diff --git a/backend/api-gateway/src/main/java/com/deepdata/gateway/infrastructure/casdoor/CasdoorUserService.java b/backend/api-gateway/src/main/java/com/deepdata/gateway/infrastructure/casdoor/CasdoorUserService.java
index d66abf0..4e61640 100644
--- a/backend/api-gateway/src/main/java/com/deepdata/gateway/infrastructure/casdoor/CasdoorUserService.java
+++ b/backend/api-gateway/src/main/java/com/deepdata/gateway/infrastructure/casdoor/CasdoorUserService.java
@@ -69,7 +69,8 @@ public class CasdoorUserService {
                     user.setEmail(claims.email());
                 }
                 applyGroupsAndRole(user, claims, username);
-                userRepository.save(user);
+                // 存量用户走更新；IRepository.save() 恒为 INSERT，带 id 调用会撞主键
+                userRepository.updateById(user);
                 return new ProvisionedUser(user, userService.generateToken(user), false);
             }
             if (!props.isAutoProvision()) {