[BUG] I can’t log in on Firefox on Windows.

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The browser-side approval during the initial login doesn’t go through.

What Should Happen?

<img width="601" height="210" alt="Image" src="https://github.com/user-attachments/assets/7424e68e-8bee-4143-a304-8928671239ba" />

If you choose option 1, an authentication screen will open in your browser, and the authorization should go through.

Error Messages/Logs

## Below is the English translation of the screenshot
Unable to connect

Firefox can’t establish a connection to the server at **localhost:49175**.

- The site could be temporarily unavailable, or the server may be too busy to respond. Please try again in a few moments.  
- If you can’t load any pages, check your computer’s network connection.  
- If your network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web.

Steps to Reproduce

Environment

Windows 11 + Firefox 147.0.4

Steps

1. Purchase the Claude Pro plan.
2. Install Claude Code with npm install -g @anthropic-ai/claude-code.
3. Launch claude from an Administrator Command Prompt.
4. Follow the Claude prompts and select 1. Claude account with subscription.
5. The approval (authorization) page opens in the browser, so approve it.

Notes

• Disabling Windows Defender Firewall did not resolve the issue.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.63 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

<img width="864" height="374" alt="Image" src="https://github.com/user-attachments/assets/91b75a84-d70b-4141-8310-fab1e73dbe14" />