[BUG] File Read/Write Operations Failing with "File has been unexpectedly modified" Error

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?

Experiencing persistent file read/write operation failures when attempting to edit files through Claude Code. The error occurs consistently when trying to modify existing files.

Edit operations consistently fail with the above error messages, making file modifications impossible.

What Should Happen?

Edit operations should work normally after reading a file.

Error Messages/Logs

"File has been unexpectedly modified. Read it again before attempting to write it."
"File has not been read yet. Read it first before writing to it."

Steps to Reproduce

1. Use Read tool to read a file (e.g., AndroidManifest.xml)
2. Attempt to use Edit or MultiEdit tool to modify the file
3. Error occurs even after multiple Read operations
4. Problem persists across different files and file types

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.0.126

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

• This started occurring this morning (2025-09-26)
• Previously worked without issues
• Affects both Edit and MultiEdit tools
• Read tool works fine, only write operations fail
• Problem occurs on Flutter/Android project files