Unless you absolutely need the job, I would consider this a great opportunity to figure out how his boss would react. Getting into a lively technical discussio

Unless you absolutely need the job, I would consider this a great opportunity to figure out how his boss would react. Getting into a lively technical discussion when you can see how well people can control their egos to find out the best course of action is very valuable. If I had a chance during an interview to find out how people behave in those circumstances I would definitely go for it. Who knows maybe the "boss" would be present in future technical discussions as well, I wouldn't want his presenc to change the discourse negatively. And as I've personally been in positions like that (being the tech lead with the boss on the call), I'm usually thrilled to learn new information and discuss technical things, raising my opinion of the interviewee greatly. Maybe that's because I come from a very straight forward culture where political subterfuge is frowned upon, but it wouldn't actually look very good to me if a member of my team would subtly alter a technical matter for the worse because of political pressure. Would I be able to trust that person? I would always have this doubt that they are "playing a deeper game", regardless if it was for my benefit or not.