# Signal SignalKit Telegram iOS: How the App Implements Reactive Programming with SwiftSignalKit

> Discover how Telegram iOS leverages SwiftSignalKit for reactive programming. Learn about its cold-observable pattern and deferred execution of async operations for efficient network and UI management.

- Repository: [TelegramMessenger/Telegram-iOS](https://github.com/TelegramMessenger/Telegram-iOS)
- Tags: deep-dive
- Published: 2026-04-07

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**Telegram iOS uses the SwiftSignalKit library (Signal Kit) to implement a cold-observable reactive pattern, where asynchronous data streams represented by `Signal<T, E>` remain inactive until subscribed to, enabling deferred execution of network and UI operations.**

The TelegramMessenger/Telegram-iOS repository builds its entire asynchronous architecture on a custom reactive framework called **SwiftSignalKit**. Unlike mainstream alternatives such as RxSwift or Combine, this library prioritizes minimal binary size while providing composable primitives for handling complex data flows across messaging, network updates