How to Fix Charles Proxy Helper Installation Error on macOS

The author encountered an error when Charles tried to install its macOS proxy helper, receiving the message:

Automatic macOS Proxy Configuration

Failed to install helper: The operation couldn't be completed. (CFErrorDomainLaunchd error 9.)

The failure occurs because macOS cannot launch the helper defined in /Library/LaunchDaemons/com.xk72.charles.ProxyHelper.plist. The user had previously disabled Charles' automatic proxy configuration, which removed the helper program.

The original plist file looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key>
    <string>com.xk72.charles.ProxyHelper</string>
    <key>MachServices</key>
    <dict>
      <key>com.xk72.charles.ProxyHelper</key>
      <true/>
    </dict>
    <key>Program</key>
    <string>/Library/PrivilegedHelperTools/com.xk72.charles.ProxyHelper</string>
    <key>ProgramArguments</key>
    <array>
      <string>/Library/PrivilegedHelperTools/com.xk72.charles.ProxyHelper</string>
    </array>
  </dict>
</plist>

To resolve the issue, replace or edit the launch daemon so that the Program and ProgramArguments point to the existing helper binary ( /Library/PrivilegedHelperTools/com.xk72.charles.ProxyHelper). After saving the corrected plist, restart the computer (or unload and load the daemon) and then launch Charles again.

Once the daemon is correctly configured and the system is restarted, Charles starts without the proxy helper error and works as expected.