### Preflight Checklist - [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) 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 I repeatedly copy paste from prompt window, the line count doubles each time, and also it crashes eventually e.g. """ A B """ -> """ A B """ -> """

[BUG] Pasting many-line text crashes Claude Code + exponential line growth on repeated copy-pasting of multiple lines

Status Open

Maintainer reply None cached

Activity 0 comments · opened Aug 31, 2026

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 I repeatedly copy paste from prompt window, the line count doubles each time, and also it crashes eventually

e.g.
"""
A
B
"""
->
"""
A

B
"""
->
"""
A

B
"""
etc.

What Should Happen?

It shouldnt crash and it shouldnt blow up the line count

Error Messages/Logs

Steps to Reproduce

Copy paste multiline test in prompt window many times or try pasting something very long

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Latest

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information