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

# Control Modes

> How AgentOS connects to and controls target machines — Host Mode vs Companion Mode.

AgentOS operates in two control modes that determine *how* it connects to and controls a target machine. Both modes expose the same core concepts (screenshots, input, automation) — but the connection method differs.

## Host Mode

AgentOS runs directly **on the target machine** as software. It controls the desktop via OS-level APIs.

* Agent code and AgentOS run on the same machine (or connect over the network).
* Full access to OS-level features: window management, process control, multi-display support.
* Can run as a [Windows service](/06-agent-os/installation/service) for SYSTEM privileges, RDP resilience, and logon screen control.
* Supports Windows, macOS, and Linux.

**Best for:** Desktop automation, CI/CD pipelines, enterprise VMs.

## Companion Mode

AgentOS runs on an **external device** and controls the target through hardware interfaces. No software needs to be installed on the target.

* Input is sent via USB or Bluetooth HID (keyboard and mouse emulation).
* Screen capture happens via HDMI-to-USB capture devices.
* Mobile devices are controlled via ADB (Android) or IDB (iOS, planned).

**Best for:** Locked-down environments, embedded systems, kiosks, mobile devices, and any target where you cannot install software.

## Comparison

|                          | Host Mode             | Companion Mode                                                       |
| ------------------------ | --------------------- | -------------------------------------------------------------------- |
| **Where AgentOS runs**   | On the target machine | On an external device                                                |
| **Connection to target** | OS-level APIs         | Hardware (USB, Bluetooth, HDMI) or device bridge (ADB/IDB)           |
| **Software on target**   | Required              | Not required                                                         |
| **OS service support**   | Yes (Windows)         | No                                                                   |
| **Platform support**     | Windows, macOS, Linux | Any device with USB/HDMI/Bluetooth; Android (ADB), iOS (IDB planned) |

For a detailed breakdown of what each mode can do, see [Capabilities](/06-agent-os/understanding/capabilities).

## What's Next?

<CardGroup cols={2}>
  <Card title="Capabilities" icon="list-check" href="/06-agent-os/understanding/capabilities">
    Full list of capabilities by control mode.
  </Card>

  <Card title="Deployment" icon="sitemap" href="/06-agent-os/how-to-guides/deployment-scenarios">
    Find the right setup for your target.
  </Card>

  <Card title="Runtime Modes" icon="toggle-on" href="/06-agent-os/understanding/runtime-modes">
    Standalone vs OS service — choose the right runtime.
  </Card>

  <Card title="Install as Service" icon="server" href="/06-agent-os/installation/service">
    Set up AgentOS as a Windows service for CI/CD and enterprise.
  </Card>
</CardGroup>