[BUG] Thai combining vowels not rendering in input field (สระ า, ำ missing)

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?

Bug Description

Thai vowels (สระ) are not rendering/displaying in the Claude Code input command field.

Affected characters:

สระ า (sara aa) - disappears when typed
สระ ำ (sara am) - disappears when typed
Possibly other Thai combining vowels (สระ อิ, อี, อื, อู, etc.)
Current behavior: When typing Thai text in the Claude Code input field, certain vowel characters are invisible/not rendered. For example, typing "สระอำ" may display as "สระอ" with the vowel missing.

Expected behavior: All Thai Unicode characters should render correctly in the input field.

Platform: thhoe 26.2 (macOS)
Terminal: VSCode integrated terminal

What Should Happen?

All Thai Unicode combining vowels (e.g. สระ า, สระ ำ) should be visible and correctly rendered in the Claude Code input field, the same as they appear in a normal text editor or terminal.

Error Messages/Logs

Steps to Reproduce

Steps to reproduce:

Open Claude Code in VSCode command
Type Thai text containing vowels (e.g., "คำ", "ทำ", "สระอา")
Observe that vowel characters are missing from the display
Environment Info

Claude Model

Other

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.31

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_