The Assumptive Close

Oliver and I have this pattern of communicating that gets me every time. It goes like this:

"Oliver do you want some fruit?"
"I want graaaapes!"
"You want grapes?" (for clarification)

"OK." (as if it was all my suggestion in the first place)

Really, tone is everything in this exchange, but seriously, he throws that "OK" in there after every clarifying question I ask these days. It's especially vexxing when he suggests something he shouldn't have or that I'd otherwise say no to, say "scissors," for example, and it's such a habit for me to restate what he's saying to make sure I have it right: "You want scissors?" -- always met with a quick and assumptive: "OK" and the unstated "Thanks for offering."