Konstantin Klein focused on backend stability and client interoperability for the Hochfrequenz/BO4E-dotnet repository, addressing a critical JSON serialization issue in C#. He reverted a previous change to the Angebotsteil class that had altered the casing of the 'lieferstellen' property, restoring consistent serialization behavior across both Newtonsoft.Json and System.Text.Json. This targeted fix minimized integration risks for downstream consumers by maintaining expected property naming conventions. Throughout the month, Konstantin prioritized code hygiene and backward compatibility, documenting changes clearly to ensure traceability. His work demonstrated depth in C# and JSON serialization, emphasizing correctness and reliability over new feature development during this period.