diff --git a/backend/internal/server/api_contract_test.go b/backend/internal/server/api_contract_test.go
index f516aa42..27358865 100644
--- a/backend/internal/server/api_contract_test.go
+++ b/backend/internal/server/api_contract_test.go
@@ -646,12 +646,21 @@ func TestAPIContracts(t *testing.T) {
 					"registration_email_suffix_whitelist": [],
 					"promo_code_enabled": true,
 					"password_reset_enabled": false,
-					"frontend_url": "",
-					"totp_enabled": false,
-					"totp_encryption_key_configured": false,
-					"smtp_host": "smtp.example.com",
-					"smtp_port": 587,
-					"smtp_username": "user",
+						"frontend_url": "",
+						"totp_enabled": false,
+						"totp_encryption_key_configured": false,
+						"login_agreement_enabled": false,
+						"login_agreement_mode": "modal",
+						"login_agreement_updated_at": "2026-03-31",
+						"login_agreement_documents": [
+							{"id": "terms", "title": "服务条款", "content_md": ""},
+							{"id": "usage-policy", "title": "使用政策", "content_md": ""},
+							{"id": "supported-regions", "title": "支持的国家和地区", "content_md": ""},
+							{"id": "service-specific-terms", "title": "服务特定条款", "content_md": ""}
+						],
+						"smtp_host": "smtp.example.com",
+						"smtp_port": 587,
+						"smtp_username": "user",
 					"smtp_password_configured": true,
 					"smtp_from_email": "no-reply@example.com",
 					"smtp_from_name": "Sub2API",
@@ -880,12 +889,21 @@ func TestAPIContracts(t *testing.T) {
 					"promo_code_enabled": true,
 					"password_reset_enabled": false,
 					"frontend_url": "",
-					"invitation_code_enabled": false,
-					"totp_enabled": false,
-					"totp_encryption_key_configured": false,
-					"smtp_host": "",
-					"smtp_port": 587,
-					"smtp_username": "",
+						"invitation_code_enabled": false,
+						"totp_enabled": false,
+						"totp_encryption_key_configured": false,
+						"login_agreement_enabled": false,
+						"login_agreement_mode": "modal",
+						"login_agreement_updated_at": "2026-03-31",
+						"login_agreement_documents": [
+							{"id": "terms", "title": "服务条款", "content_md": ""},
+							{"id": "usage-policy", "title": "使用政策", "content_md": ""},
+							{"id": "supported-regions", "title": "支持的国家和地区", "content_md": ""},
+							{"id": "service-specific-terms", "title": "服务特定条款", "content_md": ""}
+						],
+						"smtp_host": "",
+						"smtp_port": 587,
+						"smtp_username": "",
 					"smtp_password_configured": false,
 					"smtp_from_email": "",
 					"smtp_from_name": "",
diff --git a/backend/internal/service/setting_service.go b/backend/internal/service/setting_service.go
index 9dbbaa08..283a239b 100644
--- a/backend/internal/service/setting_service.go
+++ b/backend/internal/service/setting_service.go
@@ -249,16 +249,16 @@ func normalizeLoginAgreementDocumentID(raw string) string {
 	lastSeparator := false
 	for _, r := range raw {
 		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') {
-			b.WriteRune(r)
+			_, _ = b.WriteRune(r)
 			lastSeparator = false
 			continue
 		}
 		if r == '-' || r == '_' || r == ' ' || r == '.' || r == '/' {
 			if !lastSeparator && b.Len() > 0 {
 				if r == '_' {
-					b.WriteRune('_')
+					_, _ = b.WriteRune('_')
 				} else {
-					b.WriteRune('-')
+					_, _ = b.WriteRune('-')
 				}
 				lastSeparator = true
 			}