[BUG] CLI: OAuth login fails with "Invalid OAuth Request — Missing redirect_uri parameter" — Pro plan, Windows 11

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?

Claude Code's /login flow fails immediately with "Invalid OAuth Request — Missing redirect_uri parameter" in the browser. This happens on a fresh login attempt with no prior working session issues. A second user on the same network (different machine) independently hit the identical error. This also coming from having been randomly logged out, since the command line worked with no issues until yesterday.

What I've already ruled out:

No VPN, proxy, or unusual network setup
No firewall/antivirus interference confirmed via netstat -ano | findstr LISTENING before and after triggering /login — no new listening port appears at all, and no existing ports changed (consistent with this flow using a hosted callback page rather than a local listener)
Updated Claude Code to the latest version via npm install -g @anthropic-ai/claude-code@latest — issue persists after update
Cleared local auth state (rmdir /s "%USERPROFILE%\.claude") and retried in a fresh terminal — issue persists
Tried from a completely fresh terminal session (first one after system boot) — issue persists
A second person (different device, same household network) independently encountered the exact same error

Environment:

OS: Windows 11
Claude Code version: latest (updated [today's date])
Auth method: browser link from terminal
Account: Claude Pro (active subscription)
ANTHROPIC_API_KEY: not set

What Should Happen?

Clicking the login link should prompt for account credentials and complete OAuth login using my active Claude Pro subscription, as it has previously.

Error Messages/Logs

Steps to Reproduce

Open a brand-new terminal (first one since system boot)
Run claude
Hit API Error: 401 Invalid authentication credentials — Please run /login
Run /login
Click the login link provided in the terminal
Log in with Google
Browser loads and immediately shows: "Invalid OAuth Request — Missing redirect_uri parameter"

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.185

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_