Provides a scoped lifecycle for RxJS subscriptions and reactive values. `scope.behavior()` creates hot `Behavior` values that automatically complete when the scope ends, preventing memory leaks. Includes `reconcile()` for async lifecycle management and `Epoch` for consistent combineLatest. This is a foundational pattern used throughout the SDK and app for clean, composable reactive state.

A read-only wrapper around RxJS `BehaviorSubject` that exposes a typed reactive value with `subscribe()` and `observe()` methods. Supports `constant()` for immutable values and `map()` for derived behaviors. This is the core reactive primitive that enables decoupled, testable state propagation across the entire application.

Defines an interface and implementations (null, widget, component) for communication between the call application and its host environment. Abstracts join/leave notifications, hangup, always-on-screen mode, and theme changes. This pattern allows the same call logic to be embedded in different contexts (standalone, iframe, React component) without modification.

Implements a generic mute state class (`MuteState`) that handles mute/unmute, force-mute (earpiece mode), and synchronization with the host bridge. The `MuteStates` class ties audio and video mute states together, providing reactive observables for mute status and enabling features like push-to-talk and automatic muting on device change. Reusable for any media type.

An immutable collection for managing tile layouts with a builder pattern (`TileStoreBuilder`). Supports efficient reuse of unchanged tiles and provides methods for adding, removing, and updating tiles. Used by the layout system to compute grid/spotlight arrangements without unnecessary re-renders. Demonstrates a clean, functional approach to mutable UI state.

Defines a hierarchical error system (`ElementCallError` with codes, categories, and i18n support). Errors carry a `recoveryAction` hint (e.g., reconnect, rageshake) and can be translated via i18n keys. This pattern ensures consistent error presentation across the application and enables automated recovery suggestions.

A responsive modal/drawer component that adapts to screen size: renders as a centered dialog on desktop and a bottom drawer on mobile. Supports keyboard navigation, focus trapping, and ARIA attributes for accessibility. Used for settings, invite, and confirmation dialogs throughout the app. Demonstrates a reusable, accessible UI primitive.

Manages Web Audio API context for playing sound effects (ringtone, reactions, call events) with support for device routing and earpiece panning. Handles iOS Safari workarounds for controlled audio output. Provides a reactive interface for volume control and device selection. Demonstrates non-trivial audio engineering in a browser environment.