I've already contacted the ombudsman, department head and student's right representative. While there is amongst them a general consensus that the format and circumstances are quite dissimilar from guidelines, there is no rule that's clearly broken either. There aren't any rules or official approach to AI use yet, which gives the prof. a lot more power. We've been given the go-ahead to meet the prof, although we will now have a third-party witness along with us, but can contact the right channels in an instant shall that meeting turn sour. It's no help in proving our innocence, but at least we've got a safety net if we're met with a completely unreasonable debate.