125 is the exit code used by genv. See https://github.com/coreutils/coreutils/blob/master/src/env.c#L899-L903 and https://github.com/coreutils/coreutils/blob/master/src/system.h#L90 Copying the coreutils exit codes seems to be what is currently happening based on the 126 and 127 exit codes. SYSEXITS(3) does say "According to style(9), it is not a good practice to call exit(3) with arbitrary values to indicate a failure condition when ending a program. Instead, the pre-defined exit codes from sysexits should be used, so the caller of the process can get a rough estimation about the failure class without looking up the source code." If SYSEXIT(3)/STYLE(9) is what we want to follow, then exit code 64 makes the most sense to me.
It would be better to put
#define EXIT_CANCELED 125
and use that instead of the bare 125. I know we have other numbers elsewhere, but that's a good place to make this not a magic number.