[BUG] Bug where Japanese CJK characters are misaligned at the line break position

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?

Still reproducing on v2.1.143 (May 2026).

Environment

• Claude Code: v2.1.143
• OS: macOS 26.3.1 (25D771280a)
• Terminal: VS Code integrated terminal
• Model: claude-haiku-4-5-20251001
• Login: Claude Max account

Japanese text containing emoji renders with corrupted layout. Emoji embedded mid-sentence causes surrounding CJK characters to shift and wrap at incorrect positions, resulting in visually broken lines in the TUI. See attached screenshot.

The CHANGELOG mentions a fix (Fixed border-embedded text overflowing on CJK/emoji due to visual cell width miscalculation), but the issue persists in v2.1.143.

What Should Happen?

Japanese text containing emoji renders with corrupted layout. Emoji embedded mid-sentence causes surrounding CJK characters to shift and wrap at incorrect positions, resulting in visually broken lines in the TUI. See attached screenshot.

The CHANGELOG mentions a fix (Fixed border-embedded text overflowing on CJK/emoji due to visual cell width miscalculation), but the issue persists in v2.1.143.

What Should Happen?

Emoji should be treated as 2-column-wide characters consistently, so that CJK text containing emoji wraps correctly without visual misalignment.

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code in VS Code integrated terminal
2. Have a multi-turn conversation in Japanese (several exchanges)
3. Run /clear
4. Repeat steps 2–3 multiple times over an extended session
5. After an indeterminate number of cycles, Japanese text containing emoji

will start to wrap incorrectly in the TUI

Note: Does not reproduce reliably in just a few cycles.
Tends to occur after continued use within a single session.

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

v2.1.143

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_