The nested list you can open, close and walk with the arrow keys: a file explorer or file tree, a folder or directory tree, a category or taxonomy picker, an org chart, an API-schema browser, a docs sidebar with nested sections. Common asks it answers: "tree view", "tree component", "file tree", "folder tree", "directory tree", "file explorer sidebar", "nested list with expand/collapse", "collapsible tree", "expandable folder list", "VS Code-style explorer", "category tree", "org chart tree". shadcn/ui ships no tree of any kind — its collapsible is one open/closed section and its sidebar nests menus without the tree semantics — so this gets hand-rolled every time, and the part that gets dropped is always the keyboard. Pass a `data` array of `{ id, label, children?, icon? }`: a node with a `children` array is a parent (an empty array is an empty folder, which still opens), a node without one is a leaf. Open state and selection are each controlled (`expandedIds` / `selectedId` plus `onExpandedChange` / `onSelect`, which hands you the whole node) or uncontrolled (`defaultExpandedIds` / `defaultSelectedId`), so it drops into a router-driven sidebar or runs on its own. It is the real ARIA tree pattern, not a pile of nested collapsibles: role=tree / treeitem / group with aria-expanded, aria-selected and aria-level/posinset/setsize, and a roving tabindex so the whole tree is one Tab stop instead of one stop per row. Up/Down walk only the rows actually on screen, Right opens a parent and then steps into it, Left closes it or jumps out to the parent, Home/End hit the ends, Enter/Space select, and type-ahead jumps to the next row starting with what you typed (repeat a letter to cycle). Three details that are easy to get wrong are handled: closing a subtree that contains the focused row hands focus back to the row being closed instead of dropping it on <body>; the row is named by its own label via aria-labelledby, because a treeitem owns its child group and a name computed from contents would read the entire subtree as one row's name; and the disclosure arrow is a click target rather than a nested <button>, since a treeitem must not contain its own focusable elements. Renders folder/file icons by default (`showIcons={false}` for category or org trees), `indent` sets the per-level offset, and per-node `icon` overrides a single row. Styled with shadcn tokens (accent, muted-foreground, ring) so it follows light and dark themes; lucide-react is the only dependency, with no Radix and no state library. Distinct from command-palette, which is a flat searchable launcher: this is for structure you navigate rather than a name you already know. Distinct from json-viewer, which takes the parsed JSON value itself and renders its keys, types and entry counts: reach for that one to display a payload you did not author, and this one when you have your own hierarchy to express as `{ id, label, children }` nodes.