diff --git a/src/lambdas/agent-runner/handler.py b/src/lambdas/agent-runner/handler.py
index b8d39f5..bd26ccc 100644
--- a/src/lambdas/agent-runner/handler.py
+++ b/src/lambdas/agent-runner/handler.py
@@ -142,7 +142,10 @@ def handler(event, context):
     channel = first.get('channel', 'telegram')
     chat_id = first.get('chat_id', '')
     message_thread_id = first.get('message_thread_id')  # int or None
-    actor_id = f"{channel}:{chat_id}"
+    # Use sender's user ID for identity (not chat_id, which is the group ID in group chats)
+    from_info_early = first.get('messages', [{}])[0]
+    sender_id = from_info_early.get('from_id') or chat_id
+    actor_id = f"{channel}:{sender_id}"
 
     # ── User registry ─────────────────────────────────────────────────────
     from_info = first.get('messages', [{}])[0]