fix: improve business logic in prompt editor and fix cursor bugs in Plan mode

apps/web/src/components/ChatView.tsx

@@ -630,23 +630,46 @@ export default function ChatView({ threadId }: ChatViewProps) {
     pendingUserInputs.length > 0 ||
     (showPlanFollowUpPrompt && activeProposedPlan !== null);
   const composerFooterHasWideActions = showPlanFollowUpPrompt || activePendingProgress !== null;
+  const lastSyncedPendingInputRef = useRef<{
+    requestId: string | null;
+    questionId: string | null;
+  } | null>(null);
   useEffect(() => {
-    if (!activePendingProgress) {
+    const nextCustomAnswer = activePendingProgress?.customAnswer;
+    if (typeof nextCustomAnswer !== "string") {
+      lastSyncedPendingInputRef.current = null;
       return;
     }
-    promptRef.current = activePendingProgress.customAnswer;
-    setComposerCursor(activePendingProgress.customAnswer.length);
+    const nextRequestId = activePendingUserInput?.requestId ?? null;
+    const nextQuestionId = activePendingProgress?.activeQuestion?.id ?? null;
+    const questionChanged =
+      lastSyncedPendingInputRef.current?.requestId !== nextRequestId ||
+      lastSyncedPendingInputRef.current?.questionId !== nextQuestionId;
+    const textChangedExternally = promptRef.current !== nextCustomAnswer;
+
+    lastSyncedPendingInputRef.current = {
+      requestId: nextRequestId,
+      questionId: nextQuestionId,
+    };
+
+    if (!questionChanged && !textChangedExternally) {
+      return;
+    }
+
+    promptRef.current = nextCustomAnswer;
+    setComposerCursor(nextCustomAnswer.length);
     setComposerTrigger(
       detectComposerTrigger(
-        activePendingProgress.customAnswer,
-        expandCollapsedComposerCursor(
-          activePendingProgress.customAnswer,
-          activePendingProgress.customAnswer.length,
-        ),
+        nextCustomAnswer,
+        expandCollapsedComposerCursor(nextCustomAnswer, nextCustomAnswer.length),
       ),
     );
     setComposerHighlightedItemId(null);
-  }, [activePendingProgress, activePendingUserInput?.requestId]);
+  }, [
+    activePendingProgress?.customAnswer,
+    activePendingUserInput?.requestId,
+    activePendingProgress?.activeQuestion?.id,
+  ]);
   useEffect(() => {
     attachmentPreviewHandoffByMessageIdRef.current = attachmentPreviewHandoffByMessageId;
   }, [attachmentPreviewHandoffByMessageId]);

apps/web/src/components/ComposerPromptEditor.tsx

@@ -629,6 +629,7 @@ function ComposerPromptEditorInner({
   const [editor] = useLexicalComposerContext();
   const onChangeRef = useRef(onChange);
   const snapshotRef = useRef({ value, cursor: clampCursor(value, cursor) });
+  const isApplyingControlledUpdateRef = useRef(false);
 
   useEffect(() => {
     onChangeRef.current = onChange;
@@ -645,21 +646,26 @@ function ComposerPromptEditorInner({
       return;
     }
 
-    if (previousSnapshot.value !== value) {
-      editor.update(() => {
-        $setComposerEditorPrompt(value);
-      });
-    }
-
     snapshotRef.current = { value, cursor: normalizedCursor };
 
     const rootElement = editor.getRootElement();
-    if (!rootElement || document.activeElement !== rootElement) {
+    const isFocused = Boolean(rootElement && document.activeElement === rootElement);
+    if (previousSnapshot.value === value && !isFocused) {
       return;
     }
 
+    isApplyingControlledUpdateRef.current = true;
     editor.update(() => {
-      $setSelectionAtComposerOffset(normalizedCursor);
+      const valueChanged = previousSnapshot.value !== value;
+      if (previousSnapshot.value !== value) {
+        $setComposerEditorPrompt(value);
+      }
+      if (valueChanged || isFocused) {
+        $setSelectionAtComposerOffset(normalizedCursor);
+      }
+    });
+    queueMicrotask(() => {
+      isApplyingControlledUpdateRef.current = false;
     });
   }, [cursor, editor, value]);
 
@@ -705,9 +711,7 @@ function ComposerPromptEditorInner({
       focus: () => {
         focusAt(snapshotRef.current.cursor);
       },
-      focusAt: (nextCursor: number) => {
-        focusAt(nextCursor);
-      },
+      focusAt,
       focusAtEnd: () => {
         focusAt(snapshotRef.current.value.length);
       },
@@ -728,6 +732,9 @@ function ComposerPromptEditorInner({
       if (previousSnapshot.value === nextValue && previousSnapshot.cursor === nextCursor) {
         return;
       }
+      if (isApplyingControlledUpdateRef.current) {
+        return;
+      }
       snapshotRef.current = {
         value: nextValue,
         cursor: nextCursor,