Architecture

Layers

┌─────────────────────────────────────────────────────────────┐
│  Applications (packages/app, or custom apps)                 │
│  – AppDefinition: extensions, optional layout (id or { id, props }) │
│  – Layouts registered via LayoutContribution (system.layouts)│
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│  App Loader (core)                                          │
│  – App registration & lifecycle  – Extension enable/disable │
│  – Layout resolution & preferred layout  – Render layout root│
└─────────────────────────────────────────────────────────────┘
                              │
        ┌─────────────────────┼─────────────────────┐
        ▼                     ▼                     ▼
┌───────────────┐   ┌─────────────────┐   ┌───────────────┐
│  Extensions   │   │  Contributions   │   │   Commands    │
│  Registry     │   │  Registry       │   │   Registry    │
│  (per-app)    │   │  (tabs, toolbars)│   │   (handlers)  │
└───────────────┘   └─────────────────┘   └───────────────┘
        │                     │                     │
        └─────────────────────┼─────────────────────┘
                              ▼
┌─────────────────────────────────────────────────────────────┐
│  UI (core)                                                   │
│  lyra-standard-layout · lyra-tabs · lyra-toolbar · lyra-filebrowser · …    │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│  Core services                                               │
│  Workspace · Settings · Editor registry · Tasks · Events · DI│
└─────────────────────────────────────────────────────────────┘

Monorepo layout

Path	Role
packages/core (@eclipse-lyra/core)	Platform: registries, services, parts, widgets, dialogs. No extension logic; extensions live in separate packages.
packages/extension-*	One package per extension. Each depends on core and registers commands, contributions, and optionally editors.
packages/create-app	Scaffolder: npm create @eclipse-lyra/app generates a new app elsewhere (monorepo with app + example extension).
packages/app	Default app in this repo: imports core and extensions, defines AppDefinition and extensions[], registers with the app loader. Use as reference when working in the monorepo.
Root	Workspace root. Scripts: dev, build, build:app, test, docs:dev, docs:build.

Main concepts

• Apps — Register via AppDefinition: name, version, extensions[], optional layout (id or { id, props }), contributions, initialize / dispose. The app root is the chosen layout's component.
• Layouts — Registered via LayoutContribution (slot system.layouts): id, name, component, optional onShow. Core provides the standard (IDE) layout; apps can add layouts (e.g. dashboard). Users switch via the toolbar layout switcher.
• Extensions — Register with extensionRegistry; provide a loader that runs when the extension is enabled. Register commands, contributions, editors.
• Contributions — Declarative UI: tabs (sidebars, editor area), toolbar buttons, HTML blocks. Targets include SIDEBAR_MAIN, SIDEBAR_AUXILIARY, TOOLBAR_MAIN_RIGHT, TOOLBAR_BOTTOM_END, SYSTEM_LAYOUTS, etc.
• Commands — Id and handlers (optional canExecute). Toolbars and menus reference commands; the command palette and AI can execute them.

Next: Apps, Extensions, Contributions, Commands.