InjectionIII is a macOS menu bar application that enables hot reloading of Swift, Objective-C, and C++ code in iOS simulators and devices. It works by watching for source file changes, recompiling them using Xcode build logs, and dynamically loading the resulting dylib into the running app using techniques like interposing, vtable patching, and Objective-C swizzling. The app consists of a daemon with a file watcher and injection server, while the client-side code (bundled as injection bundles or via the HotReloading Swift package) handles compilation and injection. It supports standalone injection without the app running, injection on real devices, and integration with SwiftUI. The codebase is mature and actively maintained, though it contains legacy C/ObjC components and is tightly coupled to Xcode build log parsing.