My team has been working on this in the concept of Turing Test and human vs. AI discrimination: https://arxiv.org/pdf/2605.06524

Specifically, our approach is to separate classic output-based approaches (CAPTCHAs, fingerprints, etc.) and instead look at process-based traces: how are cognitive process traces and broad behavioral metrics evolving over time with continuous human/computer use

My two cents: homocodex.com

If we need a way to prove online personhood, then we've already lost. It means that the internet is no longer a place for humans and is, in fact, hostile to us.

I'm not saying that the personhood assertion is incorrect, only that it means something very bad.