[BUG] OAuth authentication fails with 500 Internal Server Error on Windows 10 — desktop app works fine

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?

Environment

• OS: Windows 10
• Shell: PowerShell
• Claude Code version: [v2.1.92]
• Login method attempted: Claude.ai Subscription & Anthropic Console
• Network: Home network, no VPN, no proxy, no corporate firewall

What's Wrong?

Claude Code OAuth authentication fails with a 500 Internal Server Error on
both available login paths. The browser completes successfully (showing "Build
something great / You're all set up for Claude Code") but the terminal never
receives the callback.

What Should Happen?

Errors received:

• OAuth error: timeout of 15000ms exceeded
• Authorization failed — Internal server error
• OAuth error: Request failed with status code 500

Error Messages/Logs

**Errors received:**
- `OAuth error: timeout of 15000ms exceeded`
- `Authorization failed — Internal server error`
- `OAuth error: Request failed with status code 500`

Steps to Reproduce

Key observation:
The Claude desktop app authenticates and works perfectly with the same account
and subscription. This confirms the account and Pro subscription are valid.
The failure is specific to the CLI OAuth callback mechanism.

Steps to reproduce:

1. Run claude in PowerShell on Windows 10
2. Select any login method (Claude.ai Subscription or Anthropic Console)
3. Browser opens and auth completes successfully
4. Terminal times out or returns 500 error

Troubleshooting already attempted:

• Cleared ~/.claude.json and ~/.claude/ directory
• Removed and re-added Windows Firewall rules for Node.js callback port
• Confirmed no ANTHROPIC_API_KEY environment variable set
• Verified system clock is accurate
• Tried both Claude.ai Subscription and Anthropic Console login paths
• Ran PowerShell as Administrator
• Full reinstall of Claude Code

Expected behaviour:
CLI authentication should succeed after browser auth completes, consistent
with how the desktop app handles the same account.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

[v2.1.92]

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_