Auth.js isn't really by Vercel even if they scooped up the creator and stuck one of their "powered by" stickers on it... it does have a fun tie-in with Rauch's cartel though

Clerk sponsors it extremely heavily so that when you get fed up with dealing with it, every single page has a CTA funneling you to them.

Honestly the whole situation has a terrible terrible smell, but that's post-Rauch JS for you.