Worked on the equinor/ert repository, focusing on simplifying and maintaining the ERT tool by removing the Iterative Ensemble Smoother (IES) feature. This involved extensive code refactoring in Python, deprecating and eliminating related command-line arguments, configuration settings, analysis modules, and GUI components. The approach reduced the codebase’s complexity, minimized potential user confusion, and lowered the ongoing maintenance burden. By narrowing the feature surface area, the changes improved overall stability and made onboarding for new contributors more straightforward. The work emphasized software maintenance and deprecation best practices, aligning with the team’s goal of keeping the ERT tool lean and stable.