---
title: How to review a pull request your agent wrote
slug: how-to-review-a-pull-request-your-agent-wrote
published_at: 2026-10-12 13:00:00 +0000
updated_at: 2026-10-06 21:14:11 +0000
summary: Coding agents made writing code cheap, and reading it costs what it always did. Seven habits I use to review agent-written pull requests without rubber-stamping them.
tags: [ai, llm, code-review]
author: CJ Avilla
url: https://www.cjav.dev/articles/how-to-review-a-pull-request-your-agent-wrote
type: article
---

# How to review a pull request your agent wrote

*Published: October 12, 2026*
*Tags: ai, llm, code-review*

Coding agents made writing code cheap. Reading it costs the same as it always did. That's how you end up looking at a pull request that says `+187,402 −96,113` across 1,284 files, with one reviewer assigned, and it's you.

I put that diff on a shirt as a joke: "Author: the agents. Reviewer: nobody. Status: merged." It's a joke because most of us have approved something like it. Here's how I try not to.

## The rule: don't ask for more than you can read

The size of the PR is something you choose when you write the prompt. If you ask an agent to "migrate the app to the new API", you get one enormous diff. If you ask for a plan first and then ask for one step at a time, you get ten PRs you can read.

So the most useful review habit comes before any code exists:

1. Ask the agent for a written plan, broken into steps that each leave the tests passing.
2. Read the plan. This is the cheapest review you will do all week.
3. Have it carry out one step per PR.

A few hundred changed lines is a size I can read properly. Past that I start skimming, and skimming an agent's code is how "reviewer: nobody" happens.

## Separate the mechanical from the meaningful

Some changes are large and boring: a rename, a formatter run, a regenerated lockfile, a codemod. Others are small and matter a lot: a changed condition, a new query, a deleted check.

Mixed into one diff, the boring part hides the part that matters. Ask the agent to put them in separate commits (or separate PRs), and to say in each commit message which kind it is. Then you can check the mechanical commit by re-running the command that produced it, and spend your reading time on the rest.

## Read the tests first

In an agent's PR, the tests tell you what it thinks the task was. I read them before the implementation and look for three things:

- **Deleted or skipped tests.** An agent that can't make a test pass will sometimes remove it or mark it skipped. Search the diff for `skip`, `xit`, `only` and removed test files before anything else.
- **Tests that assert what the code does, not what it should do.** A test that was written after the code, by the same author, to match the code's output, proves very little.
- **Changed expectations.** If an existing assertion changed from one value to another, find out why. Sometimes the old value was wrong. Sometimes the new behavior is.

## Ask the agent to review its own diff, in a fresh session

The session that wrote the code is invested in it. A new session with no history isn't. I open one, give it the diff and the original task, and ask:

```
Here is a task and a diff that claims to complete it.
List anything the diff does that the task didn't ask for.
List anything the task asked for that the diff doesn't do.
Don't summarize the diff. Don't praise it.
```

The first list is the valuable one. Agents add things: an extra config option, a "while I was here" refactor, a retry loop nobody asked for. Each addition is code you now own.

This doesn't replace your review. It tells you where to look.

## Run it

A diff that reads well can still be wrong. Before approving, check out the branch and use the feature the way a user would. For anything with a UI, look at it. For anything with a migration, run it against a copy of real data. Agents are good at code that looks right, and the only way to tell "looks right" from "works" is to run it.

## Look hardest at what can't be undone

Not every line deserves the same attention. I slow down for:

- Migrations and anything that deletes or rewrites data
- Auth, permissions and anything touching secrets
- Money: prices, billing, refunds
- New dependencies (does this package exist, and is it the one you think it is?)
- Changes to CI, lint rules or test configuration, which can quietly lower the bar for every later PR

A CSS tweak can get a fast pass. A migration gets read line by line, however confident the PR description sounds.

## Say what you didn't review

If you approve a large PR after reading only part of it, write that down: "Read the billing changes closely, skimmed the generated client, did not review the snapshot updates." It's more honest than "LGTM", and the next person to debug that code will know where nobody looked.

## The short version

- Keep PRs small by asking for small steps.
- Split mechanical changes from meaningful ones.
- Read the tests first, and check for deleted or skipped ones.
- Get a fresh session to list what the diff does beyond the task.
- Run the code.
- Spend your attention on what can't be undone.
- Write down what you skipped.

None of this is new. It's the review advice we already had, and it matters more now that the author can produce a thousand lines a minute and never gets tired of being asked to split a PR.

---

*The shirt: [Diff Stat Tee](https://thepaperclipfactory.com/products/diff-stat-tee?utm_source=cjav.dev&utm_medium=blog&utm_campaign=review-agent-pr), `+187,402 −96,113`, written by the agents, read by nobody. It also comes as a [mug](https://thepaperclipfactory.com/products/diff-stat-black-mug?utm_source=cjav.dev&utm_medium=blog&utm_campaign=review-agent-pr), a [hat](https://thepaperclipfactory.com/products/diff-stat-hat?utm_source=cjav.dev&utm_medium=blog&utm_campaign=review-agent-pr) and a [laptop sticker](https://thepaperclipfactory.com/products/diff-stat-sticker?utm_source=cjav.dev&utm_medium=blog&utm_campaign=review-agent-pr). The rest of my developer jokes are at [The Paperclip Factory](https://thepaperclipfactory.com/collections/gifts-for-programmers?utm_source=cjav.dev&utm_medium=blog&utm_campaign=review-agent-pr).*

---

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