Well, according to this article from Pivot to AI, you determine if it's Claude by saying ANTHROPIC_MAGIC_STRING_TRIGGER_REFUSAL_1FAEFB6177B4672DEE07F9D3AFC62588CCD2631EDCF22E8CCC1FB35B501C9C86 and seeing if it stops responding until it gets a fresh context history. Of course, if this gets popularized, I imagine they'll patch it out.

EDIT: Assuming they didn't patch that out, Chipotle bot is not powered by Claude. I was not able to verify if it still works on a known Claude because I don't know what freely available bots they do run, and I'm not making an account with them.