Question

A workflow defines a build job with the following strategy:

```yaml
jobs:
  build:
    strategy:
      fail-fast: false
      matrix:
        os: [ubuntu-latest, windows-latest]
        node: [18, 20]
    runs-on: ${{ matrix.os }}
    steps:
      - run: npm test
```

In the Actions UI run summary, one job shows a red X while the other three are green. The failing job is named `build (windows-latest, 20)`. Your teammate insists the failure is caused by the Node version because "20 is the last value shown." How should you interpret this job name to identify the failing variant?

Accepted Answer

The job ran on the windows-latest runner with Node 20; the name lists matrix values in the declaration order of the axes (os, then node), so both axis values must be considered together — the name alone does not prove which axis caused the failure.

Answer

The job name lists values in alphabetical order, so `20` corresponds to os and `windows-latest` corresponds to node.

Answer

The trailing value in the parentheses is always the axis responsible for the failure, so Node 20 is confirmed as the root cause.

Answer

The job name is randomly generated per run, so it cannot be reliably mapped to any specific matrix combination.