Just deprioritize it and make the mr openers do more verification

What sort of verification?

Everything that a maintainer would need to prove to themselves to merge it can be codified in a pipeline.

Or some kind of protocol for building those things in the MR so that any new behavior explicitly demonstrates the new states and transitions.

This is hard if the new MR introduces a completely different paradigm outside the mental model of the reviewer and maintainer. Might be better off completely forking the project and running it in parallel aka taking on the maintainer duties if they feel so inclined to completely change things

This makes 0 sense. It shouldn't matter if AI wrote the PR or a human.

If a person writes 100 lines of code there’s a (valid) assumption that someone thinks this 100 lines of code is worth writing. With AI it takes no effort to write 10,000 loc. Asking someone else to figure out if that code is worth merging just offloads the effort to someone else who didn’t ask for it.

It makes sense, because humans and AI write code different. Because humans aren't AI. The types of mistakes AI writes into code would never be done by a human.