fix(frontend): hide stale follow-up chips while a turn is streaming (#3395) (#3396)

* fix(frontend): hide stale follow-up chips while a turn is streaming (#3395)

Follow-up suggestion chips are generated when a turn finishes streaming,
but `showFollowups` did not exclude the streaming state. If a user sent a
new message before the previous response finished, the old chips (and the
lone close button) stayed mounted and overlapped the To-dos panel and the
input box.

Gate `showFollowups` on `status !== "streaming"` so stale chips are never
shown while a response is in progress.

* fix(frontend): suppress follow-up suggestions for user-interrupted turns (#3395)

Gating showFollowups on status alone was not enough: stopping a streaming
turn (or sending a new message mid-stream, which also stops it) flips
status back to a non-streaming state and triggers the follow-up generation
effect on that streaming->ready transition, producing chips for a
half-finished, interrupted response.

Track user interruption with a ref set in the stop path, and have the
generation effect skip that transition (and clear/hide any pending chips),
so follow-ups are only generated for turns that finished on their own.

frontend/src/components/workspace/input-box.tsx

@@ -417,6 +417,9 @@ export function InputBox({
     useState<string | null>(null);
   const lastGeneratedForAiIdRef = useRef<string | null>(null);
   const wasStreamingRef = useRef(false);
+  // Set when the user stops a streaming turn. Such a turn ends on a
+  // half-finished response, so we must NOT generate follow-up suggestions for it.
+  const stoppedByUserRef = useRef(false);
   const messagesRef = useRef(thread.messages);
 
   const clearVoiceRestartTimer = useCallback(() => {
@@ -1148,6 +1151,16 @@ export function InputBox({
     ],
   );
 
+  const handleStopStreaming = useCallback(() => {
+    // Mark the in-progress turn as user-interrupted so the next
+    // streaming->ready transition does not suggest follow-ups for it.
+    stoppedByUserRef.current = true;
+    setFollowups([]);
+    setFollowupsHidden(true);
+    setFollowupsLoading(false);
+    onStop?.();
+  }, [onStop]);
+
   const handleSubmit = useCallback(
     async (message: PromptInputMessage) => {
       if (status === "streaming") {
@@ -1200,7 +1213,7 @@ export function InputBox({
         return handleCompactCommand();
       }
       if (submitAction.kind === "stop") {
-        onStop?.();
+        handleStopStreaming();
         return;
       }
       if (submitAction.kind === "empty") {
@@ -1215,7 +1228,7 @@ export function InputBox({
       abortVoiceInput,
       handleCompactCommand,
       handleGoalCommand,
-      onStop,
+      handleStopStreaming,
       selectedSlashSkill,
       status,
       submitThreadMessage,
@@ -1923,6 +1936,10 @@ export function InputBox({
     !showSkillSuggestions &&
     !selectedSlashSkill &&
     !followupsHidden &&
+    // Never show stale follow-up chips while a turn is streaming: a message
+    // sent before the previous response finished would otherwise leave the
+    // old chips (and the lone close button) overlapping the input box.
+    status !== "streaming" &&
     (followupsLoading || followups.length > 0);
 
   useEffect(() => {
@@ -1945,6 +1962,13 @@ export function InputBox({
       return;
     }
 
+    // The turn was interrupted by the user, so skip generating follow-ups for
+    // this half-finished response.
+    if (stoppedByUserRef.current) {
+      stoppedByUserRef.current = false;
+      return;
+    }
+
     if (disabled || isMock) {
       return;
     }
@@ -2666,7 +2690,7 @@ export function InputBox({
               onClick={(e) => {
                 if (status === "streaming") {
                   e.preventDefault();
-                  onStop?.();
+                  handleStopStreaming();
                 }
               }}
             />