During May 2025, x5f developed a configurable registration flow for the element-hq/synapse repository, introducing the allow_underscore_prefixed_registration option to manage whether user registrations can begin with an underscore. This feature addressed the need to balance internal AppServices safety with external onboarding flexibility. x5f implemented the solution using Python and YAML, updating documentation and adding targeted tests to ensure reliability and traceability. The work focused on backend development and configuration management, resulting in improved system configurability and clearer governance of user management policies. The depth of the implementation is reflected in the comprehensive approach to testing and documentation updates.