Kagi Assistant renders matrices in one line. You can still distinguish between the lines, as the space between the numbers is shorter.

This line:

Should look more like this:

This behavior is consistent between different models, so I assume it is a rendering issue.
And it is probably a regression issue, as I remember it working some time ago. I also found this old feedback: https://kagifeedback.org/d/5370-latex-matrixs-not-working-correctly
I'm using Firefox 140.0.4 on Linux.
The matrices should render on multiple lines, not all squished into one.