[BUG] Korean IME: Characters completely invisible during composition in input field (macOS)

[minislively]

Environment

• Platform: macOS Darwin 25.2.0
• Terminal: iTerm2, VS Code integrated terminal, Terminal.app
• Claude Code Version: Latest (installed via npm)
• IME: macOS default Korean IME
• Locale: ko_KR.UTF-8

Description

When typing Korean in the Claude Code input field, characters are completely invisible during IME composition. The input field appears empty while typing. Only after pressing Enter does the output show the Korean text was actually received.

This is different from the cursor positioning issues (#16322, #16372) - here the characters do not display at all during composition, not even at a wrong position.

Steps to Reproduce

1. Open Claude Code in terminal
2. Switch to Korean IME
3. Type Korean characters (e.g., "안녕하세요")
4. Observe: Input field shows nothing - completely blank
5. Press Enter
6. Observe: Output correctly shows "안녕하세요"

Expected Behavior

Korean characters should be visible during IME composition, showing intermediate states:

• Type ㅎ → see ㅎ
• Type ㅎ + ㅏ → see 하
• Type ㅎ + ㅏ + ㄴ → see 한

Actual Behavior

• Input field remains completely empty during entire composition
• No characters visible at any point until Enter is pressed
• Makes Korean input essentially "blind typing"

Impact

• Severity: Critical for Korean users
• Affected users: All Korean IME users on macOS
• Workaround: Type in external editor and paste (disrupts workflow significantly)

Related Issues

• [BUG] Korean IME composition: jamo not displayed until syllable completion (Kitty + Gureumkim) #18291 - Jamo not displayed until syllable completion (Kitty + Gureumkim)
• [CRITICAL] Korean IME: Composing characters display at wrong position (unusable for Korean users) #16322 - Composing characters display at wrong position (Windows)
• [BUG] IME input causes performance issues and duplicate conversion candidates #1547 - IME input causes performance issues
• Investigation: Fixing IME Issues in Claude Code by Patching React Ink / React Inkのパッチによる Claude Code のIME問題修正について #3045 - Investigation: Fixing IME Issues by Patching React Ink

Root Cause Analysis

Based on investigation, the root cause is React Ink's TextInput component in terminal raw mode:

1. Terminal raw mode (setRawMode true) provides byte-level STDIN without IME composition events
2. Ink TextInput processes keystrokes individually without understanding multi-stage character formation
3. No composition buffer exists for tracking in-progress IME input
4. CJK double-width characters may confuse the cursor positioning/rendering logic

Suggested Fix Direction

1. Detect IME composition state heuristically from raw byte sequences
2. Maintain a separate composition buffer for pre-edit text
3. Render composition text inline with visual indicator (underline) at cursor position
4. Handle compositionend equivalent when final character is committed

This is the most requested fix across multiple CJK-related issues and would benefit Korean, Japanese, and Chinese users.

[github-actions]

Found 3 possible duplicate issues:

1. [BUG] CJK IME input not visible during composition in terminal #22147
2. [BUG] Korean IME composition: jamo not displayed until syllable completion (Kitty + Gureumkim) #18291
3. [BUG] In Linux terminal, Chinese characters do not appear while typing #19616

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
• To prevent auto-closure, add a comment or 👎 this comment

🤖 Generated with Claude Code

[cirospaciari]

This has been fixed. Korean IME characters are now visible during composition.

[github-actions]

This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.