[Bug] Vietnamese IME input broken in interactive mode (Warp terminal)

Description

Vietnamese text input using IME (Telex/VNI input method) does not work correctly in Claude Code interactive mode. Characters are garbled or not composed properly.

Environment

• Claude Code version: 2.1.12
• Terminal: Warp
• OS: macOS (Darwin 25.3.0)
• Locale: en_US.UTF-8

Steps to reproduce

1. Open Warp terminal
2. Run claude to start interactive session
3. Try to type Vietnamese text using Telex/VNI input method
4. Observe: characters are broken/garbled

Expected behavior

Vietnamese characters should be composed correctly (e.g., typing "vie^.t" with Telex should produce "việt")

Actual behavior

Characters are not composed properly, input is garbled/broken

Notes

• Vietnamese input works correctly in Warp terminal without Claude Code running
• Issue only occurs when Claude Code interactive mode is active
• Similar to Thai text issue #19365 (combining characters problem)
• Workaround: Use -p flag with piped input, or paste pre-composed text

Related issues

• #19365 (Thai text rendering with combining characters)