Developed a comprehensive Attachment Preview System for the frappe/frappe repository, enabling users to preview images, PDFs, and CSVs directly within the form interface. The solution featured a resizable preview pane with per-user width preferences, CSV data visualization, and the ability to copy attachment URLs. Implemented using JavaScript, SCSS, and front end UI/UX design principles, the system addressed state management and performance optimization, ensuring previews reset appropriately when switching documents. The work included refining iconography, calculating preview sizes accurately, and enforcing file size limits to enhance reliability. Delivered end-to-end feature development through multiple commits focused on user experience improvements.