diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 8dda3b8..0f36872 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -168,7 +168,7 @@ model Credit {
   id            String    @id @default(cuid())
   userId        String
   amount        Float     // 交易金额（正数为充值，负数为消费）
-  balance       Float     // 执行该交易后的余额
+  balance       Float @default(0)    // 执行该交易后的余额
   type          String    // "system_gift", "subscription_monthly", "user_purchase", "consumption"
   category      String?   // 消费类别: "simulation", "api_call", "export" 等
   note          String?   // 备注说明