Been building react.js & next.js apps for a while and rich text editors are honestly one of the most painful pieces to integrate as I've already tried tinymce, tiptap etc and getting AI features wired in cleanly is always a separate battle.
the part that always slows me down is keeping editor logic and AI logic in sync - prompt updates, error handling, streaming states all end up in two different layers and get messy fast, having both bundled into one SDK is a huge time save if it works the way you describe.
lexical-based + drop-in npm + BYO keys is exactly the right approach! definitely trying this on a client project next week 👏