[BUG] System-wide Korean IME breaks (jamo decomposition + U+3000 spaces in OTHER apps) while Claude Code desktop is running on Windows 11

Summary

While the Claude Code desktop app is running on Windows 11, the system-wide Korean (Hangul) IME intermittently breaks — affecting typing in other applications (browser, messengers), not just Claude Code itself. Killing/restarting explains it only partially; a reboot fully restores the IME. The user observed the breakage only occurs while Claude Code is running.

This is distinct from existing Korean IME issues (#77401, #77009, #73064 etc.), which are about composition inside the TUI/terminal. Here the damage is global (OS input stack level).

Symptoms

• Hangul jamo stop composing into syllables system-wide: typing 킵드 comes out as 킵ㅇㄴㅁㄷㅈㄴㄹ... (raw jamo, no composition) in other apps.
• Full-width ideographic spaces (U+3000 　) get inserted instead of regular spaces.
• Affects all applications while the condition persists (observed in a browser form and chat input).
• textinputhost.exe (Windows Text Services host) was present/active among visible windows when the corruption occurred.
• A full reboot restores normal IME behavior. The user reports the issue has only ever appeared while Claude Code was running.

Environment

• Claude Code: 2.1.220 (desktop app; issue observed on a day with repeated desktop session crashes/restarts after a reinstall, which may correlate)
• OS: Windows 11 Pro (build 10.0.26200)
• IME: Microsoft Korean IME (default), physical USB keyboard
• Event log: no USB/keyboard driver errors during the affected window (hardware ruled out)

Repro (best known)

Not deterministically reproducible yet. Conditions when it occurred:

1. Claude Code desktop running long sessions (with several session restarts that day)
2. Switch between Korean/English input across apps while Claude Code is running
3. At some point, Hangul composition breaks globally (jamo-only + U+3000 spaces)
4. Reboot → normal. Recurs only with Claude Code running (user observation)

Expected

Claude Code should not affect IME/TSF state outside its own window. Suspect interaction between the Electron composition handling (or a global keyboard hook) and Windows TSF (textinputhost.exe / ctfmon), leaving the composition state corrupted system-wide.

Workarounds found

• Killing textinputhost.exe (auto-respawns) sometimes resets the IME without reboot
• Reboot always fixes it