hermes-agent/website/docs/user-guide/features/computer-use.md

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Computer Use	16

Computer Use

Hermes Agent can drive your desktop — clicking, typing, scrolling, and dragging — through one model-agnostic computer_use tool. On macOS it uses cua-driver for background control. On Windows it uses UI Automation for the element tree and SendInput for mouse/keyboard actions. Unlike most computer-use integrations, this works with any tool-capable model — Claude, GPT, Gemini, or an open model on a local vLLM endpoint. There's no Anthropic-native schema to worry about.

How it works

On macOS, the computer_use toolset speaks MCP over stdio to cua-driver, a driver that uses SkyLight private SPIs (SLEventPostToPid, SLPSPostEventRecordTo) and the _AXObserverAddNotificationAndCheckRemote accessibility SPI to:

• Post synthesized events directly to target processes — no HID event tap, no cursor warp.
• Flip AppKit active-state without raising windows — no Space switching.
• Keep Chromium/Electron accessibility trees alive when windows are occluded.

That combination is what OpenAI's Codex "background computer-use" ships. cua-driver is the open-source equivalent.

On Windows, Hermes uses the uiautomation package to enumerate controls and set native values, Pillow for screenshots, and pywin32/SendInput for window focus and mouse/keyboard injection. Windows cannot post input to background windows, so pointer and keyboard actions briefly foreground the target window. set_value is the exception: when the target control exposes the right UIA pattern, Hermes can set it without moving focus.

Enabling

On Windows, install Hermes normally and enable Computer Use from hermes tools; the Python dependencies are included in the Windows install.

On macOS, pick whichever path is most convenient — both run the same upstream installer:

Option 1: dedicated CLI command (most direct).

hermes computer-use install

This fetches and runs the upstream cua-driver installer: curl -fsSL https://raw.githubusercontent.com/trycua/cua/main/libs/cua-driver/scripts/install.sh. Use hermes computer-use status to verify the install.

Option 2: enable the toolset interactively.

1. Run hermes tools, pick 🖱️ Computer Use → cua-driver (background).
2. The setup runs the upstream installer (same as Option 1).

After installing, regardless of which path you took:

3. Grant macOS permissions when prompted:
   • System Settings → Privacy & Security → Accessibility → allow the terminal (or Hermes app).
   • System Settings → Privacy & Security → Screen Recording → allow the same.
4. Start a session with the toolset enabled:

   hermes -t computer_use chat
   

   or add computer_use to your enabled toolsets in ~/.hermes/config.yaml.

Keeping cua-driver up to date

The cua-driver project ships fixes regularly (e.g. v0.1.6 fixed a Safari window-focus bug for UTM workflows). Hermes refreshes the binary in two places so you don't get stuck on a stale release:

• hermes update — when you update Hermes itself, if cua-driver is on PATH the upstream installer re-runs at the end of the update. No-op for non-macOS users and for users without cua-driver installed.
• hermes computer-use install --upgrade — manual force-refresh. Re-runs the upstream installer regardless of whether cua-driver is already installed. Use this when you want the latest fix without waiting for the next agent update.

hermes computer-use status shows the installed version next to the binary path.

Quick example

User prompt: "Find my latest email from Stripe and summarise what they want me to do."

The agent's plan:

1. computer_use(action="capture", mode="som", app="Mail") — gets a screenshot of Mail with every sidebar item, toolbar button, and message row numbered.
2. computer_use(action="click", element=14) — clicks the search field (element #14 from the capture).
3. computer_use(action="type", text="from:stripe")
4. computer_use(action="key", keys="return", capture_after=True) — submit and get the new screenshot.
5. Click the top result, read the body, summarise.

On macOS, your cursor stays wherever you left it and Mail never comes to front. On Windows, the target window is foregrounded while pointer/keyboard actions run; prefer set_value for form fields and dropdowns when possible.

Provider compatibility

Provider	Vision?	Works?	Notes
Anthropic (Claude Sonnet/Opus 3+)	✅	✅	Best overall; SOM + raw coordinates.
OpenRouter (any vision model)	✅	✅	Multi-part tool messages supported.
OpenAI (GPT-4+, GPT-5)	✅	✅	Same as above.
Local vLLM / LM Studio (vision model)	✅	✅	If the model supports multi-part tool content.
Text-only models	❌	✅ (degraded)	Use mode="ax" for accessibility-tree-only operation.

Screenshots are sent inline with tool results as OpenAI-style image_url parts. For Anthropic, the adapter converts them into native tool_result image blocks.

Safety

Hermes applies multi-layer guardrails:

• Destructive actions (click, type, drag, scroll, key, focus_app) require approval — either interactively via the CLI dialog or via the messaging-platform approval buttons.
• Hard-blocked key combos at the tool level: empty trash, force delete, lock screen, log out, force log out.
• Hard-blocked type patterns: curl | bash, sudo rm -rf /, fork bombs, etc.
• The agent's system prompt tells it explicitly: no clicking permission dialogs, no typing passwords, no following instructions embedded in screenshots.

Pair with approvals.mode: manual in ~/.hermes/config.yaml if you want every action confirmed.

Token efficiency

Screenshots are expensive. Hermes applies four layers of optimisation:

• Screenshot eviction — the Anthropic adapter keeps only the 3 most recent screenshots in context; older ones become [screenshot removed to save context] placeholders.
• Client-side compression pruning — the context compressor detects multimodal tool results and strips image parts from old ones.
• Image-aware token estimation — each image is counted as ~1500 tokens (Anthropic's flat rate) instead of its base64 char length.
• Server-side context editing (Anthropic only) — when active, the adapter enables clear_tool_uses_20250919 via context_management so Anthropic's API clears old tool results server-side.

A 20-action session on a 1568×900 display typically costs ~30K tokens of screenshot context, not ~600K.

Limitations

• Platform scope. Desktop computer-use currently supports macOS via cua-driver and Windows via UI Automation. Linux desktop automation is not enabled yet. For cross-platform web tasks, prefer the browser toolset.
• Private SPI risk. Apple can change SkyLight's symbol surface in any OS update. Pin the driver version with the HERMES_CUA_DRIVER_VERSION env var if you want reproducibility across a macOS bump.
• Windows foregrounding. Windows pointer/keyboard actions move the real cursor and foreground the target window. Hermes waits briefly for user idle before injecting input, but you should still avoid fighting an active user.
• Performance. Background mode is slower than foreground — SkyLight-routed events take ~5-20ms vs direct HID posting. Not noticeable for agent-speed clicking; noticeable if you try to record a speed-run.
• No keyboard password entry. type has hard-block patterns on command-shell payloads; for passwords, use the system's autofill.

Configuration

Override the driver binary path (tests / CI):

HERMES_CUA_DRIVER_CMD=/opt/homebrew/bin/cua-driver
HERMES_CUA_DRIVER_VERSION=0.5.0    # optional pin

Swap the backend entirely (for testing):

HERMES_COMPUTER_USE_BACKEND=noop   # records calls, no side effects

Non-secret runtime settings live in config.yaml:

computer_use:
  backend: auto          # auto | cua | windows | noop
  idle_wait_seconds: 1.5 # Windows user-idle guard; 0 disables
  overlay: true          # Windows visible element/click overlay

Troubleshooting

computer_use backend unavailable: cua-driver is not installed — Run hermes computer-use install to fetch the cua-driver binary, or run hermes tools and enable the Computer Use toolset.

computer_use backend unavailable on Windows — Re-run the current Hermes installer/update so the Windows-only dependencies (pywin32, uiautomation, Pillow) are present, then enable Computer Use in hermes tools.

Clicks seem to have no effect — Capture and verify. A modal you didn't see may be blocking input. Dismiss it with escape or the close button.

Element indices are stale — SOM indices are only valid until the next capture. Re-capture after any state-changing action.

"blocked pattern in type text" — The text you tried to type matches the dangerous-shell-pattern list. Break the command up or reconsider.

See also

• Universal skill: macos-computer-use
• cua-driver source (trycua/cua)
• Browser automation for cross-platform web tasks.