Worked on targeted improvements to the OPM/opm-simulators repository, focusing on enhancing simulation reliability in serial execution mode. Addressed a specific issue with cell ID mapping by correcting the timing of the syncDistributedGlobalCellIds call within CpGridVanguard.hpp, ensuring accurate parent-to-children relationships when toggling between global and distributed views. This change, implemented in C++ and leveraging simulation and software engineering expertise, was delivered as a concise, low-risk update. The fix improved the robustness and stability of serial-mode simulations, enabling more dependable results and easier verification, and demonstrated careful attention to detail in maintaining correctness within complex simulation workflows.