"Stipulate"

I was having an argument with a friend recently. He proposed some middle ground and then said "Can you stipulate to that?"
Being a low-level grammar fascist, I forgot about the original argument and started a new one about his usage of "stipulate." He used it as if it's interchangeable with the word "agree."
While some thesauri show "agree" as a synonym of "stipulate", none show "stipulate" as a synonym of "agree." I think this is an important distinction.
In the end, I feel he was trying to add weight to his argument by throwing in a twenty-five cent word. This might impress other people he deals with, but I actually read books and stuff from time to time. It just felt wrong, but I am open to the idea that maybe I haven't spent enough time in legal settings to be comfortable with this usage of the word.

I believe he is wrong and that, after the terms of an agreement are proposed, it is the terms themselves that do the stipulating, not the people. To stipulate is the act of negotiating the terms, not the act of agreeing to the terms. Once the terms are agreed upon, it is the terms that "stipulate", not the people under contract. Thus, you can't ask someone "do you stipulate?"... if you have reached the point of agreement, you are now beyond the stipulation, no? To use that word in seeking agreement, you'd be better off asking "would you care to stipulate further?" Does this make sense to anyone reading?
As he used it, was my friend's usage of "stipulate" correct?

TIA

Tweek