The TREX project is a collaborative initiative aimed at enhancing Quantum Monte Carlo (QMC) simulations by developing and optimizing flagship codes tailored for exascale computing. This report provides a comprehensive overview of the advancements and achievements under Work Package (WP)2, Code Modularization and Interfacing, and highlights its essential role in accomplishing the TREX project’s primary objectives. The TREX project focuses on three key goals:

1. Enhancement of accuracy and efficiency in QMC simulations.
2. Facilitation of seamless integration between different QMC codes and libraries.
3. Ensuring interoperability and data exchange capabilities across these codes.