[BUG] Major lag when pasting large text blocks

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?

When you paste a large amount of text (e.g 2000 lines or more) into Claude Code, the UI lags and there is a several second delay before the paste registers

What Should Happen?

The paste should happen without lagging

Error Messages/Logs

Steps to Reproduce

1. Copy 2000 lines of text to clipboard
2. Paste into input

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.20

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_