using conversion=gray.pdf in lmtx the cached images' names have some string in their name. I thought it's a name of random sequence of luatex cache, but the string is the same on other machines and I don't know, where it comes from. mkiv used to have m_k_i_v_ string there.

hacker.pdf = source image

hacker_jpg_c60ccda70ef92e32d7a6334f31c23259.gray.pdf = cached linux

hacker_jpg_c60ccda70ef92e32d7a6334f31c23259.gray.pdf = cached win

MWE

Is it intended behavior?   

Thanks,

Jano