Eriawan delivered nullable Encoding support for StreamReader constructors in the dotnet/runtime repository, enabling developers to specify a null Encoding parameter when creating StreamReader instances. This work involved updating the core library’s API design to align with nullable reference type guidelines in C#, ensuring improved null-safety and correctness. Eriawan also enhanced unit testing to verify proper handling of null encoding scenarios, increasing test coverage and reliability for encoding-related functionality. Although the contribution focused on a single feature over one month, it demonstrated careful attention to API consistency and robust testing practices, leveraging skills in C#, API design, and core library development.