[BUG] Claude Code CLI v2.1.104 returning 400 errors

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?

This is a known authentication classification issue where our system is incorrectly treating your Max 20x subscription requests as third-party API calls, even though you're properly authenticated.
The error occurs because our classifier is misidentifying your legitimate subscription usage. This can happen when there are server-side changes to how third-party tools are handled - we may draw use of third-party tools from extra usage rather than subscription limits at our discretion.
Since you've confirmed no API key is set and /doctor shows normal configuration, this appears to be a backend classification problem that requires investigation using your request IDs.
Your best option is to file a GitHub issue at https://github.com/anthropics/claude-code/issues with these details:
Claude Code CLI v2.1.104 returning 400 errors
Max 20x subscription with 11% session / 21% weekly usage
No ANTHROPIC_API_KEY set anywhere
Request IDs: req_011CZzH5P4nvVCsgwXxEgL7A, req_011CZzHrxANWMdNiQ5UZBwiW, req_011CZzJ17YtwEW5dYa8WzsTu, req_011CZzJ1Ze2yffqZRWZduAiU, req_011CZzKhVXiHnUPK2DcTqiaQ
These request IDs contain the server-side details needed to investigate why the authentication classifier is failing despite your valid subscription.

What Should Happen?

Claude should not be treating Claude MAX subscription as 'third-party use'. Backend classification issue is preventing legitimate use and the terminal is completely unusable due to constant 400 errors about claiming third-party usage credits. There is zero third-party use, everything is via claude code cli and claude max subscription. /help, /feedback, /bug, /debug all produce 400's. /doctor doesn't fix anything. WebUI still works, usage is 11% session/21% weekly, but claude code cli in terminal unusable.

Error Messages/Logs

Claude Code CLI v2.1.104 returning 400 errors
Max 20x subscription with 11% session / 21% weekly usage
No ANTHROPIC_API_KEY set anywhere
Request IDs: req_011CZzH5P4nvVCsgwXxEgL7A, req_011CZzHrxANWMdNiQ5UZBwiW, req_011CZzJ17YtwEW5dYa8WzsTu, req_011CZzJ1Ze2yffqZRWZduAiU, req_011CZzKhVXiHnUPK2DcTqiaQ

Steps to Reproduce

any / command produces 400's.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.104 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

this started after clearing session context to start a fresh session, and is no longer usable. Please fix ASAP.
Request IDs: req_011CZzH5P4nvVCsgwXxEgL7A, req_011CZzHrxANWMdNiQ5UZBwiW, req_011CZzJ17YtwEW5dYa8WzsTu, req_011CZzJ1Ze2yffqZRWZduAiU, req_011CZzKhVXiHnUPK2DcTqiaQ