Korean characters intermittently garbled in VS Code integrated terminal

Bug Description

Korean (Hangul) characters are intermittently garbled/corrupted when using Claude Code CLI inside the VS Code integrated terminal. The issue appears to be a character encoding problem — Korean text output occasionally renders as broken characters.

Environment

• Claude Code: 2.1.88
• VS Code: 1.110.1
• OS: macOS 14.6.1
• Shell: zsh
• LANG: en_US.UTF-8
• LC_ALL: not set
• TERM: xterm-256color

Steps to Reproduce

1. Open VS Code integrated terminal
2. Run claude in CLI mode
3. Have a conversation that involves Korean text output
4. Intermittently, Korean characters in the output will appear garbled/broken

Expected Behavior

Korean characters should render correctly and consistently in the VS Code terminal, as they do in standalone terminal apps (e.g., macOS Terminal.app, iTerm2).

Actual Behavior

Korean text output is intermittently corrupted. The issue is not consistent — sometimes the same text renders correctly, other times it appears garbled. This suggests a race condition or buffer handling issue with multi-byte UTF-8 characters rather than a missing encoding setting.

Additional Context

• The issue does not occur (or occurs far less frequently) in standalone terminal emulators
• Korean characters are multi-byte in UTF-8 (3 bytes per character), which may be relevant to buffer splitting
• LANG is set to en_US.UTF-8, so the locale should support Korean