Answer by F. Pantigny for Matrix: hline is cut by cmidrule

With {bNiceArray} of nicematrix, the vertical rules are never broken, even by a \cmidrule of booktabs (because they are drawn by PGF — which is a sublayer of Tikz).

\documentclass{article}\usepackage{nicematrix}\usepackage{booktabs}\begin{document}\begin{equation*}\begin{bNiceArray}{c|c}  a & b\\ \cmidrule(lr){1-2}  c & d\end{bNiceArray}\end{equation*}\end{document}