Chinese IME Backspace removes entire character instead of component

Phenomenon

When editing Chinese text with Pinyin IME in a contenteditable element, pressing Backspace removes the entire character 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 Chinese Pinyin IME.
3. Type a Chinese character (e.g., “你好”).
4. Press Backspace once.

Observed behavior

• The entire character is removed by a single Backspace press
• Component-level editing (e.g., editing Pinyin components) 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

• Safari: May remove entire characters instead of components, especially on macOS
• Chrome: May have different granularity behavior
• Firefox: May have different granularity behavior

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