fix: improve 404 detection for deleted conversations

- Check for 'not found' message (server response) in addition to '404'
- Only clear stored conversation ID on actual 404 errors
- Prevent unnecessary retries for deleted conversations
- Don't clear conversation on transient network errors

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ui/src/components/AssistantPanel.tsx

@@ -57,9 +57,13 @@ export function AssistantPanel({ projectName, isOpen, onClose }: AssistantPanelP
   // Clear stored conversation ID if it no longer exists (404 error)
   useEffect(() => {
     if (conversationError && conversationId) {
+      const message = conversationError.message.toLowerCase()
+      // Only clear for 404 errors, not transient network issues
+      if (message.includes('not found') || message.includes('404')) {
         console.warn(`Conversation ${conversationId} not found, clearing stored ID`)
         setConversationId(null)
       }
+    }
   }, [conversationError, conversationId])
 
   // Convert API messages to ChatMessage format for the chat component

ui/src/hooks/useConversations.ts

@@ -27,8 +27,11 @@ export function useConversation(projectName: string | null, conversationId: numb
     enabled: !!projectName && !!conversationId,
     staleTime: 30_000, // Cache for 30 seconds
     retry: (failureCount, error) => {
-      // Don't retry on 404 errors (conversation doesn't exist)
-      if (error instanceof Error && error.message.includes('404')) {
+      // Don't retry on "not found" errors (404) - conversation doesn't exist
+      if (error instanceof Error && (
+        error.message.toLowerCase().includes('not found') ||
+        error.message === 'HTTP 404'
+      )) {
         return false
       }
       return failureCount < 3