e2e-staging-canvas had a single global concurrency group:
concurrency:
group: e2e-staging-canvas
cancel-in-progress: false
That meant the entire repo shared one running + one pending slot. When a
staging push queued behind an in-flight run and a third entrant (a PR
run, a follow-on push) entered the group, the staging push got
cancelled. auto-promote-staging then saw `completed/cancelled` for a
required gate and refused to advance main.
Observed 2026-04-28 23:51-23:53: staging tip 3f99fede's e2e-staging-
canvas push run was cancelled within 2:20 of starting because a PR run
on a follow-on branch entered the group. Auto-promote-staging fired 8+
times after that, all skipped because canvas was still in the cancelled
state. The chain stayed stuck until the cancelled run was manually
re-dispatched.
e2e-api had a softer version of the same bug — `group: e2e-api-${{
github.ref }}`. Per-ref isolates push events from PR events, so this
specific scenario didn't hit it, but back-to-back pushes to staging at
SHA-A and SHA-B share refs/heads/staging and would still cancel SHA-A's
queued run when SHA-B enters.
Both workflows now use per-SHA grouping. The single-global-group's
original intent was to throttle parallel E2E provisions, but each E2E
run already isolates its state via fresh-org-per-run, and parallel
infrastructure cost at our scale (~$0.001/min × 10min × 2) is rounding
error compared to a stuck pipeline.
Per-SHA still dedupes accidental double-triggers for the SAME SHA.
It does not cancel obsolete-PR-version runs on force-push — that wasted
CI is acceptable given the alternative is losing staging-tip data that
auto-promote-staging depends on.
Other gate workflows: ci.yml uses `cancel-in-progress: true` which is
correct for unit tests (intentional cancellation on supersede). codeql.yml
is per-ref like e2e-api was; same fix probably applies if the same
deadlock pattern is observed there, but no incident yet so deferring.
b2a0703f1c