Stately is a visual editor for designing and building state machines and workflows using XState. It enables developers and teams to create, simulate, and deploy logic through a drag-and-drop interface, with AI-powered assistance for generating flows, suggesting variants, and writing code. The tool supports bidirectional updates between code and diagrams, integrates with VS Code via an extension, and works with React, Vue, Svelte, and other frameworks. Features include automatic test generation, React app scaffolding from diagrams, inspection of running apps, and visualization of actor communication. Stately aims to serve as the source of truth for application logic, keeping documentation and implementation in sync.