The user reading the code the agent produced and forming a judgement on it. Reading the diff or the changed files counts; reading the agent's description of what it did does not — narration is not the artifact. The description is a secondary source, written by the party being reviewed; the diff is the primary source, and review means reading it.
Agents raise the volume of code produced, so review becomes the bottleneck. One useful idea is layering different review strategies. Automated checks catch the mechanical failures, automated review catches the describable ones, and human review is reserved for what only you can judge — whether the change is the right change, whether the approach fits the codebase, whether this should exist at all.
Review is also cheaper earlier. Reading a plan before work starts, or a small diff mid-flight, takes minutes; excavating a finished branch after an AFK run takes longer. Where you place the review checkpoint is a human-in-the-loop decision, not an afterthought.
Avoid: "code review" alone — ambiguous between human and automated.
Usage:
"I human-reviewed the AFK output."
"You read the diff or just the summary?"
"Diff. The summary said it deleted dead code — turned out the function was called from a generated file."