GitHub Actions CI/CD Engineering Standards

This skill codifies 2026 GitHub Actions best practices — secure supply chains, efficient caching, reusable workflows, and hardened permission models.

1. Security: SHA Pinning (Mandatory)

Pin Every Third-Party Action to a Commit SHA

# ✅ Good: SHA-pinned (immutable, auditable)
- uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.2.2
- uses: actions/setup-node@1d0ff469b7ec7b3cb9d8673fde8c81c89c3166c0 # v4.2.0

# ❌ Bad: Tag-pinned (mutable, vulnerable to supply chain attacks)
- uses: actions/checkout@v4
- uses: actions/setup-node@v4

• ALWAYS pin to full-length commit SHAs — tags are mutable and can be hijacked
• ALWAYS add a trailing comment with the version for human readability
• Use tools like step-security/harden-runner or pin-github-action CLI to automate SHA resolution
• Resolve SHA Manually: See templates.md for the gh api command to resolve SHAs.
• Audit quarterly — review all pinned SHAs when updating workflow dependencies

Permission Hardening

# Set restrictive defaults at the workflow level
permissions:
  contents: read

jobs:
  build:
    runs-on: ubuntu-latest
    # Grant specific permissions per-job
    permissions:
      contents: read
      packages: write

• ALWAYS set permissions: at the workflow level — use read-all or specify individually
• NEVER use permissions: write-all — it grants maximum privileges
• Grant write only where needed — per-job, not per-workflow

2. Workflow Structure

Standard CI Template

See [templates.md](references/templates.md) for a complete, production-ready CI workflow template.

Key Structural Rules

• ALWAYS set concurrency with cancel-in-progress: true to prevent stale runs
• Use `needs:` to create a dependency chain: lint → test → build → deploy
• Use `.node-version` or .python-version files — never hardcode versions in workflows
• Use `--frozen-lockfile` — never let CI modify the lock file

3. Caching

Package Manager Caching

# Node.js (pnpm)
- uses: actions/setup-node@<sha>
  with:
    node-version-file: .node-version
    cache: pnpm

# Python (uv)
- uses: actions/setup-python@<sha>
  with:
    python-version-file: .python-version
- run: pip install uv
- uses: actions/cache@<sha>
  with:
    path: ~/.cache/uv
    key: uv-${{ runner.os }}-${{ hashFiles('uv.lock') }}
    restore-keys: uv-${{ runner.os }}-

# Go
- uses: actions/setup-go@<sha>
  with:
    go-version-file: go.mod
    cache: true

Custom Caching Rules

• Key on lock file hash — ${{ hashFiles('pnpm-lock.yaml') }}
• Use `restore-keys` for fallback to partial cache hits
• Cache the package manager's global cache, not node_modules directly
• Don't cache everything — simplicity trumps marginal speedup

4. Matrix Strategy

Basic Matrix

jobs:
  test:
    strategy:
      fail-fast: false
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
        node: [20, 22]
        exclude:
          - os: windows-latest
            node: 20
    runs-on: ${{ matrix.os }}
    steps:
      - uses: actions/setup-node@<sha>
        with:
          node-version: ${{ matrix.node }}

Dynamic Matrix

jobs:
  prepare:
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.set.outputs.matrix }}
    steps:
      - id: set
        run: |
          echo 'matrix={"include":[{"project":"api"},{"project":"web"}]}' >> "$GITHUB_OUTPUT"

  build:
    needs: prepare
    strategy:
      matrix: ${{ fromJSON(needs.prepare.outputs.matrix) }}
    runs-on: ubuntu-latest
    steps:
      - run: echo "Building ${{ matrix.project }}"

Rules

• Use `fail-fast: false` for test matrices — you want to see all failures, not just the first
• Use `include`/`exclude` to fine-tune — don't generate invalid combinations
• Use `max-parallel` if jobs contend for shared resources (APIs, databases)

5. Reusable Workflows

Defining a Reusable Workflow

# .github/workflows/reusable-build.yml
name: Reusable Build

on:
  workflow_call:
    inputs:
      node-version:
        type: string
        default: '22'
    secrets:
      NPM_TOKEN:
        required: true

permissions:
  contents: read

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@<sha>
      - uses: actions/setup-node@<sha>
        with:
          node-version: ${{ inputs.node-version }}
          registry-url: https://registry.npmjs.org
      - run: pnpm install --frozen-lockfile
      - run: pnpm build
        env:
          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}

Calling a Reusable Workflow

jobs:
  build:
    uses: ./.github/workflows/reusable-build.yml
    with:
      node-version: '22'
    secrets:
      NPM_TOKEN: ${{ secrets.NPM_TOKEN }}

Rules

• Pass secrets explicitly — avoid secrets: inherit (grants broader access than needed)
• Pin reusable workflows to SHA or tag in production
• Use `workflow_call` inputs for all configuration — don't rely on env or file conventions
• Separate concerns: reusable workflows = entire jobs; composite actions = reusable steps

6. Artifacts (v4)

# Upload
- uses: actions/upload-artifact@<sha> # v4
  with:
    name: build-output
    path: dist/
    retention-days: 7
    compression-level: 6

# Download (in a different job)
- uses: actions/download-artifact@<sha> # v4
  with:
    name: build-output
    path: dist/

Rules

• v4 artifacts are immutable — you cannot overwrite the same artifact name
• Use unique names per job — don't upload from parallel matrix jobs to the same name
• Set `retention-days` — don't rely on org defaults (storage costs add up)
• Use `compression-level: 0` for already-compressed files (.zip, .tar.gz)
• v3 and v4 are incompatible — do not mix upload-artifact@v3 with download-artifact@v4

7. Environment Protection

jobs:
  deploy:
    runs-on: ubuntu-latest
    environment:
      name: production
      url: https://myapp.example.com
    steps:
      - run: echo "Deploying to production"

• Use `environment:` for production deployments — enables approval gates
• Configure required reviewers in repo Settings → Environments
• Use environment-scoped secrets — production secrets should not be accessible in CI

8. Anti-Patterns (Never Do These)