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Day 11 of the ubuntu-latest rollout: Thursday - do the move today, while Friday is still available to watch it

The ubuntu-latest migration window opened on October 19, 2026 and runs to November 19. Inside that window, ubuntu-latest moves from Ubuntu 24.04 to Ubuntu 26.04 in stages, so any single run may land on either image.

Day 10 turned Tuesday's isolation result into a decision: pin, move, or treat it as a normal bug. Day 11 is Thursday: a decision written down is not a migration. Today the change actually lands, on the last day when the day after it is still an ordinary working day that can catch what the change broke.

Why Thursday, not Friday

A label change merged on Thursday gets a full Friday of ordinary runs to prove itself before the weekend. The same change merged on Friday is verified, if at all, by scheduled jobs running unattended on Saturday and Sunday - and the first human look at those results is Monday morning, which is November 2, the day macos-14 labels retire outright.

That stacks two unrelated failures into the same morning: a bad migration you made on Friday and a retirement you did not choose. Thursday's move keeps them separate. If the new label misbehaves on Friday, you still have Friday to revert to the old label while both labels work; a revert discovered as necessary on Monday has no old macos-14 label left to revert to.

Thursday also brings the second data point for weekly workflows. A workflow scheduled on Thursdays ran in-window for the first time on October 22 and runs again tonight. Two runs of the same workflow, one week apart, on a label that is still moving: if the results differ and the code did not change, that difference is the staged rollout sampling the two images - not a reason to reopen a closed entry, and not noise to ignore either. Record which result each Thursday produced, next to the entry, so the comparison exists when the window closes on November 19.

The 15-minute Thursday pass

  • Land the decision from Wednesday: set the explicit label you chose - ubuntu-24.04 pinned, or ubuntu-26.04 moved to - in the workflow itself, not in a note about the workflow. A decision that only exists in a checklist will be rediscovered as a failure later.
  • Do the macos-14 move today if any job still uses macos-14, macos-14-large, or macos-14-xlarge: move it to an explicit macos-15 label or to macos-latest deliberately, and merge while both labels still run. Retirement is November 2, 2026 - 4 days from today (October 29) - and those jobs will fail outright, not drift.
  • Note tonight's Thursday-scheduled runs before they happen: write down which weekly workflows run tonight and what they produced last Thursday. Tonight's result only becomes a comparison if last week's was recorded before you saw it.
  • Write the revert line next to each change you landed: the old label, and the date after which it stops being available. For an Ubuntu pin that date is the end of the window; for a macos-14 move there is no revert after November 2, which is exactly why the move belongs on Thursday and not on Friday.

Where my own re-walk stands

I have re-run my scanner (RunnerDriftAudit v0.3.8) against a frozen October 13 baseline on October 20, 21, 22, 23, 24, 25, and 26. All seven re-walks reproduced the baseline exactly - 4/2, 4/2, 0/2 across the three targets, no rows moved, no migration-effect rows yet. The October 27 and 28 re-walks were not run.

The scanner reads workflow files, and those files have not changed - Thursday's work is on the change side: the chosen label set in the workflow, the macos-14 move merged while Friday is still available to watch it, and tonight's second Thursday run recorded against the first.

Tool

I run these checks with RunnerDriftAudit, a free static scanner for GitHub Actions workflow files (it reads the YAML; it does not execute your jobs, and it cannot see runtime-only behaviour):

Day-11 field note (Gist): https://gist.github.com/alapha888/8b780ac78d295d7a31ff558c102a5862

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