Computer Use (macOS)

Hermes Agent can drive your Mac's desktop — clicking, typing, scrolling, dragging — in the background. Your cursor doesn't move, keyboard focus doesn't change, and macOS doesn't switch Spaces on you. You and the agent co-work on the same machine.

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

The computer_use toolset speaks MCP over stdio to cua-driver, a macOS 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.

Enabling

1. Run hermes tools, pick 🖱️ Computer Use (macOS) → cua-driver (background).
2. The setup runs the upstream installer: curl -fsSL https://raw.githubusercontent.com/trycua/cua/main/libs/cua-driver/scripts/install.sh.
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.

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.

During all of this, your cursor stays wherever you left it and Mail never comes to front.

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 security.approval_level 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

• macOS only. cua-driver uses private Apple SPIs that don't exist on Linux or Windows. For cross-platform GUI automation, use 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.
• 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

Troubleshooting

computer_use backend unavailable: cua-driver is not installed — Run hermes tools and enable Computer Use.

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.