Nineundrum

Well you don't beat much, I doubt they bet even KJ for this size OTR. At least I don't think they should.

Your set is very disguised and that should give you a lot of value at the river if you boat up cause doenst expect you to check sets or 2P on the flop.
Think calling is way better here.

River is so ugly that folding has to be best, I doubt he bets worse here with that sizing and there aren't many bluffs left either.

You've got a bluff catcher. How often is your pop bluffing the river at your stakes?

Looks like a call to me, but I don't know the game you're in.

Not sure if a fish/bad player is bluffing enough here. I don't think it's ever a flush but would expect a lot of straights and sets.

Raise turn. Call river.

OP dind't say any so its an unknown

I think especially considering your 3x open size it is a fold on that runout. We hope to se some Suited Ax that villain turns into a bluff so A6s-A2s and some pockets 66 55.
He still has in this line some flushes and AQ mostly.
If you go smaller pre and villain has a high 3b freq an in generall aggro then more a call realy depends on that Ax and pocket region i think.
About turn i guess value raise makes sense probably with some freq in theory but in practice we could do it always as soon villain starts to be to passive with going over the top with bluffs.
So raise vs AA KK AK AQ with a club makes sense and we can check back rivers and see showdown wich is great for our hand

You can tell by the 3b size.

Difficult to find any logical bluffs here and you don't beat any value, I think a fold is the best play on the river

AT/A7/KT and then a ton of random hands that think they can win on a 4 straight board on the turn, once the flop is checked. A5/A4, you name it.

None of those hands should bet the turn really. Maybe A7 is low enough down to turn into a bluff once the board runs out 4 straight but it seems a bit optimistic.

I suppose the counter argument is that villain's preflop sizing means he's likely a fish so could show up with more ridiculous holdings than you might expect and maybe even some worse value bets like KT and KJ because he doesn't understand relative hand strength (again, it seems a bit optimistic).

In general though, I would assume that most 3 flush/4 straight board are going to be very underbluffed more often than not. In order for villain not to be underbluffing here, he basically needs to

1) bet random low equity hands on the turn like A5dd; or
2) start bluffing with underpairs

Neither of these things are particularly intuitive or appetising for a human to do, so my intuition is telling me that this spot is underbluffed and we should fold. I could well be mistaken though.

I'd be interested to know if anyone has any MDA that would help here.

I agree, but I'm seriously starting a nickle jar for every time I have to say this. Just because it's not what you "should" do, bad opponents are bad because they do it.

This hand just comes down to simple MDA... how often are opponents bluffing on X/B/B lines on 4 straight boards?

It doesn't help that OP has 99 and blocks some of the lower straights that villain would look to get value from, but regardless, it's a close spot simply because of the odds and opponents at these stakes show up w/ hands they shouldn't.

Good point, but it does depend if villain will be turning pairs (or 2 pairs into bluffs). Not sure the stakes of the hand, but given the odd 3bet size its probably weaker player who might take their 'showdown value' of AT and not bluff.

The problem is that a lot of people at lower stakes won't do this as much as a bluff with those hands, and will occasionally bet some better hands than 99 that probably aren't supposed to bet or even exist in this line. I would guess that it's an underbluffed spot, but I don't have any access to any MDA.

Fold. They won't start bluffing random Ax/66 on turn that is so good for you.

So then it's an easy fold if that's the case.

I find it a little hard to believe that when the flop goes X/X and there's a 4 straight that hits on the turn, that people won't random bluff... but if you say so at these stakes, then looks like a straight forward fold.

Better players will bluff some amount of the time obv,, but there are so many super nits and really bad regs/players who don't even bluff in the most obvious spots that bluffcatching is usually unattractive.