fix: a greeting does not name the thread

The first message named the conversation, so a rail of them read "hi", "hello",
"hi". The name now waits for the first turn that is actually a question —
usually the very next one — and the thread stays "New chat" until then.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TqXevQJhxFrM7jJg82cgZN

backend/app/routers/ai_mode.py

@@ -212,8 +212,11 @@ async def ask(conversation_id: int, data: AskIn, db: Session = Depends(get_db),
     answer = ConversationMessage(conversation_id=conversation.id, role="assistant",
                                  content=reply, citations=citations)
     db.add(answer)
-    # The first question names the thread; "New chat" ages badly in a rail of them.
-    if conversation.title == "New chat":
+    # The first *question* names the thread; "New chat" ages badly in a rail of
+    # them, and a rail of threads called "hi" ages worse. A greeting is not what
+    # the conversation turned out to be about, so the name waits for the turn
+    # that is — which is usually the very next one.
+    if conversation.title == "New chat" and mode != "chat":
         conversation.title = question[:80] + ("…" if len(question) > 80 else "")
     conversation.updated_at = datetime.utcnow()
     db.commit()

backend/tests/test_ai_mode.py

@@ -191,6 +191,21 @@ class AiModeRouteTests(_AiModeBase):
             _, second = self.ask('And the workup?', conversation_id)
         self.assertEqual(second.json()['title'], 'What causes febrile seizures?')
 
+    def test_a_greeting_does_not_name_the_thread(self):
+        """A rail of threads called "hi" is worse than one called New chat.
+
+        The name waits for the turn the conversation turns out to be about,
+        which is usually the very next one.
+        """
+        with self.reply_with("Hello! What would you like to work on?"):
+            conversation_id, first = self.ask('hi')
+        self.assertEqual(first.json()['title'], 'New chat')
+        self.assertEqual(first.json()['source_count'], 0)
+
+        with self.reply_with("Fever, usually."):
+            _, second = self.ask('What causes febrile seizures?', conversation_id)
+        self.assertEqual(second.json()['title'], 'What causes febrile seizures?')
+
     def test_both_turns_are_stored_so_a_thread_can_be_reopened(self):
         with self.reply_with("Because of fever [[article:7]]."):
             conversation_id, _ = self.ask('why do febrile seizures happen?')