I use Claude Code every day, but if you asked me how much of my code I actually
write with it, all I had was a feeling. The data was sitting right there in git
the whole time:
$ git log --format='%b' | grep -c 'Co-Authored-By: Claude'
960
960 out of 1,107 commits in that repo. Across everything I've touched:
10,261 of 26,251 commits — 39%.
I built a small tool to render that as an
SVG card for a GitHub profile. The tool is the boring part. What I found while
building it is what I actually want to write about.
co-authored-by: search qualifier
The commit search API accepts this:
$ gh api '/search/commits?q=author:USER+co-authored-by:noreply@anthropic.com&per_page=1' \
--jq '.total_count'
It works. It is also documented nowhere — it does not appear in GitHub's commit search docs.
Since "it seems to work" is not evidence, I ran a control (counts move as I
commit, so these are one snapshot rather than fixed values):
Query (all with author:USER ) |
total_count |
|---|---|
co-authored-by:noreply@anthropic.com |
10,261 |
co-authored-by:copilot@github.com |
29 |
zzznotaqualifier:noreply@anthropic.com |
0 |
| no qualifier | 26,251 |
An invented qualifier returns zero. Change the value and the count changes.
The parser recognizes it.
But undocumented means it can vanish without notice, and the dangerous failure mode isn't returning zero. If GitHub stops parsing the qualifier, it
So the check is on both sides:
// Co-authored commits are a strict subset of all commits. A count equal to
// the total means the qualifier didn't filter at all.
const unusable = (n) => n === 0 || n >= total;
This is the one that surprised me, and it's the bug I shipped first.
My initial implementation searched co-authored-by:claude — the agent's name.
Reasonable-looking, and it returns a plausible number. Then I added Cursor and
got this:
$ gh api '/search/commits?q=co-authored-by:cursor+is:public' --jq '.total_count'
10033042
Ten million felt too round. I looked at what was actually matching:
$ gh api '/search/commits?q=co-authored-by:cursor+is:public&per_page=5' \
--jq '.items[].commit.message' | grep -i co-authored
Co-authored-by: Cursor <cursoragent@cursor.com>
The real trailer uses an address. Searching the name matches any co-author
who happens to share it. And when I checked my own supposedly-correct Claude
numbers:
name form : 10,262
email form: 10,255
Seven commits of drift. Looking at what those matched, they carried a second
trailer naming a human collaborator — a teammate, counted as an AI, because a
name is not an identity. Every agent is now keyed on the address in its
trailer.
This matters more than it sounds, because some tools put variable text in the
display name:
Co-authored-by: aider (anthropic/claude-sonnet-5) <aider@aider.chat>
Co-authored-by: aider (ollama/gemma4:e4b-mlx) <aider@aider.chat>
Aider appends whichever model it used. The name is unstable; the address isn't.
I read the trailers off real public commits rather than trusting vendor docs.
Here's what nine agents actually write, with the public commit count each one
has as of today:
| Agent | Trailer address | Public commits |
|---|---|---|
| Claude | noreply@anthropic.com |
89,025,757 |
| Cursor | cursoragent@cursor.com |
8,374,584 |
| Copilot | copilot@github.com |
4,046,637 |
| Codex | codex@openai.com ,noreply@openai.com |
1,812,065 |
| Devin | devin-ai-integration[bot]@users.noreply.github.com |
588,010 |
| Gemini | gemini-code-assist@google.com + bot address |
290,638 |
| Jules | google-labs-jules[bot]@users.noreply.github.com |
233,948 |
| Aider | aider@aider.chat |
133,041 |
| Amp | amp@ampcode.com |
104,075 |
One tool I expected to find had no dedicated trailer at all — searching for it
returned only human contributors. Worth checking before you assume.
Every image in a README is rewritten through camo.githubusercontent.com.
People repeat a lot of folklore about what survives that trip, so I read the
response headers:
content-security-policy: default-src 'none'; img-src data:; style-src 'unsafe-inline'
That single line settles it:
| JavaScript | blocked (default-src 'none' ) |
| Web fonts | blocked — system font stacks or nothing |
| External images | blocked (img-src data: only) |
| CSS animation | allowed (style-src 'unsafe-inline' ) |
Animation works, which is fun — until it doesn't. My first version grew the
bars from zero:
<rect height="0"><animate attributeName="height" to="28"/></rect>
Rasterize that locally and the bars disappear. Anything that ignores SMIL
sees height="0". Static renderers, social preview generators, and thumbnail
pipelines all land there.
The fix is to make the resting state the truth and let animation only supply a
starting point:
<rect height="28"><animate attributeName="height" from="0" to="28"/></rect>
Now it animates where animation runs and looks finished everywhere else. There
is a test for it, because I will absolutely make this mistake again:
test('animated rendering still declares the finished geometry', () => {
const svg = renderCard(sample, { animate: true });
assert.doesNotMatch(svg, /height="0"/);
});
I started out planning a github-readme-stats-style URL that returns an SVG.
Then I compared the two numbers I could offer:
| Scope | AI-written | Total | Share |
|---|---|---|---|
| including private | 10,261 | 26,251 | 39% |
| public only | 126 | 5,688 | 2% |
Work code lives in private repos. A public-only number isn't a smaller version
of the truth, it's a different number — 2% instead of 39%.
And commit search only sees repositories the token owner can reach. Other
people's public commits are searchable, but their private ones never are. So
a hosted service can only ever offer the 2% number, no matter how many tokens
it pools.
Running in the user's own CI solves it completely: their token, their private
repos, their number. No server, no one else's PAT to hold.
The API shape helps too — I only ever read total_count, never enumerate
commits. (Which is lucky, since search caps enumeration at 1,000 results while
total_count stays accurate well past it.) Repository names, commit messages
and diffs are never read.
Twelve months of history, charted:
October 2025: 42 commits. September 2026: 2,067. A 49x increase, with the
most recent months running above 80%.
I knew my workflow had changed. I didn't know it had changed that much, and I
couldn't have told you so with a number before this. That turned out to be
worth more than the card itself.
The tool is MIT licensed and has zero dependencies:
$ GITHUB_TOKEN=ghp_... npx github:yosh1/cocommit --user your-login
https://github.com/yosh1/cocommit
If your agent isn't in the table, git log --format='%b' | grep -i co-authored
will show you what it writes — send me the trailer and I'll add it.