An example of the behavior: echo "A" | sed "s/A/𝐀/g" produces (in mintty and in Windows Terminal, both running bash) sed: is_mb_char: mbrtowc (0x80) returned 3 My understanding is that this is due to the issue reported by Thomas Wolff on July 22: https://cygwin.com/pipermail/cygwin/2025-July/258513.html Any news about when this bug in Cygwin 3.6.4 will be fixed? -------------- next part -------------- A non-text attachment was scrubbed... Name: cygcheck.out Type: application/octet-stream Size: 35645 bytes Desc: not available URL: <https://cygwin.com/pipermail/cygwin/attachments/20250926/d8d33931/attachment-0001.obj>