diff --git a/internal/ai/runtime/graphs/handoff_graph.go b/internal/ai/runtime/graphs/handoff_graph.go
index 289f791..e3538e8 100644
--- a/internal/ai/runtime/graphs/handoff_graph.go
+++ b/internal/ai/runtime/graphs/handoff_graph.go
@@ -52,6 +52,9 @@ func (g *HandoffGraph) Run(ctx context.Context, argumentsInJSON string) (string,
 		}
 		handled, err := services.ConversationService.TryOffHoursHandoffByAI(g.conversation.ID, g.aiAgent, reason)
 		if err != nil || handled {
+			if handled && err == nil {
+				return services.HandoffOffHoursMessage, nil
+			}
 			return "", err
 		}
 		info := HandoffGraphInterruptInfo{
diff --git a/internal/ai/runtime/graphs/handoff_graph_test.go b/internal/ai/runtime/graphs/handoff_graph_test.go
index 0315a35..254e20e 100644
--- a/internal/ai/runtime/graphs/handoff_graph_test.go
+++ b/internal/ai/runtime/graphs/handoff_graph_test.go
@@ -25,8 +25,8 @@ func TestHandoffGraphOffHoursSendsNoticeWithoutConfirmation(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Run() error = %v", err)
 	}
-	if reply != "" {
-		t.Fatalf("expected no graph reply, got %q", reply)
+	if reply != services.HandoffOffHoursMessage {
+		t.Fatalf("expected off-hours graph reply, got %q", reply)
 	}
 
 	message := services.MessageService.FindOne(sqls.NewCnd().Eq("conversation_id", conversation.ID).Desc("id"))
diff --git a/internal/services/conversation_human_dispatch_service.go b/internal/services/conversation_human_dispatch_service.go
index 93fb87f..5c15d77 100644
--- a/internal/services/conversation_human_dispatch_service.go
+++ b/internal/services/conversation_human_dispatch_service.go
@@ -58,6 +58,9 @@ func (s *conversationHumanDispatchService) TryOffHoursHandoffByAI(conversationID
 	if err := s.createEvent(conversationID, enums.IMEventTypeTransfer, enums.IMSenderTypeAI, aiAgent.ID, "转人工失败：非服务时间", strings.TrimSpace(reason)); err != nil {
 		return true, err
 	}
+	if s.hasLatestAIText(conversationID, HandoffOffHoursMessage) {
+		return true, nil
+	}
 	if err := s.sendAIText(conversationID, aiAgent.ID, HandoffOffHoursMessage); err != nil {
 		return true, err
 	}
@@ -288,6 +291,14 @@ func (s *conversationHumanDispatchService) sendAIText(conversationID, aiAgentID
 	return err
 }
 
+func (s *conversationHumanDispatchService) hasLatestAIText(conversationID int64, content string) bool {
+	latest, err := MessageService.GetConversationReadTarget(conversationID, 0)
+	if err != nil || latest == nil {
+		return false
+	}
+	return latest.SenderType == enums.IMSenderTypeAI && strings.TrimSpace(latest.Content) == strings.TrimSpace(content)
+}
+
 func orderedPositiveIDs(value string) []int64 {
 	return uniquePositiveInt64sFromStrings(strings.Split(value, ","))
 }
diff --git a/internal/services/conversation_human_dispatch_service_test.go b/internal/services/conversation_human_dispatch_service_test.go
index f44a387..b3b1497 100644
--- a/internal/services/conversation_human_dispatch_service_test.go
+++ b/internal/services/conversation_human_dispatch_service_test.go
@@ -47,6 +47,32 @@ func TestConversationHumanDispatchAIHandoffOffHoursKeepsAIServingAndSendsNotice(
 	}
 }
 
+func TestConversationHumanDispatchAIHandoffOffHoursDoesNotDuplicateNotice(t *testing.T) {
+	db := setupConversationHumanDispatchTestDB(t)
+	aiAgent := createHumanDispatchAIAgent(t, db, enums.IMConversationServiceModeAIFirst, "1")
+	conversation := createHumanDispatchConversation(t, db, aiAgent.ID, enums.IMConversationStatusAIServing)
+
+	for i := 0; i < 3; i++ {
+		result, err := services.ConversationHumanDispatchService.HandoffByAI(conversation.ID, aiAgent, "用户要求转人工")
+		if err != nil {
+			t.Fatalf("HandoffByAI() round %d error = %v", i+1, err)
+		}
+		if result == nil || result.Decision != services.HandoffDecisionOffHours {
+			t.Fatalf("expected off_hours decision on round %d, got %+v", i+1, result)
+		}
+	}
+
+	var count int64
+	if err := db.Model(&models.Message{}).
+		Where("conversation_id = ? AND sender_type = ? AND content = ?", conversation.ID, enums.IMSenderTypeAI, services.HandoffOffHoursMessage).
+		Count(&count).Error; err != nil {
+		t.Fatalf("count off-hours messages error = %v", err)
+	}
+	if count != 1 {
+		t.Fatalf("expected one off-hours notice, got %d", count)
+	}
+}
+
 func TestConversationHumanDispatchAIHandoffAssignsAvailableAgent(t *testing.T) {
 	db := setupConversationHumanDispatchTestDB(t)
 	aiAgent := createHumanDispatchAIAgent(t, db, enums.IMConversationServiceModeAIFirst, "1")