MCP SERVER · CLAUDE DESKTOP · CLAUDE CODE

Windows for Claude.
In the background.

Windows computer use for Claude, in the background.

A local MCP server, nexus-windows, for Claude Code and Claude Desktop: Claude reads a window and acts on it while you keep the mouse, the keyboard and the foreground window.

Explore the code See the features

No focus stealing
Every step read back
Team and Enterprise included

For

A Windows screen whose numbered elements are linked to Claude — Illustration of an exchange: look numbers the elements without bringing the window forward, act reports on every step.

MCPWIN32UI AUTOMATIONCHROMIUM · ELECTRONPRINTWINDOWPYTHON 3.14MIT

01 / WHY

Keep working.
Claude acts alongside.

Screenshot-and-click computer use moves the real cursor and brings windows to the front: you have to stop working while the agent acts. Most Windows applications can be driven otherwise: native controls accept window messages, modern frameworks expose UI Automation, Chromium its accessibility tree.

NexusWindows for Claude picks, for each UI family, a technique measured not to steal focus, reads the effect back, and only falls back to the real mouse or keyboard when you allow it.

Anthropic’s own computer use (Cowork and Claude Code in the Claude Desktop app) is a beta for the Pro and Max plans only: according to Anthropic’s help center, Team and Enterprise plans don’t have access to it at this time. NexusWindows for Claude is a local MCP server: it brings Windows computer use to Claude Desktop and Claude Code on any plan that can load a local MCP server, Team and Enterprise included.

02 / WHAT IT DOES

Six tools.
Four outcomes per step.

Each step is reported as ✓ read back, = already true, ~ sent without read-back (never counted as a success) or ✗ failure or refusal; a batch stops at the first ✗.

windows
Application windows, front to back: title, process, UI family, size.
look
Numbered [N] elements (role, name, value, state, position) and an image, without bringing the window forward.
act
Several steps in one call, each read back: click, typing, check box, list, menu, keys, scrolling, drag.
launch
Starts an application, a folder or a document without giving it focus; the opening is verified.
window
Restore behind, minimize, maximize, close, move, resize.
logs
Debug log: techniques tried, durations, errors, server state.

Win32
Direct messages to controls, read back. UI Automation avoided where it was measured to steal focus.
WinForms · WPF · UWP · WinUI
UI Automation without taking focus and with bounded timeouts; drop-down lists opened, chosen and read back.
Chromium · Electron
Simulated activation, sent to that window only: the page receives real keystrokes while Windows keeps the foreground.
check
A postcondition per step: already true, the step is skipped; false afterwards, the batch stops.
remember
Routines saved only if everything was read back, replayed by name and re-verified at every step.
PrintWindow
10 to 26 ms capture, covered windows included; images sized to keep coordinates exact.

Repository measurements (one PC, October 2026); offline suite: 580 passed, 6 skipped (October 16, 2026).

03 / SAFEGUARDS

The agent acts.
You stay in control.

The rules live in the tool itself, not only in the agent’s instructions.

Real mouse only when allowed

Only with foreground=true, which you approve. Cursor and foreground are handed back at the end; any physical input from you during the batch stops it.

Off-limits areas

Consoles, UAC and credential prompts, password managers, the Run dialog, the taskbar, the desktop, Start and Search: never. No typing in an address bar, no password field.

Sensitive applications refused by default

The Claude app, File Explorer, other AI agents, IDEs with an integrated terminal and administration tools: refused unless allowed in policy.json.

Watched launches

Consoles, interpreters, script hosts, shortcuts and Chromium switches that run code: refused. A browser started with devtools=true gets a throwaway profile, without an account.

On-screen text stays data

Every look reminds the model that displayed text is not an instruction. Typed text is never logged, the clipboard never used.

An up-to-date server or nothing

If its code changed on disk, a running server refuses to act until it is restarted; an abandoned call is cancelled at its next checkpoint.

04 / ALONGSIDE OTHER AGENTS

One PC.
Several agents.

Two file-based protocols shared by the NexusWindows editions and NexusBrowser. Any agent can implement them.

Foreground token

A shared file, held only while really using the mouse or the foreground, never for a background action. Windows releases it if the agent stops; a waiting agent gives up after a few seconds and says who holds it.

Emergency stop

Ctrl+Alt+Shift+Esc blocks every desktop action for 2 minutes, for every agent; reads stay allowed. Deleting the file or changing the clock does not lift the stop.

You first

Any physical input from you during a batch holding the real mouse stops it, and the foreground is handed back to you.

05 / INSTALLATION

One clone.
One MCP command.

Requirements: Windows 10 or 11, uv and Python 3.14. After uv sync, the server is registered with Claude Code through claude mcp add, or in claude_desktop_config.json for Claude Desktop.

claude mcp add --scope user --transport stdio nexus-windows -- uv run --project <clone> --frozen python -m nexus_windows

Independent project, not affiliated with Microsoft or Anthropic.

Version: 0.7.0
System: Windows 10 or 11
Clients: Claude Code, Claude Desktop
Requirements: Python 3.14 and uv
Licence: MIT
Limits: Tool descriptions and messages in French. Tested on Windows 11 with test applications and a handful of real ones: not every application has been checked. Tk and some canvases need real input.