Download & install

Fettle runs in whatever shape fits your workflow — one engine, many surfaces. Cross-platform by construction: the CLI is plain Node, so Windows, macOS and Linux use the same commands.

1 · Install the Codex CLI (the engine)

Fettle drives OpenAI Codex to do the fixing. Install it, then sign in with your ChatGPT plan or an API key.

Windows

powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"

macOS / Linux

curl -fsSL https://chatgpt.com/codex/install.sh | sh

Verify with codex --version. Codex is included across ChatGPT plans (or use an OpenAI API key).

2 · Get Fettle in the form you want

CLI

Command line

The core tool. Runs anywhere Node 18+ runs — same command on every OS.

npm install -g fettle

fettle check

Skill

Codex / Claude skill

Drop the SKILL.md into your agent so it can run Fettle on demand.

cp -r skills/fettle ~/.codex/skills/

# then: “use fettle to check my agents”

Web

Web dashboard

Self-host the maintenance dashboard for your team.

cd web && npm install

npm run dev   # http://localhost:3000

From source

git clone https://github.com/Vector897/Fettle.git

cd Fettle/cli && npm install && npm run build && npm link

fettle check