Japanese IME Backspace removes entire character instead of component

Phenomenon

When editing Japanese text with IME in a contenteditable element, pressing Backspace removes the entire character or word instead of allowing component-level editing. This makes fine-grained correction difficult and differs from native input fields on the same platform.

Reproduction example

1. Focus the editable area.
2. Activate Japanese IME.
3. Type a Japanese character or word (e.g., “漢字”).
4. Press Backspace once.

Observed behavior

• The entire character or word is removed by a single Backspace press
• Component-level editing (e.g., editing individual kanji or hiragana) is not possible
• The event log shows only one beforeinput / input pair for the deletion
• Behavior differs from native input fields

Expected behavior

• Each Backspace press should allow more granular deletion, matching how native inputs behave
• Component-level editing should be possible
• Behavior should be consistent with native input fields

Browser Comparison

• Chrome: May remove entire characters instead of components
• Edge: Similar to Chrome
• Firefox: May have different granularity behavior
• Safari: Not applicable on Windows

Notes and possible direction for workarounds

• Compare behavior with a plain <input> element in the same environment to confirm the difference
• This behavior can affect cursor movement, undo granularity, and diff calculation
• Consider implementing custom backspace handling for finer control