Math Parameters Can Not Be Resolved From Libertinus Math.

\definefontfamily [MF] [rm] [libertinusserif]
\definefontfamily [MF] [ss] [libertinussans]
\definefontfamily [MF] [tt] [libertinusmono]
\definefontfamily [MF] [math] [libertinusmath]
\setupbodyfont [MF,10.5pt]
\starttext
1234567890
\im{12_{34}}

\stoptext
resolvers       | formats | executing runner 'run luametatex format': /home/lsl_046/Project-Outer/tex/texmf-linux-64/bin/luametatex --jobname="./test.tex" --socket --shell-escape --fmt=/home/lsl_046/Project-Outer/tex/texmf-cache/luametatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luametatex/cont-en.fmt --lua=/home/lsl_046/Project-Outer/tex/texmf-cache/luametatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luametatex/cont-en.lui  --c:currentrun=1 --c:fulljobname="./test.tex" --c:input="./test.tex" --c:kindofrun=3 --c:maxnofruns=1 --c:once --c:synctex="repeat" --c:texmfbinpath="/home/lsl_046/Project-Outer/tex/texmf-linux-64/bin"
system          > 
system          > ConTeXt  ver: 2026.02.19 11:49 LMTX  fmt: 2026.4.3  int: english/english
system          > 
system          > 'cont-new.mkxl' loaded
open source     > level 1, order 1, name '/home/lsl_046/Project-Outer/tex/texmf-context/tex/context/base/mkxl/cont-new.mkxl'
system          > beware: some patches loaded from cont-new.mkxl
close source    > level 1, order 1, name '/home/lsl_046/Project-Outer/tex/texmf-context/tex/context/base/mkxl/cont-new.mkxl'
system          > files > jobname './test', input './test.tex', result './test'fonts           > latin modern fonts are not preloaded
languages       > language 'en' is active
system          > synctex functionality is enabled, expect 5-10 pct runtime overhead!
open source     > level 1, order 2, name './test.tex'
fonts           > bodyfont '10.5pt' is defined (can better be done global (maybe use \usebodyfont)
tex error       > tex error on line 8 in file ./test.tex: Math error: parameter 'subshiftdown' with id 49 in style 2 is not set

<macro> \im 
    #1->\relax \ifmmode \mathconstruct {\textstyle \indisplaymath \conditionalfalse #1}\else \Ustartmathmode \textstyle \indisplaymath \conditionalfalse \expand \everyinsidemathematics \relax #1\Ustopmathmode 
    \fi 
<line 3.8> 
    \im{12_{34}}

 1     \definefontfamily [MF] [rm] [libertinusserif]
 2     \definefontfamily [MF] [ss] [libertinussans]
 3     \definefontfamily [MF] [tt] [libertinusmono]
 4     \definefontfamily [MF] [math] [libertinusmath]
 5     \setupbodyfont [MF,10.5pt]
 6     \starttext
 7     1234567890
 8 >>  \im{12_{34}}
 9     
10     \stoptext
11     
Sorry, but I can't typeset math unless various parameters have been set. This isnormally done by loading special math fonts into the math family slots. Your font
set is lacking at least the parameter mentioned earlier.
mtx-context     | fatal error: return code: 1
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