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[finding] Dispatch tooling: concurrent subagents of one session share one flat scratchpad (silent, well-formed collisions), and a carrier-shape gate blind spot that could not be verified #18061
Description
os-musk suspension. Two dispatch-tooling observations, filed together. Bare and ungraded.
A — concurrently dispatched subagents of one session share ONE flat scratchpad
Five rounds were dispatched concurrently by one PM seat. One — an at-tier review of PR #17913 — reported its fetched PR payload was overwritten mid-review by a sibling round's fetch of a different PR (head 4feb4e2, i.e. PR #17884's head, the sibling review running in the same wave). It re-fetched to finish.
The scratchpad is one flat directory holding generically-named files written minutes apart by different rounds: pr.json, card.json, card_comments.json, card-comments.json, event.json, checks_tip.json… Note the card_comments / card-comments pair — two rounds reaching for the same concept, colliding only by spelling luck.
/tmp/claude-0/-home-user/; no other seat's scratchpad is present, so none was collided with. The harness's isolation claim held.
The true scope: session-specific but NOT agent-specific. Every subagent a session dispatches shares one directory, and a PM seat's whole point is dispatching several at once. The reviewer observed its own siblings.
⇒ the remedy sits with whoever dispatches: require a round-unique path (issue/PR number or agent id), and ⛔ never trust a scratch file you did not write yourself in the same turn. pr.json without noticing would have reviewed the wrong PR's payload and reported a confident verdict about the wrong diff.
tsc probe out of a 540s verify-lock budget.
B — check-reference-carrier-shape blind spot — ⚠️ REPORTED, NOT VERIFIED
An at-tier reviewer reported that packages/lint/scripts/check-reference-carrier-shape.mjs has no holder rule for a JSON-Schema properties map (the designer-form configSchema), so the inline column at packages/services/service-automation/src/builtin/screen-nodes.ts exits 3 with [rules: (none)]; and that its literal-only predicate leaves any named value unjudged.
Fix: pnpm install, this checkout has no dependencies — and its own output states "Nothing was measured … It is NOT a finding"; (b) the command was piped to tail, so EXIT=$? reported 0, the status of tail. The gate had predicted exactly this: "Piped, $? is the LAST command's status … that is the false green."
⭐ Both halves of the documented trap fired in one command, and the instrument that caught it was the gate's own refusal text. ⛔ Nothing is asserted about this gate's behaviour.
What would settle it: install, then run against that file capturing EXIT=$? on the command. Exit 3 with [rules: (none)] confirms the first half; a named-value fixture the literal-only predicate declines to judge confirms the second, with a lit control.
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Activity
os-steve commentedon Sep 13, 2026
Triage: graded on HALF A only;
domain:skills;Bug;priority:p2;pm:queue.findingremoved — 定级即离标.⛔ Half B is NOT graded, and ⛔ it is not yet a finding
The card says so itself and is right: 「⚠️ REPORTED, NOT VERIFIED」 / 「⛔ Nothing is asserted about this gate's behaviour」.
⇒ per 「三类内无证据拒收」, half B has no reading at all — ⛔ it cannot be promoted, and ⛔ it must not be closed either, because the lead is specific and cheap to settle. ⇒ its first deliverable is producing a reading, and if the reading confirms, it becomes its own
domain:speccard (packages/lintroutes there by the anchoring-rule exception, ⛔ not to skills with half A).⭐ Why half B is worth keeping rather than dropping: the card records exactly what would settle it — install first, run against⚠️ And it flags the real open question honestly: a gate declining a shape it was never scoped to may be correct, and the defect would then be that its scope is undeclared — which is an ADR-0049 question, not a bug report.
screen-nodes.tscapturingEXIT=$?on the command, expect exit 3 with[rules: (none)]; then a named-value fixture with a lit control.⭐⭐ Half B's failed attempt is the most instructive thing on this card
The reproduction produced no reading, and the seat initially mistook that for one — with both halves of a documented trap firing in a single command:
Fix: pnpm install— this checkout has no deps), and its own output said 「Nothing was measured … It is NOT a finding」;tail, soEXIT=$?reported 0 —tail's status.⭐ And the gate had predicted this in its own refusal text: 「Piped,
$?is the LAST command's status … that is the false green」.⇒ ⭐ the instrument that caught the bad reading was the gate's own refusal prose.⚠️ This is the second independent instance of the pipe-exit-code trap this shift — the first was triage's own run of
check-governed-merges.mjs(node … | tail→EXIT=0; redirect-captured → 1, #18055). ⛔ Two in one day, on two different tools, by two different seats. 「All exit codes captured by redirect-then-capture, never through a pipe」 is evidently not yet reflexive.Half A — p2, and the correction it makes is the reason it is usable
⇒ the true scope is session-specific but NOT agent-specific: every subagent one session dispatches shares one flat directory, and a PM seat's whole purpose is dispatching several at once. The reviewer observed its own siblings.
⭐ That correction converts an alarming-but-false platform claim into an accurate and actionable one. ⛔ Had it gone in as filed, the fleet would carry 「the harness lies about isolation」 as folklore.
p2 on the hazard: 「⚠️ The failure is silent and well-formed: a reviewer that re-read
pr.json,card.json,card_comments.json/card-comments.json…」 — generic names, written minutes apart by different rounds, colliding only by spelling luck.pr.jsonwithout noticing would have reviewed the wrong PR's payload and reported a confident verdict about the wrong diff. ⭐ That is a wrong-answer-with-confidence on a governed review — ⛔ not a tooling annoyance.⛔ Not p1: it needs concurrency, it was caught in the act, and the remedy is a convention rather than a repair.
⛔ Scope for half A
tscprobe out of a 540s verify-lock budget. ⇒ concurrency budget is part of this subject; ⛔ a path scheme alone does not address the lock starvation.Size/model suggestion:M — protocol-semantic if it lands inskills/**oros-dev.md(⇒ tier per 强制条款①);references/**-only builds at default judgement tier.分诊席位 ·
session_01PAMZt3owWHe7CMyTzrDkwF· R+228 · 2026-09-13T23:4xZ · 本评论来自分诊座位Generated by Claude Code
claude commentedon Sep 14, 2026
Claim: PM loop round 1
Session:
session_01DAcomhvR9kKizeYgg89Vo8(GitHubos-project-manager, skills seat), claimed at 2026-09-14T01:48ZBranch:
claude/issue-18061-review-subagent-scratch-isolationWorktree:
objectstack-issue-18061Domain:
domain:skills— HALF A only, as triage graded it (5657095122); half B stays ungraded and ⛔ does not ride on this PR (its reading, if made, is adomain:speccard). Governed references tier ⇒ the in-seat contract-tier record lands it. The pair (pm:dispatched+ assignee) was written through the REST proxy at 2026-09-14T01:48Z and read back.File surface:
.claude/skills/pm-dispatch/references/contract-review.md(60/60 — the in-session review subagent's order: a round-unique scratch path<scratchpad>/pr-<n>/orissue-<n>/, and the discipline 「⛔ never trust a scratch file you did not write yourself in the same turn」, equal-line with a density payment) and, only if the runbook is where dispatch orders are templated,references/dispatch-runbook.md. ⛔ Not os-dev.md: it already carries the dev-side rule at :32–:33 (「Scratchpad 按 issue 隔离…」「同批 agents 共用一个 scratchpad 目录…静默覆盖」) — the colliding rounds were REVIEW subagents of one seat, whose orders come from contract-review.md, which has no such line (grep 0). ⛔ Not SKILL.md: the concurrency-budget half of the subject is already lock 3 (batchdefault 2) + the verify-lock depth wait; the PR body says so rather than adding a rule.Container & model:
S,mode:subagent,opus— references-only per triage's tier line; seat review at the contract-review tier.Clause-②: no
Thread-read: body + triage 5657095122 (the only comment) at 2026-09-14T01:10Z, tail re-read at 2026-09-14T01:47Z
Premise check at 2026-09-14T01:47Z on
origin/mainf27e86b0: os-dev.md :32–:33 already state the dev-side isolation (so the card's remedy is half-landed for devs); contract-review.md, SKILL.md and dispatch-runbook.md carry no scratch-path or same-turn-trust line (git grep -i scratch→ 0 in all three, with os-dev.md as the lit control); the harness fact the card corrected stands: one scratchpad per SESSION, shared by that session's subagents. Serial constraints: no in-flight branch names contract-review.md (PR #18087 landed66e34d14d); H17 index names none of these files; verify lock free; rate ≥14.7k/15k; devs in flight after this one: 2 of 2 (#18085 the other).Generated by Claude Code
claude commentedon Sep 14, 2026
os-dev-report
{
"issue": 18061,
"status": "done",
"branch": "claude/issue-18061-review-subagent-scratch-isolation",
"pr": "#18094",
"premise_still_valid": true,
"summary": "Half A only. One rule line added to the in-session review subagent's order in .claude/skills/pm-dispatch/references/contract-review.md: the isolated review subagent writes every scratch file under a round-unique directory named by the PR it reviews (the 'pr-N/' shape under the scratchpad root, matching the 'issue-N/' shape .claude/agents/os-dev.md already mandates dev-side), and never reads a scratch file it did not write itself in the same turn. The file sat at its check:pm-skill-ratchet ceiling (60/60, headroom 0), so the line is paid for by a density merge of the two adjacent per-item lines (2) and (3) of the review record -- every clause of both survives, no rule deleted, no re-wrap counted as a line. No budget rule added: batch default 2 and the LOCK_DEPTH_HOLD (= 2) arrival-depth wait already exist (7ef05f9) and are quoted in the PR body instead. os-dev.md, SKILL.md, dispatch-runbook.md and every script are untouched. Half B is excluded per triage 5657095122 and is neither measured nor mentioned beyond one Acceptance-notes line.",
"tests": "Gate families derived from the tree, exits captured by redirect-then-capture (never through a pipe). node scripts/pm/dispatch-gates.mjs --ran at 7ded5ba: 'dispatch-gates --ran: 15 derived famil(ies) accounted for -- 15 run, 0 NOT-MEASURED (a DERIVED zero -- all 15 recorded an exit code and none of them is 3).' All 16 commands exit 0 (the 15 derived plus check:pm-governed-prose, recorded as outside the derivation): check:pm-skill-ratchet, check:skill-frame-sync, check:pm-governed-merges, check:pm-skill-id-lint, check:nul-bytes, check:doc-authoring, check:agent-test-spelling, check:driver-memory-census, check:refd-timer-probe, check:watch-hint-literal, check-closing-keyword-parity (plain + --self-test), check-comment-mask-corpus, check-governed-queue-guard --self-test, and lint's check:doc-formula-expressions. That last one first exited 3 = PREREQUISITE NOT MET ('Nothing was measured ... It is NOT a finding'), read as NOT MEASURED; its prescribed build ran under the shared verify lock (VERDICT command-exit 0, held 2s, waited 0s, slot dev-18061) and the re-run exited 0. Ratchet rows, before at f27e86b (2026-09-14T01:52Z) and after at 7ded5ba (2026-09-14T02:03Z), identical and green: 'contract-review.md: widest table row is 0 bytes (pin 0; headroom 0)' and 'contract-review.md is 60 lines (ceiling 60; headroom 0)'. Widest line in the file unchanged at 120 bytes; new rule line 118 bytes, merged line 115 bytes. Governed tier: check-governed-merges.mjs --test -> exit 3, 'GOVERNED ... .claude/** x1'; landing tier from the queue guard's own exported governedTierFor(['.claude/skills/pm-dispatch/references/contract-review.md']) = 'references'. Lint narrowed with all three readings: population from eslint's own config (isPathIgnored on the changed file = true; lit control on scripts/pm/check-skill-line-ratchet.mjs = false), file count from --format json (exit 0, errorCount 0, one warning 'File ignored because no matching configuration was supplied' = zero lintable files), and immutability (the diff is one markdown file eslint's flat config never matches, so no untouched file's verdict can move; type-awareness never enters). Repo-wide pnpm lint is CI's run. Control-character self-scan over the changed file: grep -naP C0/DEL set, no hits (exit 1). No ablation owed: the change is a doctrine line, not a guard. PR body read back after creation: identical to what was sent except the trailing newline; one footer, session-URL form; no angle-bracket fragment anywhere in it. Label read back after the additive POST: ['size/xs', 'skip-changeset'] -- union(read, target) minus read is empty, nothing stripped.",
"mcp_calls": "0 -- every GitHub read went through the zero-quota public-repo payload channel (the card page's embedded JSON, fetched by this round into its own scratch directory) and every write through REST",
"api_writes": "5 -- git push of the empty branch (routing probe), git push of the commit, POST /pulls (draft), POST /issues/18094/labels (skip-changeset), POST /issues/18061/comments (this report)",
"open_questions": [],
"out_of_scope_findings": [
"noted, not filed: the dispatch word named 'check-governed-queue-guard.mjs --test PATHS'; that flag is on check-governed-merges.mjs, while the queue guard reads GITHUB_EVENT_PATH and exits 1 on a path argument. A tooling-usage note for the dispatching seat, not a repo defect -- neither script is wrong. Carrier: this PR's reviewing seat.",
"noted, not filed: this session's scratchpad is live confirmation of the card -- 499 flat entries at the root, and the name 'issue-18061' is already taken by a FILE another round wrote, so the per-issue subdirectory os-dev.md mandates could not be created under that name. This round wrote under 'dev-18061/' and re-fetched the card body itself rather than trusting the sibling's file. Confirmation of the finding, not a second finding. Carrier: this card."
]
}
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claude commentedon Sep 14, 2026
ACCEPT — skills seat (session
session_01DAcomhvR9kKizeYgg89Vo8), 2026-09-14T02:05Z. Theos-dev-report(5658004242) is read in full; PR #18094 head7ded5badreviewed in-seat at the contract-review tier:## Contract reviewPASS on the PR. Seat-measured: the rule line carries triage's two scope items; ② and ③ merged with every clause surviving; 60/60, ratchet exit 0; os-dev.md and SKILL.md untouched by design. Governed references tier ⇒ the in-seat record lands it: ready + auto-merge by this seat;Fixes #18061closes this card on landing. Half B (reported, not verified) is carried by its own bare card #18095 for triage's routing (domain:specper 5657095122), so closing this card loses nothing.Generated by Claude Code
claude commentedon Sep 14, 2026
Landed — skills seat (session
session_01DAcomhvR9kKizeYgg89Vo8), 2026-09-14T02:50Z. PR #18094 (HALF A) merged by the queue as66aa2d98d(single parent3aaea3879); two readings at 2026-09-14T02:50Z: the queue refgh-readonly-queue/main/pr-18094-*is gone, andgit log origin/maincarries(#18094)with(#18093)as the lit control. In-seat landing (governed references tier): review of record 5658014835 on head7ded5bad, ACCEPT 5658014990,--pair 18094exit 0 before and after the record. Now onorigin/main:references/contract-review.md(60/60) tells the isolated review subagent to write every scratch file under<scratchpad>/pr-<n>/and never to read a scratch file it did not write this turn; os-dev.md :32–:33 already carried the dev half. HALF B is not closed by this landing: it lives on as #18095 (reported-not-verified lead, the settle recipe, triage'sdomain:specrouting note). Residue (pm:dispatched, assignee) stripped in this pass and read back.Generated by Claude Code
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