Taken after asking twice for reassignment with no reply, and after the
same failure bit a **third** time. No open PR touches the census CLI, so
this is unowned in practice — **U12, say so if you have started and I
will close this in favour of yours.**
## What changed
A **drop** now tightens the baseline instead of failing. Failing hard
was defensible in isolation — a stale allowance is a hole, since those
guards can return up to the old count while the check stays green. What
it missed:
**The drop is almost never the failing author's to fix.** Eleven files
dropped during one merge wave, none of those PRs re-recorded, and none
of their authors did anything wrong. Measured three times since CI began
gating this: `columnRoles.ts` 0 → 1, then `executor.ts` twice.
A permanently-red gate is a bigger hole than a stale allowance, because
it gets ignored and then nothing is guarded at all. **The rise check —
the ratchet's actual purpose — is untouched and still fails hard.**
## The residual, named rather than glossed
In CI the write is discarded with the runner, so the committed baseline
stays stale until someone commits a tightened one. The exposure is
bounded (regrowth only up to the old count), printed on every run, and
strictly smaller than the exposure from a check people route around.
`--strict --exact` restores hard failure for the pinned end state.
**One writer:** the write is now a named `writeBaseline()` shared by the
tighten path and `--update-baseline`, rather than a second
`writeFileSync`. Two writers for one artifact is how they drift — a
lesson this file already learned once.
## Exercised end to end
| scenario | result |
|---|---|
| drop, `--strict` | exit **0**, `TIGHTENED`, allowance rewritten 9 → 6
|
| drop, `--strict --exact` | exit **1**, baseline untouched |
| rise, `--strict` | exit **1** |
| clean | exit **0** |
Pinned through the real CLI with an isolated baseline. Revert proof:
restoring the hard failure fails **1 of 32**.
## Two of my own mistakes, recorded
**A vacuous assertion, in the case that guards against vacuity.** I
first wrote `expect(allowedAfter).toBeLessThan(4 + allowedAfter)` — true
for every number. Replaced with a comparison against the inflated value
the fixture started from. This file documents that trap repeatedly and I
still walked into it, which is the argument for the mechanical revert
check over careful reading.
**The env override is `FUSION_CENSUS_BASELINE_PATH`**, not the
`FUSION_CENSUS_BASELINE` I used in the first draft — so the first
version of these cases silently ran against the **real** baseline and
passed for the wrong reason. A test whose fixture never took effect is
the same failure as a test whose fixture can't fail.
## Verification
32/32 census suites, `pnpm test:gate` **71/71**, `--strict` exits 0,
`pnpm lint` clean, `docs/testing.md` updated.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---
## Update — the base-ref ratchet (review round 2, commit `4895845579`)
The first version of this PR shipped a **named residual**: the
tightening write dies with the CI runner, so the committed allowance
stays high and a later PR can regrow guards up to it while `--strict`
prints green. I called the exposure bounded and moved on. Greptile
flagged it P1 and was right — naming a hole is not closing one.
`--strict` now stops trusting the committed number for files the branch
touched. It measures each **changed** file at the base commit
(`FUSION_CENSUS_BASE_REF`, else the PR base branch, else `origin/main`)
and fails if the file carries more guards than the base ref has. **The
enforced ceiling is what main has today**, so a stale, missing, or
long-unrecorded baseline no longer opens a window.
| decision | why |
|---|---|
| changed files only, `<ref>...HEAD` | untouched files have main's
counts by construction; censusing all ~400 at the base ref is ~400 `git
show` calls to re-derive numbers that cannot have moved. Three-dot also
stops charging this branch for guards that landed on main after the
fork. |
| a new file's base allowance is **0** | "absent at the base ref" as
unbounded would make a new file the cheapest place to hide a fresh guard
|
| fails **open** on an unresolvable ref, printing `SKIPPED` | a shallow
clone cannot produce an honest comparison; a degraded run must not read
as a clean one. The baseline comparison still applies. |
| merged into the existing `regressions` list | one failure per file,
and `--update-baseline` keeps working as the deliberate escape hatch. No
new exit path. |
**Revert proof, measured both ways.** With the base-ref block removed,
the regrowth fixture — base commit 2 guards, HEAD 5, baseline allowing 9
— exits **0** with `TIGHTENED`, which is precisely the reported
scenario. With it: exit **1**, `column-guard count ROSE`, `above its
count on the base ref`, baseline left at 9. **3 of the 4** end-to-end
cases go red on revert. The fourth passes without the fix by design — it
is the genuine-conversion case the auto-tighten exists to keep green,
and a case that reddens either way proves nothing.
The end-to-end suite builds a throwaway two-commit `git init` repo under
the temp dir, because this exploit is a property of the **plumbing**,
not of the comparison: resolving a ref, working out the changed set,
reading base source through `git show`. The comparator itself is pure
with the reader injected (`findRegrowthAgainstBase`), with its own cases
in `lifecycle-column-census-ast.test.ts` — including the one that would
silently pass everything, looking up the wrong key in
`summarize().byFile`.
**Rebased onto `origin/main` @ bc782d8d92** (the branch was forked
before the recent merge wave; its baseline read 746 against a tree of
722).
Verification on the rebased branch: census **722** / `--strict` exit 0 ·
**70/70** across both census suites · `pnpm test:gate` **71/71** · `pnpm
lint` clean.
---------
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
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