Windows: Chrome, Browser, and Computer Use mentions recognized but callable tools are not attached (26.707.12708.0)

Start by reproducing the Windows fresh-task steps for @Chrome, @Browser, and @Computer Use, then read the plugin-mention and task capability attachment paths alongside related issues #21791, #23805, #24838, and #25809. Done means each mention exposes its callable tool, or the UI reports that attachment failed before sending the task.

Summary

On Windows, the bundled @Chrome, @Browser, and @Computer Use plugin mentions are recognized by Codex Desktop, but the corresponding callable tools are not attached to the active task.

This persists after a clean Codex Desktop reinstall and after reinstalling the official plugins and Chrome extension.

Environment

• OS: Windows x64
• Codex Desktop: 26.707.12708.0
• Bundled Chrome / Browser / Computer Use plugins: 26.707.91948
• Codex Chrome extension: 1.2.27203.26575
• Browser: Google Chrome Stable

Verified local state

• Chrome extension popup shows Connected.
• Chrome plugin is installed and enabled.
• Browser plugin is installed and enabled.
• Computer Use plugin is installed and enabled.
• Native Messaging registry entry exists at:
  HKCU\Software\Google\Chrome\NativeMessagingHosts\com.openai.codexextension
• Native host manifest exists at:
  C:\Users\<user>\AppData\Local\OpenAI\extension\com.openai.codexextension.json
• extension-host.exe is running.
• The plugin mention is inserted from the UI and arrives in the task as a real plugin capability, not plain text.

Steps to reproduce

1. Start a new Codex Desktop task on Windows.
2. Select the real Chrome plugin mention from the @ menu.
3. Send a minimal request such as:
   @Chrome Open a new tab and tell me the page title.
4. Observe that the Chrome capability/instructions are recognized, but the task does not receive a callable Chrome control tool.
5. Repeat in fresh tasks with @Browser and @Computer Use.

Actual behavior

All three mentions are recognized, but none of the executable browser/Windows-control tools are exposed to the agent. The agent can use normal local shell tools, but cannot open or control Chrome, the in-app browser, or Windows applications.

The failure occurs before accessing any target website and reproduces with an innocuous new-tab request.

Expected behavior

• @Chrome should expose the extension-backed Chrome control tool.
• @Browser should expose the in-app browser control tool.
• @Computer Use should expose the Windows UI control tool.
• If a tool cannot be attached, the UI should report that before allowing the mention to be sent.

Troubleshooting already completed

• Restarted Chrome and Codex Desktop.
• Started multiple fresh tasks.
• Selected each plugin from the @ menu.
• Reinstalled Codex Desktop.
• Reinstalled/enabled the official Chrome, Browser, and Computer Use plugins.
• Reinstalled the official Chrome extension.
• Confirmed the extension is connected, Native Messaging is registered, the manifest exists, and extension-host.exe is active.
• Did not manually modify the registry or native host manifest.

Related issues

• #21791
• #23805
• #24838
• #25809

The important additional data point here is that this reproduces on the newer 26.707.12708.0 Windows build and affects all three bundled control surfaces in fresh tasks.