With quads facing a river shove getting 2:1, folding is reasonable versus a value-heavy range, even though solver prefers calling.
Flop 2s9s9c multiway: we have an overpair but the board is semi-wet and SB/BU have a lot of 9x and spade draws. Solver prefers a mix of checking and using a medium or overbet size; the small c-bet we chose is fine but slightly under-sized for multiway.
Turn 3c is a good card to barrel for value and protection versus spade draws; the 11.5bb bet is a reasonable medium size. SB’s call keeps their range fairly strong and sets up a river where we’re often ahead but not invulnerable.
River 9h gives us quads and SB leads 39.5bb into 78.5bb, giving us about 2:1 and needing ~33.5% equity. Solver prefers calling here, but the range strategy is more conservative and prefers folding. The key is that SB’s range is heavily weighted to value (quads, full houses) and we don’t block those, so folding is defensible.
Note: Folding quads versus a river shove getting 2:1 is defensible versus a value-heavy range, but solver prefers calling.