[Question] How could AIs ‘see’ each other’s source code?

I’m NOT confused about ‘how could AIs send each other a link to their Git repo?’.

I’m confused as to what other info would convince an AI that any particular source code is what another AI is running.

How could any running system prove to another what source code it’s running now?

How could a system prove to another what source code it will be running in the future?