CJK IME: Leading roman letter inserted while composing (e.g. “kかきくけこ”, “sさしすせそ”) on Text app (NC 31.0.10)

[jg-shinji-ueda]

Describe the bug
On Chromium-based browsers (Chrome/Edge), the Nextcloud Text web editor inserts an unexpected leading latin letter from the romaji sequence during Japanese IME composition. For example, typing:

かきくけこ
さしすせそ

typing keyboard ( k a k i k u k e k o \n s a s h i s u s e s o )

becomes:

ｋかきくけこ
ｓさしすせそ

This reproduces consistently even with all extensions disabled and in a private window.

To Reproduce
Steps to reproduce the behavior:

1. Go to Files in the Web UI.
2. Create a new Text file (plain text) and open it (Nextcloud Text editor).
3. Use Chrome or Edge on the client.
4. Switch to a Japanese IME (e.g., Microsoft IME, Hiragana mode).
5. Type the two lines:

かきくけこ
さしすせそ

6. See error: a leading latin letter (“k”, “s”) is inserted at the start of each composed line.

Expected behavior
Only the committed Japanese characters should be inserted. No stray latin letters should appear during IME composition, and the caret position should remain correct.

Screenshots

Server details:

• Nextcloud version: 31.0.10 (Hub 10) [snap]
• PHP Version: 8.3.23
• Database: **MySQL **
• Nextcloud Text app: 5.0.2 (nextcloud.occ app:list | grep text)

Client details:

• OS: Windows 11 25H2
• Browser: Chrome, Edge
• Browser version:
• Chrome: ** 142.0.7444.60**
• Edge: 142.0.3595.53
• Device: laptop

I tried in demo site

tiptap
tiptap

Works as expected.

[xuhaida76]

also reported #7789