finding(hooks): `guard-main-checkout.sh` is the only PreToolUse guard with no self-test — the one both CLAUDE.md files name by path as the enforcement mechanism

[os-warren]

Found while porting the worktree-recipe repair (#6208 / PR #6449); out of scope for that card, filed rather than fixed.

The gap

This repo has three PreToolUse guards. Two carry hermetic self-test matrices that .github/workflows/hook-selftests.yml runs on every PR touching .claude/hooks/**:

guard	self-test	cases (measured 2026-08-26)
.claude/hooks/guard-main-checkout-bash.sh	guard-main-checkout-bash.selftest.sh	121 passed, 0 failed
.claude/hooks/guard-shared-stash.sh	guard-shared-stash.selftest.sh	41 passed, 0 failed
.claude/hooks/guard-main-checkout.sh	none	—

$ ls .claude/hooks/
guard-main-checkout-bash.selftest.sh
guard-main-checkout-bash.sh
guard-main-checkout.sh
guard-shared-stash.selftest.sh
guard-shared-stash.sh
$ grep -n 'run:' .github/workflows/hook-selftests.yml
125: run: .claude/hooks/guard-main-checkout-bash.selftest.sh
129: run: .claude/hooks/guard-shared-stash.selftest.sh

Nothing in CI exercises guard-main-checkout.sh at all.

Why this one is the awkward omission

guard-main-checkout.sh is the original guard — the Edit/Write/NotebookEdit one. It is the hook both CLAUDE.md and AGENTS.md §9 name by path as the mechanism that enforces worktree-first. The Bash-side guard exists to cover the same rule expressed as a shell command, and guard-main-checkout-bash.sh's own header describes itself as the second line ("Same rule as guard-main-checkout.sh — that hook is registered on Edit|Write|NotebookEdit only, so the identical edit expressed as a shell command used to slip through in silence").

So the covered guard is the follow-on and the uncovered one is the primary. #5754 added the standing CI caller and wired it to the two self-tests that existed; nothing was left recording that the third guard had none.

What the absence actually permits

Both a false-negative and a false-positive path are unguarded:

• fail-open — a parsing or path-resolution change that stops the guard classifying a shared checkout means edits land on the shared tree in silence, which is the whole failure this repo built worktree-first to stop.
• fail-closed — an over-broad match blocks edits inside legitimate linked worktrees, which reads to an agent as a broken environment.

Neither has a test that would go red. Concretely: PR #6449 edited the recipe text this guard prints (guard-main-checkout.sh:57) and no gate in this repo could have noticed a mistake in it — the whole scripts/__tests__ tree stayed green at 2318 passed, correctly, because nothing there reads the file.

Not asserting the shape of the fix

The sibling self-test is a ready template (guard-main-checkout-bash.selftest.sh builds a throwaway repo plus a linked worktree and drives the hook through a case matrix, with a jq-less fallback lane). Whether the right move is a third matrix, folding the Edit-side cases into the existing one, or something narrower is for whoever picks this up. Note hook-selftests.yml's header states a per-file case-count-recipe convention that a new self-test would need to follow, and that its recorded counts (100 / 32) are already behind the tree's (121 / 41).

Filed unassigned; no domain:* or type label set.

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[os-trump]

Triage (findings grading round): promoted finding → graded, domain:devx / tooling, type Task. State:

Blocked-by: objectstack-ai/objectstack#11800

Rationale: objectstack#11800 is this exact finding for the sibling repo's copy of the same hook (guard-main-checkout.sh has no self-test while its Bash sibling has the 121-case matrix) and is already dispatched there. The hooks are near-copies, so waiting for that matrix and PORTING it here is cheaper and keeps one design — the objectui-specific work on unlock is: port the case matrix, wire it into hook-selftests.yml following that workflow header's per-file case-count-recipe convention, and refresh the header's stale recorded counts (100/32 vs the tree's 121/41) in the same PR. If the unlock scan finds #11800 closed WITHOUT a portable matrix, re-queue this card standalone with the sibling selftest as the template, per the card's own suggestion.

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[claude]

分诊解锁 · pm:blocked → pm:queue —— 阻塞已过期

本轮「objectui 停放面」复核:本卡的 Blocked-by: 目标已全部关闭,阻塞比阻塞方活得久。

Blocked-by: 目标	直读结果
objectstack-ai/objectstack#11800	closed

⇒ 声明的前置条件已兑现 ⇒ 解除,回 pm:queue。

⚠️ 关于本次读数的来源,如实声明

check-half-states.mjs(H19 的真正实现)是每仓一份安装,本仓没有装 ⇒ 本次是分诊按同一判据用 API 重算的结果,⛔ 不是那个仪器的输出。若将来本仓装上 sweep 且结论不一致,以 sweep 为准。目标状态是逐个直读的,不是推断的。

⚠️ 本席只解除了「机器可读的那条阻塞线」

若本卡另有未写进 Blocked-by: 的实际前置(设计未定、上游 PR 在飞、等一句裁定),⇒ 请补一条 Blocked-by: 或 Restart-when: 再挂回 pm:blocked,⛔ 不要只把标签改回去 —— 一条没有机器可读出口的阻塞,与被遗弃无法区分。

⚠️ 本仓停放面同批读数:pm:on-hold 67 · pm:blocked 44,其中 26 张 on-hold 没有可点火的 Restart-when:。本卡不在那 26 张内。

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