Japanese IME Input Issue: Enter Key Submits Chat Instead of Confirming Conversion

Description

When using Japanese IME (Input Method Editor) in the Claude Code chat input field, pressing Enter to confirm Japanese character conversion immediately submits the message instead of just confirming the conversion. This makes it very difficult to input Japanese text.

Steps to Reproduce

1. Open Claude Code chat interface
2. Switch to Japanese IME (e.g., macOS Japanese input method)
3. Start typing in Japanese (e.g., type "にほんご")
4. Press Enter to confirm the conversion
5. Expected: The Japanese text is confirmed and remains in the input field
6. Actual: The message is immediately submitted

Expected Behavior

• Enter key during IME composition should only confirm the text conversion
• Enter key after composition is complete should insert a new line
• A different key (e.g., Shift+Enter or Cmd+Enter) should submit the message

Actual Behavior

Enter key always submits the message, even during IME composition.

Environment

• OS: macOS 14.5 (Darwin 24.5.0)
• VSCode Version: 1.104.2
• Claude Code Version: (latest)
• IME: macOS Japanese Input Method

Attempted Solutions

Tried the following VSCode keybindings without success:

\\\json
{
"key": "enter",
"command": "-workbench.action.chat.submit",
"when": "inChat && !composing"
},
{
"key": "shift+enter",
"command": "workbench.action.chat.submit",
"when": "inChat"
}
\\\

The keybinding doesn't seem to apply to the Claude Code chat input field, likely because it's implemented in a WebView.

Additional Context

This issue affects all users who need to input text using IME (Japanese, Chinese, Korean, etc.). The VSCode keyboard shortcuts troubleshooting log shows:

\\\
[KeybindingService]: \ From 36 keybinding entries, no when clauses matched the context.
\\\

This suggests the Claude Code chat input context is not recognized by standard VSCode keybindings.

Suggested Fix

• Detect when the user is in IME composition mode (\composing\ event)
• Only submit on Enter when NOT in composition mode
• Alternatively, provide a setting to customize the submit keybinding (e.g., require Shift+Enter or Cmd+Enter to submit)