Rubicon-ObjC is a Python library that provides a bridge between Python and the Objective-C runtime on macOS and iOS. It allows Python code to instantiate Objective-C objects, invoke methods, access properties, subclass Objective-C classes, and interact with Foundation and AppKit/UIKit frameworks. The library uses ctypes to directly interface with the Objective-C runtime, with modules for high-level wrappers (api.py), low-level message sending (runtime.py), type encoding conversion (types.py), Foundation collection wrappers (collections.py), asyncio event loop integration (eventloop.py), and a ctypes patch for struct return from callbacks (ctypes_patch.py). It is part of the BeeWare project and is used by frameworks like Toga for building native GUI applications. The codebase demonstrates careful handling of memory management, thread safety, and Python version compatibility (3.11–3.16), though it relies on internal ctypes details that may be fragile across Python releases.