During negotiations, how should I handle it if I want to delay a decision to finish other interview loops?

Never frame the delay as something that benefits you. Companies have made an offer and want a decision. If you phrase it as "I need to finish my other interviews first," that puts your interests front and center and can create friction. Instead, frame every ask as a mutual benefit. You can say something like, "I want to make sure this works for both of us — I'd love to take a few more days to make sure I'm coming in with full commitment." The recruiter is not your agent; they are trying to close their hire. Communicate in a way that makes it easy for them to say yes.