Stream Chat Swift is an iOS/macOS SDK for building real-time chat and messaging applications. It provides a modular architecture separating core networking (StreamChat), UI components (StreamChatUI), and shared utilities (StreamChatCommonUI). The SDK supports features like channels, messages, reactions, threads, polls, attachments, typing indicators, and presence. It uses Combine for reactive programming, Core Data for persistence, and WebSocket for real-time communication. The repository includes demo applications, example implementations (SlackClone, MessengerClone, etc.), and extensive testing infrastructure. The SDK follows protocol-oriented programming with dependency injection via Appearance and Components providers, enabling high customization.