CodeGen & Lean Core

CodeGen — Suppose to make the JS side a Single Source Of Truth. Can let you create static types of the js so the native side (Fabric and Turbo Modules) will be aware to them and avoid validating the data each time => better performance and less place for mistakes when passing data.

Lean Core — A change in React native repository structure. The purpose is to make the lib lighter and help the community resolve more pull requests faster than before. Facebook splits some of its parts to an external repo. It is already a process in progress that you can follow in their Github here.