Ergon
Ergon is an installable agent plugin and CLI containing a curated set of portable software-development skills. Install the whole team as a managed plugin in Codex, Claude Code, or Antigravity, or use the CLI when you intentionally want project-local files for Cursor, Windsurf, and other runners. Everything works without telemetry.
Install as a plugin
The GitHub repository is a marketplace, so agents can install Ergon straight from EJDonato/Ergon.
Codex
codex plugin marketplace add EJDonato/Ergon
codex plugin add ergon@ergon-marketplace
Start a new Codex chat, then ask for a workflow naturally or invoke a persona skill such as $ergon:cyra, $ergon:kael, or $ergon:aegis. Codex enforces plugin:skill identities and uses $ for explicit skill invocation, so $ergon:cyra is its platform-native equivalent of Antigravity's /ergon-cyra.
Claude Code
claude plugin marketplace add EJDonato/Ergon
claude plugin install ergon@ergon-marketplace
Start a new Claude Code session. Skills are available as /ergon:cyra, /ergon:kael, /ergon:aegis, and the other persona names listed below.
For local development, either host can load the checked-out repository directly through its local plugin workflow; Claude Code also supports claude --plugin-dir ..
Antigravity
Ergon includes a native Antigravity plugin bundle at .agents/plugins/ergon. After downloading or cloning this repository, install that bundle globally:
agy plugin install /absolute/path/to/Ergon/.agents/plugins/ergon
In Antigravity, you can instead open /plugin, choose Install from local directory, and select the same folder. The plugin manager stages and manages the bundle globally rather than generating skills in the current project.
Start a new Antigravity session. The plugin provides /ergon-cyra, /ergon-juno, /ergon-orion, /ergon-kairos, /ergon-kael, /ergon-iris, /ergon-argus, /ergon-aegis, and /ergon-foundation.
Direct installation from Antigravity's Discover marketplace requires the plugin to be accepted into Google's curated marketplace. The repository bundle is ready for that submission; until it is listed, use Install from local directory.
Install with the CLI
npx --yes --package github:EJDonato/Ergon ergon init --runner codex
npx --yes --package github:EJDonato/Ergon ergon add foundation --runner claude
npx --yes --package github:EJDonato/Ergon ergon add backend --runner cursor
npx --yes --package github:EJDonato/Ergon ergon list
The unscoped npm name ergon belongs to an unrelated package. The explicit GitHub package source above guarantees that npx runs this repository from any project directory.
When --runner is omitted, Ergon detects existing .claude, .codex, Antigravity .agents/skills or .agents/workflows, and .cursor configuration. If no marker is found in an interactive terminal, it asks which runners to configure. In CI or another non-interactive shell, pass --runner explicitly.
Existing files are preserved by default. Pass --force to replace generated skill files:
npx --yes --package github:EJDonato/Ergon ergon add market --runner codex --force
Included skills
| CLI skill | Persona | Managed plugin identity | Purpose |
|---|---|---|---|
market | Cyra | ergon:cyra | Market, audience, competitors, and positioning |
prd | Juno | ergon:juno | Scoped product requirements and acceptance criteria |
arch | Orion | ergon:orion | Architecture, schemas, contracts, and tradeoffs |
plan | Kairos | ergon:kairos | Dependency-aware implementation tasks |
foundation | Cyra → Juno → Orion → Kairos | ergon:foundation | Complete four-pass project foundation |
backend | Kael | ergon:kael | Server, persistence, validation, and integrations |
frontend | Iris | ergon:iris | Responsive and accessible product interfaces |
qa | Argus | ergon:argus | Unit, integration, and end-to-end quality coverage |
sec | Aegis | ergon:aegis | Read-only application security audits |
ergon add foundation installs the four individual foundation personas and the composite pipeline. ergon add specialists installs all four implementation specialists. ergon init installs all nine skills.
Runner outputs
| Runner | Generated path |
|---|---|
| Claude Code | .claude/commands/<skill>.md |
| Codex CLI | .codex/skills/<skill>/SKILL.md |
| Antigravity | Managed ergon plugin with skills/ergon-<persona>/SKILL.md |
| Cursor / Windsurf | .cursor/rules/<skill>.mdc |
Commands
ergon init [--runner <runner>] [--force]
ergon add <skill-or-bundle> [--runner <runner>] [--force]
ergon list
ergon --help
Supported runner IDs are claude, codex, agy, and cursor.
Plugin layout
The repository root is a portable Agent Plugins package. plugin.json is the portable manifest, .codex-plugin/plugin.json and .claude-plugin/plugin.json provide host compatibility, and skills/<persona>/SKILL.md contains the portable skills. The Codex and Claude marketplace catalogs are committed under .agents/plugins/ and .claude-plugin/. Antigravity's strict native bundle lives at .agents/plugins/ergon/ with its own manifest and hyphenated persona skill names.
The nested skills/foundation/* and skills/specialists/* files remain the canonical registry consumed by the npm CLI. Tests keep the plugin skill bodies synchronized with those source prompts.
Development
The CLI supports Node.js 18 or later. Developing and running the current test toolchain requires Node.js 20 or later.
npm install
npm run typecheck
npm test
npm run build
node bin/ergon.js list
Canonical skills live in skills/ as a skill.yaml manifest plus prompt.md. The CLI validates manifests, transforms prompts through runner adapters, and uses collision-safe atomic writes. It performs no telemetry or network access for bundled skills.
License
MIT