Error with 20211008 ConTeXt:

    ConTeXt  ver: 2021.10.08 20:18 LMTX fmt: 2021.10.9  int: english/english

    ...

    tex error       > tex error on line 1 in file ./mmm.tex: Undefined
    control sequence \??markingfilter



    <argument>
         \csname \??markingfilter
         \v!default \endcsname {chapter}
    <macro> \sectionheadmarkingtitle
         #1#2->\clf_markingtitle {#1}{#2
         }
    <macro> \strc_markings_get_yes
         ...rking \begincsname \??markingclass #1\endcsname {#2}{#3}}\fi
    \orelse \ifparameter #2\or \markingcommand {#1}{\csname
    \??markingfilter #2\endcsname {#1}}\else \markingcommand
    {#1}{\csname \??markingfilter \v!default \endcsname {#1}}
         \fi \endgroup ...
    <to be read again>

         \fi
    <macro> \page_layouts_process_element_indeed
         ...andcolor #1#2\begincsname \??layouttextstrut
    \layoutelementparameter \c!strut \endcsname \ignorecrlf \edef
    \p_width {\layoutelementparameter #3}\ifempty \p_width \else
    \expandafter \page_layouts_process_element_limited \fi \p_text
         \endgroup
    <macro> \currentlayoutelement
         ...kern -\makeupwidth \fi \letfromlayoutelementparameter
    \p_text \c!righttext \ifempty \p_text \kern \makeupwidth \else \hbox
    to \makeupwidth \bgroup \hss \page_layouts_process_element_indeed
    \c!rightstyle \c!rightcolor \c!rightwidth
         \egroup \fi
      ...

    <line 3.12>
         \stoptext

      1 >>
      2     %\setupheadertexts [][][{\it\getmarking[chapter]}][]  % fails
      3     \setupheadertexts [][][{\getmarking[chapter]}][]     % fails
      4     %\setupheadertexts [][][\getmarking[chapter]][]       % succeeds

    MWE to create. Note that the \it is not necessary to trigger the
    error, just the braces.

    %\setupheadertexts [][][{\it\getmarking[chapter]}][]  % fails
    \setupheadertexts [][][{\getmarking[chapter]}][]     % fails
    %\setupheadertexts [][][\getmarking[chapter]][]       % succeeds

    \starttext

    \chapter{abc}
    abc
    \chapter{def}
    def
    \stoptext

-- 
Rik