MacVim selects one letter more to the right when selecting by mouse

Steps to reproduce

1. write text
2. put cursor in the middle of the word
3. select backwards few letters by clicking mouse
4. One letter more to the right has been selected

Screen recording with --clean parameter

https://github.com/user-attachments/assets/df0712a1-63de-4231-8d8f-b7c1bb2ccd0a

Expected behaviour

Other editors, input fields and terminals doesn't exhibit this behaviour. They select exactly the text requested to be selected.

I've tried: Notes.app, Terminal.app, Kitty, Alakritty, VSCode/VSCodium, Jetbrains editors, chat apps, various browsers

Screen recording from Notes.app

https://github.com/user-attachments/assets/8b10f823-66a6-46fc-a2cf-31ae5adb1bbb

Version of MacVim

MacVim r182 (Vim 9.1.1887)

MacVim installation method

GitHub releases

Environment

macOS Version: 15.7.2

Logs and stack traces

Vim and MacVim configuration where issue is reproducable

No response

How was MacVim launched?

• by launching MacVim.app in macOS (by using the Dock, Spotlight, or the open command)
• by running mvim/gvim in the terminal

Issue has been tested with clean configuration

• by running mvim --clean (or gvim, supplied by MacVim distribution). You can also use the File → "New Clean Window" menu item within MacVim.
• by running vim --clean (in terminal, supplied by MacVim distribution)
• by running vim --clean (in terminal, other suppliers, e.g. /usr/bin/vim)

Inizia riproducendo la selezione all'indietro con il mouse in MacVim r182 su macOS 15.7.2 con --clean, quindi confrontala con il comportamento di Vim nel terminale e con le registrazioni dell'editor fornite. Il lavoro è completato quando la selezione all'indietro con il mouse evidenzia esattamente i caratteri richiesti, senza il carattere aggiuntivo a destra.