In January 2025, Sonso focused on streamlining the equinor/ert repository by removing the Iterative Ensemble Smoother (IES) feature, including all related command-line arguments, configuration settings, analysis modules, and GUI components. This work involved extensive code refactoring and deprecation using Python, with an emphasis on software maintenance and long-term stability. By eliminating unused and deprecated code paths, Sonso reduced the maintenance burden and minimized potential confusion for users and new contributors. The changes aligned with the team’s goal of maintaining a lean, stable codebase, ultimately improving onboarding and supporting future development within the ERT tool’s Python ecosystem.