[BUG] Opus 4.8 no longer follows instructions

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 don't know how to describe this, but Opus 4.8 has been lobotomized.
It no longer follows instructions, when I call it out it says - oops, my bad.
It is producing a lot of prose, even when I ask it to be concise.
This is major model degredation.

What Should Happen?

Released models should not change behavior.

Error Messages/Logs

Just lots of word salad. I cannot be the only one seeing this.

Steps to Reproduce

In a large project, open Claude Code CLI using Opus 4.8 and observe its behavior.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Don't know - I don't track the versions.

Claude Code Version

2.1.207 (Claude Code)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

_No response_