[BUG] Vietnamese character input issues in Interactive Mode (IME Handling)

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?

I am experiencing issues when typing Vietnamese characters while in the Claude CLI's interactive mode on Windows (PowerShell/Windows Terminal).

What Should Happen?

The CLI should properly handle IME composition events or provide a way to bypass raw key interception for non-Latin character inputs. Many Node-based CLIs solve this by using libraries that better support Windows' native input handling.

Error Messages/Logs

Steps to Reproduce

While Vietnamese input works perfectly fine in the standard PowerShell prompt, once I enter the interactive session by running claude, the input becomes buggy. Specifically:

• Characters are dropped or deleted while typing (likely due to how the CLI handles Backspace/Input events from IMEs like Unikey or EVKey).
• Diacritics (tone marks) cause the cursor to jump or the entire word to disappear.
• This is a common issue in Node.js CLI tools that intercept raw keypresses without proper IME support.
• Steps to Reproduce:
• Open PowerShell or Windows Terminal on Windows.
• Ensure a Vietnamese IME (like Unikey or EVKey) is active using Telex or VNI input methods.
• Run claude to enter interactive mode.

Try to type a Vietnamese word with marks, e.g., "tiếng Việt".
Observe that characters are mangled or deleted as you type.
Environment:
OS: Windows 10/11
Terminal: PowerShell / Windows Terminal
Claude CLI Version: [Điền phiên bản của bạn vào đây, ví dụ: 0.1.x]
IME used: Unikey / EVKey (Vietnamese Telex)

Claude Model

Not sure / Multiple models

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude Opus 4.6

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

<img width="452" height="79" alt="Image" src="https://github.com/user-attachments/assets/ef8f78fa-c7aa-49e8-96a5-a4aea1c80ef7" />