[BUG] incorrect selection with zero-width characters in terminal.app

Version of Kakoune

2026.05.21

Reproducer

open kakounse in Terminal.app; enter a̲bcdefg in insert mode, then in normal mode move selection cursor past the b

Outcome

selected letter decouples from the highlighted letter

Screenshot example: c has background highlight but d is selected letter. The actual selection is the selected letter; typing rx from normal mode replaces the d with x.

Expectations

background highlight should match foreground selection

Additional information

MacOS 26.5.2, Terminal.app