[BUG] Japanese IME input causes unintended message submission on Enter key after recent update

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?

After a recent update to Cursor/Claude Code, pressing the Enter key while using Japanese IME (Input Method Editor) causes the message to be sent immediately, even when the user only intends to confirm the IME conversion.

What Should Happen?

Expected Behavior:

• Enter key should only confirm IME conversion
• Message should be submitted with Cmd+Enter or after a second Enter press

Actual Behavior:

• Message is immediately submitted on first Enter press
• Causes frequent accidental submissions while typing Japanese

Environment:

• OS: macOS (Darwin 25.0.0)
• Editor: Cursor
• Language: Japanese IME

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code chat in Cursor
2. Switch to Japanese input mode (IME)
3. Type Japanese text
4. Press Enter to confirm IME conversion
5. The message is immediately submitted instead of just confirming the conversion

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Claude Code for VS Code

Claude Code Version

Claude Code for VS Code

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Cursor

Additional Information

• This issue started occurring after a recent update
• The setting "cursor.chat.sendOnEnter": false is already configured but does not prevent this behavior
• Multiple related settings ("aichat.sendOnEnter": false, "chat.submitOnEnter": false) also do not resolve the issue
• Also experiencing display issues where previous text overlaps in the input field

Impact:
This makes Japanese input nearly unusable, as every IME confirmation triggers message submission.

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Reporting URLs:

• Cursor Forum: https://forum.cursor.com/
• Claude Code GitHub Issues: https://github.com/anthropics/claude-code/issues