[Fasteddy]

You and pard conduct the following auction:

1♦ (must be an unbalanced hand), 1♥ (4+ hearts); 1♠ (4 spades), 2♣ (XYZ, forces 2♦; 2♦ (forced), 2NT (denies 5 hearts, the only way to bid 2NT nonforcing); 3♦ (6+ diamonds, nonforcing), 3♠.

So far, you've shown a minimum hand with 6+ diamonds and 4 spades; pard has shown a balanced invite with something in spades. The question is, is partner trying to play in a 4-3 fit for a superior matchpoint partscore or does he have a hand that's been improved by your extra diamond length and is now looking for the best game, maybe something like KQx QTxx xx Axx or even Kx Axxx xxx Axxx?

[hanp]

I don't think that either of these two hands has been improved by your extra diamond length. I think that partner is exactly 3415. And of course it is non-forcing, partner has shown an invite and we have shown a minimum (and a minimum 4-6 can be lighter than a minimum balanced hand).

By the way, it doesn't seem right to play that 2NT denies 5 hearts. First of all, if partner has 3 hearts we will usually hear about it over 2NT (perhaps partner passes with a minimum 4342). Secondly, I would hate to invite in hearts holding something like AJx J10xxx x KQxx, this is a 2NT bid imo.