In all honesty it does depend on if we know the opponent is a reg or a fish, but I don’t think people are triple barrel bluffing OOP at 5NL enough for this to be a call, so I think we can make an exploitative fold here. We should be making some calls here with KQo though, preferably combos that don’t hold spades.

Flop Qh9s9c

BB has a range advantage here as BB has AA, KK, QQ but we never have these hands. BB also has hands like 89ss/910ss/A9ss but so do we.

Turn 6s

This card is actually a great card for BB because it doesn’t change anything as he still has an advantage on this board. We do have combos of 66 on BTN but these hands should be folding to .5P Cbet on the flop. This is also a bad card for us on the button because we have the Ks which blocks hands in BBs turn barreling bluff range.

River 4c

Another horrible card for our range.

Overall, 3better has a range advantage on this board over flatter in BTN.

BB could be barreling some combos of 10J that aren’t spades as bluffs, as well as hands like AJ suited that blocks JQ/J9 and maybe some combos of Kx suited. BB could also be barreling 89/910/A9/QQ/KK/AA/AQ/KQ. Even tho we’re blocking some hands that he is turn barreling with like AQ/QQ/KK/KQ we are also blocking spade draws that he would turn barrel with like AK, KQ, KJ, K10, and unblocking 9s that he would be 3betting with.

In general blocking hands in his bluffing range and unblocking hands at the very top of the range isn’t a good thing. Added with the fact that people are bluffing the river very often, id make an exploitable fold here. But we do need to call combos of KQ that don’t have spades.