I let Claude write my React compiler. I only reviewed the tests.

Open the React DevTools "highlight updates" panel on any React app you've ever worked on. Count the flashes. You've done this before, probably in an interview, probably while defending a useCallback. That counting habit is a React-specific anxiety, not a universal one - and the reason matters less for this post than what I did about it. I spent about a month building a thin wrapper around an existing state library ( Legend-State ) that tries to compile that anxiety away. The piece I want to write about isn't the wrapper itself. It's how I built the compiler behind it.