diff --git a/backend/internal/server/api_contract_test.go b/backend/internal/server/api_contract_test.go
index 08291faa..44c3f0e4 100644
--- a/backend/internal/server/api_contract_test.go
+++ b/backend/internal/server/api_contract_test.go
@@ -58,6 +58,11 @@ func TestAPIContracts(t *testing.T) {
 					"allowed_groups": null,
 					"created_at": "2025-01-02T03:04:05Z",
 					"updated_at": "2025-01-02T03:04:05Z",
+					"balance_notify_enabled": false,
+					"balance_notify_threshold_type": "",
+					"balance_notify_threshold": null,
+					"balance_notify_extra_emails": null,
+					"total_recharged": 0,
 					"run_mode": "standard"
 				}
 			}`,
@@ -606,7 +611,12 @@ func TestAPIContracts(t *testing.T) {
 					"payment_cancel_rate_limit_max": 0,
 					"payment_cancel_rate_limit_window": 0,
 					"payment_cancel_rate_limit_unit": "",
-					"payment_cancel_rate_limit_window_mode": ""
+					"payment_cancel_rate_limit_window_mode": "",
+					"balance_low_notify_enabled": false,
+					"account_quota_notify_enabled": false,
+					"balance_low_notify_threshold": 0,
+					"balance_low_notify_recharge_url": "",
+					"account_quota_notify_emails": []
 				}
 			}`,
 		},
@@ -699,7 +709,7 @@ func newContractDeps(t *testing.T) *contractDeps {
 		RunMode: config.RunModeStandard,
 	}
 
-	userService := service.NewUserService(userRepo, nil, nil)
+	userService := service.NewUserService(userRepo, nil, nil, nil)
 	apiKeyService := service.NewAPIKeyService(apiKeyRepo, userRepo, groupRepo, userSubRepo, nil, apiKeyCache, cfg)
 
 	usageRepo := newStubUsageLogRepo()
diff --git a/backend/internal/server/middleware/admin_auth_test.go b/backend/internal/server/middleware/admin_auth_test.go
index aafe4a58..ed2578c8 100644
--- a/backend/internal/server/middleware/admin_auth_test.go
+++ b/backend/internal/server/middleware/admin_auth_test.go
@@ -39,7 +39,7 @@ func TestAdminAuthJWTValidatesTokenVersion(t *testing.T) {
 			return &clone, nil
 		},
 	}
-	userService := service.NewUserService(userRepo, nil, nil)
+	userService := service.NewUserService(userRepo, nil, nil, nil)
 
 	router := gin.New()
 	router.Use(gin.HandlerFunc(NewAdminAuthMiddleware(authService, userService, nil)))
diff --git a/backend/internal/server/middleware/jwt_auth_test.go b/backend/internal/server/middleware/jwt_auth_test.go
index ad9c1b5b..c483a51e 100644
--- a/backend/internal/server/middleware/jwt_auth_test.go
+++ b/backend/internal/server/middleware/jwt_auth_test.go
@@ -41,7 +41,7 @@ func newJWTTestEnv(users map[int64]*service.User) (*gin.Engine, *service.AuthSer
 
 	userRepo := &stubJWTUserRepo{users: users}
 	authSvc := service.NewAuthService(nil, userRepo, nil, nil, cfg, nil, nil, nil, nil, nil, nil)
-	userSvc := service.NewUserService(userRepo, nil, nil)
+	userSvc := service.NewUserService(userRepo, nil, nil, nil)
 	mw := NewJWTAuthMiddleware(authSvc, userSvc)
 
 	r := gin.New()
diff --git a/backend/internal/service/admin_service_apikey_test.go b/backend/internal/service/admin_service_apikey_test.go
index 5c18a438..7f0a24da 100644
--- a/backend/internal/service/admin_service_apikey_test.go
+++ b/backend/internal/service/admin_service_apikey_test.go
@@ -70,6 +70,9 @@ func (s *userRepoStubForGroupUpdate) UpdateTotpSecret(context.Context, int64, *s
 }
 func (s *userRepoStubForGroupUpdate) EnableTotp(context.Context, int64) error  { panic("unexpected") }
 func (s *userRepoStubForGroupUpdate) DisableTotp(context.Context, int64) error { panic("unexpected") }
+func (s *userRepoStubForGroupUpdate) RemoveGroupFromUserAllowedGroups(context.Context, int64, int64) error {
+	panic("unexpected")
+}
 
 // apiKeyRepoStubForGroupUpdate implements APIKeyRepository for AdminUpdateAPIKeyGroupID tests.
 type apiKeyRepoStubForGroupUpdate struct {
@@ -152,6 +155,9 @@ func (s *apiKeyRepoStubForGroupUpdate) ResetRateLimitWindows(context.Context, in
 func (s *apiKeyRepoStubForGroupUpdate) GetRateLimitData(context.Context, int64) (*APIKeyRateLimitData, error) {
 	panic("unexpected")
 }
+func (s *apiKeyRepoStubForGroupUpdate) UpdateGroupIDByUserAndGroup(context.Context, int64, int64, int64) (int64, error) {
+	panic("unexpected")
+}
 
 // groupRepoStubForGroupUpdate implements GroupRepository for AdminUpdateAPIKeyGroupID tests.
 type groupRepoStubForGroupUpdate struct {
@@ -194,7 +200,7 @@ func (s *groupRepoStubForGroupUpdate) ListActiveByPlatform(context.Context, stri
 func (s *groupRepoStubForGroupUpdate) ExistsByName(context.Context, string) (bool, error) {
 	panic("unexpected")
 }
-func (s *groupRepoStubForGroupUpdate) GetAccountCount(context.Context, int64) (int64, error) {
+func (s *groupRepoStubForGroupUpdate) GetAccountCount(context.Context, int64) (int64, int64, error) {
 	panic("unexpected")
 }
 func (s *groupRepoStubForGroupUpdate) DeleteAccountGroupsByGroupID(context.Context, int64) (int64, error) {
diff --git a/backend/internal/service/auth_service_register_test.go b/backend/internal/service/auth_service_register_test.go
index 0999b4f0..103bafe7 100644
--- a/backend/internal/service/auth_service_register_test.go
+++ b/backend/internal/service/auth_service_register_test.go
@@ -119,6 +119,14 @@ func (s *emailCacheStub) SetPasswordResetEmailCooldown(ctx context.Context, emai
 	return nil
 }
 
+func (s *emailCacheStub) GetNotifyCodeUserRate(ctx context.Context, userID int64) (int64, error) {
+	return 0, nil
+}
+
+func (s *emailCacheStub) IncrNotifyCodeUserRate(ctx context.Context, userID int64, window time.Duration) (int64, error) {
+	return 0, nil
+}
+
 func newAuthService(repo *userRepoStub, settings map[string]string, emailCache EmailCache) *AuthService {
 	cfg := &config.Config{
 		JWT: config.JWTConfig{
diff --git a/backend/internal/service/user_service_test.go b/backend/internal/service/user_service_test.go
index 29267c19..a998d5f4 100644
--- a/backend/internal/service/user_service_test.go
+++ b/backend/internal/service/user_service_test.go
@@ -49,6 +49,9 @@ func (m *mockUserRepo) AddGroupToAllowedGroups(context.Context, int64, int64) er
 func (m *mockUserRepo) UpdateTotpSecret(context.Context, int64, *string) error      { return nil }
 func (m *mockUserRepo) EnableTotp(context.Context, int64) error                     { return nil }
 func (m *mockUserRepo) DisableTotp(context.Context, int64) error                    { return nil }
+func (m *mockUserRepo) RemoveGroupFromUserAllowedGroups(context.Context, int64, int64) error {
+	return nil
+}
 
 // --- mock: APIKeyAuthCacheInvalidator ---