fix: sanitize JSON responses in automatic chat renaming

extensions/python/monologue_start/_60_rename_chat.py

@@ -53,6 +53,42 @@ async def change_name(self):
             # update name
             if new_name:
                 new_name = " ".join(str(new_name).split())
+                # P028: Guard against JSON-looking names (utility model echoes)
+                stripped = new_name.lstrip()
+                if stripped and stripped[0] in "{[":
+                    import json as _json
+                    extracted = None
+                    # Step 1: Try to parse JSON and extract headline (best quality)
+                    try:
+                        parsed = _json.loads(stripped)
+                        headline = parsed.get("headline")
+                        if isinstance(headline, str) and headline.strip():
+                            extracted = headline.strip()
+                        else:
+                            thoughts = parsed.get("thoughts")
+                            if isinstance(thoughts, list) and thoughts:
+                                first = thoughts[0]
+                                if isinstance(first, str) and first.strip():
+                                    extracted = first.strip()
+                    except (_json.JSONDecodeError, ValueError, AttributeError):
+                        pass
+                    # Step 2: Fall back to first user message topic
+                    if not extracted:
+                        try:
+                            msgs = self.agent.history.output()
+                            for msg in msgs:
+                                if not msg.ai and msg.content:
+                                    content = str(msg.content)
+                                    first_line = content.split(chr(10))[0].split(".")[0].strip()
+                                    if first_line:
+                                        extracted = first_line[:40]
+                                        if len(first_line) > 40:
+                                            extracted += "..."
+                                        break
+                        except Exception:
+                            pass
+                    # Step 3: Last resort
+                    new_name = extracted or "Conversation"
                 if len(new_name) > 40:
                     new_name = new_name[:40] + "..."
                 if not new_name: