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Saying what the agent did, in the commit and the review

An agent fixed a bug in the nightly sales import, the tests pass, and you are about to open a pull request. A reviewer reads what you send this week and decides how closely to look. Someone who reads the history a year from now wants to know who made the change and who checked it. In this lesson we write the commit message and the pull request for both readers. The first half covers the team’s review agreements, and the second half covers how the commit says that an agent helped, and what only a person may add to it.

The lesson on saying that AI helped gave a disclosure line three parts: what the AI did, what the person checked, and who is accountable. A pull request needs the same three parts, and a commit holds them in a form that tools can read.

Before you ask for a review

Section titled “Before you ask for a review”

Review norms are the agreements a team makes on how agent-assisted changes are reviewed. Teams write them down in different words. These are the points most of them share.

The author reads every line first. You asked for the change, and you are its first reviewer. The steps are the ones from reviewing the diff. When you request a review, you tell the reviewer that you understand the change and think it is right. If they find a line you never read, they learn that your request meant less than that.

The description says what the agent did and what you verified. Name the part the agent wrote, the checks you ran yourself, and what you didn’t check. “The agent ran the tests” reports what the agent said. “I ran the tests, and the new one fails on main and passes here” reports what you saw.

The reviewer reads the diff. The description tells the reviewer where to look, and the diff is what gets merged. A description written by an agent can describe the change it meant to make and not the one it made. An agent’s change goes through the same gates as any other change: the CI run and a reviewer’s approval. “The agent tested it” doesn’t replace either, because the agent’s tests are part of the change under review.

The change is small enough to read. An agent writes code much faster than a person can review it. A diff that’s too large to read gets skimmed or blocked. Split it before you ask. Put a mechanical rename in its own pull request, and keep each change to one purpose. A tidy-up the agent made on the side belongs in a separate pull request, or at least in the description.

Your team may have its own list, often in the project’s agent instructions file or in CONTRIBUTING. Where the two differ, follow the team’s list. When you disagree with one of its rules, propose a change to the file and keep to the rule until the team agrees.

Checkpoint · scenario

A 3000-line agent diff

Section titled “A 3000-line agent diff”

You asked an agent to add a monthly report to a service. The branch it produced also renames the logging calls in forty files, “for consistency”. The diff has about 3000 changed lines and CI passes. What do you do before anyone reviews it?

Saying it in the commit

Section titled “Saying it in the commit”

Attribution means recording in the change itself that an agent contributed, next to the person who directed and checked the work. In a commit it goes in a trailer. Git reads trailers from the last paragraph of a commit message, after a blank line, as lines in the form Key: value [1]. Tools read them from there, so a line in the middle of the body that looks like a trailer is only text.

Several forms are in use. GitHub shows a commit as written by more than one person when the message ends with a Co-authored-by: name <email> line for each of them [2]. The Linux kernel asks for an Assisted-by tag that names the AI help, in a format its guideline gives [3]. Claude Code adds a Co-Authored-By trailer to its commits by default. Its attribution.commit setting changes that trailer to the one the project asks for, and an empty value removes it [4]. Whichever agent you use, check the form the project asks for, and read the trailer block of each commit before you push it.

The commit’s author is still you. Git records an author for every commit, the identity of the person who made it unless someone sets another one [5]. The trailer adds the agent. It doesn’t take your name off.

The fixture for this lesson is in the course repository under site/examples/coding-with-agents/attribution-and-review-norms/. The agent wrote commit-message.txt, and trailers.py runs git interpret-trailers --parse on it, which prints only the lines git reads as trailers.

Checkpoint · predict

Which lines are trailers?

Section titled “Which lines are trailers?”

This is the agent’s commit message:

fix: read quoted amounts in the nightly import


The importer split "1,250.00" into two fields. It now reads each row
with the csv module, so a quoted amount stays one field.
Assisted-by: Claude:claude-sonnet-4-6
I also tidied up the date parsing while I was in the file.


Signed-off-by: Coding Agent <agent@example.com>

Before you run it, write down what the script prints for this message. Then copy the directory and run it to check.

Terminal window
python3 trailers.py

Output verified in CI from site/examples/coding-with-agents/attribution-and-review-norms/trailers.py.

The only trailer git finds is the one line the agent must not write. The Assisted-by line is in the body, so a tool that counts agent-assisted commits misses this one.

The sign-off only a person gives

Section titled “The sign-off only a person gives”

The Signed-off-by trailer is older than coding agents. git commit -s adds one with the committer’s name, and the git documentation says that what it means depends on the project. In the Linux kernel and Git projects, and in others that adopted it, it certifies the Developer Certificate of Origin (DCO) [5]. The DCO is a short statement in four parts. In our words: I made the contribution, in whole or in part, and have the right to submit it under the project’s license, or it is based on earlier open-source work I may submit, or someone who certified one of these gave it to me and I didn’t change it. And I agree that the contribution and my sign-off are kept on public record [6].

Each part is a statement about a person’s rights and knowledge, and an agent has neither. The Linux kernel guideline says it directly: an AI agent must not add a Signed-off-by tag. The person who submits the change reads the code, makes sure its license fits the project, signs off in their own name and answers for the result [3]. Sign off yourself only after you have read the change, because the sign-off says you know where the code came from.

This course’s own repository is a worked example. The last commit on main when this lesson was written ended like this:

Co-Authored-By: lsimons-bot <bot@leosimons.com>
Assisted-by: Claude:claude-opus-5-5

The Co-Authored-By line names a bot account, and the Assisted-by line names the agent and the model. The commit’s author is the maintainer, and the message has no sign-off.

Checkpoint · choice

Which trailer block?

Section titled “Which trailer block?”

Ana’s project requires a DCO sign-off on every commit and asks for an Assisted-by trailer when AI helped. An agent wrote the change, and Ana read every line and ran the tests. Which trailer block does the commit end with?

Exercise

Rewrite the agent’s commit message and pull request description from the fixture directory, commit-message.txt and pr-description.md. The pull request says only that “the agent fixed the bug” and that the agent ran the tests. Write both as you would send them, in a copy of the directory. Then run python3 trailers.py with your message file as its argument to see which trailers git finds.

Take out the agent’s sign-off. If your project asks for a sign-off, write your own Signed-off-by line in the file, the line git commit -s would add. In real work, add it only once you have read the change. Decide what to do with the date-parsing tidy-up: take it out of this change, or name it in both texts.

A good result: the message says what changed and why, and ends with one trailer paragraph that trailers.py prints in full, Assisted-by in the form this lesson used or the form your team uses. The pull request says what the agent wrote, what you ran yourself and what you saw, and what you didn’t check. A reviewer could tell from it where to look hardest.

Reflect: which sentence in your pull request would you have left out if this exercise had not asked for it, and what would the reviewer have assumed without it?

Stretch: Look at the last ten commits in a repository your team uses with agents. Count how many name the agent in a trailer, and how many say so only in the body or not at all.

Recap

  1. Before you ask for review, read every line yourself and split a change that’s too large to read. The pull request says what the agent did and what you checked, and the change goes through the same review and CI gates as any other.
  2. Reviewers read the diff, and the description tells them where to look. Answer for the whole change as its author, including the parts the agent wrote.
  3. Put the attribution in a trailer in the last paragraph of the commit message [1], in the form the project asks for, such as Assisted-by or Co-authored-by.
  4. In a project that uses the Developer Certificate of Origin, a Signed-off-by line certifies it, and only a person can give that. An agent never signs off, and you sign off only after you have read the change [3].

You can now

  • Attributes agent work honestly in commits and reviews
  • Follows the team's review and CI norms for agent changes

References

Section titled “References”
  1. The Git project. git-interpret-trailers. Git reference documentation. Reference. Git docs git-interpret-trailers
  2. GitHub. Creating a commit with multiple authors. GitHub documentation. Reference. GitHub docs creating-a-commit-with-multiple-authors
  3. The kernel development community. AI Coding Assistants. The Linux kernel documentation. Reference. Linux coding assistants
  4. Anthropic. All settings. Claude Code documentation. Reference. Claude Code all settings
  5. The Git project. git-commit. Git reference documentation. Reference. Git docs git-commit
  6. The Linux Foundation and its contributors. Developer Certificate of Origin, version 1.1. developercertificate.org. Reference. DCO