And they believe Zig comptime wouldn’t do that? For the same inputs? I’d love an example.

Traditional stuff in this space are:

* floating point differences between the build machine and the target. By far the most common

* endiannes - code assumes little median runs on big endian

There’s other more subtle issues that can crop up but those are the big two.

Not saying I agree though - those can happen anyway when you run on two different machines anyway.

sin(x) can produce different results at comptime and runtime. In Rust there is no sin(x) at comptime for precisely this reason.