# Lampson — an open-source AI coding agent that lives in your project

> Terminal or browser, any OpenAI- or Anthropic-compatible model, and tools that cannot leave your repo by construction. Lampson is a coding agent written entirely in Synsema.

Published 2026-09-02 · https://synsema.org/blog/lampson-open-source-ai-coding-agent


Lampson is a coding agent you point at a folder. It reads, edits and runs code, asks before anything
risky, and works from the terminal or a browser tab. It is free, open source, and written in Synsema
from the first line — which is why it can promise things most agents cannot.

## Two commands

```sh
npm i -g lampson          # or the one-line installer for Windows, macOS, Linux
cd your-project
lampson                   # terminal · lampson --web → http://127.0.0.1:8080
```

Pick a provider on first run: DeepSeek, Anthropic, OpenAI, Groq, Ollama, MiniMax, OpenRouter — one
line in `.env` to switch.

## Confined by the language, not by a prompt

Every Lampson tool declares its capabilities, and the Synsema runtime enforces them: file tools can
only touch the mounted project (absolute paths, `..` and sibling folders are refused before the
tool runs), the shell runs from the project root, and a destructive system command is refused in
every mode. Permission modes are yours: `ask` (approve dangerous commands), `yolo`, `strict`.

## What comes in the box

- **Sub-agents** that run in parallel on real threads, with their own context and a restricted
  toolset, or in the background with the report landing in the parent's inbox.
- **Scheduled tasks** — "every morning run the tests and tell me" — with approvals you answer from
  your phone through one-time links.
- **Plugins** in any language, off by default until you switch them on; **MCP servers** with the
  JSON you already have; language servers for real go-to-definition; project memory it rereads
  next session; a real terminal in the browser.

## Why Synsema

A harness is a server, a tool runner, a permission system, a process supervisor and a UI. In Synsema
those are language features — `serve`, `proc_spawn`, capabilities, agents on threads, `approve` —
so the whole of Lampson fits in a codebase one person can read. Lampson is the proof that the
language is enough for a real agent.

**Try it:** [lampson.org](https://lampson.org) has the quickstart and the docs. If you would rather
see the language first, [try.synsema.org](https://try.synsema.org) runs it in your browser.