> ## Documentation Index
> Fetch the complete documentation index at: https://docs.open-harness.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

> Build capable, general-purpose AI agents in code

OpenHarness is an open-source framework for building general-purpose AI agents programmatically. Built on [Vercel's AI SDK](https://sdk.vercel.ai), it provides the building blocks inspired by Claude Code, Codex, and similar advanced agent harnesses — but in a lightweight, composable form you can use in your own applications.

## Why OpenHarness?

Agent harnesses like Claude Code, Codex, and OpenCode are powerful general-purpose agents. While their creators offer SDKs (Claude Agent SDK, Codex App Server, etc.), these are heavy to use programmatically.

OpenHarness gives you the same building blocks — multi-step tool loops, subagent delegation, context compaction, streaming UI integration — as composable primitives you control entirely in code.

## Key Features

<Columns cols={2}>
  <Card title="Stateless Agents" icon="robot">
    Agents are pure executors: pass in history, get back events. Full control over conversation state.
  </Card>

  <Card title="Composable Middleware" icon="layer-group">
    Add compaction, retry, persistence, and hooks as independent, composable layers.
  </Card>

  <Card title="Subagent Delegation" icon="sitemap">
    Agents can spawn child agents for subtasks, with configurable nesting depth and background execution.
  </Card>

  <Card title="Provider Abstraction" icon="plug">
    Filesystem and shell access through swappable providers — run locally, in sandboxes, or in the cloud.
  </Card>

  <Card title="MCP Integration" icon="server">
    Connect to Model Context Protocol servers for external tools via stdio, HTTP, or SSE transports.
  </Card>

  <Card title="AI SDK 5 UI Streaming" icon="display">
    Stream agent sessions directly to React or Vue chat UIs with typed data parts.
  </Card>
</Columns>

## Quick Example

```typescript theme={"dark"}
import { Agent, createFsTools, createBashTool, NodeFsProvider, NodeShellProvider } from "@openharness/core";
import { openai } from "@ai-sdk/openai";

const agent = new Agent({
  name: "dev",
  model: openai("gpt-5.4"),
  tools: {
    ...createFsTools(new NodeFsProvider()),
    ...createBashTool(new NodeShellProvider()),
  },
  maxSteps: 20,
});

for await (const event of agent.run([], "Refactor the auth module")) {
  if (event.type === "text.delta") process.stdout.write(event.text);
}
```