Addresses the root cause of a pattern I have now measured four times.
## The finding
**Every fleet worker pushes as the same GitHub account.** `gh pr list
--author "@me"` returns **all 17 open PRs** — mine and teammates' are
indistinguishable. So "is this file already being converted?" can only
be answered by fetching every open PR's file list by hand: 25+ API calls
that no worker makes before starting. I didn't either.
## The measured cost
| PR | Outcome | Landed instead as |
|---|---|---|
| #3096 | shrank to a test | teammate's serialisation + union |
| #3116 | shrank to a test | `preExecLiveColumns`,
`starvedWaitingColumns`, … |
| #3140 | shrank to a test | #3137 |
| #3125 | **shrank to nothing — closed** | #3135 |
Plus #3118, a teammate independently writing the same coverage I wrote
for #3112.
**In every case both implementations were correct and independently
reached the same design** — #3137 chose payload-first-with-sync-fallback
for the same reason I did. This is not carelessness; the fleet is doing
correct work twice and discovering coverage gaps by accident, when
rebases collide.
## What this adds
```
$ node scripts/check-file-claimed.mjs packages/engine/src/self-healing.ts
CLAIMED packages/engine/src/self-healing.ts
#3152 fix(self-healing): 18 recovery rebounds hardcoded `todo` …
```
**On its first run it reported `self-healing.ts` claimed by #3152 —
which I had no way to know a moment earlier.** Exits non-zero when
claimed, so it can gate work: `node scripts/check-file-claimed.mjs
<path> && start-work`.
## Deliberate limits
- **It cannot see unpushed work**, so it narrows the collision window
rather than closing it. Two workers starting the same file minutes apart
still collide. Closing that needs **distinguishable authorship** — a
per-worker `Co-Authored-By` or a title prefix — which is a coordination
decision, not a script.
- **A `gh` failure exits 2 and says UNKNOWN, not unclaimed.** A claim
check that fails open is worse than none, which is the same false-green
shape this program keeps finding elsewhere.
Also adds a short AGENTS.md pointer next to the other standing rules.
## Verification
Run against a claimed and an unclaimed path; both answers correct, exit
codes as documented.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Added a command-line check for open pull requests that may already be
modifying specified files.
* Reports matching pull request details and clearly indicates whether
each file is claimed.
* Returns distinct statuses for claimed files, unclaimed files, and
unavailable GitHub checks.
* **Documentation**
* Added guidance for checking file ownership before beginning conversion
work.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
---------
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
b8bfcd031b