Codex Computer Use

Codex Computer Use

Purpose

Use Codex.app bundled CLI as a Computer Use bridge for another coding agent. The goal is to let an agent that can run shell commands delegate GUI work to codex exec, instead of depending on native Computer Use support in that agent.

Do not register OpenAI's bundled SkyComputerUseClient directly in another agent's MCP config; macOS launch constraints can kill it when the parent process is not Codex.

Use this pattern:

codex exec --sandbox read-only --ephemeral --skip-git-repo-check -C "$PWD" "PROMPT"

Install This Skill

Install from the shared skills repository:

npx skills add schroneko/skills -g -a claude-code -a codex -s codex-computer-use -y

Use the equivalent agent selection flags for other skill managers if they support Agent Skills.

Preconditions

Installing this skill is not enough by itself. The host machine also needs Codex.app's Computer Use plugin, the Codex.app bundled CLI, and per-app Computer Use approval.

Check these before diagnosing Computer Use failures:

which codex
codex --version
codex mcp list

When running from Claude Code, also confirm:

which claude
claude --version

Expected:

• codex should be the Codex.app bundled CLI, usually /Applications/Codex.app/Contents/Resources/codex
• claude should run if the caller is Claude Code
• codex mcp list should include computer-use
• Target apps must be installed and running before get_app_state

If which codex points to a CLI that is not bundled with Codex.app and Computer Use fails with Apple Event authentication errors, prefer the Codex.app bundled CLI.

The standalone CLI installed under ~/.codex/packages/standalone (verified with codex-cli 0.142.0) launches SkyComputerUseClient from the plugin cache and passes Apple Events authentication as is. Switch to the bundled CLI only after an actual authentication failure.

For Homebrew cask installs specifically, one working pattern is to remove the Homebrew cask and symlink the app bundled binary:

brew uninstall --cask codex
ln -s /Applications/Codex.app/Contents/Resources/codex /opt/homebrew/bin/codex

Only do this after confirming both conditions:

• The machine installed codex through Homebrew.
• The user wants the Codex.app bundled CLI to own codex.

First-Time Setup

1. Install and open Codex.app.
2. Confirm codex mcp list shows computer-use.
3. Confirm the target app exists and has a bundle identifier:

mdls -name kMDItemCFBundleIdentifier -raw /Applications/Google\ Chrome.app

4. Approve the app for Computer Use, either interactively or by editing the approval JSON after user consent.
5. Start the target app before running codex exec.
6. Run a read-only get_app_state smoke test before clicking or typing.

The app approval file is:

/Users/username/Library/Group Containers/2DC432GLL2.com.openai.sky.CUAService/Library/Application Support/Software/ComputerUseAppApprovals.json

Expected shape:

{
  "approvedBundleIdentifiers": ["com.google.Chrome", "com.apple.Safari", "com.apple.finder"]
}

Agent Usage

Invoke Computer Use through codex exec from the calling agent's shell tool. Keep the prompt explicit and constrained. Claude Code can use this skill directly, but the same bridge pattern also works from any agent that can run codex exec.

Read-only app inspection:

codex exec --sandbox read-only --ephemeral --skip-git-repo-check -C "$PWD" \
  "Do not run shell commands. Use computer-use MCP only. Call get_app_state for Google Chrome exactly once. Do not click, type, scroll, drag, press keys, or switch apps. Report only whether the call succeeded or failed and the exact error if it failed."

Single click:

codex exec --sandbox read-only --ephemeral --skip-git-repo-check -C "$PWD" \
  "Do not run shell commands. Use computer-use MCP only. In Safari, inspect the visible page. Click the visible Increment button exactly once. Do not navigate away, do not interact with browser chrome controls, extensions, account UI, or other tabs. Report whether it succeeded."

Single input:

codex exec --sandbox read-only --ephemeral --skip-git-repo-check -C "$PWD" \
  "Do not run shell commands. Use computer-use MCP only. In Safari, inspect the visible page. Set the visible text input to 'hello-codex'. Do not submit forms, navigate away, or interact with other tabs. Report whether it succeeded."

Use --sandbox read-only to protect files. Remember that it does not make GUI clicks or typing read-only; the prompt must constrain GUI behavior.

Browser Choice

Prefer Chrome when it is installed and visible to LaunchServices:

ls -ld /Applications/Google\ Chrome.app
mdls -name kMDItemCFBundleIdentifier -raw /Applications/Google\ Chrome.app
open -a "Google Chrome"

Fallback to Safari when Chrome is missing, being reinstalled, or returns appNotFound:

open -a Safari

Browser Use is separate from Computer Use. If browser-use is not shown by codex mcp list, use Computer Use for Chrome/Safari GUI operations.

Approvals

codex exec cannot answer Computer Use approval elicitation interactively. If a target app is not approved, one of these errors can appear:

Computer Use approval denied via MCP elicitation for app '...'

Fix by either:

• Run interactive codex, request a harmless get_app_state for the target app, and choose Always allow
• Add the target bundle identifier to ComputerUseAppApprovals.json when the user has approved broad app access

Common bundle identifiers:

ai.elementlabs.lmstudio
com.1password.1password
com.amazon.Lassen
com.anthropic.claudefordesktop
com.apple.Safari
com.apple.dt.Xcode
com.apple.finder
com.electron.ollama
com.google.Chrome
com.google.GeminiMacOS
com.google.antigravity
com.google.drivefs
com.google.drivefs.shortcuts.docs
com.google.drivefs.shortcuts.sheets
com.google.drivefs.shortcuts.slides
com.hnc.Discord
com.mitchellh.ghostty
com.tinyspeck.slackmacgap
com.todesktop.230313mzl4w4u92
pl.maketheweb.cleanshotx
ru.keepcoder.Telegram
us.zoom.xos

Failure Handling

For Apple event error -10000: Sender process is not authenticated, verify that codex points to the Codex.app bundled CLI. Homebrew-only CLI can see tools but fail Apple Events.

For Code Signature Invalid or SkyComputerUseClient quit unexpectedly when started by Claude, do not retry direct MCP registration. Use codex exec as the bridge.

For appNotFound("Google Chrome"), check whether Chrome is installed, currently being reinstalled, or not running. Start it and retry.

For sensitive pages, avoid quoting page text, URLs, filenames, account data, or UI tree details. Ask Codex to report only success/failure and exact errors.

Safe Prompt Rules

Always specify:

• Target app name
• Target page or window when known
• Allowed tool family: computer-use MCP only
• Forbidden actions: no shell commands, no navigation, no other tabs, no account UI
• Exact action count: click once, type one value, inspect once
• Reporting limits: no private page contents or UI tree dumps

Use a local throwaway page for destructive or uncertain tests before touching real pages.