[BUG] major quality and performance regression

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?

I am experiencing a massive degradation in performance. I spend much longer waiting for each response, and the responses are far, far lower quality.

What Should Happen?

I should be getting consistent performance, and consistent quality. Some variation would be expected, but this is severe.

Error Messages/Logs

Steps to Reproduce

Use Claude Code with Opus 4.6 on any effort level.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.108

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_