Local by default
Agents, files, commands, and model keys stay on your computer. The Runtime listens only on 127.0.0.1 and accepts calls only from local origins.
Saturn App · Open source · Free
A desktop AI agent that runs on your computer. Free, open source, yours.
Saturn App is a local agent for macOS and Windows. Connect your own models and MCP servers, give it a workspace, and let it read, write, run, and browse — on your machine, under your rules. No subscription, no telemetry, no lock-in.
MIT licensed. Works offline with local models. Connects to Saturn MCP when you want governance.
$ git clone \ https://github.com/Saturn-Technology-Project/Saturn-App.git $ cd Saturn-App $ npm install --prefix runtime $ npm install --prefix desktop $ npm run desktop Saturn Runtime listening on 127.0.0.1:4700 Saturn Desktop ready
macOS and Windows (x64). Packaged builds include the Runtime — no separate Node install needed.
Bring your own model
Use OpenAI, Claude, Gemini, or a local model through LM Studio. Switch per agent. Keys are stored in a local credential broker and never returned to the UI.
Free and open source
MIT licensed, built in the open. Read the code, build it yourself, or ship it inside your organization. There is no paid tier for the App.
Everything an agent needs, built in.
Saturn App ships with a complete agent runtime. You add models and tools.
01 / Two processes, one app
A desktop shell and an independent local runtime
- Saturn Desktop is the window: sign in, chat, connect models and MCP servers, read logs
- Saturn Runtime is the core: it calls models, runs skills, connects to MCP, and stores state
- Desktop talks to Runtime only over http://127.0.0.1:4700 — Runtime also runs headless
- Clean architecture: domain rules never depend on Electron, Express, or React
02 / Built-in skills
Files, code, web, and MCP out of the box
- files — list, read, write, or patch files in the workspace with structured patches
- code — run commands in the workspace and capture the result
- web — read public web pages; local and private addresses are refused
- mcp and multi_step — call attached MCP tools and keep a step-by-step plan
03 / Your MCP servers
Attach any MCP server, including Saturn MCP
- Connect local or remote MCP servers to any agent
- Tools from every server appear in one catalog per agent
- Point the App at Saturn MCP to get tool sets, policies, and approvals on top
- The same agent works with or without the gateway
04 / Safe by construction
A confined workspace and a local credential broker
- All file and command access stays inside the workspace directory
- Model API keys live in the local credential broker; the API never returns the secret
- Private and link-local addresses are blocked for web access
- Every run can be stopped, and every turn is logged locally
Requirements
Platforms
macOS and Windows (x64). Packaged builds include the Runtime — no separate Node install needed.
Models
OpenAI, Claude, Gemini, LM Studio (local).
Data
Stored in ~/.saturn-app by default. Override with SATURN_DATA_DIR.
License
MIT. Copyright Prism Capital LLC.
Download the source, build it, run it.
Saturn App is free for everyone. Star the repository, open an issue, or send a pull request.