Andrew Esterson enhanced the CI workflow for the pybamm-team/PyBaMM repository by implementing a feature that pins GitHub Actions to specific release hashes, using YAML and leveraging his expertise in CI/CD practices. This approach ensured that all continuous integration pipelines became deterministic, preventing unexpected updates from upstream changes and improving both security and reproducibility. By explicitly specifying action versions, Andrew reduced operational risk and made the audit process more straightforward. Although the work focused on a single feature, it addressed a core aspect of CI reliability, demonstrating a thoughtful application of automation and workflow governance within the project’s development lifecycle.