Small pull requests
Keeping each pull request to one reviewable idea, often a few hundred lines at most. Long changes get split so that each piece makes sense and passes its checks by itself.
An agent can produce 2,000 lines as easily as 20, and it doesn't feel the difference. The reviewer does. Long diffs get skimmed, and a skimmed diff is a diff that wasn't reviewed. Size is the limit you have to set, since nothing about the agent will.
Say it to your agent
“This is 1,400 lines, which is too much to review well. Split it: first a refactor with no change in behaviour, then the schema, then the feature, each under 300 lines and each passing bun test by itself.”