +754,7 @@ export default function AssistantChatPage() {
     } finally {
       setPreviewLoading(false)
     }
-  }, [previewKind])
+  }, [guardCurrentChat, previewKind])
 
   // Trigger preview refresh with a 500ms debounce. The backend cache short-
   // circuits same-state calls, but the network round-trip is still avoidable
@@ -880,7 +889,7 @@ export default function AssistantChatPage() {
     }
     // No draft, no template — route to the Script Builder tab.
     setChatTab('script_builder')
-  }, [activeFix])
+  }, [activeFix, activeChatId])
 
   // Phase 9 Task 13: TemplateMatchPanel "I ran this" — stamps applied_at so the
   // ProposalBanner transitions from Proposed to Verifying. Shared useCallback so
@@ -1108,13 +1117,13 @@ export default function AssistantChatPage() {
       // Guard: if the user switched to a different chat while this API call was
       // in flight (e.g. clicked "New Chat"), discard stale results so we don't
       // clobber the new session's task lane state.
-      if (currentChatRef.current !== chatId) return
+      if (!guardCurrentChat(chatId, 'selectChat')) return
       setActiveSessionStatus(detail.status)
       setActivePsaTicketId(detail.psa_ticket_id)
       if (detail.psa_ticket_id) {
         integrationsApi.getTicket(detail.psa_ticket_id)
           .then(ticket => {
-            if (currentChatRef.current !== chatId) return
+            if (!guardCurrentChat(chatId, 'selectChat.ticket')) return
             setLinkedTicket(ticket)
           })
           .catch(() => {})
@@ -1149,7 +1158,7 @@ export default function AssistantChatPage() {
     } catch {
       setMessages([])
     }
-  }, [refreshSessionDerived])
+  }, [guardCurrentChat, refreshSessionDerived, resetSessionDerivedState])
 
   const handleAIAnalysis = useCallback(async () => {
     if (!urlSessionId || !magicHandoff) return
@@ -1162,7 +1171,7 @@ export default function AssistantChatPage() {
       setMagicState('dismissed')
       void loadChats()
       await selectChat(urlSessionId)
-      if (currentChatRef.current !== sentForChatId) return
+      if (!guardCurrentChat(sentForChatId, 'handleAIAnalysis.afterSelect')) return
 
       const assessment = magicHandoff.ai_assessment_data
       const snapshot = magicHandoff.snapshot as Record<string, unknown>
@@ -1192,7 +1201,7 @@ export default function AssistantChatPage() {
       setMessages(prev => [...prev, { role: 'user', content: briefing }])
       setLoading(true)
       const response = await aiSessionsApi.sendChatMessage(urlSessionId, { message: briefing })
-      if (currentChatRef.current !== sentForChatId) return
+      if (!guardCurrentChat(sentForChatId, 'handleAIAnalysis.chatResponse')) return
       setMessages(prev => [
         ...prev,
         {
@@ -1233,7 +1242,7 @@ export default function AssistantChatPage() {
       setActiveOptionKey(null)
       setLoading(false)
     }
-  }, [urlSessionId, magicHandoff, setSearchParams, selectChat])
+  }, [guardCurrentChat, urlSessionId, magicHandoff, setSearchParams, selectChat])
 
   const handleNewChat = async () => {
     // Invalidate currentChatRef BEFORE the await so any in-flight handleSend/handleTaskSubmit
@@ -1306,7 +1315,7 @@ export default function AssistantChatPage() {
         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
+      if (!guardCurrentChat(sentForChatId, 'handleSend')) return
       analytics.aiFeatureUsed({ feature: 'assistant_chat' })
       setMessages(prev => [
         ...prev,
@@ -1396,7 +1405,7 @@ export default function AssistantChatPage() {
     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
+      if (!guardCurrentChat(sentForChatId, 'handleTaskSubmit')) return
       setMessages(prev => [
         ...prev,
         { role: 'assistant', content: response.content, suggestedFlows: response.suggested_flows, fork: response.fork, actions: response.actions, questions: response.questions },
@@ -1491,7 +1500,7 @@ export default function AssistantChatPage() {
 
       const response = await aiSessionsApi.sendChatMessage(session.session_id, { message: resumePrompt })
       // Guard: discard if user switched to a different chat while this was in flight
-      if (currentChatRef.current !== session.session_id) return
+      if (!guardCurrentChat(session.session_id, 'handleResumeNew')) return
       setMessages(prev => [
         ...prev,
         { role: 'assistant', content: response.content, suggestedFlows: response.suggested_flows, fork: response.fork, actions: response.actions, questions: response.questions },