Harry developed a tag-based service advertising enforcement feature for the tailscale/tailscale repository, focusing on improving security and correctness in service discovery. By requiring an Access Control List (ACL) tag before a service can be advertised, Harry’s work reduced the risk of misconfiguration and ensured that only authorized nodes could participate in service advertisement. The implementation included explicit error handling for untagged nodes and clear command-line interface messaging to support operators. Using Go for CLI development and network services, Harry delivered a policy-driven change that maintained compatibility with existing deployments while strengthening governance and aligning service advertisement with ACL-based policies.