Skill-local scripts (scripts/workflow_gen.py) are stdlib-only and run base-directory-relative with python3 (py -3 on Windows).

GitHub Actions Workflow Writing

Write production-ready GitHub Actions workflows with security and performance built in.

When to Use

• Creating new CI/CD workflows
• Optimizing slow or expensive workflows
• Adding deployment pipelines
• Security scanning and compliance
• Debugging workflow issues

Run modes

Invoked as <generate|optimize|troubleshoot> [workflow file]. For the full
rubric per mode, read refs/actions-rubric.md (relative to this skill's base directory)
— security/performance checklists, stack detection, and output format. Then
apply it directly:

• generate: detect the project stack first
  (ls package.json pyproject.toml Cargo.toml go.mod pom.xml 2>/dev/null),
  then produce complete workflow YAML.
• optimize: read the target workflow file, apply the optimization
  checklist, return annotated diff.
• troubleshoot: run gh run list --status failure --limit 1, fetch logs
  (gh run view {id} --log-failed), diagnose root cause inline.

Security-First Principles

Every workflow should follow these rules:

1. Explicit Permissions

# ALWAYS declare permissions explicitly
permissions:
  contents: read  # Minimum needed

# NEVER use write-all or leave permissions implicit

2. Pin Action Versions

# Good - pinned to SHA
uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608  # v4.1.0

# Acceptable - pinned to major version
uses: actions/checkout@v4

# Bad - unpinned
uses: actions/checkout@main

3. Sanitize Inputs

# NEVER interpolate untrusted input directly
run: echo "${{ github.event.issue.title }}"  # DANGEROUS

# Use environment variables instead
env:
  TITLE: ${{ github.event.issue.title }}
run: echo "$TITLE"  # Safe

Core Patterns

Full copy-paste templates live in refs/templates.md. Quick reference:

Template	Key shape	See
Minimal CI	permissions: contents: read + concurrency + actions/setup-node@v4 cache	refs/templates.md § Node.js CI
Multi-Environment Deploy	Deploy job with environment: approval gates + OIDC-based AWS auth	refs/templates.md § Deploy to AWS (OIDC)
OIDC for Cloud (No Secrets)	permissions: id-token: write + aws-actions/configure-aws-credentials@v4	refs/templates.md § Deploy to AWS (OIDC)
Docker build/push	docker/setup-buildx-action + docker/build-push-action with GHA cache	refs/templates.md § Docker Build and Push
Security scanning	CodeQL on schedule + push, security-events: write permission	refs/templates.md § Security Scanning

Performance Optimization

1. Caching

# Node.js (built into setup-node)
- uses: actions/setup-node@v4
  with:
    cache: 'npm'

# Python
- uses: actions/setup-python@v5
  with:
    cache: 'pip'

# Custom cache
- uses: actions/cache@v4
  with:
    path: ~/.cache/my-tool
    key: ${{ runner.os }}-my-tool-${{ hashFiles('**/lockfile') }}

2. Concurrency Control

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true  # Cancel stale runs

3. Path Filtering

on:
  push:
    paths:
      - 'src/**'
      - 'package.json'
    paths-ignore:
      - '**.md'
      - 'docs/**'

4. Matrix Strategy

strategy:
  matrix:
    node: [18, 20, 22]
    os: [ubuntu-latest, windows-latest]
  fail-fast: false  # Don't cancel others on failure

Common Mistakes

Mistake	Fix
No timeout	Add timeout-minutes: 15
No concurrency	Add concurrency group
Implicit permissions	Declare explicitly
pull_request_target misuse	Use pull_request unless you need write access
Unpinned actions	Pin to SHA or major version
Direct input interpolation	Use env vars

Workflow Generation

When generating workflows, follow this checklist:

1. Detect stack - Check for package.json, requirements.txt, Cargo.toml, etc.
2. Set permissions - Start with contents: read, add only what's needed
3. Add caching - Use built-in cache options when available
4. Set timeout - Default 10-15 min for CI, 30 for deploys
5. Add concurrency - Cancel stale runs
6. Document secrets - Comment required secrets at top

References

• refs/actions-rubric.md - Generate/optimize/troubleshoot rubric with checklists
• refs/security.md - Detailed security practices
• refs/templates.md - Copy-paste templates
• refs/troubleshooting.md - Common errors and fixes