Cannot type Vietnamese diacritics on Windows in Claude Code CLI

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?

aIt is impossible to type Vietnamese characters with diacritics directly in Claude Code CLI on Windows. This affects all terminals (cmd, PowerShell, Windows Terminal).

When using a Vietnamese IME (e.g., Unikey with Telex or VNI input method), characters are entered without diacritics. For example, typing "xin chao" with Telex should produce "xin chao" with diacritics but instead outputs the raw ASCII characters.

Environment:

• OS: Windows 10 Home (10.0.19045)
• - Terminals tested: cmd, PowerShell, Windows Terminal
• - - Input method: Unikey (Telex/VNI)

What Should Happen?

aVietnamese characters with diacritics should display correctly as typed. For example, typing "xin chao" using Telex method should produce the correctly accented Vietnamese text.

Additionally, proper IME/Unicode input support should be implemented for Windows terminals so that Vietnamese (and other non-Latin) characters are handled correctly without needing to copy-paste from external applications.

Workaround: Copy-pasting Vietnamese text from external applications (e.g., Notepad) into the Claude Code CLI works correctly — only direct typing via IME is broken.

Error Messages/Logs

Steps to Reproduce

a1. Install Claude Code on Windows 10

1. Open any terminal (cmd, PowerShell, or Windows Terminal)
2. 3. Install and enable a Vietnamese IME (e.g., Unikey with Telex or VNI input method)
3. 4. Run claude to start Claude Code CLI
4. 5. Try typing Vietnamese text with diacritics (e.g., type "xin chao" using Telex method to get "xin chào")

Result: Characters appear without diacritics — the raw ASCII keystrokes are passed directly instead of the composed Unicode characters from the IME.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.71 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

This issue affects all Vietnamese Windows users who use IME-based input methods (Unikey, EVKey, etc.). The same problem likely affects other languages that use IME composition on Windows (e.g., Chinese, Japanese, Korean).

Request: Please add proper IME/Unicode input support for Windows terminals so that composed characters from IME are correctly passed to the Claude Code CLI input handler.