Selwyn Theo enhanced authentication reliability and service maintainability in the finos/architecture-as-code repository by refining both the authentication flow and Calm service architecture. He implemented memoization for service instances using React and TypeScript, addressing lint warnings and optimizing render performance. Selwyn expanded test coverage for authentication services, exported the AuthHeaders type, and introduced JSDoc documentation to support future type safety improvements. By adding public modifiers to CalmService methods and simplifying error status tests, he improved API clarity and maintainability. His work focused on front end development and testing, enabling faster feature delivery and safer refactoring within the codebase.