Diff Review

What is a Diff Review

Diff review is reviewing exactly the lines an agent changed, rather than re-reading the entire file or codebase around them. It is the fastest practical way for a human to verify what an agent actually did, since it shows precisely what changed instead of asking the reviewer to spot the difference by comparing a whole file against memory.

A good diff review checks more than whether the change works: does every changed file trace back to what was actually requested, is the change scoped to the task or does it wander into unrelated territory, does anything here look like it was asserted rather than verified. This is where scope creep and silent failure both tend to surface, if they surface at all.

Diff review and automated review complement rather than replace each other, an automated pass can catch a lot of mechanical issues before a human ever opens the diff, but the human pass is still where judgment calls about whether this was the right approach, not just a working one, actually get made.