How? If one PR builds off another, won’t either:

  PR 1 is size 400
  PR 2 is size 400 + 400 new
  PR 3 is size 800 + 400 new

At least that’s how it’s worked on teams I’ve worked on that have soft size limits.

Size is an issue, but it isn't just about size. Ideally, agile development builds linearly in complexity. Rather than dumping a huge new feature, first introduce the building blocks and the reason you are introducing them, then the glue that ties them together, then the actual feature.

From what I've seen (not in software dev anymore, however I've been in it for close to 30 years), AI just tends to pile everything in, and it is very hard to review. No public model performs even average under the rules I've mentioned.

Also, simply breaking up a PR doesn't count if instead you dump all the PRs on maintainers at once. Humans are the bottleneck here, and can only review so much at once. If i were still involved in PR reviews, it doesn't matter if you gave me a single 4,000 line PR or 4 1,000 line PRs, I"d reject them.

What I want to see. Small, easily reviewable features with a build up to the main course, along with a good explanation for each. After that? I'd probably still reject it for a breach of code standards, or documentation, or because I don't like you sending me a PR at 4:59pm on a Friday. ;)

Humans also can't blindly rely on AI for review, so the models (more precisely, the folks building the underlying stuff) must adapt.