Sourish Basu enhanced diagnostic error messaging within the GEOS-ESM/MAPL repository, focusing on the MAPL_CFIO and ExtDataConfig modules. He improved debugging workflows by adding detailed context—such as filenames, variable names, and offending collection identifiers—to error messages, which streamlined root-cause analysis for I/O and configuration issues. Using Fortran and leveraging skills in debugging and error handling, Sourish validated these updates through targeted tests and code reviews to ensure stability and maintainability. This work reduced investigation time and helped prevent misconfiguration cycles, reflecting a thoughtful approach to reliability and developer experience in a complex scientific software environment.