# Plugin Architecture A plugin architecture lets separately packaged modules extend a stable host through defined discovery, loading, and lifecycle rules. Shazam's capability files, XApps libraries, XDO extensions, and AutoSites modules are related historical forms. A modern implementation would add manifests, versions, declared permissions, schemas, and isolation. Related: [[wiki/Capability Discovery|Capability Discovery]], [[wiki/Filesystem-Based Agent Skills|Filesystem-Based Agent Skills]], [[wiki/Host Adapter|Host Adapter]].