Korean IME toggle key (한영키) prints raw escape sequence `[57358u`

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?

Pressing the Korean/English IME toggle key (한영키) inside Claude Code prints the raw Kitty keyboard protocol escape sequence [57358u as text input instead of toggling the input method.

This only happens inside Claude Code — the same key works correctly in all other terminal applications and the host terminal emulator itself (Terminal.app, iTerm2, etc.).

What Should Happen?

The 한영키 press should either:

• Be silently ignored and let the OS handle IME switching
• Trigger the OS-level input source switch normally

No raw escape sequence should be printed as text.

Error Messages/Logs

[57358u

Steps to Reproduce

1. Set up macOS with Korean input source (2-Set Korean / 두벌식)
2. Open Claude Code CLI in terminal
3. Press the 한영키 (Korean/English toggle key) on your keyboard
4. Observe [57358u printed in the input area

Note: This does not happen in any other terminal application — only inside Claude Code's TUI.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.84

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

• Running Claude Code as VS Code extension (not standalone CLI)
• The 한영키 keycode 57358 is from the Kitty keyboard protocol (CSI 57358 u)
• Claude Code's TUI framework intercepts the key but doesn't handle it, causing the raw sequence to be printed as text
• Workaround: Use Caps Lock or Control+Space for input source switching instead of 한영키
• This affects all Korean macOS users who use the dedicated 한영 key for IME toggling