alt Hacker NewsThis is only ideally true. From the perspective of the user of a large closed LLM, this isn't quite right because of non-associativity, experiments, unversioned changes, etc.
It's best to assume that the relationship between input and output of an LLM is not deterministic, similar to something like using a Google search API.
And even on open LLMs, GPU instability can cause non-determinism. For performance reasons, determinism is seldom guaranteed in LLMs in general.