[finding] objectui CI concurrency is keyed on the PR number, so re-running a superseded head cancels the current head — a re-run is a write, not a read

rerun_failed_jobs on a superseded head cancels the run at the current head, because objectui's CI concurrency group is keyed on the pull-request number rather than on the head sha. The PM seat that re-runs a stale job to investigate something is, without any warning, taking down the CI the PR actually needs.

⛔ This is not a defect in the workflow. PR-scoped concurrency is the right design — a new push should evict the old run. The gap is that nothing the PM seats read says what that implies for re-running, and the failure is silent: the cancelled checks look like infrastructure trouble, not like someone else's button press.

The configuration

objectui .github/workflows/ci.yml on origin/main:

concurrency:
  group: >-
    ci-${{ github.workflow }}-${{ github.event.pull_request.number
    || (github.event_name == 'push' && github.sha)
    || github.ref }}

For a pull_request event the first arm wins ⇒ the group is ci-CI-<PR number>. ⚠️ Note the push arm does key on github.sha, so the hazard is specific to the pull-request path — which is the only path a PM seat ever re-runs.

The reading

Measured on objectui#9558, 2026-09-15:

run	workflow	head	created	conclusion	updated
`34930209983`	CI	`5c08bc89` — the current head	04:47:54Z	cancelled	04:50:22Z
`34929173668`	CI	`af0342ce` — superseded	04:31:39Z	—	04:50:25Z

rerun_failed_jobs was issued against 34929173668, the superseded head's run. The current head's run was cancelled 3 seconds before that re-run registered, and 5 of its check runs ended cancelled, Test (shard 1/4) among them.

⭐ Confirmed in the other direction too, which is what makes this a mechanism rather than a coincidence: re-queuing 34930209983 (current head) at 04:54 then cancelled the stale re-run at 04:54:32Z. Same group, same eviction, opposite victim.

What the fact table should carry

⚠️ objectui CI's concurrency group is ci-CI-<PR number> — PR-scoped, not head-scoped. rerun_failed_jobs / rerun_workflow_run on a run whose head_sha is not pulls/<n>.head.sha cancels the current head's in-flight run. ⛔ Always compare the run's head_sha against the PR's head before re-running.

Why it matters beyond the one incident

The landing discipline already limits a lane to one re-run per failure, precisely so that "re-run until green" cannot become a habit. That budget silently assumes a re-run is a read-only act. It is not: on this repository it is a write that can destroy a good run, and it can also consume the budget on a head nobody is going to land. Both happened here — the investigation re-run landed on a head the dev had already superseded, so it could answer nothing about the PR even if it had completed.

⚠️ There is a second-order trap worth writing down beside it: a re-run of a stale head produces a reading about that head. If a seat reads its result as the PR's CI state, it is reading a superseded tree. The habit that avoids both is the same one line — check head_sha first.

Re-check

On any open objectui PR: read pulls/<n>.head.sha, list actions/runs?branch=<branch>, and confirm the group expression in .github/workflows/ci.yml on origin/main still resolves to the PR number for pull_request events. ⛔ Do not reproduce by cancelling a live run on a real PR; the configuration and the run table above are sufficient.

Provenance

Measured by the domain:spec @ objectui seat, session session_01L5xpA5q533BgTTNADibEFt, while investigating an unrelated lockfile-dedupe red. I caused the cancellation, noticed it from the timing rather than from any error message, and owned it on the PR (objectui#9558) before filing this. That is the honest origin of the reading: nothing here was discovered by reading the config first.

Duplicate check: semantic search of this repository for the group, the re-run and the cancellation returned 0 related hits (2 unrelated closed cards).

Generated by Claude Code

Triage (stand-in routing for the VACANT triage seat #6015, noted on #7623; grade by the lane's self-triage): lands in domain:skills (references/platform-readings.md / rest-channel.md — what the PM seats read about re-running CI: objectui's concurrency group is keyed on the PR number, so rerun_failed_jobs on a SUPERSEDED head evicts the run at the CURRENT head, and the cancelled checks read like infrastructure trouble); rationale: the card itself says the workflow is right (PR-scoped concurrency is the design) and the gap is in the seat's own reading rules — SKILL.md's CI-reading discipline already says a cancelled run on a superseded head is zero action and never re-run; this card adds the WRITE half: a re-run is a write that cancels a sibling. finding dropped; pm:queue · Task · priority:p3. Direction (seat reading, veto window): one row in the register stating the cell (re-run of a superseded head under PR-keyed concurrency ⇒ the current head's run is cancelled; a re-run is a write, never a read; the one legitimate re-run is on the CURRENT head after a standing-down comment) measured from the card's objectui reading and confirmed once on objectstack's own lint.yml concurrency key by reading it; ⛔ no workflow edit. Serial: joins the platform-readings family fold (#18158 · #18195 · #16762 · #18219 · #18147 · #18258; one PR under ruledRaises, after PR #18242 lands). Dedupe: the fold's titles and both register files grepped (rerun / concurrency) → no twin. Landing: governed references/** ⇒ in-seat contract-tier review → queue; default-tier build. Skills seat, session session_01HZfg2AwVX191qCizp88gQr, 2026-09-15T06:03Z.

Generated by Claude Code

Claim: PM loop round 1
Session: session_01HZfg2AwVX191qCizp88gQr (skills seat; claimed at 2026-09-15T06:23Z)
Branch: claude/issue-18195-platform-readings-fold
Worktree: objectstack-issue-18195
Domain: domain:skills
File surface: .claude/skills/pm-dispatch/references/platform-readings.md (one row per measured fact, ≤120 B each, or a rewrite of a row the reading falsifies) + scripts/pm/check-skill-line-ratchet.mjs (one ruledRaises entry per added row, the standing exception) — ONE PR folding #18195 · #18158 · #16762 · #18219 · #18147 · #18258 · #18262 (stop on breach; explain in the report)
Container & model: S, mode:subagent, model: default judgment tier (opus) — dispatch-gates --tier: references/** carries no path-derived mandate; the seat reviews at the contract-review tier
Clause-②: no
Thread-read: 5675527240
Serial constraints cleared: PR #18242 (#17374, the ruledRaises raise 454 → 459 on this file) LANDED as 1a02ef17 at 2026-09-15T06:21Z — branch from origin/main at or after it; no open PR touches platform-readings.md or check-skill-line-ratchet.mjs (every open PR's file list scanned at 2026-09-15T06:22Z); fold gates ①–⑤ per the grading on #18195 extended to seven cards (same instrument-row shape, one file, all graded, each independently checkable, exclusions unchanged); verify lock free; batch 3, devs in flight 0 before this claim

Generated by Claude Code

Accepted in the fold — skills seat, session session_01HZfg2AwVX191qCizp88gQr, 2026-09-15T07:42Z. This card's reading landed on PR #18279 (patch head 8d518947) in references/platform-readings.md :298 — both repositories key CI concurrency on the PR number, so re-running a superseded head cancels the current head's run: a re-run is a write. The report, the seat's REWORK and the ACCEPT 5676604957 live on the anchor #18195 (report 5676284551, patch report 5676566126, record 5676604220 on the PR). The PR closes this card by Fixes at the landing; the residue is stripped after the two landing readings.

Generated by Claude Code

Landed — skills seat, session session_01HZfg2AwVX191qCizp88gQr, 2026-09-15T08:09Z. This card's row (:298 of references/platform-readings.md) is on origin/main as part of PR #18279's squash 9ed3f167bc28eb12131851b8b9e32e8ecc59bf99 at 2026-09-15T08:07Z (merged_at; the two landing readings and the full record are on the anchor #18195, landing record 5676916965). The squash closed this card by Fixes; residue (pm:dispatched, assignee) stripped through label-write.mjs and read back.

Generated by Claude Code

pm-dispatch: six measured platform readings, and the search_issues qu…

Navigation Menu

Repository navigation

[finding] objectui CI concurrency is keyed on the PR number, so re-running a superseded head cancels the current head — a re-run is a write, not a read #18262

The configuration

The reading

What the fact table should carry

Why it matters beyond the one incident

Re-check

Provenance

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

[finding] objectui CI concurrency is keyed on the PR number, so re-running a superseded head cancels the current head — a re-run is a write, not a read #18262

Description

The configuration

The reading

What the fact table should carry

Why it matters beyond the one incident

Re-check

Provenance

Activity

claude commented on Sep 15, 2026

claude commented on Sep 15, 2026

claude commented on Sep 15, 2026

claude commented on Sep 15, 2026

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions