[IOS] No/disappearing Conversion Line when Typing CJK (Chinese, Japanese, Korean) Characters into TextInput (0.76.5)

Description

When typing CJK characters into TextInput, the conversion line (the line under the group of pre-formatted characters) disappears after typing the first character or doesn't appear at all.

https://github.com/user-attachments/assets/6afb4b71-cb77-406b-a768-8b5fbd775cf7

Steps to reproduce

1. npx create-expo-app@latest
2. In the home screen, add

import { useState } from 'react';
import { TextInput } from 'react-native';
...
  const [text, setText] = useState('')
  ...
    <TextInput value={text} onChangeText={setText} style={{ height: 50, width: '100%' }} />

3. Run the project with npm run ios
4. Type Japanese, Chinese, or Korean

React Native Version

0.76.5

Affected Platforms

Runtime - iOS

Output of npx react-native info

System:
  OS: macOS 15.1.1
  CPU: (8) arm64 Apple M2
  Memory: 164.45 MB / 8.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 22.5.1
    path: ~/.nvm/versions/node/v22.5.1/bin/node
  Yarn:
    version: 1.22.19
    path: /opt/homebrew/bin/yarn
  npm:
    version: 10.8.2
    path: ~/.nvm/versions/node/v22.5.1/bin/npm
  Watchman:
    version: 2024.12.02.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.15.2
    path: /usr/local/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.2
      - iOS 18.2
      - macOS 15.2
      - tvOS 18.2
      - visionOS 2.2
      - watchOS 11.2
  Android SDK: Not Found
IDEs:
  Android Studio: 2022.3 AI-223.8836.35.2231.10671973
  Xcode:
    version: 16.2/16C5032a
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 20.0.2
    path: /Users/personal/.jenv/shims/javac
  Ruby:
    version: 2.6.10
    path: /usr/bin/ruby
npmPackages:
  "@react-native-community/cli": Not Found
  react: Not Found
  react-native: Not Found
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: Not found
  newArchEnabled: Not found
iOS:
  hermesEnabled: Not found
  newArchEnabled: Not found

Stacktrace or Logs

N/A

Reproducer

https://github.com/haruki-m/react-native-text-input-issue

Screenshots and Videos

No response

Inizia con il riproduttore react-native-text-input-issue collegato ed eseguilo con npm run ios, quindi traccia il comportamento di iOS TextInput durante l’inserimento di caratteri giapponesi, cinesi e coreani. L’issue non indica alcun file sorgente o test specifico; il lavoro è completato quando la riga di conversione rimane visibile durante la composizione CJK nei passaggi di riproduzione forniti.