Typed character is duplicated when replacing a selection (single block or cross-block)

[wiebkevogel]

When text is selected (either within a single block or across multiple blocks) and a character is typed to replace the selection, the typed character appears twice instead of once (e.g. typing "a" results in "aa").

Steps to reproduce:

1. Go to the Editor.js playground (https://editorjs.io/)
2. Type some text into a block, e.g. "Hello world"
3. Select the block(s) with the mouse so they become highlighted (works when selecting a single block, and also when dragging the selection across multiple blocks)
4. Type a single character, e.g. "a"

Expected behavior:

The selected text is removed and replaced by the single typed character ("a").

Screencast:

Bildschirmaufnahme.2026-07-09.um.10.39.06.mov

Device, Browser, OS:

• Browser: Chrome (latest)
• OS: macOS 26.5.2
• Reproducible on official playground: Yes

Editor.js version:

• Version: 2.31.6