[2.1.83+] Korean IME toggle key outputs [57358u in input area (regression from 2.1.81)

Bug Description

When pressing the Korean IME toggle key (한/영 or Caps Lock configured for Korean input switching) in the Claude Code input area, the raw escape sequence [57358u is printed instead of switching the input method silently.

Environment

• OS: macOS
• Terminal: VSCode integrated terminal
• Claude Code version with bug: 2.1.83, 2.1.84
• Claude Code version without bug: 2.1.81 (confirmed working)

Steps to Reproduce

1. Open Claude Code in VSCode integrated terminal
2. Press the Korean IME toggle key (한/영 key or Caps Lock remapped for Korean input)
3. Observe [57358u being printed in the input area

Expected Behavior

The IME toggle key should switch the input method without printing any characters.

Actual Behavior

[57358u is printed in the input field every time the key is pressed.

Additional Context

• The issue started appearing after Claude Code auto-updated from 2.1.81 → 2.1.83
• Existing sessions that were opened before the update (running 2.1.81) work correctly
• New sessions (running 2.1.83+) reproduce the issue consistently
• Other users on the same version may not have encountered it yet (haven't opened new sessions)
• 57358 decimal = 0xDFEE — this is a Kitty Keyboard Protocol encoding for a key without a standard Unicode codepoint

🤖 Generated with Claude Code