Jard Nijholt developed a formal proof component for the HEPLean/PhysLean repository, focusing on the harmonic oscillator model in classical mechanics. Using Lean and formal verification techniques, Jard established a mathematical lemma that rigorously ties a trajectory’s zero velocity to a position magnitude derived from initial conditions, grounded in energy conservation principles. This work enhanced the model’s validation framework by enabling more robust scenario testing and reducing simulation risk. Jard’s contribution included updating model checks to leverage the new proof, as well as improving documentation and traceability, thereby supporting future audits and ongoing maintenance of the simulation codebase.