Bark is a native iOS application that turns APNs push notifications into a self-hostable, customizable notification delivery system. It is not a data or research project; it is a polished consumer iOS app with a companion widget, notification service extension, and App Intents. In production, the app maintains a device registration key per user, listens for remote notifications via Apple Push Notification service, and enriches incoming payloads through a chain of processors in the Notification Service Extension: decrypting AES-encrypted bodies (CBC/ECB/GCM with CryptoSwift), rendering Markdown, setting badges, auto-copying text, archiving to Realm, muting groups, triggering call interruptions, and attaching images/icons. The main app provides a history list with group/section rendering, server management (defaults to api.day.app but supports custom self-hosted servers), QR-code server import, encryption settings, archive retention controls, sound selection, and a modern home screen demonstrating usage via curl-like examples. A WidgetKit timeline widget shows recent messages from a shared JSON snapshot, and Siri/Shortcuts intents can trigger pushes to the current or another device. The architecture follows a reactive MVVM pattern using RxSwift/RxCocoa throughout, with Realm as the local persistence layer shared across app and extensions via an App Group container. The project targets iOS 15+ with five Xcode targets (main app, notification service extension, notification content extension, widget, tests) and is distributed via the App Store and TestFlight through fastlane and GitHub Actions.