Self-hosted agent runtime

Define once. Run anywhere.

nui is a self-hosted agent runtime: define agents declaratively in ADL, run them on any harness or model — Claude Code, Codex, OpenCode, pi, Antigravity, hosted APIs, or free local models via Ollama — and reach them from a web UI, the CLI, or a REST/AG-UI/MCP API. Extensions add new harnesses, tools, and storage without touching nui's own code.

Install View on GitHub
nui web UI showing a chat session with an AI agent.

Built-in agents

nui Claude Code pi codex opencode Antigravity Anthropic API OpenAI Gemini OpenRouter Ollama

Access anywhere

Web UI, CLI, API, and MCP — same backend.

The chat UI is one client of the nui server, not a privileged one. Type a task on the home screen and the nui master agent routes it to the right specialist — or drive the same agents headlessly with nui run, over REST/AG-UI, or as MCP tools from Cursor and Claude Desktop.

Explore features → 
# Start the server and open the UI
nui server --open

# Launch with a specific agent and prompt
nui server -a claude-code -m "Review the README" -w . --open

Define in ADL

Declarative agents, workflows, councils, and evals.

Define custom agents in YAML with the Agent Definition Language — pick a harness, set a system prompt, compose workflows or sub-agents, and run locally, in sandboxes, Docker, or on remote servers. Same definition, swap the model for cost.

ADL and custom agents → 
name: Review Agent
harness:
  type: claude-code
  sandbox: none
systemPrompt: |
  You are a code reviewer. List issues by severity and suggest fixes.

Extend everything

Platform-grade extensions — without forking nui.

Install extensions via extension.yaml from a local dir, zip, or git URL. Contribute harnesses, MCP servers, skills, HITL channels, storage backends, and deployers. Built-in harnesses use the same contribution path as third-party ones.

Extensions → 
nui extension add ./my-extension
nui extension add https://github.com/example/my-extension.git

MCP integration

Expose nui to Cursor, Claude Desktop, and other MCP hosts.

Run nui mcp to expose agent tools to external MCP clients. nui also injects built-in MCP servers into harnesses for human-in-the-loop prompts, inline visualizations, agent memory, and home-launcher routing.

MCP integration → 
{
  "mcpServers": {
    "nui": {
      "command": "nui",
      "args": ["mcp"],
      "env": { "NUI_URL": "http://127.0.0.1:8080" }
    }
  }
}

Operate like software

Headless runs, schedules, and evals.

Use nui run for headless agent execution against a running server. Schedule recurring runs with nui schedule. Regression-test ADL agents with nui agent eval — no browser required.

CLI reference → 
# Headless run (server must be running)
nui run -a claude-code -m "Review README" -w . --wait

# Auto-start server if not running
nui run -m "Summarize changes" -w . --spawn --wait

First run

Install and try it in two minutes.

Install the CLI with the one-liner below, or download the desktop app from GitHub Releases (it bundles the CLI and installs it on first launch).

curl -fsSL https://nui.plmbr.dev/install.sh | sh

  1. Install. Run the curl one-liner above, or grab the desktop package / CLI archive from GitHub Releases.
  2. Start. Run nui server (listens on :8080), or open the desktop app.
  3. Open the UI. Pick an agent and a working directory. nui creates a session on first launch.
  4. Chat. Send a prompt, attach files, or use @ mentions for context.

Full install guide →