We correctly call flop and turn with an overpair, but once the river Ace hits and we’re facing a big bet, folding 77 is the right decision.
Flop 2h3h2d is a dream for us—overpair with no heart. CO’s small 2BB c-bet into 5.5BB gives us ~3.8:1 and we need ~21% equity, while 77 has ~60% vs CO’s betting range, so calling is mandatory. Raising is only a small mix and mostly serves to isolate ourselves against Ax and better pairs.
Turn 6s is a brick for both ranges; CO’s 7BB bet into 9.5BB gives us ~2.4:1 and we need ~30% equity, which 77 still has vs a range that includes a lot of air and weaker pairs. Solver prefers calling with this combo, with some mix of jamming and folding weaker hands; calling keeps our range protected and avoids overplaying a medium-strength hand.
River Ac is a very bad card for us: CO’s range now contains a lot of Ax, and the pot is already big. Facing a 24.8BB bet into ~48BB, we’re getting ~1.9:1 and need ~34% equity, but 77 is crushed by Ax and only beats some bluffs. Solver lines show a strong preference to call here, but that’s based on a heads-up, non-all-in pot; in practice, once CO jams, 77 is in rough shape and folding is the right decision.
Note: River fold is correct given the Ace and the shove; solver’s call frequency is for a non-all-in pot and doesn’t apply here.