That's like saying the '9' in kill -9 might change someday. However it really does depend on which numbers. In the APE blog post I mention the importance on focusing on the subset of numbers that systems share in common. In other words, the really old ones. https://github.com/jart/cosmopolitan/blob/master/libc/sysv/c...

Not quite–kill is part of POSIX, and platforms that expose a libc interface must keep signal numbers consistent for applications. Syscall numbers need not be stable if they are not exposed, as is true on pretty much every platform but Linux.