[BUG] jumping cursor while in Code mode in desktop app (MacOS)

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?

Summary: Cursor jumps to beginning of input field while typing during tool execution, causing text to appear in reverse order.
Environment:

macOS (M1 MacBook)
Claude Desktop app (latest version)
Occurs in code/computer use mode with MCP tools active

What Should Happen?

cursor in user input window remains stable until user enters

Error Messages/Logs

Steps to Reproduce

Steps to Reproduce:

Start a conversation that triggers tool execution (e.g., file operations, web search, MCP tools)
While Claude is actively running tools, begin typing your next message
Cursor intermittently jumps to the beginning of the input field mid-keystroke

Result: Text appears scrambled/reversed (e.g., typing "hello world" produces "dlrow olleh" or similar fragments in wrong order)
Expected: Input field should maintain stable cursor position regardless of background tool activity
Workaround: Wait for tool execution to complete before typing, or compose text elsewhere and paste

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude for Mac Version 1.1.1520 (48ced7)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_