Fold river versus BB’s shove; A-high with a weak kicker doesn’t meet the ~39% equity requirement.
Flop 3-5-6 rainbow, we have bottom pair with a gutshot and the Ah blocks some of BB’s strongest Ax. Solver prefers a lot of checking here, with some medium bets mixed in. Our small c-bet is fine but slightly lower EV than checking; it still works well as a mixed line.
Turn 8d connects the board further and gives BB more straight and draw possibilities. Solver leans toward checking here with this combo, but a medium-sized bet is also reasonable. The 7.5bb bet is a bit on the small side for a board this dynamic; a larger sizing or check would be slightly higher EV.
River Ks, BB shoves 72.5bb into a pot of 113bb, giving us about 1.6:1 and needing ~39% equity. A3s is just A-high with a weak kicker and doesn’t have the equity to continue versus a polarized shove range. Solver would fold this combo here; calling would be overcalling with a marginal bluff-catcher.