Sometimes using \setextrafontkerns can cause an infinite loop. Example 1: \setextrafontkerns[max] \starttext l\it l \stoptext Example 2: \setupbodyfont[libertinus] \setextrafontkerns[max] \starttext x\ss x \stoptext Both of these examples cause ConTeXt to get stuck until it runs out of memory. This happens in both MkIV and MkXL. This patch seems to fix the issue (although it may break other things...): --- texmf-context/tex/context/base/mkiv/typo-fkr.old 2022-06-30 03:05:17.702804200 -0600 +++ texmf-context/tex/context/base/mkiv/typo-fkr.lua 2022-06-30 03:05:22.286858200 -0600 @@ -57,6 +57,7 @@ end if kern ~= 0 then head, current = insertbefore(head,current,new_kern(kern)) + current = getnext(current) end lastdata = data else @@ -69,6 +70,7 @@ local kern = getkernpair(lastdata,lastchar,char) if kern ~= 0 then head, current = insertbefore(head,current,new_kern(kern)) + current = getnext(current) end end lastchar = char -- Max