Question

A teammate shares this workflow snippet and asks how many jobs the matrix will produce and whether the shared config applies to every variant:

```yaml
jobs:
  test:
    strategy:
      matrix:
        os: [ubuntu-latest, windows-latest]
        node: [18, 20]
    runs-on: ${{ matrix.os }}
    steps: &common-steps
      - uses: actions/checkout@v4
      - run: node --version
```

You notice `&common-steps` is defined here but no `*common-steps` alias is referenced anywhere else in the file. What is the actual behavior of this workflow?

Accepted Answer

The matrix produces 4 jobs, and the `&common-steps` anchor has no effect beyond defining the steps for this job because it is never aliased elsewhere.

Answer

The matrix produces 2 jobs because the anchor collapses duplicate os/node combinations into a single set of steps.

Answer

The workflow fails to parse because an anchor (`&`) must always be paired with at least one alias (`*`) reference in the same file.

Answer

The matrix produces 4 jobs, but only the first variant runs the steps; the remaining three inherit an empty step list from the anchor.