I don't think this is inevitable. How do you define an absolute mess? Whatever you come up with, give the agent instructions to not do that. Then audit the code to make sure it's not happening.
> Not only does the code become impossible for humans to reason about very quickly,
What makes it actually impossible? It's using logic that is beyond human comprehension? It's using the programming language in a clever way no human would expect? Have you tried instructing it to code in a way that's more comprehensible to humans, e.g. literate programs?
> it actually becomes difficult for agents to reason about it.
I don't think this is inevitable. How do you define an absolute mess? Whatever you come up with, give the agent instructions to not do that. Then audit the code to make sure it's not happening.
> Not only does the code become impossible for humans to reason about very quickly,
What makes it actually impossible? It's using logic that is beyond human comprehension? It's using the programming language in a clever way no human would expect? Have you tried instructing it to code in a way that's more comprehensible to humans, e.g. literate programs?
> it actually becomes difficult for agents to reason about it.
This I have not seen. Do you have an example?