diff --git a/backend/internal/handler/user_handler.go b/backend/internal/handler/user_handler.go
index 04712326..13733228 100644
--- a/backend/internal/handler/user_handler.go
+++ b/backend/internal/handler/user_handler.go
@@ -330,6 +330,7 @@ func (h *UserHandler) CreateUser(c *fiber.Ctx) error {
 
 	// [Resolve TenantID and LoginID before Kratos creation]
 	var tenantID string
+	synced := false
 	if req.CompanyCode != "" && h.TenantService != nil {
 		if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), req.CompanyCode); err == nil && tenant != nil {
 			tenantID = tenant.ID
@@ -337,9 +338,28 @@ func (h *UserHandler) CreateUser(c *fiber.Ctx) error {
 			// Sync custom field to LoginID if configured
 			if loginIdField, ok := tenant.Config["loginIdField"].(string); ok && loginIdField != "" {
 				syncLoginID(attributes, req.Metadata, tenantID, loginIdField)
+				synced = true
 			}
 		}
 	}
+	
+	// Fallback: Try syncing based on the tenant namespaces being updated
+	if !synced && h.TenantService != nil {
+		for k := range req.Metadata {
+			if len(k) >= 32 { // Looks like a UUID (tenant ID)
+				if tenant, err := h.TenantService.GetTenant(c.Context(), k); err == nil && tenant != nil {
+					if tenantID == "" {
+						tenantID = tenant.ID
+					}
+					if loginIdField, ok := tenant.Config["loginIdField"].(string); ok && loginIdField != "" {
+						syncLoginID(attributes, req.Metadata, tenant.ID, loginIdField)
+						break
+					}
+				}
+			}
+		}
+	}
+
 	attributes["role"] = role
 	if tenantID != "" {
 		attributes["tenant_id"] = tenantID
@@ -1202,10 +1222,28 @@ func (h *UserHandler) UpdateUser(c *fiber.Ctx) error {
 	// [LoginID Sync based on Tenant Settings]
 	// Perform sync AFTER metadata merge to ensure traits contains current values
 	syncCompCode := extractTraitString(traits, "companyCode")
+	synced := false
+
 	if syncCompCode != "" && h.TenantService != nil {
 		if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), syncCompCode); err == nil && tenant != nil {
 			if loginIdField, ok := tenant.Config["loginIdField"].(string); ok && loginIdField != "" {
 				syncLoginID(traits, req.Metadata, tenant.ID, loginIdField)
+				synced = true
+			}
+		}
+	}
+
+	// Fallback: If companyCode is empty or didn't sync, try syncing based on the tenant namespaces being updated
+	if !synced && h.TenantService != nil {
+		for k := range req.Metadata {
+			if len(k) >= 32 { // Looks like a UUID (tenant ID)
+				if tenant, err := h.TenantService.GetTenant(c.Context(), k); err == nil && tenant != nil {
+					if loginIdField, ok := tenant.Config["loginIdField"].(string); ok && loginIdField != "" {
+						syncLoginID(traits, req.Metadata, tenant.ID, loginIdField)
+						synced = true
+						break // Apply first matched tenant config
+					}
+				}
 			}
 		}
 	}