[BUG] Command line tool becomes slower and slower as session progresses, slowness seen in keyboard response when typing and pressing enter on the prompt submission

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?

Latest version, I think 2.1.25+, now 2.1.27, as session goes, the time between I press the key when typing the prompt and the char appearing on the CLI takes longer and longer. What is more noticeable is that when you press enter, it takes longer and longer to send the prompt, even slower than typing response by like 100x.

What Should Happen?

When you type, chars should show up immediately.

When you press enter, the prompt should show as submitted immediately.

Error Messages/Logs

Steps to Reproduce

Run a session in MacOS latest and see for yourself, it is always now happening.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.17

Claude Code Version

2.1.27

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_