[BUG] Authentication fails with 403 error when using Claude extension via SSH remote connection

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?

Authentication through the Claude extension fails when working in a remote SSH environment on Windows. The browser-based authorization flow completes successfully on the local machine, but the extension returns to the login screen and displays a 403 error.

Possible Cause: The authentication callback may be attempting to reach claude.ai directly from the remote Linux VM, which has no internet connectivity. The browser authorization completes on the local machine (Windows), but the extension running on the VM cannot finalize the authentication flow due to network isolation.
Note: This workflow was previously functional.

What Should Happen?

After completing the browser-based authorization flow in the browser, the extension should authenticate successfully and grant access to Claude.

Error Messages/Logs

403 error displayed in the extension panel
Link to troubleshooting resources shown alongside the error
No errors displayed on the browser authorization page (confirms "You're all set")

Steps to Reproduce

1. Connect to a remote Linux VM (on an isolated network with no internet access) via SSH using VS Code
2. Open the Claude extension panel
3. Click "Subscription" to initiate login
4. A browser window opens on the local (physical) machine requesting acceptance of Terms of Service
5. Accept the terms — the web page confirms successful authorization
6. Return to VS Code — the extension panel displays the 403 error

Note: I tried downgrading to 2.1.21 but same issue

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.25

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_