[BUG] Spell checking cannot be turned off, making all entered text hard to read

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?

Re-opened version of #35706

I have a German Windows installation and am not going to change that. Claude Desktop's UI translation is so poor that I had to switch to English. Also, when coding, it's often easier to express things in English, so I'm typing in that language.

The problem is that now all of my typed text has a thick red underline. Almost every single word is marked a wrong in such an intense way that it's really distracting to read anything in there. I know this issue from Microsoft Outlook and Teams where I'm typing in both German and English and either language is always unrecognised. How stupid.

So please let me turn this spell checking off in Claude Desktop and make the app usable again. I'm not writing an executive announcement here, just chatting with the AI that would understand me anyway. So a totally uncritical feature causes a critical usability degrading here. That's not justifyable.

What Should Happen?

No spell checking

Error Messages/Logs

Steps to Reproduce

Run Claude Desktop and type in a different language than your Windows installation

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude 1.6608.2 (ebf1a1) 2026-05-08T23:17:27.000Z

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

<img width="1247" height="83" alt="Image" src="https://github.com/user-attachments/assets/f2525bc9-a025-4acc-9d90-b54a5e0cf730" />

Spell checking is broken anyway because the non-underlined words are not correct German either (except for "in").