Willem van Reeven developed and integrated HVAC System Interface Updates for the lsst-ts/ts_xml repository, focusing on new commands, events, and telemetry to enhance subsystem control and observability. He designed and implemented the interface changes using Python and XML, ensuring compatibility with existing telemetry pipelines and maintaining API stability. Comprehensive documentation was authored to support maintainers and users, detailing the updated interface and its integration points. The work was merged through a CI-backed pull request process, validating the changes and ensuring seamless adoption. This feature improved automation readiness for the HVAC subsystem and demonstrated careful attention to integration and maintainability.