Chrome plugin backend unavailable despite extension showing Connected

Summary

Codex Chrome plugin cannot be used from the Codex app: the Chrome extension is installed and shows Connected, but the Codex browser runtime does not expose an extension browser backend. Direct @Chrome tasks fail with Browser is not available: extension.

Environment

• Codex app: 26.527.60818 / build 3437
• Bundled Chrome plugin: 26.527.60818
• Google Chrome: 139.0.7258.155 stable, arm64
• Codex Chrome extension: 1.1.5_0
• Platform: macOS on Apple Silicon

What was tried

• Confirmed Chrome is installed and running.
• Confirmed the Codex Chrome extension is installed and enabled in the active Chrome profile.
• Confirmed the Chrome extension popup shows Connected.
• Confirmed the native messaging host manifest exists and validates correctly.
• Removed and reinstalled the Codex Chrome extension from the Chrome Web Store.
• Disabled and re-enabled the Chrome plugin in the Codex app.
• Restarted the Codex app.
• Started a new Codex thread and retried.
• Opened Chrome with the active profile and retried.

Expected behavior

Using @Chrome in the Codex app should register and use the Chrome extension backend, open/control Chrome tabs, and complete browser tasks.

Actual behavior

The Codex browser runtime only lists the in-app browser backend. The Chrome extension backend is not available.

Observed result from the browser backend list, sanitized:

{
  "browsers": [
    {
      "name": "Codex In-app Browser",
      "type": "iab"
    }
  ]
}

Attempting to get the Chrome extension backend fails:

Browser is not available: extension

A direct prompt such as @Chrome open https://www.baidu.com/ fails with the same error.

Privacy note

No local usernames, account emails, thread IDs, private URLs, screenshots, or logs are included in this report.