I’m dumb, but maybe this can save someone else as well. I’d been playing around with my terrain size a lot, so had things running off variables for the map size (like mapX, mapZ, to scale the positions of meshes, etc.)… like the shadowGenerator. Anyways I ended up setting the map to not-a-power-of-2, and that’s why shadow generation it was broken for me. Props to Chrome for working despite it all, but it let me get sloppy!
TL;DR – shadow map must be power-of-2! (512, 1024, etc.)