[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. The browser-based authorization flow completes successfully on the local machine, but the extension returns to the login screen and displays a 403 error.
Environment:

Remote VM: Linux Ubuntu (isolated network, no direct internet access)
Local machine: Windows
Connection: VS Code connected via SSH to the VM

Possible Cause: The authentication callback may be attempting to reach claude.ai directly from the remote VM, which has no internet connectivity. The browser authorization completes on the local machine, but the extension running on the VM cannot finalize the authentication flow due to network isolation.
Note: This workflow was previously functional. Downgrading the extension to version 2.1.21 did not resolve the issue.

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 Ubuntu VM (on an isolated network with no internet access) via SSH using VS Code from a Windows machine
2. Open the Claude extension panel
3. Click "Subscription" to initiate login
4. A browser window opens on the local Windows 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

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.25

Platform

Other

Operating System

Ubuntu/Debian Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

This issue is currently blocking my daily workflow. My development environment relies entirely on SSH remote connections to Linux VMs, which is a standard setup in many professional and enterprise contexts.
As a paying subscriber, I am unable to use the service I am paying for within my primary work environment. This represents both a productivity loss and an ongoing cost without any return value.
I would appreciate any guidance on a workaround or an estimated timeline for a fix.