[BUG] Windows Terminal + Korean IME: Shift+Enter carries last composing character to next line

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?

Korean IME composing character is carried to the next line when pressing Shift+Enter in Windows Terminal, instead of staying on the current line.

What Should Happen?

Pressing Shift+Enter should finalize the IME composition first, then insert a newline. The composing character should stay on the current line.

Error Messages/Logs

Steps to Reproduce

Open Claude Code in Windows Terminal on Windows 11
Add the following keybinding in Windows Terminal settings:
{"keys": "shift+enter", "command": {"action": "sendInput", "input": "\^[[13;2u"}}
Type Korean text (e.g. 테스트) without pressing space or arrow key
Press Shift+Enter while the last character is still in IME composing state
The last character (트) is carried to the next line instead of staying on the current line

테스
트

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude Code v2.1.81

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

IME: Microsoft Korean IME
Windows Terminal keybinding used: {"keys": "shift+enter", "command": {"action": "sendInput", "input": "\^[[13;2u"}}
Workaround: Pressing right arrow key before Shift+Enter to finalize IME composition