actions

GitHub Actions

Activate when creating, modifying, troubleshooting, or optimizing GitHub Actions components. This skill covers action development, marketplace integration, and best practices.

Action Types

JavaScript Actions

Execute directly on runners with fast startup and cross-platform compatibility.

Structure:

my-action/
├── action.yml        # Metadata and interface
├── index.js          # Entry point
├── package.json      # Dependencies
└── node_modules/     # Bundled dependencies

Key Requirements:

• Use @actions/core for inputs/outputs
• Use @actions/github for GitHub API access
• Bundle all dependencies (use @vercel/ncc)
• Support Node.js LTS versions

Current toolkit majors are ESM-only — @actions/core 3.x, @actions/github 9.x, @actions/exec 3.x, @actions/cache 6.x. Each publishes "type": "module" with an exports map offering only an import condition, so require('@actions/core') throws ERR_PACKAGE_PATH_NOT_EXPORTED even on node24: Node's require(esm) finds no require or module-sync condition to match. Set "type": "module" in the action's package.json and use import — ncc emits an ES module automatically inside such a package boundary, so the bundling step below is unchanged. An action that cannot migrate must use dynamic await import(...).

Example action.yml:

name: 'My JavaScript Action'
description: 'Performs custom task'
inputs:
  token:
    description: 'GitHub token'
    required: true
  config:
    description: 'Configuration file path'
    required: false
    default: 'config.yml'
outputs:
  result:
    description: 'Action result'
runs:
  using: 'node24'
  main: 'dist/index.js'

Docker Container Actions

Provide consistent execution environment with all dependencies packaged.

Structure:

my-action/
├── action.yml
├── Dockerfile
├── entrypoint.sh
└── src/

Key Requirements:

• Use lightweight base images (Alpine when possible)
• Set proper file permissions
• Handle signals gracefully
• Output to STDOUT/STDERR correctly