Text input caret jumps to start when typing while using the mention feature and unable to select and delete correctly

Reproduction steps

Click on the message input field.
Type @ and select user or role from the mention list.
Type something short after the mention.
Try selecting the mention’s text and deleting it.
Try also selecting any part of the text while doing all that, it won't paste.

Expected behaviour

The text input caret should stay where the user placed it, and any selected text should remain highlighted. About the mention part, it should be able to delete any part of a mention by clicking anywhere inside the word, without having to select the whole mention or rely only on backspace.

Actual behaviour

The text input caret it's jumping to start or end, and when trying to delete the mention I cannot click on it and select any part to delete, also unable to select part of the text and paste it.

Build information

Stable Web 2026.1108.30803, Windows NT 10.0 (x64), Opera 138.0.0.0, Locale en-US

Platform

Windows, Web