While I have a sibling comment to yours saying I'm quite happy with the imposition of the limit, in my day job I frequently find code that pushes the boundaries of "reasonable" and I'm fairly sure we will exceed 14kB. But we don't use Vercel at work, so it's fine.

I suspect that while it's a reasonable limit for them, it probably won't work very well to impose a limit on an established code base that's not been built with a limit in mind.

Agreed. Cloudflare limits URLs to 16KB, AWS ALBs are also 16KB, so 14KB doesn’t seem out of place.