---
title: Claude Code Plugin
summary: Scaffold, run, and verify a FastYoke app from inside Claude Code. One command spins up a working workflow app on the local runtime and drives a first state transition through the real engine.
order: 1
---

# Claude Code Plugin

The FastYoke Claude Code plugin turns a one-line description into a working
FastYoke app — scaffolded, running on the local runtime, with a first
workflow transition already verified — without leaving your terminal.

It is distributed as a Claude Code **marketplace** from the public
[built-on-fastyoke](https://github.com/fastyoke/built-on-fastyoke) gallery,
and it drives the same [local runtime](/docs/getting-started/run-modes) and
[SDK](/docs/sdk) you'd use by hand.

## What it does

- **`/fy-new-app`** — describe an app in one line ("a vacation-approval
  workflow", "a support-ticket queue") and the plugin scaffolds the entity
  schema, the FSM, and seed data, boots it on the local runtime, and fires a
  first transition so you see the state machine actually move before you
  write any code.
- **Authoring skills** — bundled guidance Claude pulls in on demand for the
  four things you'll actually do: authoring FSMs, authoring schema-driven
  entities and their UI, using the SDK, and writing sandboxed WASM scripts.
- **App reviewer** — an on-demand reviewer agent that reads a FastYoke app
  and flags workflow mistakes: unreachable states, transitions pointing at
  states that were never declared, unbounded self-loops, and guards written
  as raw strings instead of sandboxed predicates.
- **Save-time validation** — a hook that validates FSM schema files as you
  write them, catching the same class of mistakes inline so a broken
  workflow never reaches the runtime.

Everything runs locally against the real FastYoke engine — no cloud account
is required to scaffold, run, and iterate.

## Install

::callout{type="info" title="Prerequisites"}
[Claude Code](https://claude.com/claude-code) and Node.js. The plugin uses
the `fastyoke` local runtime from npm; the scaffold flow installs it for you
on first run.
::

1. Add the marketplace:
   ```
   /plugin marketplace add fastyoke/built-on-fastyoke
   ```
2. Install the plugin:
   ```
   /plugin install fastyoke
   ```
3. Scaffold your first app:
   ```
   /fy-new-app
   ```

Already have the [gallery](https://github.com/fastyoke/built-on-fastyoke)
checked out locally? Point the marketplace at the path instead:
`/plugin marketplace add /path/to/built-on-fastyoke`.

## How the scaffold runs

The generated app installs **as data**: a `seed.json` carries the entity
kinds, the FSM schema, and a starting job row. `npx fastyoke dev` boots a
local HTTP runtime, and the plugin drives transitions through the standard
jobs API — the same shape the [SDK](/docs/sdk/reference) and
[CLI](/docs/cli) speak. Guards are sandboxed JSONLogic evaluated against the
job's data payload, exactly as they are in production, so what you verify
locally is what runs in the cloud.

## See also

- [Built on FastYoke](/oss) — the open-source gallery of example apps the
  plugin's marketplace is published from.
- [SDK](/docs/sdk) and [CLI](/docs/cli) — the same runtime surface the
  plugin builds on, for driving apps by hand.
- [VS Code Extension](/docs/vscode) — author and preview `fy-app.json` in
  your editor.
- [Workflows](/docs/workflows) — how FSMs, guards, and transitions fit
  together.