Records two instrument-level defects found this session. Both were in
the tools the program uses as ground truth, and both looked exactly like
a pass.
## 1. A ratchet that could not fail from the command I typed
`check-move-target-literals` is report-only unless given `--strict`,
which `package.json` supplies. Probed bare, it returned **exit 0 for
every probe** — including a blatant `moveTask(id, "in-review")` pasted
into `scheduler.ts`.
That is the exact signature of a dead ratchet, and I nearly reported
another worker's guard as inert on the strength of it. The guard was
fine; my invocation could not fail. What makes it dangerous is the
output: a report-only run prints its normal summary line and exits 0, so
the terminal is indistinguishable from a genuine pass.
## 2. A ratchet that could not see the file I had just written
`lifecycle-column-census` and `check-move-target-literals` discovered
files with `git ls-files` — **tracked only** — while the other five walk
the filesystem.
| new file with a plain legacy guard | result |
| --- | --- |
| same guard in an already-tracked file | caught |
| new file, untracked | **missed, exit 0** |
| identical file, `git add`ed | caught, exit 1 |
The detectors are fine. The blindness is discovery, and it lands at the
one moment the number is consulted: add a helper, check your own work,
read zero, commit — and it surfaces later in someone else's CI run,
attributed to a push instead of to the edit. The tool was answering
about the last commit while being asked about the working tree.
## 3. Why it is worth a doc rather than two one-line fixes
Individually these are cheap. Together they cost a day.
Because `check-inert-sync-lane-conversions` walks the filesystem and the
census did not, the **same probe file** was caught by one and missed by
the other. I read that differential as a claim about expression walking
and investigated it as one — the real cause was that two instruments in
the same program disagreed about which files exist.
When the measuring tools disagree about their own domain, every
differential between them is unreadable until someone notices. That is
the transferable lesson, and it is not visible from either fix alone.
## Status of the fixes
- Census discovery scope: **#3254** (open).
- Type-assertion blind spot in the sync-lane ratchet: **#3252** (open).
- `check-move-target-literals` discovery scope: reported to **#3253**,
whose author is already in that file — not touching it.
## Verification
Docs only; no code paths change. All eight ratchets exit 0. No changeset
— AGENTS.md excludes internal docs.
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