Gnasher, I totally agree with your assessment of the auction. Thanks. FWIW, what happened was partner thought 2NT promised stoppers in the unbid suits, and therefore 3♦ was unambiguously a slam try, and I was not only showing ♥Hx with 3♥, but implicitly cooperating with his slam try with a maximum hand. I had something like xxx, KQ, AQ108x, xxx (yeah it's a fairly shitty opener, but add ♦J and the point stands), and to me 3♦ was natural, either a slam try or uncertainty about which game. I showed my strong heart doubleton (maybe he has a good five-card suit and a distributional hand and 4♥ is better than 3NT), and over 3♠ I was never bidding 3NT without a club stopper. We ended up in 6♦-2.