Impressively unhelpful error from the LX image builder

So we're trying to build some newer LX images for SmartOS, and we decided to do so with Alpine. We built the LX image builder, and we get this incredibly and shockingly unhelpful error message when we try to use it:

fractal@stardust:~/smartos-lx-img-builder$ pfexec target/release/smartos-lx-img-builder --tar alpine-minirootfs-3.21.1-x86_64.tar --image_name alpine3.21_x64 --description "Alpine Linux 3.12 (x64) (LX)" --zfs-parent stardust --url https://highenergymagic.net/downloads/smartos/lx created dataset stardust/c7f17e59-2336-450d-93e7-da3caf84997c-20250109 creating dir /stardust/c7f17e59-2336-450d-93e7-da3caf84997c-20250109/root set permissions for /stardust/c7f17e59-2336-450d-93e7-da3caf84997c-20250109/root to owner: 0 group: 0 mode: 755 created zroot /stardust/c7f17e59-2336-450d-93e7-da3caf84997c-20250109/root destroyed dataset stardust/c7f17e59-2336-450d-93e7-da3caf84997c-20250109 Error: No such file or directory (os error 2) fractal@stardust:~/smartos-lx-img-builder$

So...which file would that be, exactly, that it can't find? It has the tar, it has the 'guest' folder in the current directory for the files it imports, what the actual hell is going on? Anyone know what's going on, and/or if the LX image support is, as we are increasingly coming to believe, very much an afterthought, and also kinda broken?