If you run AI agents in production, how do they actually get access to your systems?

I have been thinking a lot about how teams give their AI agents access to real systems, and I would rather hear how people are doing it in practice than in theory. On one end I see teams hand an agent a single API key or service credential that can basically touch everything, because it was the fastest way to ship. On the other end I see people trying to give each agent its own scoped identity, short-lived tokens, and some kind of audit trail, which is a lot more work to stand up. Most teams seem to sit somewhere uncomfortable in the middle. If you are running agents in production today, what does your setup actually look like, how did you land on it, and is there a part of it that quietly worries you when you think about it late at night?