Worked on the Crossmint/crossmint-sdk repository to deliver a feature that enhances UI theming and customization for payment method management. Focused on exposing the rules property within the PaymentMethodManagementAppearance type, this change allows consumers to override styles for various UI elements, increasing flexibility for merchants and supporting consistent branding. The implementation involved TypeScript and front end development, with careful attention to client SDK API surface design and theming patterns. All changes were tracked through commit-based workflows, ensuring traceability and alignment with internal issue tracking. This work reduced integration overhead and enabled more tailored user experiences for payment method management interfaces.