diff --git a/src/tools/task/runtime.rs b/src/tools/task/runtime.rs
index 94fc4aa..c01746c 100644
--- a/src/tools/task/runtime.rs
+++ b/src/tools/task/runtime.rs
@@ -338,7 +338,7 @@ impl DefaultSubAgentRuntime {
                 sender_id: None,
                 chat_id: Some(session.parent_chat_id.clone()),
                 session_id: Some(session.session_id.clone()),
-                topic_id: session.parent_topic_id.clone(),
+                topic_id: None,
                 message_id: None,
                 message_seq: None,
                 subagent_description: Some(session.description.clone()),