[BUG] Claude Code Intellij plugin showing UTF-8 BOM markers in diffs

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?

If a file has BOM markers, every diff shown in the IntelliJ Claude Code plugin shows the first line of the file being changed.

What Should Happen?

The first line of the file should not be shown as being changed. This makes the experience confusing and clunky as it means the diff always scrolls to the top of the file initially even if the changes are much further down.

Error Messages/Logs

Steps to Reproduce

This is a revival of #2788.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.69

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

IntelliJ IDEA terminal

Additional Information

_No response_