[BUG] IME Enter key incorrectly triggers message send during Japanese input

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When using Japanese IME in the chat input field, pressing Enter to confirm IME conversion incorrectly triggers message send. The text is sent immediately instead of just being confirmed.

This makes it impossible to compose multi-line Japanese messages without using Shift+Enter workaround.

What Should Happen?

The first Enter keypress during IME composition should only confirm the conversion (not send the message).

Sending the message should require a second Enter press after the IME conversion is fully confirmed.

This is the standard behavior in other chat applications like Slack, Discord, and Teams.

Error Messages/Logs

No error messages. This is a behavioral issue with IME event handling.

Technical analysis: The event.isComposing flag appears to not be checked before the send action is triggered.

Steps to Reproduce

1. Open Claude Code chat input field
2. Switch to Japanese IME (Input Method Editor)
3. Type: "こんにちは、" (Konnichiwa,)
4. Press Enter key to confirm IME conversion
5. Observe: Message is immediately sent (incorrect behavior)
6. Expected: Text should be confirmed but remain in input field (not sent)

Frequency: 100% reproducible (happens every time)
Environment: Latest Claude Code version, Japanese IME

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.1 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

I use Windsurf