ci: keep the reporting aliases off the shared hosted pool#6446
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An alias job is the last job in the run: it waits for its matrix leg and reports the outcome. Starve it of a runner and it never starts, so the RUN never reaches a terminal state. A run that never terminates holds its `concurrency` group, and build.yml sets `cancel-in-progress` on that group — so the next push's run sits at status `pending` with ZERO jobs and never dispatches. The pull request is then wedged: no checks, no failure, nothing to re-run. It survives further pushes and clears only by cancelling the older run by hand. It cost #6437 two hours, and #6437 was the fix for the starvation that caused it. `macos` already resolved its runner through PULP_PREAMBLE_RUNS_ON_JSON so the required gate could not be starved on a pool it does not control. `linux` and `windows` were still pinned to `ubuntu-latest` — which means two ADVISORY lanes could each strand a pull request indefinitely. An advisory lane must not be able to do that, so they ride the same toggle. This removes the wedge mechanism rather than documenting a recovery for it, and it costs nothing: these jobs poll an API and echo a result. The test asserts all three aliases resolve through the toggle and that none is pinned to a bare `ubuntu-latest`; reverting either job fails it. The guide records the diagnosis signature — a `Build and Test` run that is `pending` with an empty jobs array while its sibling workflows dispatched normally — because that state is otherwise indistinguishable from ordinary queue latency.
danielraffel
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The failure this removes
A pull request that shows no check activity at all after a push — not red, not queued, simply nothing. It is not slow CI, and it does not recover on its own.
build.ymlgroups bybuild-<ref>withcancel-in-progress. The reporting aliases (macos/linux/windows) are the last jobs in the run: they wait for their matrix leg and echo the outcome. Starve one of a runner and it never starts, so the run never reaches a terminal state. A non-terminal run holds its concurrency group, and every later run on that ref then sits atpendingwith zero jobs. Pushing again does not help — the new run queues behind the same held group.This cost #6437 two hours, which is pointed, because #6437 was the fix for the hosted-pool starvation that caused it.
Why
linuxandwindowsspecificallymacosalready resolved its runner throughPULP_PREAMBLE_RUNS_ON_JSONso the required gate could not be starved on a pool it does not control.linuxandwindowswere still pinned toubuntu-latest— meaning two advisory lanes could each strand a pull request indefinitely.An advisory lane must not be able to do that. Routing them through the same toggle removes the mechanism rather than documenting a recovery for it, and costs nothing: these jobs poll an API and echo a result.
Diagnosis signature (now in the ci skill + local-ci guide)
Unambiguous: run
statusispendingand itsjobsarray is empty, while sibling workflows from the same trigger dispatched normally.Verification
tools/scripts/test_windows_runner_policy.pyasserts all three aliases resolve through the toggle and none is pinned to a bareubuntu-latest. Negative control: reverting either job toubuntu-latestfails the test; 13/13 pass with the change.actionlintclean,gates.shgreen.🔎 Provenance
claudem3/Volumes/Workshop/Code/pulp-mq1dd2217d-ca26-4de4-b90e-6360ee343606Resume
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Restore URL — https://claude.ai/code/session_01363VPyLiV9Er9DJ1pcmC9c
stamped 2026-07-22 00:41 UTC