villain who cold called is 26/19/3. regfish, never seen him before only 50 hands.

original opener opens 28% in MP and folds to 3bs 74% over 858 hands so i think it's an easy 3b/fold spot. i don't expect to get called very often.

so villain cold calls, i check back flop? thoughts on this? i figured it smacks his cold calling range pretty hard and if he has like 44-99 i can get him off on later streets if i miss.

timing tell, he bet river fairly quickly. i'm not folding river obv, wondering if this is a jam or a call? he can certainly have QQ,JJ,1010, and possibly even something like J10s,Q10s he's fishy enough. on the other hand i doubt he folds AK to a jam.

jam or call? 125bb deep

Flop looks good vs a 3bet cold caller. I think I shove now. I'd expect him to bet a little larger with a boat because we look like we're calling down. If he flats TT-QQ/AK then he's got 12 AK combos and 7 boat/quads combo which I do think are discounted a little when he bets 30 into 51. Plus your line is weird so he might get suspicious.

In general players will just bet big with nutted hands but at the same time we look so weak when we check behind this type of flop so I wouldn't be surprised if he's betting small with a boat to entice us.

That said, considering we're a bit deep, villain will probably have AK in his range so it's probably a jam. Also, he will have AA, KK, and AQ a non-zero percent of the time when he bets river which might call because we look so FOS when we take this line on this board texture.

shove looks good, people don't like fold in big pots

this is a very close decision. i think i would just go allin because your line is weird and he wouldnt expect us to have flush since we checked the flop. it will be very hard for him to put us on a hand and he might be very tempted to call mb even with smth like AQ (im being very optimistic there ).