GitHub Actions workflow validation or action reference error

What this failure means

GitHub Actions rejected the workflow definition or could not resolve a referenced action, so the workflow could not validate cleanly before the intended job logic ran.

Symptoms

Faultline looks for one or more of these log fragments:

Invalid workflow file
You have an error in your yaml syntax
yaml: line
did not find expected key
mapping values are not allowed here
could not parse the workflow file
error reading
Unrecognized named-value

Diagnosis

GitHub Actions failed while validating the workflow file or resolving a referenced action revision. Common causes include malformed YAML, invalid expressions, and action references that point to a missing tag, branch, or commit.

Fix steps

1. Validate the workflow locally: pip install yamllint && yamllint .github/workflows/*.yml.
2. Use the GitHub Actions VS Code extension which provides schema validation in the editor.
3. Check the exact line number from the error message and inspect indentation carefully.
4. Ensure expressions like ${{ secrets.TOKEN }} are quoted when they appear in string values.
5. Verify action references such as uses: actions/checkout@v4 point to a real released ref and are not being truncated or templated into an invalid value.
6. Verify on: trigger syntax using the GitHub Actions documentation.

Validation

• Re-run the local reproduction command after the fix.
• yamllint .github/workflows/
• actionlint

Why it matters

Workflow YAML files and referenced actions must validate before GitHub can schedule the job. Common causes include incorrect indentation, unquoted expressions containing colons, invalid on: trigger syntax, missing required fields, or an action ref that points at a missing tag or partial value.

Prevention

• Install a YAML linter into your editor and CI pre-flight.
• Use actionlint in CI: actionlint .github/workflows/*.yml.
• Use GitHub’s built-in workflow editor which validates syntax on save.

Try it locally

yamllint .github/workflows/
actionlint
yamllint .github/workflows/
actionlint

How Faultline detects it

Use faultline explain github-actions-syntax to see the full playbook.

faultline analyze build.log
faultline explain github-actions-syntax

Generated from playbooks/bundled/log/ci/github-actions-syntax.yaml. Do not edit directly.