San is a Baidu-developed, production-grade frontend component framework that enables building reactive UIs with a Vue/React-like model, but using custom template syntax and a standalone runtime. It provides a template parser (producing an ANode AST), a reactive data system (Data class, Proxy-based this.d), directives (s-if, s-for, s-bind, s-show, s-html, s-ref, s-transition), slots (named, scoped, dynamic), computed properties, filters, lifecycle hooks, two-way binding, and server-side rendering hydration. The library is monolithic but modularly organized, targeting browsers from IE8 upward with conditional compilation. It is actively maintained with frequent releases and extensive test coverage, but carries legacy complexity and a self-contained build toolchain (AMD module loading, custom feature blocks). The ecosystem includes companion libraries (san-router, san-store, san-cli) and TypeScript typings.