Architecture

XamlVisualEditor is layered around a passive Avalonia UI, ReactiveUI ViewModels, domain/services projects, and infrastructure adapters. The app composition root is src/XamlVisualEditor.App/App.axaml.cs.

Layers

Layer	Responsibilities
UI	Avalonia views, control themes, resource dictionaries, and bindings.
Presentation	ReactiveUI ViewModels, commands, state composition, interactions, and Dock model orchestration.
Domain/Services	XAML parsing, AST, serialization, sync, workspace, language, terminal, debugger, and collaboration rules.
Infrastructure	File system, processes, PTY providers, protocol transports, package loading, persistence, and external tools.

Shell

The shell owns application lifetime, main window creation, service registration, Dock layout factories, top-level command orchestration, and built-in extension activation. Feature panels are contributed through extension contracts whenever possible.

Extension-first feature model

Built-in extensions are registered in the app DI container and activated by BuiltInExtensionHost. They register command handlers, metadata, views, menus, toolbars, property editors, language/debugger services, and panel providers.

Docking

Dock state is modeled in ViewModels and factories. Views render the Dock model without owning layout rules. Persisted layout support should remain in the presentation/service layer rather than in view code.