Fusion energy is a promising technology for high density, CO2-free energy production. The next generation of magnetic fusion experiments aims to demonstrate net energy gain for the first time. The increased complexity and scale of these experiments compared to present-day devices requires a leap in computational capabilities for predicting the behaviour of the fusion reactor plasma, magnets, and wall materials. This is vital for experimental performance optimization, plasma control, and safe reactor operation. Central to these efforts is how to efficiently design software that couples together different physics and engineering codes that separately describe parts of the interacting system, into a single and consistent description. Coupled with ongoing international efforts, this project implements methods and standards vital for a tokamak simulation suite which is modular, robust,easy to maintain, and with a user toolkit that enables efficient application for large numbers of simulations needed for designing experiments and assessing sensitivities.