Ghost

The computer-use layer for AI agents, on Windows and Linux. Ghost lets an agent operate any desktop app - including the ones with no API - in the background without taking your screen or cursor, and it proves every action actually happened.

Like Playwright, but for native desktop apps, and built for agents: an MCP server any model can mount to see and drive the desktop.

One MCP surface, two engines: Win32 UI Automation on Windows, AT-SPI2 over D-Bus on Linux. The verbs, the locator tiers and the act-then-verify loop are written once and behave the same on both. Platform support · Linux setup

Why Ghost is different

• Runs in the background, and that is enforced. An agent can click, type, and use shortcuts inside an app while you keep working in another window - no focus steal, no cursor jump. It posts window messages to real controls; most tools can only drive whatever is in the foreground. Since 0.19 this is a policy, not a preference: the focus policy defaults to background, and every call that could only work by grabbing your cursor or foreground window fails with an error naming the action instead of quietly taking the screen. Raise it per target with ghost_set_focus_policy when you actually want real input. (how)
• Many agents at once. Requests are dispatched in parallel, so a 15-second wait in one tab does not stall an instant query behind it, and a second Ghost process runs its own browser alongside the first without contending for the mouse.
• Prove it on your machine. ghost verify drives the real MCP server over stdio and audits every claim above against hard timing budgets, exiting non-zero if any of them does not hold on your hardware.
• Every action is verified. Ghost re-checks the screen (or reads the control's value back) after acting and returns verified / focus_confirmed - never a blind ok:true. Agents fail by acting and not knowing if it worked; Ghost closes that loop.
• Drives apps with no API. Legacy Win32, WPF, Electron, UWP, vendor portals - the software that has no integration and most needs automating. No CDP, no browser, no app cooperation required.
• Model-agnostic. Vision grounding works with any OpenAI-compatible model (NVIDIA, OpenAI, Gemini, Groq, local vLLM/Ollama) or Anthropic. No vendor lock-in.
• Accessibility-native and deep. Real element discovery through the OS's own accessibility API - UI Automation on Windows, AT-SPI2 on Linux - not pixel-guessing. Elements come back with real names, roles and bounds.

See it in one script: examples/background_agent_demo.py drives an app in the background while the foreground stays yours. Honest comparison vs Playwright-MCP / cua-driver / Computer Use: docs/comparison.md.

What is Ghost?

Ghost gives you programmatic control over any desktop application - native Win32, Electron, WPF, UWP, GTK, Qt, or otherwise.

On Windows it uses UI Automation for element discovery, SendInput for keyboard/mouse injection, and DXGI/GDI for screen capture. On Linux it uses AT-SPI2 over D-Bus for discovery and actions, XTEST (X11) or the RemoteDesktop portal / uinput (Wayland) for input, and X11 GetImage or the Screenshot portal for capture. The Linux engine is pure Rust - no -devel packages to install.

Ship it three ways:

• ghost CLI - one-shot commands, great for scripts and CI (ghost click --name "Submit")
• ghost-http server - local REST API, call it from Python, Node, curl, anything (curl http://127.0.0.1:7878/list-windows)
• ghost-mcp server - Model Context Protocol server for Claude, Cursor, and any MCP client (54 tools on Windows)

The MCP surface is 20 desktop verbs, 19 ghost_browser_* / ghost_tab_* tools for driving individual browser tabs in the background (Chrome, Comet, Edge, Brave), and 15 Windows-only tools: the focus policy plus ghost_desktop_*, which runs an app on an isolated Windows desktop the user never sees. UIA and capture work fully there. Input is limited to what an app accepts by window message: real SendInput does not work off the input desktop because Windows refuses it, and typing is proven by reading the control's value back, so a target that drops posted characters returns an error rather than a false success. The desktop verbs and the browser tools build on Linux as well; the focus policy and isolated desktops are Windows-only.

No Claude required. No browser required. No CDP. It drives apps through the OS's own automation and input APIs, so it works with native apps that have no API and no automation hooks of their own - the same reliability whether or not an app was built to be automated.

Platforms

Platform	Status	Engine
Windows	✅ full and verified	ghost-core - Win32 UI Automation, SendInput, posted window messages, DXGI/GDI capture
Linux	✅ functional - X11 + AT-SPI2 verified by live CI tests	ghost-linux - AT-SPI2 over D-Bus, XTEST / RemoteDesktop portal / uinput, X11 GetImage / Screenshot portal
macOS	🚧 scaffold	Accessibility + CGEvent + ScreenCaptureKit - to be built on a Mac

ghost-session and ghost-mcp are shared: the locator tiers, grounding cascade, act-then-verify loop and the 20 core MCP verbs are written once and run on both platforms. Only the engine underneath changes, behind a one-line cfg alias. The browser and tab tools are engine-independent and build for both; the focus policy and isolated desktops are Windows-only and are reported as such rather than faked.

The wedge survives the port. On Windows, driving an app without stealing focus is built on posted window messages. Linux has a cleaner analogue in AT-SPI2 actions: the application performs the operation through its own toolkit, so there is no pointer to move and no window to raise - and it behaves the same under X11 and Wayland. Synthetic input is only the fallback there.

This is tested, not asserted: CI stands up a real desktop (Xvfb + D-Bus + at-spi-bus-launcher), drives a real GTK application, and requires that text written through AT-SPI reads back from the app and that invoking a button actually dismisses the dialog. Wayland portal input and capture are implemented but not yet verified on hardware.

Linux setup, verification checklist and honest limitations: docs/linux-fedora.md. Capability matrix across all three: docs/cross-platform.md.

Ghost is a general-purpose automation tool. Use it on systems you own or are authorized to automate, and in line with the terms of the software you drive.

Install

Option A - Prebuilt binaries (free). Every release ships signed-by-checksum archives for both platforms on the Releases page:

# Linux x86_64
curl -LO https://github.com/NORTHTEKDevs/ghost/releases/latest/download/ghost-linux-x86_64.tar.gz
curl -LO https://github.com/NORTHTEKDevs/ghost/releases/latest/download/ghost-linux-x86_64.tar.gz.sha256
sha256sum -c ghost-linux-x86_64.tar.gz.sha256
tar -xzf ghost-linux-x86_64.tar.gz && ./install.sh

Windows: download ghost-windows-x64.zip from the same page. Verify the checksum, unzip, and add the folder to your PATH. Then run ghost doctor.

Option B - Ready-to-run Windows kit ($20, one-time). Prebuilt Windows binaries (ghost.exe, ghost-http.exe, ghost-mcp.exe) plus a quick-start, MCP config, and examples - no Rust toolchain, runs in two minutes. Every kit is built by scripts/package-kit.ps1, which refuses to package unless the full live desktop suite passes. Get it at northtek.io/ghost.

The binaries are not code-signed, so Windows SmartScreen will warn you on first run (click More info → Run anyway). The kit buys convenience, not capability - everything Ghost can do is in the free source below, and building it yourself takes one command.

Option C - Build from source (free, MIT). Ghost is open source. Compile it yourself:

git clone https://github.com/NORTHTEKDevs/ghost
cd ghost
cargo build --release --bin ghost --bin ghost-http --bin ghost-mcp
# binaries in target/release/

Requirements: Windows 10 build 19041+, or Linux with at-spi2-core (and Rust stable only if building from source).

On Linux:

sudo dnf install at-spi2-core xdg-desktop-portal xdg-desktop-portal-gnome
gsettings set org.gnome.desktop.interface toolkit-accessibility true
./scripts/install.sh          # build, install, register the MCP server, run doctor

No -devel packages are needed - the Linux engine is pure Rust. Full setup and troubleshooting: docs/linux-fedora.md.

Check your machine first:

ghost doctor

Reports PASS/WARN/FAIL and exits 1 if anything is FAIL. Run it before opening an issue - it usually names the problem outright.

• Windows: build version, interactive desktop, UI Automation, DPI awareness, monitor layout, screen capture, optional vision credentials.
• Linux: session type (X11/Wayland), AT-SPI bus reachability, whether applications are actually exposing accessible trees, the selected input backend, and screen capture.

Quick Start - CLI

# Launch Notepad and type into it
ghost launch notepad.exe
ghost focus-window "Notepad"
ghost type --role edit --text "hello from ghost"

# Keys and hotkeys
ghost press Enter
ghost hotkey --mods Ctrl --key s

# Screenshot
ghost screenshot --out shot.png

# Enumerate windows or UI
ghost list-windows
ghost describe --window "Notepad"

# Click at coords or by name
ghost click-at 500 300
ghost click --name "Save"

# Run a JSON intent (finite-state machine with retries, timeouts, conditions)
ghost run my-flow.json
echo '{"ops":[{"op":"launch","exe":"notepad.exe"}]}' | ghost run -

Everything outputs JSON for easy piping into jq or scripts.

Quick Start - HTTP Server

Start the server:

ghost-http --addr 127.0.0.1:7878

Then from any language:

# Bash / curl
curl http://127.0.0.1:7878/list-windows
curl -X POST http://127.0.0.1:7878/click \
  -H 'content-type: application/json' \
  -d '{"name":"Submit"}'
curl http://127.0.0.1:7878/screenshot -o shot.png

# Python
import requests
requests.post("http://127.0.0.1:7878/launch", json={"exe": "notepad.exe"})
requests.post("http://127.0.0.1:7878/type",
              json={"role": "edit", "text": "hello from python"})

// Node
await fetch("http://127.0.0.1:7878/hotkey", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({ mods: ["Ctrl"], key: "s" }),
});

Endpoints: /health, /tools, /click, /click-at, /type, /press, /hotkey, /screenshot, /launch, /list-windows, /focus-window, /window-state, /describe, /clipboard (GET/POST), /run.

Quick Start - Rust SDK

[dependencies]
ghost-session = { git = "https://github.com/NORTHTEKDevs/ghost" }

use ghost_session::{GhostSession, By, session::Region};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let session = GhostSession::new()?;
    session.launch("notepad.exe").await?;
    let edit = session.find(By::role("edit")).await?;
    edit.type_text("hello world")?;
    let png = session.screenshot(Region::full()).await?;
    std::fs::write("screen.png", png)?;
    Ok(())
}

Quick Start - Claude Desktop / MCP

cargo build -p ghost-mcp --release

Add to Claude Desktop config (%APPDATA%\Claude\claude_desktop_config.json):

{
  "mcpServers": {
    "ghost": { "command": "C:/path/to/ghost-mcp.exe" }
  }
}

Works with any MCP client (Claude, Cursor, etc.). 54 tools on Windows (legacy names stay dispatchable): 20 desktop verbs covering see/snapshot/find/act/keys/scroll/drag/clipboard/screenshot/windows/shell/waits/query/run, 19 ghost_browser_* / ghost_tab_* tools, and 15 Windows-only tools for the focus policy and isolated desktops.

Every tool runs on its own task, so a slow call does not block a fast one, and a second Ghost process can run alongside the first. Once it is mounted, run ghost verify to audit that on your own machine.

Shell control (ghost_shell)

Ghost drives GUIs and the command line. ghost_shell runs terminal commands and persistent PowerShell sessions - builds, git, CLIs, file edits on hosts without file tools, or launching apps. op=run is a one-shot (powershell/pwsh/cmd); op=open starts a persistent PowerShell whose variables and cwd survive across op=send calls. Output is merged stdout+stderr, tail-capped for the agent's context window; a timed-out command keeps running and is drained with op=read; ghost_stop kills a runaway.

Spawn a fresh Claude Code session from the agent: ghost_shell op=run cmd='Start-Process wt -ArgumentList "pwsh","-NoExit","-Command","claude"', then drive the new terminal window with ghost_see / ghost_act / ghost_key.

Security: shell access is powerful. Set GHOST_SHELL=off in the server's env to disable the verb entirely - every op then returns a clear refusal, leaving the GUI automation verbs fully usable.

Reliability Model

Desktop automation driven from an MCP client has a hostile focus environment: between tool calls, the client's own terminal usually retakes OS focus. Ghost is built for that:

• ghost_act is atomic - find → act → verify via screen delta. One call, no cross-call race. Under the default background policy it drives the control in place and never raises the window; raise the policy and it additionally brings the target's window to the foreground first (AttachThreadInput, confirmed).
• Every action response is honest: verified (did the screen actually change), focus_confirmed (was the right window foreground), and a warning when either is off - never a blind ok:true. Check verified before re-issuing an action.
• Anchor to a window - ghost_key, ghost_find, and ghost_act all take window; with it, input/resolution is guaranteed to target that window or the call errors. Use it for any multi-window flow.
• Disambiguate duplicates - index selects the nth match when several elements share a name/role (multiple "Close Tab" buttons); responses carry a matches count.
• Read, don't screenshot - ghost_see mode=text extracts a window/page's readable text straight from the accessibility tree: faster and ~10x cheaper in tokens than images.
• Latency is visible: every response carries ms, and escalated: true flags when a find had to pay a network VLM round trip (local tiers: cache → UIA → OCR are all on-device).
• Windows never disappear: minimized windows stay in ghost_window list (with state) and op=focus auto-restores them.
• Stop always works: ghost_stop preempts the in-flight call the moment it arrives (dedicated stdin reader), and Ctrl+Alt+G remains the OS-level kill switch.

Background mode (agent-harness / computer-use)

Agent harnesses (OpenClaw, Hermes/cua-driver, and any MCP client) mount a computer-use tool to let an LLM operate the desktop. Ghost is that tool - and it acts without stealing your focus or moving your cursor, so an agent drives an app while you keep working in another window.

Since 0.19 this is the default and it is enforced. The process-wide focus policy starts at background, and every primitive that could only work by taking the real cursor or foreground window is gated behind it. There is no silent fallback: a call with no background path returns an error naming the action and the policy that would unblock it. Set GHOST_FOCUS_POLICY in the server env, or call ghost_set_focus_policy for a target that genuinely needs real input, and set it back afterwards. ghost_focus_policy reports the current setting.

// Drive Calculator-in-the-background style call:
ghost_act { "background": true, "window": "Character Map",
            "action": "click", "name": "Select", "role": "button" }
// -> { "verified": true, "focus_preserved": true, "cursor_preserved": true, "mode": "background" }

• True background via posted window messages. Real Win32 controls are driven with BM_CLICK / WM_LBUTTONDOWN·UP (click) and WM_SETTEXT (type). These do not activate the window - unlike UIA Invoke/SetValue, whose providers pull the window to the foreground.
• Verified even while occluded. type is confirmed by reading the control's value back; click by a PrintWindow before/after delta that renders a window that isn't visible. Every response carries verified, focus_preserved, cursor_preserved - Ghost never claims a background action it can't confirm.
• Honest about the edge. Windowless controls (UWP/WinUI/Chromium - no window handle) can't be message-posted by any tool. Under the default policy Ghost refuses those rather than reaching for the screen, and the error names the action and the policy that would allow it; raise the policy and it falls back to UIA dispatch, which activates the window, and says so in the response. Classic Win32 line-of-business apps - the software that has no API and most needs automating - drive cleanly in the background.
• Or give it a desktop of its own. ghost_desktop_* runs an app on a separate Windows desktop that is never displayed, so UIA, window messages and capture all work on a window the user cannot see. Real SendInput still does not work there: Windows refuses it off the input desktop, and making that desktop the input desktop would put it on screen. An app that answers only real hardware input needs the foreground policy on your own desktop.

Supports click, type, double_click, right_click, and hover (posted mouse messages), plus ghost_key background=true for single keys (Enter/Tab/F-keys/char via WM_KEYDOWN/WM_CHAR).

The clipboard and edit combos work in the background too - Ctrl+C, Ctrl+X, Ctrl+V, Ctrl+Z and Ctrl+A are sent as the semantic messages an app actually implements (WM_COPY, WM_CUT, WM_PASTE, WM_UNDO, EM_SETSEL) rather than as a posted modifier that apps reading GetKeyState would ignore. Combos outside that set are rejected rather than silently dropped, because posting cannot set the modifier state those apps read; use the foreground policy for them.

Vision is model-agnostic

Description-based grounding works with any tool-capable vision model behind an OpenAI-compatible endpoint - NVIDIA (free default), OpenAI, Gemini, Groq, or a local vLLM / Ollama / LM Studio server - or Anthropic. Point GHOST_VISION_BASE_URL

• GHOST_VISION_MODEL at your endpoint and set GHOST_VISION_API_KEY (a keyless local server needs only the base URL). No vendor lock-in.

Emergency Stop

Press Ctrl+Alt+G at any time to immediately halt every acting call. Read-only queries (ghost_see, ghost_snapshot, ghost_window list) keep answering, so you can still inspect what happened while everything is stopped.

• All queued actions are cancelled
• Any held modifier keys (Shift, Ctrl, Alt) are released immediately
• No stuck keys, no stuck modifier states
• Session-wide since 0.19. The stop is a named kernel event (Local\ghost-emergency-stop-event), so one press halts every Ghost process in your logon session, not just the one that happened to register the hotkey. ghost_reset resumes service, again for all of them.

Element Locators

session.find(By::name("Save")).await?          // by accessible name (substring)
session.find(By::role("edit")).await?          // by UIA control type
session.find(By::role("button")).await?

From the CLI: ghost click --name "Save" or ghost click --role button.

Intents - Declarative Flows

Write reproducible multi-step flows as JSON. The FSM executor supports retries, timeouts, and JSONLogic conditions for abort_if / retry_if.

{
  "ops": [
    { "op": "launch", "exe": "notepad.exe" },
    { "op": "focus_window", "name": "Notepad" },
    { "op": "type", "role": "edit", "text": "hello" },
    { "op": "hotkey", "mods": ["Ctrl"], "key": "s" }
  ]
}

Run with ghost run flow.json, POST /run, or ghost_execute_intent over MCP.

Architecture

ghost-cli     ghost-http     ghost-mcp     Rust SDK
    \            |            /   |           |
     \           |           /    |           |
      +-----> ghost-session <-----|-----------+   ← safe Rust API
              /           \       |
      ghost-core      ghost-linux |               ← one cfg alias picks the engine
          |                |      |
    Win32 UIA,       AT-SPI2 over |               ← ghost-core: SendInput, DXGI/GDI
    posted msgs      D-Bus, XTEST |               ← ghost-linux: portal / uinput
          |                |      |
      Windows OS        Linux     +-> ghost-browser  ← CDP over the DevTools port,
                                                        engine-independent

Supporting crates: ghost-cache (UIA snapshot + delta), ghost-intent (FSM + JSONLogic executor), ghost-ground (the locator tier cascade), ghost-platform (the capability matrix reported per OS).

Vision grounding (Set-of-Marks)

When you locate an element by natural-language description (ghost_find description="the blue submit button", or when a name/text lookup misses and escalates to the VLM), Ghost does not ask the model to guess pixel coordinates - models are unreliable at that (in testing, a plain "give me the coordinates of the equals button" landed ~250px off the target). Instead it uses Set-of-Marks: it overlays numbered badges on the window's detected elements, sends that marked screenshot plus each badge's accessible-name label, and asks the model which number matches. The number maps back to that element's exact rect, so the result is a real on-element coordinate, not a regression guess.

In a live check on Calculator, four descriptions ("the equals button", "the plus button", "the number seven key", "the multiply button") each landed exactly on the correct button - versus ~250px off with coordinate regression.

Honest scope: when detected elements carry accessible names (most apps), the labels do much of the disambiguation; for unlabeled icons the model leans on the badge's visual position/appearance.

Canvas / no-accessibility-tree apps. When the UIA tree is sparse (custom-drawn UIs, remote-desktop surfaces, game canvases), Ghost augments the Set-of-Marks candidates with a built-in CPU classical-CV detector (ghost_ground::cv_detect): edge density → connected components → size/aspect filter, no GPU and no model download. It gives the VLM real boxes to pick from where the accessibility tree has nothing. It is coarser than a trained detector - an optional OmniParser ONNX tier (--features yolo + GHOST_YOLO_MODEL) plugs into the same Set-of-Marks path when a GPU model is available. The CV-marks → VLM-pick end-to-end needs a configured vision key.

Benchmark - task success, not "did the call return ok"

bench/ holds a reproducible end-to-end benchmark: it drives the real ghost-mcp binary through 14 Windows desktop tasks and scores each by re-observing the actual result (does the Calculator display really read 42? is the typed value really present?), never by trusting a tool call's return.

Latest run (see bench/results/latest.md):

14/14 tasks passed (100%), median ~2.7 s per task (full wall-clock incl. app launch) - perception, click/keyboard action+verify, waits, window management (list/minimize/restore), text extraction, disambiguation, flow chaining, clipboard round-trip, structured errors, element screenshots, and value assertions.

And it proves it can fail: --self-test runs deliberately-wrong negative controls (assert the display reads 99 when it reads 42, etc.) and passes only if the harness scores every one as FAIL - so the green run above is a real signal, not a rubber stamp.

Reproduce on any Windows 10/11 machine:

cargo build --release -p ghost-mcp
python bench/run_bench.py             # exit 0 iff every task passed
python bench/run_bench.py --self-test # exit 0 iff the harness caught every planted failure

Reliability soak

bench/soak.py drives many act-then-verify cycles and gates on the signals unit tests can't see: how often verified comes back null/false, focus-loss rate, error rate, whether each action's real effect happened (the display is re-observed, never trusted from the return), and latency percentiles.

Latest (160 acts): PASS - verify-null 0.0, focus-loss 0.0, effect-mismatch 0 (100% correct), p50 85ms / p95 117ms. See bench/results/soak.md.

python bench/soak.py                  # exit 0 iff every reliability threshold holds
python bench/soak.py --cycles 250     # ~1000 acts
python bench/soak.py --self-test      # exit 0 iff the harness flags a planted-wrong effect

We deliberately publish only Ghost's own measured numbers - never invented columns for other tools. bench/README.md gives an honest protocol for comparing against Playwright-MCP / Computer Use / UI-TARS, and explains why a naive same-suite comparison isn't apples-to-apples (Playwright is browser-only; vision agents need an API + VM).

Microbenchmarks

Operation	Measured
Region capture, GDI, any size	~16.5 ms
Region capture, DXGI, 1600x900	~70-83 ms
BGRA→RGBA convert, 400x300 region	~206 µs
JSONLogic eq/var	32.2 ns
Intent compile (3op)	1.49 µs

End-to-end capture measurement (release, tests/capture_latency_probe.rs) corrected the v0.10.0 assumption: the DXGI acquire dominates and hits a cliff on large windows, so region captures (act-verify, screenshots, Set-of-Marks) route through flat ~16.5ms GDI BitBlt in v0.11.0; full-screen still uses DXGI. Run the convert microbench: cargo bench -p ghost-core --bench convert. Older baselines: docs/benches/v030-baseline.md.

Requirements

• Windows 10 build 19041 or later
• Linux with at-spi2-core and a desktop session (X11 or Wayland); xdg-desktop-portal-gnome additionally for Wayland input and capture
• A Chromium-family browser (Chrome, Comet, Edge, or Brave) for the ghost_browser_* / ghost_tab_* tools only; the desktop verbs need none
• Rust stable (only for building from source)

License

MIT - Copyright 2026 Northtek