pm-dispatch: re-read the PR head before trusting any `check_suite.completed` event — the event can name a stale SHA (#15803 section B2)

[claude]

Split out of #15803 (section B2) by the skills seat at grading, as that card's triage prescribed; the maintainer's principle question in #15803 section A stays on that card.

The reading

A check_suite.completed event can name a head that is no longer the PR's head. Measured by the domain:spec @ objectui seat on 2026-09-05: the event named dfec57b5e while the PR's actual head was e46a218c9. Acting on it would have flipped a Clause-② PR ready on evidence from a commit no longer on the branch.

The protocol's existing corrective — read the full check farm by name on the head, then arm — already prevents the bad outcome, but it reads as being about aggregate-vs-by-name. This is a distinct failure: right method, wrong commit.

The rule to land

One clause in .claude/skills/pm-dispatch/SKILL.md's 入队与落地 block (line-neutral, paid by a fold in the same block): before trusting any suite or check event, re-read the PR object and take the head from it; a check reading is bound to that head, never to the event's SHA. references/platform-readings.md gains the fact as one line in the fifth readings increment (with #15977 · #16006 · #16104 section 1 · #15803 section C), not here.

Acceptance

• SKILL.md 811/811 (pin 342), the clause in the 落地 block; check-skill-line-ratchet, check-skill-id-lint, check-skill-frame-sync, check-governed-prose, check-half-states --self-test, check-governed-merges --test exit 3, whole-repo lint — exits captured before any pipe.
• Governed (.claude/**): draft PR, seat review, os-zhuang + hotlong, human merge.

Serial

SKILL.md is held by PR #16339 (flight A) and PR #16271 (devx); this card folds into the SKILL.md flight that follows both (with #16352 and #16229 — same file, same register, no conflicting ruling).

Refs #15803.

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[claude]

Blocked-by: #16004

Same file as flight A's PR #16339 and the devx seat's PR #16271 (SKILL.md); folds into the SKILL.md flight that follows both, with #16352 and #16229.

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[claude]

Claim: PM loop round 9 — flight Z, the SKILL.md batch: five folds under the unchanged line pins (SKILL.md 811, core-rules 150, and each named reference's own ceiling), one governed PR. (1) #16386 乙 — the human-floor row gains the one-file exception for references/platform-readings.md: an increment raises the ceiling to the landed line count without a decision card provided the seat's acceptance comment shows every fact verified and deduplicated (candidates / landed / already-present / declined), one line per fact, no re-wrapping counted; recorded in ruledRaises citing the standing ruling (5563909225). (2) #15803 §A option (c) — batch independence reads FILE SURFACE, not package; the exemption clause becomes the rule (region-level file-surface declaration in the claim; merge main before opening the PR and again after a sibling lands; conflicts arbitrated by the merge queue, no manual PM ordering; same-file strictly serial), with the sentence that cross-file semantic coupling is caught by the queue's CI (5563910163). (3) #16352 — the selection order reads priority:p1/p2/p3 where it reads p0 today, in the order the card's ruling states. (4) #16372 — re-read the PR head before trusting any check_suite.completed event. (5) #16343 — the director carve-out in the seat mutex, the seat-post protocol's multi-summon status form, the ratchet-map comment refresh.
Session: session_019RfFHiRCSs3JXLK4cwcfox
Branch: claude/issue-16386-skill-batch-62
Worktree: objectstack-issue-16386
Domain: domain:skills
File surface: .claude/skills/pm-dispatch/SKILL.md, references/core-rules.md, and whichever of references/seat-post-protocol.md and the ratchet map comment in scripts/pm/check-skill-line-ratchet.mjs the five cards name — measured per card before editing; folds only, no ceiling raise.
Container & model: L, mode:subagent, fable — dispatch-gates.mjs --tier: MANDATORY on .claude/skills/pm-dispatch/SKILL.md; on a fable 429 the seat's exemption applies, opus, recorded here.
Clause-②: no
Serial: devx's PR #16271 (draft, mergeable_state: dirty) collides on 候选与批次 and owes the re-fold per note 5560027553; this flight branches from origin/main and takes no proof against a dirty head — whichever merges second re-folds. T's PR #16437 is in the queue on the ratchet script's self-test region; merge origin/main in after it lands or prove clean twice. Governed ⇒ draft PR, in-seat contract-tier review, then the seat requests os-zhuang + hotlong, adds needs-user-decision and posts the final 维护者速读; human merge. The PR carries Fixes #16386, Fixes #15803, Fixes #16352, Fixes #16372, Fixes #16343.

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