[BUG] Polish/Unicode diacritics not working when typing directly in CLI (copy/paste works)

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?

Polish diacritical characters (ą, ę, ó, ś, ć, ż, ź, ł, ń) cannot be typed directly
in Claude Code CLI using keyboard input. When typing these characters on the keyboard,
they either don't appear or are stripped of their diacritical marks.

However, the same characters work perfectly when copy/pasted (Cmd+C / Cmd+V) into
the Claude Code prompt.

Examples:

• Typing "zażółć" directly → appears as "zazoc" or similar (diacritics lost)
• Pasting "Zażółć gęślą jaźń" → displays correctly with all diacritics

Terminal locale is properly configured:

• LANG=en_US.UTF-8
• LC_ALL=en_US.UTF-8
• LC_CTYPE=UTF-8

What Should Happen?

Polish and other Unicode diacritical characters should work when typed directly
from the keyboard, just like in standard terminal applications (bash, zsh, vim, nano, etc.).

Direct keyboard input should preserve all diacritical marks, not just when copy/pasting.

Error Messages/Logs

Error Messages/Logs:                                                                                                                                   
  No error messages - characters are silently stripped or not captured

Steps to Reproduce

Steps to Reproduce:

1. Open Claude Code CLI (claude)
2. Try to type Polish characters directly from keyboard: ą, ę, ó, ś, ć, ż, ź, ł, ń
3. Observe that diacritical marks are lost or characters don't appear
4. Now copy this text: "Zażółć gęślą jaźń"
5. Paste it (Cmd+V) into Claude Code prompt
6. Observe that all diacritical marks display correctly

Note: Other terminal applications (bash, vim, nano) handle Polish keyboard input
correctly in the same terminal with the same locale settings.

Claude Model

Sonnet (default)

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.0.72 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

## Workaround
Users can write text in an external editor and copy/paste into Claude Code.

## Impact Analysis
Since copy/paste works but direct typing doesn't, this suggests the issue is
in Claude Code's keyboard input handling layer, not in text rendering or
terminal encoding.

This affects users of ANY language with diacritical marks, including:

• Polish (ą, ć, ę, ł, ń, ó, ś, ź, ż)
• French (é, è, ê, ë, à, ù, ç)
• German (ä, ö, ü, ß)
• Spanish (ñ, á, é, í, ó, ú, ü)
• Czech, Slovak, Portuguese, and many others

## Environment Details

• Shell configuration: zsh with Oh My Zsh
• Prompt: Powerlevel10k theme
• Plugins: git, zsh-autosuggestions, zsh-syntax-highlighting