Yui worked on the sp-tarkov/server-csharp repository, focusing on backend stability for the Flea Market workflow. During this period, Yui addressed a bug where invalid flea offers could be generated due to missing LoyalLevelItems. By implementing a defensive check and integrating targeted warning logs, Yui improved error handling and observability, making it easier to diagnose and prevent similar issues in the future. The solution was delivered with minimal code changes and adhered to existing repository patterns. Using C# and leveraging backend development and logging skills, Yui contributed to product reliability and reduced support overhead by preventing faulty offer generation.