Worked on the cypht repository to enhance CardDAV integration by improving the reliability of contact synchronization. Addressed issues in PHP back end code related to URL construction, ensuring that CardDAV PROPFIND requests correctly handle non-default ports and IPv6 hosts by preserving port information and proper bracketing. Refactored the CardDAV source configuration to use a dedicated configuration structure, which clarified the Account dropdown in the Add Contact form and reduced potential confusion for users. Focused on targeted bug fixes and maintainability, the work demonstrated strong skills in API integration and back end development, with clear, intent-driven commit documentation throughout.