Korean IME input lag on Windows 10 at Claude Code startup (Ink TUI raw mode conflict)

Environment

• OS: Windows 10 (10.0.19045)
• Claude Code version: latest
• Terminal: Windows Terminal 1.23.20211.0 / VS Code integrated terminal (both affected)

Description

When typing Korean (Hangul) immediately after launching claude, there is a ~10 second lag before the input appears all at once. This happens only once at the very first input after startup, then resolves on its own.

Reproduction steps

1. Launch claude in Windows Terminal or VS Code terminal on Windows 10
2. Immediately type Korean characters (Hangul IME)
3. Cursor freezes for ~10 seconds, then all typed characters appear at once

Key observations

• Only occurs at first input after launch — subsequent Korean input is normal
• Claude Code specific — Korean input in the terminal prompt (before running claude) works fine
• Renderer-independent — occurs in both Windows Terminal and VS Code terminal
• Windows 10 only — same setup on Windows 11 has no issue (Win11 has a redesigned IME engine)
• Started occurring suddenly after a recent Claude Code update

Root cause hypothesis

When Claude Code (Ink TUI framework) switches the terminal to raw mode on startup, it appears to conflict with the Windows 10 IME composition handling for the first input event.

Workaround

Running claude inside WSL (Ubuntu) resolves the issue — Korean input works normally there.