Show HN: OpenComputerUse – Background computer use for agents, as an MCP server

Computer use for agents that runs in the background, as an MCP server. Start a session with an app and get back a session id. Drive the app with that id, then end the session. The app works behind your other windows, and your pointer, keyboard focus and frontmost app stay where they are. Sessions end when the MCP server exits, including when it is killed.

Every action returns a fresh screenshot unless you pass screenshot: false. Pass ui_tree: true to also get the tree. Coordinates are points from the window's top-left, the same grid as its screenshot.

run_recipe runs straight-line chores without the calling model in the loop:

{ "session_id": "…", "steps": [
  "click the address bar",
  "type \"example.com\" into the address bar",
  "press enter",
  { "click": "the More information link" }
] }

For each step, the runner sends the window's interactive elements to a decision model as the options of one choice question. It acts on the chosen element when the model is confident enough. There is no branching, and the model generates no text. A step it cannot place stops the recipe and returns a screenshot and the tree so the caller can take over. Two models are supported, chosen in the app's settings:

• TypeSafe Jev (api.typesafe.ai , modeljev-latest )
• Cloudflare Clef / Clef-flash on Workers AI (@cf/cloudflare/clef-flash )

Each platform implements the Platform and Session traits in crates/ocu-core. Everything above them is shared: session ids, ownership, cleanup, the MCP tools and recipes.

• Launch: apps open without activating. Your app's windows are put back on top, so the session window sits behind them.
• Screenshots: ScreenCaptureKit captures the window itself, so covered windows capture as they look.
• Tree and element actions: the Accessibility API, which works on background windows.
• Pointer and keys: posted to the app's process through SkyLight. The app is first told its window is active, without being raised; this "focus without raise" approach comes from yabai and trycua/cua.

The MCP server is a thin client. The OpenComputerUse app owns the sessions, holds the Accessibility and Screen Recording permissions, and draws a halo and a gliding cursor over the window being driven. It is built with GPUI (the IAmJSD/gpui fork). The MCP server starts the app through LaunchServices when needed, so the app keeps its own permissions whichever client started the server. Opening the app shows its window: permissions, one-click install into Claude Code, Claude Desktop, Codex or OpenCode, live sessions, and recipe settings.

CODESIGN_IDENTITY="Developer ID Application: …" scripts/bundle-macos.sh   # universal (arm64 + x86_64)
cp -R dist/OpenComputerUse.app /Applications/ && open /Applications/OpenComputerUse.app

The icon is assets/icon.svg; packaging/macos/icon.sh rebuilds the .icns from it.

Sign the bundle with a real identity. An ad hoc signature changes on every build, and macOS then asks for the permissions again.

• Display: each session gets a private Xvfb display with its own cookie. The app starts on it viaDISPLAY andXAUTHORITY , with Wayland disabled.
• Input and screenshots: input goes through XTEST; screenshots read the framebuffer, so menus and popups are included.
• Cleanup: Xvfb and the app getPR_SET_PDEATHSIG , so they die with the server.
• Where Xvfb is found:$OCU_XVFB , next to the binary, or onPATH .
• Not yet: the accessibility tree (AT-SPI), so element actions and recipes are unavailable on Linux for now.
• Watching a session: connect a VNC server to its display, for examplex11vnc -display :N -auth <xauthority> . The display and auth file are in the session details.

docker build -f scripts/linux/Dockerfile -t ocu-linux . && docker run --rm ocu-linux

• Launch: apps start suspended inside a kill-on-close Job Object, so their whole process tree dies with the server. They are shown without activating and sent to the back.
• Screenshots:PrintWindow with full-content rendering.
• Input: window messages posted to the control under the point, or to the focused control.
• Tree and element actions: UI Automation.

From the app's window, or:

opencomputeruse install claude          # claude mcp add --scope user opencomputeruse -- <path> mcp
opencomputeruse install claude-desktop  # an "mcpServers" entry in claude_desktop_config.json
opencomputeruse install codex           # codex mcp add opencomputeruse -- <path> mcp
opencomputeruse install opencode        # an "mcp" entry in ~/.config/opencode/opencode.json(c)
opencomputeruse clients                 # which clients run this copy

Claude Desktop reads its config when it starts, so quit and reopen it after installing. A client whose entry runs another copy (an old build, or the app before it moved) shows as "points elsewhere"; installing again points it here.

For other clients, use { "command": "<path to opencomputeruse>", "args": ["mcp"] }.

Off by default. Turn on Serve over HTTP in the app (or the local MCP server's http_server tool) and other devices can drive this computer through an HTTP API on port 8642, usually over Tailscale. While it is on, it starts again at login, so it survives reboots.

Each device needs a key. Generate Skill asks for the device's name and the URL it reaches this computer at (this computer's Tailscale name by default), and gives back a SKILL.md to install on that device. The skill carries the URL, the key and how to call every tool with curl. Keys are stored only as hashes, so the skill is the one place a key appears. Devices are listed in the app with Regenerate Key and Remove, and in the local MCP server as list_devices, generate_skill, regenerate_key and remove_device. Regenerating or removing a key ends that device's sessions. None of this management is reachable over HTTP.

The API:

• POST /v1/tools/<tool> with JSON arguments returns{content, isError} , the same as an MCP tool call.GET /v1/tools lists the tools.
• POST /mcp is MCP over HTTP:claude mcp add --transport http <name> <url>/mcp --header "Authorization: Bearer <key>" .
• Every request needs Authorization: Bearer <key> , exceptGET /health .

There is no TLS, so use it over Tailscale or another trusted network. On Linux and Windows, opencomputeruse serve runs the server, and serve --install starts it at login.

The settings file is at opencomputeruse config-path. On macOS it is edited from the app. Elsewhere, edit it by hand or set TYPESAFE_API_KEY, CLOUDFLARE_ACCOUNT_ID, CLOUDFLARE_API_TOKEN and OCU_RECIPE_PROVIDER. Set OCU_LOG=debug for logs on stderr. The macOS agent logs to ~/Library/Application Support/OpenComputerUse/agent.log.

Bump version in Cargo.toml, commit, and push a matching tag ( v0.2.0). .github/workflows/release.yml builds the signed universal app (OpenComputerUse.zip for the updater, OpenComputerUse.dmg for first installs) and plain Linux and Windows binaries of the MCP server, then publishes them as a GitHub release. The app checks for releases daily and from its menu, and installs them in place when they are signed by the same team.

The macOS job signs and notarizes with these repository secrets, and builds unsigned without them: MACOS_CERT_P12_BASE64, MACOS_CERT_P12_PASSWORD (a Developer ID Application certificate), APPLE_ID, APPLE_APP_SPECIFIC_PASSWORD and APPLE_TEAM_ID.

cargo test                                     # core, recipes and the updater
cargo run -p ocu-macos --example smoke         # drive TextEdit directly
python3 scripts/mcp_smoke.py                   # drive it through the MCP server

The widget kit in src/agent/ui comes from Schist (MIT; see LICENSE-SCHIST).

MIT, © 2026 Astrid Gealer. See LICENSE.