A chat?
>I am not talking about an "AI agent", but really a model that we call in a reproducible manner.
An LLM is just as deterministic as any other computer program. For identical inputs (which includes the PRNG seed) it produces identical outputs.
>compressed version of the git kernel
The git kernel, got it.
>But would this count as "compression" at all?
Yes. The decompressor is several tens of gigabytes though.
This is not really true in practice because of multi-threading and out-of-order execution. Mathematically equivalent orderings of operations are not equivalent when dealing with floating point values, so most practical LLM implementations end up being non-deterministic.
If you wanted to and had enough engineering effort to spare, you could run an LLM deterministically at relatively small impacts to performance.
One approach is to make sure you run things in the same order. Another is to change your operations so that more of them become associative or even commutative.
See eg the paper 'A Lattice-Based Approach to Deterministic Parallelism' for some interesting ideas on the latter.