[BUG] Claude Code consistently degrades in performance over long sessions

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?

After long sessions (Claude Max with several autocompacts), Claude Code becomes slower and slower to the point that it becomes so slow that takes several minutes between requests. The current solution is to shut it down and start fresh. It looks as if something accumulates (data structure or something) and causes a terrible performance issue. I have /rewind disabled (disabled it due to the performance issue) and nothing improoves that doesn't seems to be the cause. I am using streaming MCP.

What Should Happen?

Stay at the same performance level during long sessions by using performant O(nlogn) data structures and not slow to a crawl. Or not have some memory leak (could be the cause too)

Error Messages/Logs

No error, just heavy performance degradation.

Steps to Reproduce

Run during a very long session and several auto compacts. Monitor the performance with performance counters scattered around blocks of code to locate the culprit region.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

v2.0.31

Platform

Anthropic API

Operating System

Windows 11

Terminal/Shell

Windows Terminal

Additional Information

_No response_