Jelle worked on build system improvements and configuration standardization across two repositories over a two-month period. In the biomejs/biome repository, Jelle updated the Rustfmt configuration to align with the 2024 edition, ensuring consistent code formatting and reducing future maintenance overhead. The work focused on Shell scripting and TOML configuration, applying best practices for reproducible and maintainable codebases. In gitlabhq/gitlab-shell, Jelle enhanced build reproducibility by modifying the Makefile to honor SOURCE_DATE_EPOCH, making build artifacts deterministic across environments. This approach improved auditability and reliability in CI/CD workflows, demonstrating a methodical focus on reproducible builds and robust configuration management.