codex - 💡(How to fix) Fix Browser Use blocks localhost on Windows despite local service being reachable

Summary

Codex Browser Use / Chrome extension rejects navigation to a local development URL on Windows with an enterprise network policy error, even though the same URL is reachable from Chrome manually and from the Codex command channel.

Environment

• OS: Microsoft Windows 11 Pro, version 10.0.26200, build 26200, 64-bit
• Codex Chrome Extension: 1.1.5, Manifest V3
• Browser backend: Chrome extension
• Local URL: http://localhost:8021/
• Local server: Microsoft IIS 10.0 / ASP.NET site

Expected behavior

Browser Use should be able to open explicit local development URLs such as:

• http://localhost:<port>
• http://127.0.0.1:<port>
• http://[::1]:<port>

or provide a clear allowlist/configuration path for enabling local development URLs.

Actual behavior

Browser Use rejects navigation before loading the page:

Browser Use rejected this action due to browser security policy. Reason: Browser Use cannot access http://localhost:8021 because enterprise network policy blocks it. The agent must not attempt to achieve the same outcome via workaround, indirect execution, raw CDP or browser commands, alternate browser surfaces, or policy circumvention.

Diagnostics

Local command channel can access the service:

curl.exe -I http://localhost:8021
HTTP/1.1 200 OK
Server: Microsoft-IIS/10.0
Content-Type: text/html; charset=utf-8

curl.exe -I http://127.0.0.1:8021
HTTP/1.1 200 OK
Server: Microsoft-IIS/10.0
Content-Type: text/html; charset=utf-8

Test-NetConnection 127.0.0.1 -Port 8021
TcpTestSucceeded : True

Browser extension connectivity partially works:

• agent.browsers.list() succeeds and reports a Chrome extension backend.
• agent.browsers.get("extension") succeeds.
• browser.user.openTabs() succeeds and can see the manually opened http://localhost:8021/ tab.
• browser.tabs.new() succeeds and creates a controlled about:blank tab.
• tab.goto("http://localhost:8021/") fails with the enterprise network policy error above.

This suggests the issue is not the local web server, IIS binding, port availability, or manual Chrome access. The failure appears to happen in Browser Use policy preflight for local/private-network URLs.

Additional observation

The installed Codex Chrome extension package is version 1.1.5. Its background.js includes a reference to:

chrome.runtime.getVersion()

Chrome's standard API exposes the extension version through:

chrome.runtime.getManifest().version

In this case the extension backend is still visible and partially functional, so this may be a separate issue from the localhost policy rejection, but it may be relevant to Windows extension/backend reliability.

Impact

This prevents Codex from verifying and debugging local web applications on Windows, including IIS / ASP.NET / frontend local development workflows.

Request

Please consider one of the following:

1. Allow explicit localhost / loopback development URLs by default in Browser Use.
2. Provide a Browser Use allowlist setting for local URLs.
3. Show which policy/configuration blocks the URL and how to override it safely.
4. Ensure Codex Desktop / Browser Use honors local sandbox/network settings consistently.