CJK (Chinese/Japanese/Korean) IME input is fundamentally broken on iOS Fabric — affecting all New Architecture users since 0.76

Description

CJK (Chinese, Japanese, Korean) IME input on iOS TextInput has been broken since the introduction of the New Architecture (Fabric). This affects hundreds of millions of potential users across East Asia — arguably the largest language group using IME-based input.

The issues include:

• Composition underline disappears or never renders — users cannot see which characters are being composed
• Composition state is destroyed mid-input — typed characters are lost or corrupted during IME conversion
• maxLength blocks IME mid-composition — Korean syllable building (ㅎ→하→한) and Chinese Pinyin input are truncated prematurely
• Controlled value prop interferes with composition — standard React patterns break CJK input entirely

This is not a minor visual glitch — it makes TextInput unusable for CJK languages on Fabric. Users are forced to either disable the New Architecture entirely or build native workarounds.

Steps to reproduce

1. Create a new React Native project with New Architecture enabled (Fabric)
2. Add a TextInput component (controlled with value/onChangeText or uncontrolled)
3. Run on iOS
4. Switch to a CJK keyboard (Japanese Romaji, Chinese Pinyin, or Korean)
5. Type text — e.g., "shinkansen" for Japanese, "zhongguo" for Chinese Pinyin, or any Korean syllable
6. Observe: Composition underline is missing, composition state is destroyed, or characters are corrupted

React Native Version

0.76.5 ~ 0.82+ (all Fabric-enabled versions)

Affected Platforms

• Runtime - iOS

Areas

• Fabric - The New Renderer

Output of npx @react-native-community/cli 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
  npm:
    version: 10.8.2
    path: ~/.nvm/versions/node/v22.5.1/bin/npm
SDKs:
  iOS SDK:
    Platforms:
      - iOS 18.2
      - macOS 15.2
IDEs:
  Xcode:
    version: 16.2/16C5032a
    path: /usr/bin/xcodebuild
npmPackages:
  react: 18.3.1
  react-native: 0.76.5 ~ 0.82+

(Aggregated from multiple reporters — see #48497 and #55257 for individual environment details)

Stacktrace or Logs

No crash — this is a rendering/input behavior regression.
The IME composition state is silently destroyed by Fabric's synchronous
updateEventEmitter:/updateState: calls and defaultTextAttributes reapplication.

Reproducer

Expo Snack: https://snack.expo.dev/@hujbvf/missing-underline-during-japanese-ime-composition-on-ios?platform=ios

Reproducer repo (from #48497): https://github.com/haruki-m/react-native-text-input-issue

Screenshots and Videos

Reproduction video — Japanese IME composition underline missing (from #55257)

https://github.com/user-attachments/assets/85b9b7a0-ca40-4ac3-bcea-75ef00a636f1

Reproduction video — CJK composition broken (from #48497)

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

Fix verification — CJK (Chinese, Japanese, Korean) working correctly after fix (from PR #56082)

https://github.com/user-attachments/assets/50aa22d0-d374-4bbd-a438-d83c3494207d

Fix verification — English no regression (from PR #56082)

https://github.com/user-attachments/assets/5ee0a093-211a-4331-b42e-f902de416cb1

---

Impact

• Languages affected: Chinese (Pinyin, Wubi, Zhuyin), Japanese (Romaji, Kana), Korean
• Versions affected: 0.76.5 through at least 0.81.4 (all Fabric-enabled versions)
• Workaround: Disable New Architecture, or use a native module workaround
• User reports: See #48497 (open since Jan 2025, 15+ months) and #55257 (14 👍, open since Jan 2026)

Existing Fix

PR #56082 provides a comprehensive fix addressing 7 distinct root causes in the Fabric TextInput implementation. It includes:

• 22 native XCTests covering full composition lifecycles for Korean, Japanese, Chinese, and mixed input
• 18 JS tests covering controlled/uncontrolled components, maxLength interaction, and cross-language switching
• Manual verification videos demonstrating correct behavior in all four languages (English, Chinese, Japanese, Korean)
• Detailed root-cause analysis for each of the 7 issues

The PR was submitted on March 13, 2026, test videos were provided upon request on March 19, and it has been waiting for review since then — over 4 weeks with no further feedback.

Why This Needs Attention

1. New Architecture is now the default — CJK users cannot simply opt out forever
2. The fix is ready — thoroughly tested, well-documented, and waiting for review
3. The community is waiting — multiple users in #48497 have reported the same issue over 15 months, with no official fix in sight
4. East Asian market adoption risk — apps targeting Chinese, Japanese, or Korean users cannot confidently adopt the New Architecture while basic text input is broken

References

• Original issue: #48497 (Jan 2025)
• Related issue: #55257 (Jan 2026)
• Fix PR: #56082 (Mar 2026, awaiting review)

Bắt đầu bằng việc xem xét PR #56082 cùng với các chi tiết tái hiện từ #48497 và #55257. Chạy Expo Snack hoặc reproducer được liên kết trên iOS với Fabric và kiểm tra quá trình ghép ký tự của IME cho tiếng Trung, tiếng Nhật và tiếng Hàn. Được xem là hoàn tất khi các XCTests native và các bài kiểm thử JS được tham chiếu đều đạt, đồng thời quá trình ghép ký tự hoạt động mà không gây hồi quy đối với tiếng Anh.