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GitHub Actions · actionlint · Checked November 4, 2026

actionlint: label "ubuntu-26.04" is unknown. available labels are ...

You changed runs-on to ubuntu-26.04, or Renovate did in a pull request titled "Update dependency ubuntu to v26". The jobs run fine, but the lint job fails. Ubuntu 26.04 runners are generally available since September 17, 2026 (GitHub changelog). The last release of actionlint, v1.7.12 of March 30, 2026, is older than that, and its list of GitHub-hosted labels stops at ubuntu-24.04 and ubuntu-24.04-arm. ubuntu-latest is in the list, so this only shows when you name ubuntu-26.04 or ubuntu-26.04-arm.

The message

.github/workflows/ci.yml:10:14: label "ubuntu-26.04" is unknown. available labels are "windows-latest", ..., "ubuntu-24.04", "ubuntu-24.04-arm", "ubuntu-22.04", "ubuntu-22.04-arm", ... if it is a custom label for self-hosted runner, set list of labels in actionlint.yaml config file [runner-label]

It is the lint's word, not GitHub's: ubuntu-26.04 is a real hosted label. Through reviewdog it shows as a review comment or a failed check on each workflow; in jekyll-github-deploy #93 all ten workflows failed this way with reviewdog/action-actionlint@v1.72.0.

Why a new actionlint has not fixed it

The label has been asked for since June: issue #682, and pull requests #683 (June 12), #723 and #743, all still open on November 4. The last commit to rhysd/actionlint is from April 19, 2026. Builds of rhysd/actionlint, whether from its releases, go install or its Docker image, are v1.7.12 or older and do not know the label. super-linter copies rhysd/actionlint:1.7.12 into its image, so it does not either.

Fix 1: tell actionlint the labels

actionlint reads .github/actionlint.yaml (or .yml). Labels listed under self-hosted-runner are accepted:

self-hosted-runner:
  labels:
    - ubuntu-26.04
    - ubuntu-26.04-arm

This works however you run actionlint: the command line, pre-commit, the Docker image or reviewdog. super-linter reads the file from .github/linters/actionlint.yml instead (its LINTER_RULES_PATH and GITHUB_ACTIONS_CONFIG_FILE defaults). turbo-themes #1186 adds the same two lines with a comment to remove them once its actionlint knows the labels, which is a good habit.

Fix 2: reviewdog/action-actionlint v1.75.0 or later

From v1.75.0 (September 16, 2026), reviewdog/action-actionlint installs kjanat/actionlint 1.17.0 instead of rhysd/actionlint 1.7.12. That fork knows ubuntu-26.04 and ubuntu-26.04-arm (we checked its releases from v1.10.0 to v1.17.0). So if you use reviewdog, moving from v1.74.0 or older to the current version is enough:

- uses: reviewdog/action-actionlint@v1.81.1

The fork is maintained by someone else than the original author (see #719, "Any active forks?"). If you would rather not run it, Fix 1 keeps rhysd/actionlint.

Your own labels

The same message comes for the labels of self-hosted runners, and for the names of larger runners you created. The fix is the same list, and it takes path.Match patterns:

self-hosted-runner:
  labels:
    - ubuntu-26.04
    - ubuntu-26.04-arm
    - build-*

Telling it apart

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