fix(agent): address message send races

Generated-By: PostHog Code
Task-Id: a0ce6802-e1c9-4c53-bcf0-85bacfdf2536

Author: tatoalo

packages/ui/src/features/sessions/components/SessionView.tsx

@@ -1,4 +1,5 @@
 import { Pause, Spinner, Warning } from "@phosphor-icons/react";
+import { contentToXml } from "@posthog/core/message-editor/content";
 import {
   createLatestPlanTracker,
   SESSION_SERVICE,
@@ -299,6 +300,9 @@ export function SessionView({
   ]);
 
   const isCloudRun = useIsWorkspaceCloudRun(taskId);
+  const editorRef = useRef<PromptInputHandle>(null);
+  const sendInFlightRef = useRef(false);
+  const [isSendingPrompt, setIsSendingPrompt] = useState(false);
 
   const latestPlanTrackerRef = useRef<ReturnType<
     typeof createLatestPlanTracker
@@ -309,22 +313,25 @@ export function SessionView({
     (): Plan | null => latestPlanTracker.update(events) as Plan | null,
     [events, latestPlanTracker],
   );
-  const [isSendingPrompt, setIsSendingPrompt] = useState(false);
-
   const handleSubmit = useCallback(
     async (text: string): Promise<void> => {
-      if (!text.trim() || isSendingPrompt) return;
+      if (!text.trim() || sendInFlightRef.current) return;
 
+      sendInFlightRef.current = true;
       setIsSendingPrompt(true);
       try {
         if (await onSendPrompt(text)) {
-          editorRef.current?.clear();
+          const editor = editorRef.current;
+          if (editor && contentToXml(editor.getContent()) === text) {
+            editor.clear();
+          }
         }
       } finally {
+        sendInFlightRef.current = false;
         setIsSendingPrompt(false);
       }
     },
-    [isSendingPrompt, onSendPrompt],
+    [onSendPrompt],
   );
 
   const handleBeforeSubmit = useCallback(
@@ -345,7 +352,6 @@ export function SessionView({
   const cancelQueuedEdit = useCancelQueuedMessageEdit(taskId);
 
   const [isDraggingFile, setIsDraggingFile] = useState(false);
-  const editorRef = useRef<PromptInputHandle>(null);
   const promptRecallRef = useRef<PromptRecallHandler | null>(null);
   const handlePromptRecall = useCallback<PromptRecallHandler>(
     (direction) => promptRecallRef.current?.(direction) ?? null,