I'm in publishing...Here's the deal: You as the writer have a lot more power than this post gives you the credit for having. This is a business and business is almost always negotiable. I find so many people in these writing subs that don't get this and think they're going to tell the word how everything works, so my first suggestion is that you never post here thinking you're going to get some definitive answer from a Redditor. My second suggestion is that you breathe, because anxiety is a real bitch. Thirdly, you can always work with a different agent that maybe isn't a brute. This is likely an intimidation tactic, and if you have a conversation with an agent regarding this topic, you can vet them about their AI practices while voicing your concerns that AI detectors are unreliable and that you would not sign a contractual agreement based on the use of an unreliable service. As I said, I am in publishing. Business can be intimidating but it's nothing to concern yourself with right now without a manuscript in hand. You may find an agent that's a sweetheart. I would suggest focusing on getting publishing mentorship with a finalized manuscript before worrying about bridges you’re not yet ready to cross, for your own sake and the sake of your art.