Hi, It was reported on TeX.SE[1] that there is a bug when math matrix is used inside a math align: \starttext \startformula \startalign[n=2,align={right,left}] \NC x \NC = a ~ long ~ sequence ~ of ~ terms \NR \NC y \NC = ok ~ left \NR \NC \startmatrix[left={\left\lbrack},right={\right\rbrack}] \NC x \NR \NC y \NR \stopmatrix \NC = why ~ right? \NR \NC y \NC = ok ~ left ~ again \NR \stopalign \stopformula \stoptext gives https://i.stack.imgur.com/ZTAp3.png It appears that \startmatrix globally resets \NC. I haven't looked into the code yet to see why this is happening. Aditya [1]: https://tex.stackexchange.com/q/481411/323