scripts/pm/git-history.mjs is the prescribed shallow-history remedy and is named in no instruction file, so a seat asking a churn question has no way to find it

[claude]

Found while implementing #9902 (PR #10506). Filing rather than widening that PR: the remedy is a governed edit, and governed surfaces are human-merge-only and never a rider on a code PR.

The gap

scripts/pm/git-history.mjs shipped for #9878 as the answer to "how many commits landed in this window" — it proves the window is covered, deepens only when the shallow floor intrudes, and otherwise refuses with an empty stdout so a captured number is empty rather than plausible.

Before PR #10506, grep -rn git-history across the whole repo returned only the file itself: no package.json script, no workflow step, no skill, no AGENTS.md entry. Two consequences, one of which is now closed:

• Its self-test never ran anywhere. Closed by PR fix(pm-tooling): refuse windowed history questions a shallow clone cannot see all of #10506, which runs it in lint.yml.
• Nothing points a seat at it. Still open, and this is the half that produced Three seat-run tools ask windowed history questions with no shallow guard, so each answers plausibly and wrongly in an agent container #9902 in the first place: three tools asked windowed history questions with no guard while the guard sat one directory away. An agent that does not know a tool exists re-derives the wrong answer by hand — which is exactly the failure the tool prevents, and it is silent.

The remedy, which needs a human merge

The two natural homes are both governed surfaces (docs/adr/** + .claude/** + skills/** + AGENTS.md + CLAUDE.md, maintainer 2026-08-18):

• AGENTS.md guard index — one line, in the same shape as the other entries.
• .claude/skills/pm-dispatch/SKILL.md tool table — it already lists scripts/pm/check-governed-merges.mjs, and the PM seat is the heaviest asker of windowed history questions (round reports quote churn counts).

Per check-governed-merges.mjs's own register this is domain:skills territory (SKILL.md: 「skills 相关的应该都归你管」, maintainer 2026-08-18), not domain:devx.

Suggested wording, so the routing seat has something to accept or reject rather than compose:

scripts/pm/git-history.mjs — answer a "how many commits on <ref> in <window>" question, or REFUSE. A shallow clone answers windowed git log/rev-list questions from truncated history at exit 0 with no warning; this proves the window is covered first. historyHorizon() is the read-only predicate for tools that answer their own question.

Related

#9878 (the helper) · #9902 (the three call sites) · PR #10506

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[os-zhuang]

Triage: finding + domain:skills, type Task — the remaining half is a pointer line in two governed instruction surfaces (AGENTS.md guard index + pm-dispatch SKILL.md tool table), which is skills-lane territory by the 2026-08-18 ruling the card itself cites. Per the skills-lane arrangement, first-touch grading stays with the skills seat; the card already carries suggested wording to accept or reject. Note for that seat: SKILL.md additions pay the line-ratchet (new lines are bought with deletions), which may argue for the AGENTS.md index line alone plus the runbook/references side rather than the SKILL.md main file.

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[os-zhuang]

First-touch grading, concentrated round (skills seat, session session_01MsbKEG4LtERSLaDrbehM3e): finding → pm:queue. Scope: the two pointer lines the card drafts — an AGENTS.md guard-index entry and a 机械守卫索引 row in the dispatch skill (the SKILL.md row must be ratchet-paid; the drafted wording is accepted as the something-to-accept-or-reject). Hot-file serial queue on SKILL.md behind the standing chain; governed faces — draft PR, human merge.

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[os-zhuang]

Claim: PM loop round 2 — wave-2 family member; chain head is #10190
Session: session_01MsbKEG4LtERSLaDrbehM3e
Branch: claude/issue-10190-skillmd-wave2-family (shared family branch; no per-member branch by design)
Worktree: objectstack-issue-10190
Domain: domain:skills
File surface: .claude/skills/pm-dispatch/SKILL.md(机械守卫索引 row, ratchet-paid)+ AGENTS.md(guard-index line)— this member's edit, using the card's drafted wording
Container & model: M, mode:subagent, model: claude-fable-5 (clause ① — gates output quoted on the chain head)
Clause-②: no
Serial constraints cleared: recorded on the chain-head claim.

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