Two PRs can ship the identical diff under two card numbers — the duplicate-claim gate is issue-keyed, not diff-keyed

What happened

#9393 (card #9356) and #9398 (card #8893) reached green independently, as separate PRs, shipping the same physical change:

both add the same path, .changeset/console-82a94170c405.md
both rewrite .objectui-sha 665661ab093263f39f2e660a295ea615dbcee35a → 82a94170c4058d451ce3ac179d99296d90554479 — a byte-identical hunk

#9393 entered the merge queue. #9398 was green and one flip away from enqueueing behind it, where it would have conflicted on both files.

Why nothing objected

The repo has a gate for exactly this shape — No other open PR may claim the same issue — and it passed on both, correctly. It compares the card each PR claims. These claim #9356 and #8893, two genuinely different cards. Nothing in CI compares what the PRs actually do.

The gate is not broken. Its key is the issue number, and the collision is in the diff.

Why the two cards existed

Both are legitimate, independently-filed cards that happen to be dischargeable by the same commit:

chore: bump the console pin past objectui#3951 — releases parked PR #9355 (#9227 strict inlineColumns) #9356 — bump the objectui pin
v17 GA follow-through: objectui's lockfile still resolves @objectstack/spec@17.0.0-rc.6, so the console keeps vendoring a pre-GA spec and #7804's key stays unreachable #8893 — bump the objectui pin so the vendored console carries spec 17.0.0 GA

#8893 names a reason for a bump; #9356 names the bump. Neither is a duplicate of the other as written, which is why triage kept both, and why a human reading the two titles would not obviously flag them. The duplication only becomes visible at the diff.

This one is my fault as PM — I dispatched both — and no existing gate would have caught it. That combination is the reason this is worth filing rather than just fixing.

Why it matters beyond the wasted run

Two agents independently derived the same changeset narrative from the same commit range and produced different answers (110 vs 137 non-merge commits; 18 vs 20 no-changeset commits; and two different, both-partly-wrong commit-attribution tables — see #9393 for the measurement).

That disagreement is the only reason the attribution defect was found at all. Had the dispatch not been duplicated, one table would have landed unchallenged and been compiled into the release notes. The duplicate cost a CI run; it bought a defect that a single run would have shipped.

Candidate responses

Not a prescription — the trade-offs differ a lot and this needs a ruling, not an implementation:

Diff-keyed duplicate detection in CI. A gate that flags two open PRs whose changed-path sets intersect on an exclusive file. Cheap for singleton files like .objectui-sha and any .changeset/*.md path; noisy in general, since ordinary concurrent PRs touch shared files constantly. Probably worth scoping to a small declared list of at-most-one-writer paths rather than attempting it repo-wide.
Make .objectui-sha an explicitly single-claim surface — one open PR at a time may modify it, enforced. Narrow, cheap, and covers the concrete recurrence (pin bumps are routine and will collide again).
Nothing in CI; fix it at dispatch. Require the dispatching seat to check for an open PR already touching the surface a card implies. Puts the cost on the seat that caused it, adds no gate, but is exactly the discipline that just failed.

Option 2 addresses the observed case at the lowest cost. Option 1 generalises but I have no measurement of its false-positive rate, and I would not want it landed without one.

Not filed as blocking

#9393 lands as-is (its payload is correct); #9398 is held and repurposed into the attribution correction. Neither depends on this card. Filing unassigned — recording, not claiming.

Related: #9393, #9398, #8653 (release hold), #9356, #8893.

Premise checked — it holds. Plus the root cause of the duplicate's consequence is now known.

I said on #9398 that I would verify this card's premise before letting it stand, because PR #9398 was closed at 23:05Z by an actor nobody could identify (all agents share one GitHub identity, so the author field is uninformative). If a repo gate had closed it as a duplicate, this card's core claim — "nothing in CI compares what the PRs actually do" — would have been false.

It was not a gate. Reading .github/workflows/duplicate-fix-guard.yml on main:

it is issue-keyed, exactly as this card describes — it parses closing keywords (close|closes|closed|fix|fixes|fixed|resolve|resolves|resolved) to find which card a PR claims, then looks for another open PR claiming the same one;
it performs zero close operations (no closePullRequest, no state: closed, no gh pr close). It fails the check and tells a human what to do: "If this PR is the duplicate, close it and add anything it uniquely covers to the earlier PR or a follow-up issue."

Both PRs passed it, because they claimed different cards (#9356 and #8893). So the 23:05Z close was a manual act by another actor — which, if anything, reinforces this card: a person or agent spotted by eye what no gate could see.

The premise stands. No amendment needed.

What the duplicate bought — the underlying defect is now root-caused and filed

This card notes that the duplicate dispatch "cost a CI run; it bought a defect that a single run would have shipped." That defect has since been traced to a repo-owned tool, filed as #9408.

scripts/bump-objectui.sh tests whether it can walk the pin range like this:

if [[ "$OLD_SHA" != "<none>" ]] && git -C "$OBJECTUI_ROOT" cat-file -e "${OLD_SHA}^{commit}" 2>/dev/null; then
  RANGE_OK=1
fi

That tests object presence, not walk completeness. In a shallow objectui clone whose graft boundary sits inside the range, OLD_SHA is present, so RANGE_OK=1, and the honest degraded path — which exists, is correctly written, and cites #4731's "a degraded list and a complete one must never look alike" — is never reached. The grafted boundary commit, being parentless, is diffed against the empty tree and credited with every .changeset/*.md in its tree.

Proven two independent ways. By arithmetic identity — the range is 191 commits, 183d09b78 sits at index 110 and 75444e38a at index 137, which are exactly the commit counts the two records reported; each record's count was the position of its own sink. And by exact reproduction — writing 183d09b78 into .git/shallow of a fresh clone makes cat-file -e still pass, the digest still exit 0, and the resulting entry list diff byte-identically against the landed artifact.

Neither 110 nor 137 was ever right.

Why this makes the case for option 1 or 2 stronger, not weaker

My original write-up leaned toward option 2 (make .objectui-sha a single-claim surface) as the cheapest fix for the observed case. That still holds for the collision itself.

But note what the duplicate actually did: it was the only reason the misattribution was caught. Two derivations of one range disagreed, and the disagreement forced the question. A single un-duplicated run would have shipped a complete-looking, silently-truncated release record — the artifact carries no marker distinguishing it from a correct one. That is the property that makes this class of failure expensive.

So the duplicate-detection question and #9408 are related but separable, and #9408 is the more urgent of the two: the collision wastes a CI run, while the truncation silently corrupts a published release record.

Whatever is decided here, #9408's cheap mitigation is worth taking on its own merits — no commit may be credited with more added changesets than git show --name-only attributes to it. It validates the output instead of trusting the input, is independent of clone depth, and would have caught all three known-bad runs.

Related: #9408, #9393, #9398, #8653.

Generated by Claude Code

Triage — first-touch grading (concentrated round, triage seat, session session_0138jAR5jeREBpm4dhVvbWY7): promoted to pm:queue, type Task, domain:devx, auto-adjudicated — option 2: make a small declared list of at-most-one-writer paths (starting with .objectui-sha; add sibling pin files as the list's owner sees fit) an enforced single-claim surface — at most one open PR may modify a listed path, checked in CI alongside the existing issue-keyed gate.

Within the adjudication lane: this adds a narrow gate over process hygiene, changes no product semantics or public contract, and weakens nothing. Four-facet block: ① coherence — pin files are already single-writer by landing discipline; the gate declares reality; ② pull — measured: the collision just happened (#9393/#9398, byte-identical hunk, one flip from a queue conflict) and pin bumps are routine; ③ AI error-resistance — structural check over seat discipline, and seat discipline is the thing that measurably failed (the filer's own accounting); ④ scope — option 1 (general diff-keyed detection) is explicitly unmeasured for false positives and is not adjudicated here; option 3 alone is the status quo that failed. Option 3's dispatch-time check remains good practice on top, and the dispatch-side runbook already carries it.

Dispatch note: keep the list literal and tiny in the workflow/gate script with a comment saying additions need a reason; do not attempt repo-wide diff intersection. Veto window open; listed in this round's adjudication section.

Generated by Claude Code

{
  "issue": 9402,
  "status": "done",
  "branch": "claude/issue-9402-diff-keyed-duplicate-guard",
  "pr": "https://github.com/objectstack-ai/objectstack/pull/9598",
  "premise_still_valid": true,
  "summary": "Implemented the adjudicated option 2: a declared, literal list of at-most-one-writer paths (one entry today, the objectui pin), enforced by a new PR-scoped blocking check that runs alongside the existing issue-keyed gate. Shipped as a separate workflow plus scripts/check-single-claim-paths.mjs with a 54-case --self-test, following the house shape of the Part-of Closing-Keyword Guard rather than adding a second question inside a gate whose name says 'claim the same issue'. The existing Duplicate Fix Guard is untouched and verified still green. Premise re-verified against origin/main and it holds, including the part my own retrospective sweep could not see: the files endpoint returns diffs against a MOVING merge base, so PR #9398's pin write had already left its cumulative diff by today; read commit by commit, its first commit ffc79b028 does touch .objectui-sha, so the incident pair is a true positive the sweep can no longer observe. Action is red-on-the-later-PR (first come, first served, naming the earlier PR by number, URL and branch), not a warning: #9424 ruled that an invisible signal is the expensive half, and the adjudication asked for an enforced surface.",
  "tests": "All at final commit 99e3c060f (git rev-parse --short HEAD), tree clean, remote at the same sha. (1) pnpm check:single-claim-paths -> '✓ check-single-claim-paths self-test: 54 cases pass.' (2) Gate families derived from ACTUAL changed paths via `node scripts/pm/dispatch-gates.mjs scripts/check-single-claim-paths.mjs .github/workflows/single-claim-path-guard.yml .github/workflows/lint.yml package.json` — the derivation discovers the new gate itself, confirming registration. Results: check:node-version PASS ('OK (28 setup-node step(s) across 25 workflow(s), all on Node 22)'), check:required-contexts PASS, check:shard-attestation PASS ('2 aggregate gate(s) count 3 declared leg(s)'), check:workflow-status-functions PASS ('scanned 25 workflow file(s), 44 job(s)'), check:type-check-coverage PASS ('64/77 workspace packages type-checked'). check:type-check-debt FAILS — PRE-EXISTING, not from this diff: it needs a built package closure and says so itself ('Build the closure first, exactly as lint.yml does before this step'); reproduced byte-identically on a pristine origin/main worktree at 1c6da6eaf in the same unbuilt container, and this diff touches no TypeScript. eslint clean. Prettier is not enforced for scripts/ (siblings deviate) and no new deviation in lint.yml (its pre-existing ones are at lines 22/56/1167, this insertion is 224-253; an earlier check of main's copy under /tmp was invalid config resolution and was redone in-repo). (3) REVERSE-VERIFICATION BY ABLATION, from committed state, 7 mutations each proven to reach the file, each reddening a NAMED assertion: lock file added to the declared list -> 'the measured high-collision paths are NOT declared'; blanked reason -> 'every declared entry carries a reason'; short-circuit removed -> '...and it costs exactly ONE api call' (got 3, want 1); first-come-first-served flipped -> 'an EARLIER open PR on a declared path fails THIS PR' +5 more; 'synchronize' dropped -> 'the wiring subscribes to synchronize'; UNDETERMINED silenced -> 'an unwalkable file list is reported as UNDETERMINED'; contents:read revoked -> 'the wiring can read contents, which its checkout step requires'. No dist/ ablation was involved, so no package rebuild applies. THE SWEEP FOUND A REAL BUG IN MY OWN TESTS, fixed in 99e3c060f: revoking contents:read left the self-test GREEN because the comment explaining that scope contains the same two words and the assertion scanned the whole file — a phantom check. Both permission assertions now scan comment-stripped content, and the ablation reddens with the string still in the file. I also ablated the SIBLING partof gate for the same defect class: it is clean (its patterns carry colons absent from its comments; deleting its real env: block reddens 2 assertions), so nothing was filed there. (4) LIVE end-to-end against the real API, which the fake-API self-test cannot prove: PR #9584 (no declared path) -> exit 0 via the short-circuit, one API call; PR #9393 (the incident PR, writes the pin) -> exit 0 having walked all 9 open PRs, exercising the expensive branch; no PR_NUMBER -> exit 2 NOT WIRED. (5) REAL CI at 99e3c060f: 'No other open PR may claim the same single-writer path' = success; 'No other open PR may claim the same issue' = success (unweakened); 'Check Changeset' = skipped (skip-changeset label read back live alongside the bot's size/l). Remaining checks in_progress at report time, per the report-at-draft-PR contract. (6) FALSE-POSITIVE MEASUREMENT over the 300 most recent PRs (#8936-#9584, complete file sets, 0 pagination truncation), counting pairs whose OPEN WINDOWS overlapped and which shared a changed path: repo-wide 'any shared changed file' = 68 pairs (top: pnpm-lock.yaml 33, plugin-auth/package.json 21, root package.json 15); identical ADDED path = 0; the declared list = 0. The 68 is the number that decides the design; the 0 is a floor, not a proof, for the moving-merge-base reason in the summary. Those three measured hot paths are now pinned by name in the self-test as paths that must stay OUT of the list.",
  "open_questions": [
    {
      "question": "Should 'No other open PR may claim the same single-writer path' become a REQUIRED context in branch protection? Today it publishes a check run that a merge can proceed past, exactly like the existing Duplicate Fix Guard.",
      "options": [
        "A — leave it advisory-by-default (publishes a red check run, not required), matching the Duplicate Fix Guard's current position",
        "B — make it a required context, so a claimed single-writer path mechanically blocks the second PR"
      ],
      "recommendation": "A for now, and it is not mine to change either way: the protection endpoint answers 403 to agent seats and the required-context registry convention says entries must report on merge-queue builds, which this cannot — a merge_group event carries no pull request, so the check has nothing to judge there. B needs a maintainer ruling plus a decision about the queue-build gap. Recording it so the gap is visible rather than assumed closed."
    },
    {
      "question": "The declared list ships with exactly one entry. Two adjacent surfaces were considered and deliberately NOT added, and the list's owner may want them.",
      "options": [
        "A — keep the single entry (.objectui-sha) until a second collision is actually measured",
        "B — also declare the generated console changeset family, whose filename scripts/bump-objectui.sh derives deterministically from the target sha (.changeset/console-<sha12>.md), so two bumps of the same target collide by exact name",
        "C — declare other hot files (lock file, root manifest)"
      ],
      "recommendation": "A. C is measurably wrong — those are the 33/21/15-pair false positives. B is real but bought nothing here: in the incident the changeset and the pin moved together, so keying the pin already catches it, and B would need the list to hold a pattern rather than a literal, which the adjudication explicitly warned against. Worth revisiting only if a bump ever lands the changeset without the pin."
    }
  ],
  "out_of_scope_findings": []
}

Generated by Claude Code

✅ ACCEPT — PR #9598 · 两个 open question 都裁 A

PR 9598  head=99e3c060f  draft=True  base=main  files=4  +692/-0
labels: ['ci/cd','size/l','dependencies','skip-changeset']
body first line: 'Fixes #9402'
files: single-claim-path-guard.yml · check-single-claim-paths.mjs · lint.yml · package.json
gates(按名取最新): non-green=none(重型套件在跑)

1. ⭐ 它验出了一件它自己的回溯扫描看不见的事

我要求先测假阳性率再定 key。它测了,但更要紧的是它发现了测量工具本身的性质:

PR #9398 的 files 端点今天返回:   ['.changeset/console-82a94170c405.md']   ← 无 .objectui-sha
但它的首个 commit ffc79b028 触碰:  ['.changeset/…', '.objectui-sha']        ← 有

我独立复核,一致。

⇒ files 端点回答的是「这个 PR 相对当前merge base 改了什么」,不是「这个 PR 曾经改过什么」。 main 往前走过之后,那次 pin 写入就离开了累积 diff。

⭐ 后果是双向的,而它两边都说了:

事故对是真阳性,只是回溯扫描再也观察不到它;
所以它给的 identical ADDED path = 0 被明确标为 「a floor, not a proof」 —— 不是「零假阳性」,是「用这个数据源看到的下界」。

⚠️ 这条对门禁自己同样成立:它读的就是那个端点。诚实地把这条写进报告,比一个漂亮的 0 有价值得多。

2. 假阳性测量给出了决定设计的那个数

300 个最近的 PR(#8936–#9584),完整文件集,零分页截断,按开放窗口重叠统计:

repo-wide 「任意共享改动文件」 : 68 对   (pnpm-lock.yaml 33 · plugin-auth/package.json 21 · root package.json 15)
identical ADDED path          : 0
声明清单                       : 0

⇒ 68 是决定设计的那个数。若按「同一文件」当 key,第一天就是 68 对噪声 —— 正是我在派发里担心的。

⭐ 而且那三个热点路径现在被按名钉进自测,作为「必须留在清单之外」的路径 —— 不是靠后人记得,是靠一条会红的断言。

3. 形状选对了:独立门禁,不塞进旧的那个

我在派发里说「它可能更该是一个独立 check,而不是塞进一个名字写着『claim the same issue』的门禁里」。它选了独立,并沿用 Part-of Closing-Keyword Guard 的既有形状 ⇒ 不发明新范式。旧门禁未被削弱,实测仍绿(裁决 6 遵守)。

4. ⭐⭐ 消融扫描在它自己的测试里抓到一个幻影断言

撤销 contents:read 后自测保持绿 —— 因为解释该 scope 的那条注释里含有同样的两个词,而断言扫的是整个文件。

⇒ 一个永远不会失败的检查。修法:两条权限断言改为扫剥掉注释后的内容,消融时字符串仍在文件里但断言正确变红。

⭐ 而且它顺手对兄弟门禁 partof gate 做了同类消融 —— 那个是干净的(它的 pattern 带冒号,注释里没有;删掉真的 env: 块会红 2 条),所以没有立卡。⇒ 查了才说没有,不是没查就说没有。

⚠️ 这是今天第三次在测试自身里抓到 vacuous green(#9399、#9505、本卡)。而这一次的成因恰好是注释污染 —— 与 #9367 落地的那个 comment mask 同源。

5. 真实 API 端到端跑了,补上假 API 测不到的那半

PR #9584(无声明路径) → exit 0,走短路,1 次 API 调用
PR #9393(事故 PR,写 pin) → exit 0,走遍全部 9 个开着的 PR,触发昂贵分支
无 PR_NUMBER          → exit 2 NOT WIRED

并且真实 CI 上两个 check 都绿:新的 No other open PR may claim the same single-writer path 与旧的 No other open PR may claim the same issue。

check:type-check-debt 失败 是既有的,在同一个未构建容器里对 pristine origin/main(1c6da6eaf)逐字节复现,且本 diff 不含 TypeScript。⇒ 归因做实了才敢说「与我无关」。

6. 裁决

open_question 1(要不要变成 required context):A —— 维持 advisory。

而且你指出的那条结构性理由是决定性的,我要点名保留:

required-context registry 的约定要求条目能在 merge-queue build 上报告,而**merge_group 事件不携带 pull request** ⇒ 这个 check 在队列构建里没有可判之物。

⇒ 这不是「暂时不做」,是它在当前形状下无法满足登记条件。B 需要维护者裁决加上一个关于队列构建缺口的决定。已记在卡上,不假装缺口已闭合。

open_question 2(清单只留一条):A —— 保持单条。

C 已被实测否定(那三个就是 33/21/15 的假阳性来源);
B 是真的但这里买不到东西 —— 事故里 changeset 与 pin 同行,钉 pin 已经抓到;且 B 需要清单持有模式而非字面量,而裁决明确警告过这一点。

⇒ 只在「某次 bump 真的只落了 changeset 没落 pin」时重议。

Verdict: ACCEPT. 重型门禁收敛后武装(面不受管)。⚠️ GraphQL 配额当前打满,武装排队等恢复。

Generated by Claude Code

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Two PRs can ship the identical diff under two card numbers — the duplicate-claim gate is issue-keyed, not diff-keyed #9402

What happened

Why nothing objected

Why the two cards existed

Why it matters beyond the wasted run

Candidate responses

Not filed as blocking

Premise checked — it holds. Plus the root cause of the duplicate's consequence is now known.

What the duplicate bought — the underlying defect is now root-caused and filed

Why this makes the case for option 1 or 2 stronger, not weaker

✅ ACCEPT — PR #9598 · 两个 open question 都裁 A

1. ⭐ 它验出了一件它自己的回溯扫描看不见的事

2. 假阳性测量给出了决定设计的那个数

3. 形状选对了:独立门禁,不塞进旧的那个

4. ⭐⭐ 消融扫描在它自己的测试里抓到一个幻影断言

5. 真实 API 端到端跑了,补上假 API 测不到的那半

6. 裁决

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Two PRs can ship the identical diff under two card numbers — the duplicate-claim gate is issue-keyed, not diff-keyed #9402

Description

What happened

Why nothing objected

Why the two cards existed

Why it matters beyond the wasted run

Candidate responses

Not filed as blocking

Activity

os-zhuang commented on Aug 17, 2026

Premise checked — it holds. Plus the root cause of the duplicate's consequence is now known.

What the duplicate bought — the underlying defect is now root-caused and filed

Why this makes the case for option 1 or 2 stronger, not weaker

os-support-ai commented on Aug 18, 2026

claude commented on Aug 18, 2026

os-steve commented on Aug 18, 2026

✅ ACCEPT — PR #9598 · 两个 open question 都裁 A

1. ⭐ 它验出了一件它自己的回溯扫描看不见的事

2. 假阳性测量给出了决定设计的那个数

3. 形状选对了:独立门禁,不塞进旧的那个

4. ⭐⭐ 消融扫描在它自己的测试里抓到一个幻影断言

5. 真实 API 端到端跑了,补上假 API 测不到的那半

6. 裁决

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