---
title: "Install LemmaScript"
description: "Two ways in: the npm package plus the agent skills, or the source kit with everything bundled."
last_updated: 2026-07-20
---

# Install LemmaScript

Two ways in. Use the package if you're **using** LemmaScript; take the kit if you're **changing** it.

## Option A — the package

The standard setup: the `lsc` toolchain from npm, plus the skills that teach your agent to drive it.

1. **Check the prerequisites** — Node ≥ 18, [Dafny ≥ 4.x](https://dafny.org/latest/Installation) (the engine that does the checking), and git.

   ```sh
   node -v          # ≥ 18
   dafny --version  # ≥ 4.x
   ```

2. **Install the package** — one global install puts `lsc` (and companions like `lsc claimcheck`) on your PATH.

   ```sh
   npm install -g lemmascript
   ```

3. **Add the skills** — mount the skills repo at your agent's skills directory (e.g. `.claude/skills` for Claude Code). Your agent picks them up and drives the whole loop itself.

   ```sh
   git clone https://github.com/midspiral/lemmascript-skills <your/skills/dir>
   ```

4. **Check something** — point it at a file or your whole project.

   ```sh
   lsc check --backend=dafny path/to/file.ts
   ```

## Option B — from source: lemmascript-kit

Working on the toolchain itself, or want the tools and skills pinned together? The kit bundles the toolchain source and the skills as git submodules — one clone, one setup script, skills already in place.

```sh
git clone --recurse-submodules https://github.com/midspiral/lemmascript-kit.git
cd lemmascript-kit
./setup.sh
```

Run the same commands straight out of the source tree (the skills write the CLI as `npx lsc`; in the kit, substitute this form or `npm link` the package):

```sh
npx tsx LemmaScript/tools/src/lsc.ts check --backend=dafny path/to/file.ts
```

The kit already mounts the skills at `.claude/skills/` — no separate step.

## Next

- [Documentation](https://docs.lemmascript.org)
- [Ecosystem](https://lemmascript.org/ecosystem.md)

## Sitemap

- [All pages](https://lemmascript.org/sitemap.md)