How do I use the Generated-by trailer for commits made by AI coding agents like Copilot?

Use Assisted-by, not Generated-by. I found no standard Generated-by trailer in the docs I checked. Copilot's own commits already name the agent and the human, so you do not add the trailer for them.

What the sources say

How Copilot cloud agent attributes its commits

GitHub states that Copilot cloud agent's commits are authored by Copilot. The developer who assigned the task is marked as co-author. The commits are signed and show as "Verified." Each commit message links to the agent session log (Copilot risks and mitigations). You do not write these trailers yourself for Copilot's commits.

If you commit AI-assisted work yourself

1. Use the kernel format if you contribute to the Linux kernel. Add Assisted-by: LLM <tool> only for specialized analysis tools, such as coccinelle or sparse. The kernel says basic tools such as git or gcc are not listed.
2. Do not add Signed-off-by for the AI. The kernel rule says only a human can certify the Developer Certificate of Origin.
3. Add your own Signed-off-by if the project requires it.
4. On GitHub, add Co-authored-by: Name <email> for a human co-author. Use an email linked to their GitHub account so the commit counts toward their contributions.

Using Generated-by anyway

Git accepts any key made of letters, digits, and hyphens as a trailer (git-interpret-trailers). So Generated-by: Copilot is valid syntax. Git and GitHub do not give it special meaning, and no tool I checked reads it. Use it only if your team agrees on it in writing.

Recommendation

Use Assisted-by for kernel work. Use Co-authored-by on GitHub to credit a human. Let Copilot cloud agent set its own author and co-author fields.

If you run several agents and want each commit to name the agent, the human, and the run, githug writes those trailers for you. It is in beta and free to use.