[traverseda]

If memory serves the cachyos-nix flakes sets a cache for pre-built kernels, but that cache isn't available until you rebuild. So if you want to use the cache you need to do two steps, add cachyos to your inputs, rebuild, switch the kernel, rebuild.

Then reboot to use the new kernel.

[arikrahman]

Correct, I should've worded that better for more clarity.