During February 2025, Tom Wier focused on backend development and error handling in the medic/cht-core repository, addressing a critical reliability issue in outbound mapping configuration. He implemented validation logic in JavaScript to ensure that outbound configurations are defined and that either an expression or path is provided, throwing descriptive errors when these conditions are not met. This approach reduced runtime failures caused by misconfigurations and improved diagnosability for outbound data flows. Tom also expanded test coverage by adding a unit test to verify the new error condition, demonstrating a methodical approach to robust backend engineering and comprehensive testing practices.