Caps Lock key leaks Kitty protocol escape sequence [57358u (regression in 2.1.84)

Bug Description

Pressing the Caps Lock key to switch between Chinese/English input methods (IME) outputs the raw Kitty keyboard protocol escape sequence [57358u as text in the terminal. This did not happen in previous versions.

Environment

• Claude Code version: 2.1.84
• Terminal: VS Code integrated terminal
• OS: macOS
• Input method: macOS built-in Chinese/English IME toggle via Caps Lock

Steps to Reproduce

1. Open Claude Code 2.1.84 in VS Code terminal
2. Press Caps Lock to switch between Chinese and English input
3. Observe [57358u characters appearing in the input

Expected Behavior

Caps Lock key press should be silently consumed (as a modifier-only key event) without outputting any characters.

Actual Behavior

The Kitty keyboard protocol escape sequence for Caps Lock (keycode 57358) leaks through as literal text [57358u.

Additional Context

• This is a regression — previous versions of Claude Code did not exhibit this behavior.
• This does not happen in iTerm2, only in Claude Code's terminal.
• The 57358 keycode corresponds to Caps_Lock in the Kitty keyboard protocol specification.
• Workaround: Use Ctrl+Space instead of Caps Lock for IME switching.