Korean input broken in Claude Code CLI on iOS/iPadOS - displays separated jamo

[junhocho]

Checklist

• Using latest version on the [App Store](http://itunes.apple.com/app/id1156707581)
• Read the [docs](http://blink.sh/docs/)
• Searched for [existing GitHub issues](https://github.com/blinksh/blink/issues)

Configuration

• Blink version: v18.3.0
• iOS/iPadOS version: iPadOS 18.4, iOS 18.5
• Device: iPad and iPhone
• Remote server: Ubuntu 24.04 (via SSH)
• Claude Code CLI version: v1.0.11
• Korean keyboards tested: iOS touch keyboard, iPadOS touch keyboard, Magic Keyboard (hardware)

Describe the bug

When typing Korean in Claude Code CLI (and other similar AI CLI tools like Codex-cli) through Blink Shell on iOS/iPadOS, Korean characters are displayed broken with separated jamo (individual Korean letters).

Current behavior:

• When typing "안녕하세요", it displays as "ㅇ아ㄴ녀ㅇ하ㅅ세ㅇ요" (with separated jamo characters)
• The issue only occurs in REPL environments like Claude Code CLI
• Korean input works perfectly fine in regular SSH sessions, tmux, and Python REPL
• Issue occurs with both software keyboards and hardware Magic Keyboard on iPadOS

Expected behavior:
Korean characters should be displayed as complete syllables (e.g., "안녕하세요") without showing intermediate jamo states.

Screenshots:

ScreenRecording_06-05-2025_08-09-19_1.mov

Analysis from investigation:
The issue appears to be caused by:

1. iOS/iPadOS Korean IME sends both intermediate jamo and completed syllable with backspace (0x08)
2. Blink passes these raw bytes unchanged through SSH
3. Claude Code's Ink-based TUI doesn't properly handle the 0x08 backspace, leaving both jamo and syllable on screen

Additional information:

• The same issue occurs with Termius on iOS
• Works correctly on iTerm2 and Linux terminals
• Only affects REPL environments using Ink-based TUI, not regular shell sessions

Steps to reproduce:

1. Connect to Ubuntu 24.04 server via SSH using Blink on iPad/iPhone
2. Launch Claude Code CLI (claude)
3. Try typing Korean text (e.g., "안녕하세요")
4. Observe that jamo characters remain visible alongside completed syllables

**Potential solutions: (not by me, suggested by AI) **

• Terminal-side: Filter out intermediate jamo/0x08 sequences before sending to REPL
• CLI-side: Proper handling of CJK IME composition in Ink-based TUI
• Workaround: Use terminals that handle IME composition differently (e.g., iTerm2 on macOS)

[junhocho]

our conversation in discord
https://discord.com/channels/441939332442619905/441940293240225793/1379962677354561538