both Vul at MP.
LHO bids 2♥ weak, partner bids 2♠ which is F1 but not GF. You bid 3♥ now, which is GF, either looking for a stopper or a hand with ♠ support. Partner bids 3♠. You have a choice of signing off now, or cue-bidding. If you bid 4♣, there's obviously some confusion whether it could be simply show a good hand with ♣s, as a direct 3♣ over 2♠ would be NF and a direct 4♣ over 2♠ would be conventional showing at least 4-6 in the blacks, whereas 4♦ and 4♥ are free from such ambiguity. But the more important question is whether you should bid more at all.
Partner's 3♠ obviously denies a stopper. What he'd bid with a stronger hand is not something if you've discussed at length. Presumably he could bid a new suit or may be planning to bid more over opener's rebid.