Korean IME toggle (한/영 key) outputs "[57358u" in VS Code integrated terminal since v2.1.84

Bug Description

Since updating to Claude Code v2.1.84 (released 2026-03-25), pressing the Korean IME toggle key (한/영) in VS Code's integrated terminal causes [57358u to be printed as raw text.

This did not occur in v2.1.83 or earlier.

Steps to Reproduce

1. Open VS Code integrated terminal (macOS)
2. Launch claude in any directory
3. Toggle Korean/English IME (한/영 key or Caps Lock on Korean keyboard)
4. [57358u appears in the terminal output

Expected Behavior

IME toggle should not produce any visible output.

Actual Behavior

[57358u is printed every time Korean IME is toggled.

Environment

• OS: macOS 26.3.1 (Darwin 25.3.0)
• Terminal: VS Code integrated terminal (v1.112.0)
• Shell: zsh
• Claude Code: 2.1.84
• Input method: macOS Korean IME

Additional Notes

• The issue does not occur in iTerm2
• 57358 (0xDFEE) appears to be a kitty keyboard protocol flags response
• VS Code partially supports kitty keyboard protocol; the IME toggle event seems to trigger Claude Code to re-query \e[?u, and VS Code echoes the response (57358) as raw text
• Workaround: use iTerm2 instead of VS Code integrated terminal