diff --git a/internal/services/sync/service.go b/internal/services/sync/service.go
index 39f5762..7318f10 100644
--- a/internal/services/sync/service.go
+++ b/internal/services/sync/service.go
@@ -484,6 +484,9 @@ func (s *Service) pushConfigurationCreate(change *localdb.PendingChange) error {
 
 	// Create repository
 	configRepo := repository.NewConfigurationRepository(mariaDB)
+	if err := s.ensureConfigurationOwner(mariaDB, &cfg); err != nil {
+		return fmt.Errorf("resolve configuration owner: %w", err)
+	}
 
 	// Create on server
 	if err := configRepo.Create(&cfg); err != nil {
@@ -536,6 +539,9 @@ func (s *Service) pushConfigurationUpdate(change *localdb.PendingChange) error {
 
 	// Create repository
 	configRepo := repository.NewConfigurationRepository(mariaDB)
+	if err := s.ensureConfigurationOwner(mariaDB, &cfg); err != nil {
+		return fmt.Errorf("resolve configuration owner: %w", err)
+	}
 
 	// Ensure we have a server ID before updating
 	// If the payload doesn't have ID, get it from local configuration
@@ -585,6 +591,32 @@ func (s *Service) pushConfigurationUpdate(change *localdb.PendingChange) error {
 	return nil
 }
 
+func (s *Service) ensureConfigurationOwner(mariaDB *gorm.DB, cfg *models.Configuration) error {
+	if cfg == nil {
+		return fmt.Errorf("configuration is nil")
+	}
+
+	ownerUsername := cfg.OwnerUsername
+	if ownerUsername == "" {
+		ownerUsername = s.localDB.GetDBUser()
+		cfg.OwnerUsername = ownerUsername
+	}
+	if ownerUsername == "" {
+		return fmt.Errorf("owner username is empty")
+	}
+
+	userID, err := models.EnsureDBUser(mariaDB, ownerUsername)
+	if err != nil {
+		return err
+	}
+	if userID == 0 {
+		return fmt.Errorf("resolved user ID is 0 for owner %q", ownerUsername)
+	}
+
+	cfg.UserID = userID
+	return nil
+}
+
 func (s *Service) pushConfigurationRollback(change *localdb.PendingChange) error {
 	// Last-write-wins for now: rollback is pushed as an update with rollback metadata.
 	return s.pushConfigurationUpdate(change)