Plugin authoring
Roslyn Workbench 1.0 publishes Lantean.Roslyn.Workbench.Mcp.Plugins as the supported compile-time package for trusted, in-process third-party plugins. A plugin project references this package only; it must not reference or deploy the Host, Workspace, CodeActions or bundled Core projects.
The package supplies the Plugins and Abstractions assemblies plus the C# authoring analyser. Query and mutation handlers compile against those contracts, while the installed Host supplies the matching runtime assembly identities and owns plugin loading, validation, execution leases, Workspace access and transaction staging. Do not copy the Plugins or Abstractions assemblies into the deployed plugin directory.
Plugins remain a manual installation for 1.0. Start the Host with --enable-plugins and one or more explicit --plugin-directory values only after reviewing and trusting the plugin code and its dependencies. The Host does not treat an in-process plugin as a hostile tenant.
The plugin API version is independent of the NuGet package version. A plugin declares an exact PluginApiVersions value, and the Host rejects unsupported API versions before publishing any of that plugin's tools.
See the complete authoring guide for entry-point, handler, result, transaction and deployment requirements, and plugin authoring diagnostics for analyser rules and remediation.