Japanese IME (ATOK) Enter key incorrectly triggers message submission during text conversion

Environment

• OS: macOS (Darwin 25.0.0)
• IME: ATOK (Japanese Input Method)
• Claude Code: VS Code Extension

Problem

When using ATOK for Japanese input, pressing Enter to confirm conversion candidates is incorrectly interpreted as a command submission (message send) by Claude Code. This causes incomplete messages to be sent in the middle of composing text.

Expected Behavior

The extension should distinguish between:

1. Enter key pressed during IME composition (for confirming conversion) - should NOT submit
2. Enter key pressed after IME composition is complete - should submit message

Steps to Reproduce

1. Open Claude Code chat interface
2. Use ATOK to type Japanese text
3. Press Enter to confirm a conversion candidate
4. The message is sent prematurely instead of just confirming the conversion

Technical Context

This is a common issue with VS Code extensions that don't properly handle IME compositionstart, compositionupdate, and compositionend events. The extension needs to track the IME composition state and ignore Enter key events during active composition.

Workaround

Currently using alternative text input methods and pasting, but this significantly impacts workflow efficiency for Japanese users.