diff --git a/pkg/agent/loop.go b/pkg/agent/loop.go
index db9efa2cf..e9ed57c91 100644
--- a/pkg/agent/loop.go
+++ b/pkg/agent/loop.go
@@ -571,7 +571,7 @@ func (al *AgentLoop) processSystemMessage(
 		UserMessage:     fmt.Sprintf("[System: %s] %s", msg.SenderID, msg.Content),
 		DefaultResponse: "Background task completed.",
 		EnableSummary:   false,
-		SendResponse:    true,
+		SendResponse:    false,  // Prevent duplicate responses caused by system message processing
 	})
 }
 
diff --git a/pkg/tools/subagent.go b/pkg/tools/subagent.go
index 69f1a49a2..4e08c70af 100644
--- a/pkg/tools/subagent.go
+++ b/pkg/tools/subagent.go
@@ -20,6 +20,7 @@ type SubagentTask struct {
 	Status        string
 	Result        string
 	Created       int64
+	announcedOnce sync.Once  // Ensures the completion announcement is sent only once
 }
 
 type SubagentManager struct {
@@ -216,7 +217,7 @@ After completing the task, provide a clear summary of what was done.`
 	}
 
 	// Send announce message back to main agent
-	if sm.bus != nil {
+	task.announcedOnce.Do(func() {
 		announceContent := fmt.Sprintf("Task '%s' completed.\n\nResult:\n%s", task.Label, task.Result)
 		pubCtx, pubCancel := context.WithTimeout(context.Background(), 5*time.Second)
 		defer pubCancel()
@@ -227,7 +228,21 @@ After completing the task, provide a clear summary of what was done.`
 			ChatID:  fmt.Sprintf("%s:%s", task.OriginChannel, task.OriginChatID),
 			Content: announceContent,
 		})
-	}
+	})
+
+		task.announcedOnce.Do(func() {
+			// Send announce message back to main agent
+			announceContent := fmt.Sprintf("Task '%s' completed.\n\nResult:\n%s", task.Label, task.Result)
+			pubCtx, pubCancel := context.WithTimeout(context.Background(), 5*time.Second)
+			defer pubCancel()
+			sm.bus.PublishInbound(pubCtx, bus.InboundMessage{
+				Channel:  "system",
+				SenderID: fmt.Sprintf("subagent:%s", task.ID),
+				// Format: "original_channel:original_chat_id" for routing back
+				ChatID:  fmt.Sprintf("%s:%s", task.OriginChannel, task.OriginChatID),
+				Content: announceContent,
+			})
+		})
 }
 
 func (sm *SubagentManager) GetTask(taskID string) (*SubagentTask, bool) {