diff --git a/internal/service/package/usage_service.go b/internal/service/package/usage_service.go
index a00d1db..323d7a2 100644
--- a/internal/service/package/usage_service.go
+++ b/internal/service/package/usage_service.go
@@ -88,13 +88,22 @@ func (s *UsageService) DeductDataUsage(ctx context.Context, carrierType string,
 			return err
 		}
 
+		today := time.Now().Format("2006-01-02")
+
 		if len(packages) == 0 {
+			// 无生效套餐：尝试找 Depleted 套餐记录溢出流量详单，避免详单断档
+			if recordErr := s.recordOverflowToDepletedPackage(ctx, tx, targetCarrierType, targetCarrierID, deductUsageMB, today); recordErr != nil {
+				s.logger.Warn("记录溢出流量到已耗尽套餐失败",
+					zap.String("carrier_type", targetCarrierType),
+					zap.Uint("carrier_id", targetCarrierID),
+					zap.Int64("usage_mb", deductUsageMB),
+					zap.Error(recordErr))
+			}
 			return errors.New(errors.CodeNoAvailablePackage, "没有可用套餐")
 		}
 
 		// 按优先级扣减流量
 		remainingUsage := deductUsageMB
-		today := time.Now().Format("2006-01-02")
 
 		for index, pkg := range packages {
 			if remainingUsage <= 0 {
@@ -446,3 +455,40 @@ func (s *UsageService) triggerSuspensionAfterCommit(carrierType string, carrierI
 		}(cardID)
 	}
 }
+
+// recordOverflowToDepletedPackage 在所有套餐已耗尽时，将溢出流量写入最近的 Depleted 套餐日记录。
+// 目的：保持流量详单连续性，即便套餐用完期间上游仍有流量使用，详单不会断档。
+// 只写日记录和累加 data_usage_mb，不改变套餐 status，不触发停机。
+func (s *UsageService) recordOverflowToDepletedPackage(ctx context.Context, tx *gorm.DB, carrierType string, carrierID uint, overflowMB int64, today string) error {
+	query := tx.Where("status = ?", constants.PackageUsageStatusDepleted)
+	switch carrierType {
+	case constants.AssetTypeIotCard:
+		query = query.Where("iot_card_id = ?", carrierID)
+	case constants.AssetTypeDevice:
+		query = query.Where("device_id = ?", carrierID)
+	default:
+		return nil
+	}
+
+	var pkg model.PackageUsage
+	if err := query.Order("id DESC").First(&pkg).Error; err != nil {
+		// 找不到 Depleted 套餐，静默忽略
+		return nil
+	}
+
+	newUsage := pkg.DataUsageMB + overflowMB
+	if err := tx.Model(&pkg).Update("data_usage_mb", newUsage).Error; err != nil {
+		return errors.Wrap(errors.CodeDatabaseError, err, "更新溢出流量失败")
+	}
+
+	if err := s.updateDailyRecord(ctx, tx, pkg.ID, today, overflowMB, newUsage); err != nil {
+		return err
+	}
+
+	s.logger.Info("记录溢出流量到已耗尽套餐",
+		zap.Uint("package_usage_id", pkg.ID),
+		zap.Int64("overflow_mb", overflowMB),
+		zap.Int64("new_usage_mb", newUsage))
+
+	return nil
+}