Worked on enhancing diagnostic error messaging within the GEOS-ESM/MAPL repository, focusing on the MAPL_CFIO and ExtDataConfig modules. The update introduced more informative error messages by including filenames, variable names, and offending collection names, which streamlined root-cause analysis for I/O and configuration issues. Leveraging Fortran and applying strong debugging and error handling skills, the changes aimed to reduce investigation time and prevent repeated misconfiguration cycles. The work involved targeted testing and code reviews to validate stability and maintainability, resulting in improved clarity for developers troubleshooting data flow and configuration problems within the MAPL infrastructure during the development cycle.