Rubicon-ObjC is a bridge library enabling Python to interact with Objective-C runtime and frameworks. It allows instantiation and invocation of Objective-C objects from Python, subclassing Objective-C classes in Python, and automatic conversion between Python and Objective-C data types. The library is part of the BeeWare suite for cross-platform Python GUI development, targeting iOS/macOS platforms. Architecture centers around modular submodules: api (high-level decorators and wrappers), runtime (low-level Objective-C interactions), types (data conversion), collections (Foundation collection wrappers), and eventloop (asyncio integration). Key features include bidirectional type conversion, decorator-based exposure of Python to Objective-C, block handling, and memory management automation. The library is used in production iOS apps (e.g., Travel Tips) and serves as a dependency for other BeeWare projects like Toga.