[BUG] Thai text renders garbled/staggered and screen flickers on Windows Terminal (2 machines, 2 accounts)

Environment

• Claude Code version: 2.1.289
• OS: Windows 11 Home 10.0.26300
• Terminal: Windows Terminal (PowerShell profile)
• Language of conversation: Thai

What happens

• Thai text (which uses zero-width combining vowel/tone marks) is drawn at the wrong horizontal positions: lines are shifted/staggered and wrap mid-word.
• Markdown tables break apart completely.
• The bottom status line ("auto mode on · ...") gets duplicated several times.
• The screen flickers while output streams, and gets much worse when scrolling with the mouse wheel.
• The user cannot even see the text they are typing in the input box, so the CLI is unusable.

Reproduced on

• 2 different computers (home and office) and 2 different Claude accounts, so it is not specific to one machine.

Steps to reproduce

1. Run claude in Windows Terminal on Windows 11.
2. Have a conversation in Thai where the assistant replies with paragraphs, lists and a markdown table.
3. Scroll with the mouse wheel.

Expected

Thai text aligned normally, as in other terminal programs.