For work we use Vercel for certain bits of the architecture. I was a huge fan of Vercel's early iterations. Lately/last few years they're kind of everywhere and all of a sudden looking to cement themselves as The Platform, and though Next.js is pitched as a separate thing, it's pretty clear that it's undoubtedly intertwined with Vercel's hosting.
Still, ignoring the politics for a second, I recently ran into an issue with preview/branch deploys and testing.
We were trying to debug a RESTful API I was working on and Vercel adds a layer in front of preview deploys, so this is how to get around that.
Short version is: tucked away in their docs is Protection Bypass for Automation.