My Claude Code hook silently ate every Korean character, and it took me an hour to figure out why

I spent an hour last week debugging a hook that wasn't broken. Here's the setup: I run Claude Code on Windows, and I'd written a little UserPromptSubmit hook in PowerShell — a keyword router that reads my prompt and, if it sees something like mcp 서버 or 코드 리뷰, injects a hint so Claude pulls up the ri