Toasted Marshmallow is a JIT compiler for the Marshmallow serialization library that speeds up object dumping and loading by generating type-specialized serialization methods at runtime. It works by creating optimized serializers for instance objects, dictionaries, and hybrid objects (those with __getitem__), then using a proxy to adaptively select the best serializer based on input type patterns. The project includes a forked Marshmallow submodule to provide necessary hooks for JIT integration. Architecture-wise, it's a Python library with core logic in toastedmarshmallow/jit.py, utility modules for code generation and compatibility, and performance benchmarks. Entry points involve setting schema.jit = toastedmarshmallow.Jit on a Marshmallow Schema instance.