Worked on the maybe-finance/maybe repository to implement a feature enforcing a single-level category hierarchy, ensuring that subcategories cannot be assigned to other subcategories. This involved updating both backend validation and frontend UI to align behavior, using Ruby on Rails, ERB, and HTML. The category model was enhanced to prevent parent category selection for existing parent categories, effectively maintaining a clean and manageable taxonomy. By addressing both backend logic and user interface, the work reduced the risk of invalid nesting and improved downstream filtering and reporting. The approach demonstrated a balanced focus on data integrity and user experience across the stack.