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Does "gate before you commit" survive when its only justification is false?

This is a decision about an INSTRUCTION, not about the sentence. The factually wrong sentence in CLAUDE.md is being corrected as an ordinary fix (routed to frankB, both sources in the commit). That correction is not blocked on this ticket and this ticket must not delay it.

The fork

CLAUDE.md carries two things in one paragraph:

  1. A claim: "gate.sh quick's FPC seed canary only runs while compiler/** has UNCOMMITTED changes; on a clean tree it prints SKIP and you get no FPC coverage at all." — FALSE against the code.
  2. An instruction derived from it: "GATE BEFORE YOU COMMIT, NOT AFTER."

Correcting (1) leaves (2) standing with nothing under it. That is the fork.

What the code actually does

tools/gate.sh arms the canary against the merge-base, not HEAD:

seed_base=$(git merge-base origin/master HEAD)
if   ! git diff --quiet "$seed_base" -- compiler/          # committed-but-unpushed ARMS it
elif [ -z "$seed_green" ] || ! git cat-file -e ...         # no recorded green seed ARMS it
elif ! git diff --quiet "$seed_green" HEAD -- compiler/    # compiler/ moved since ARMS it

Its own comment: "ARMED AGAINST THE MERGE-BASE, not against HEAD." An adjacent check names the divergence as deliberate: "CLAUDE.md's rule that quick's canary only fires on an UNCOMMITTED tree is a footgun worth not copying."

Three independent observations, and the first two are predictions that FAILED. frankS and frankA each predicted a SKIP on a clean tree and each reported the prediction failing rather than quietly dropping the caveat — which is the only reason this surfaced at all.

AND ONE TESTED ON PURPOSE, which is a cleaner citation than any of the three predictions. frankA, 2026-09-05 at tip 7fda453d4: a gate run on a CLEAN tree — everything committed and pushed, git status --porcelain empty at the moment of the run — with FPC seed canary (concurrent) ARMED and PASSED. The three earlier instances were all sessions predicting a SKIP and being surprised by a PASS; this one is the same claim tested deliberately, under known and stated conditions. If this ticket needs a single citation for "the rule is false", use this one — a surprise is evidence, a designed test is proof.

Scoped by its own author, and the scope matters because this line will be quoted: that run proves the canary arms on a clean tree at that tip, which is one of the three arming conditions in tools/gate.sh (compiler/ differing from the last recorded green seed). It does NOT establish which of the three fired. So it settles "the rule is false" and does not settle "the rule is false for reason X" — that distinction is unmeasured, and a designed test must not be read as broader than its design (frankA, flagging the limits of its own citation before anyone quoted it).

Two sources, failing differently. frankS observed PASS FPC seed canary (concurrent) with 0 SKIPs on a clean tree (it had pulled the revert plus three other compiler/-touching commits, so the third branch armed). frank-coordinator then read the source. Neither settles it alone.

THE MEASURED HARM IS OVER-GATING; THE UNMEASURED ARM POINTS THE OTHER WAY

Everything observed is over-gating. The stale rule makes sessions gate more carefully than needed, which is why it survived unnoticed — it breaks nothing and nobody complains. Measured cost to date: fleet-wide sequencing friction, and one session publishing a pessimistic caveat about a real green and then retracting it.

Rank on that friction. No defect has been shown to reach anyone through it. But see the next section before recording the hazard as one-sided: no lane has been measured to under-gate and no lane could be, and those are different sentences.

But the harm is not strictly one-directional, and frankA named the arm this ticket first missed. Two sessions (frankS, frankA) independently predicted their clean-tree gate would SKIP the canary and hedged their own greens as narrower than they were — the optimistic direction, and harmless. The same belief read the other way is not: a session that believes the canary is dead on a clean tree may gate after committing and think it got no FPC coverage when it did — or skip a gate it has concluded is worthless. That is a live mechanism for under-gating, and it is why "correct the sentence" is not optional even if the instruction survives.

No instance of that arm has been observed — and it is UNOBSERVABLE BY CONSTRUCTION, which is the part that should decide how this is read. An earlier revision of this ticket said both sessions checked their compiler commits had compiler/** genuinely uncommitted. That check never happened and could not have (frankA, correcting its own sentence, which this seat had quoted as measured because it arrived beside things that were): nothing durable captures working-tree state at gate time, and because the canary arms off the merge-base, a gate run before a commit and a gate run after it emit the identical PASS line. The very property that makes CLAUDE.md's sentence false is what destroys the evidence that would settle whether anyone acted on it.

So the honest form is neither session has any reason to believe it under-gated, and neither can demonstrate it — not both checked. That is still a fine reason to rank on the friction. It is not a reason to record a check that cannot exist, and an absence of instances is here weak evidence, not strong: this detector has zero reach into its own question.

Options

Recommendation (frank-coordinator)

A, unless someone can supply B's missing reason. The rule's whole force came from "you get no FPC coverage at all", which is untrue. A surviving instruction with a deleted rationale is exactly the stale imperative obeyed by tooling while false in the world that CLAUDE.md warns about — and CLAUDE.md is the one file every session loads at startup and cannot re-derive, so its authority converts an out-of-date sentence into fleet behaviour.

Not decided here. Option A changes what every lane does, which makes it the owner's, not this seat's.