Matrix builds: fail-fast and include/exclude patterns

Matrix builds cancel all in-progress jobs when any single job fails (fail-fast: true is the default). This wastes useful signal from other matrix legs. Conversely, include/exclude misconfiguration silently drops matrix jobs.

Disable fail-fast when you want to see all results. Use explicit include for additive combinations and exclude for subtractive ones:

jobs:
  test:
    strategy:
      fail-fast: false
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
        node: [18, 20, 22]
        exclude:
          - os: windows-latest
            node: 18
        include:
          - os: ubuntu-latest
            node: 22
            experimental: true
    runs-on: ${{ matrix.os }}
    continue-on-error: ${{ matrix.experimental == true }}

fail-fast: false surfaces failures across all combinations. continue-on-error on experimental legs lets the overall job succeed even if the experimental leg fails, so you get data without blocking merges.