Guard isinstance(event, dict) in SSE parser

src/lambdas/agent-runner/handler.py

@@ -224,6 +224,8 @@ def handler(event, context):
                         event = json.loads(data)
                     except (json.JSONDecodeError, ValueError):
                         continue
+                    if not isinstance(event, dict):
+                        continue
                     # Extract text delta from contentBlockDelta
                     delta = event.get('event', {}).get('contentBlockDelta', {}).get('delta', {})
                     token = delta.get('text', '') or event.get('data', '')