ember-sortable is an Ember.js addon providing sortable UI primitives for drag-and-drop reordering of lists, grids, and tables. It implements modifiers (sortable-group, sortable-item, sortable-handle) that attach drag-and-drop behavior to DOM elements, with built-in support for mouse, touch, and keyboard input. The architecture centers around a service (ember-sortable-internal-state) that manages state between sortable groups and items, enabling features like visual feedback during drag, automatic container scrolling, and accessibility support including screen reader announcements and keyboard navigation. The library follows Ember addon conventions with a modular structure, clear separation of concerns, and comprehensive test coverage.