Chatto is a lightweight iOS chat UI framework developed by Badoo, written in Swift. It provides a complete set of components for building chat interfaces, including a core controller (`BaseChatViewController`), a collection view layout optimized for chat, an extensible input bar, and support for various message types (text, photo, compound messages with multiple content blocks). The framework is designed around a presenter pattern where each chat item type has a dedicated presenter responsible for cell sizing, configuration, and interaction handling. It also includes a composable layout system for constructing complex bubble views. The repository includes two library targets (Chatto and ChattoAdditions) and a demo app showcasing features like pagination, swipe-to-reply, message selection, and custom input items. No backend, networking, or data persistence code is present; the demo simulates message sending. The codebase demonstrates solid architectural patterns and has reasonable test coverage, but shows signs of partial migration to a newer collection adapter, deprecated API usage (e.g., keyboard notifications), and some force unwraps. The repository has not seen active development in several years, with many open issues and stale pull requests.