diff --git a/CONTEXT.md b/CONTEXT.md
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@@ -8,7 +8,19 @@ Don't ask for unrelated files to be added to the chat.
 
 ## Architecture
 
-...
+The application is structured using a Model-View-Controller (MVC) architecture to ensure a clear separation of concerns, making the codebase easier to maintain and extend.
+
+*   **Model:** This layer represents the application's data and business logic. It knows nothing about the user interface.
+    *   `Document`: Manages the collection of all features.
+    *   `Feature`, `SketchFeature`: Represent individual components or operations in the CAD model.
+
+*   **View:** This layer is responsible for displaying the data from the Model and capturing user input. It should be as "dumb" as possible, delegating all actions to the Controller.
+    *   `MainWindow`: The main application window, toolbars, and menus.
+    *   `ViewportWidget`: The 3D OpenGL viewport for rendering the model.
+    *   `FeatureBrowser`: The UI component that lists the features in the document.
+
+*   **Controller:** This layer acts as the intermediary between the Model and the View. It contains the application's core logic.
+    *   `ApplicationController`: The "brains" of the application. It is created in `main()` and passed to the UI. It responds to user actions from the View, manipulates the Model, and uses signals and slots to notify the View of any state changes.
 
 ## Development Log