Same here. It compiles well when the math font definition is commentend. The error seems to be there:

\setfontid

<to be read again>

\3>mainface-12pt-mm-mr--1

<macro> \font_helpers_low_level_define_compact ...ec \empty \let \lastrawfontcall \relax \mutable \letcsname #2\endcsname \relax \else \edef \somefontspec {at \number \ETC.

<macro> \font_helpers_trigger_define ...\def \v_font_size_relative {#1}\def \v_font_size_absolute {#2}\font_helpers_low_level_define {#3}\v_font_identifier_class

\csname \v_font_identifier_class \endcsname \setfalse \c_font_auto_size \ifskipfontcharacteristics \else \setfontcharacter...

<macro> \m_font_class_direction ...fcsname \??fontinstanceready \fontclass -\fontbody -\s!mm -\fontfamily \endcsname \settrue \c_font_auto_size \lastnamedcs

\else \font_helpers_set_math_family_b \fi

<macro> \font_helpers_set_math_family_indeed_compact ..._family_set_scales_compact \let \mathsizesuffix \mathtextsuffix \let \fontface \!!plusone \font_helpers_set_math_family_a

\textfont #1\font \font_helpers_set_math_family_a \textfont #1\font \scriptfont #1\font \scriptscriptfont #1\font \let \ma...

<macro> \font_helpers_set_math_family ...!mm -#2-\fontsize -1\endcsname \font_helpers_preset_math_family_indeed #1#2\else \font_helpers_set_math_family_indeed #1#2

\fi \else \font_helpers_set_math_family_indeed #1#2\fi

Jairo

El vie, 29 de ene. de 2021 a la(s) 15:59, Pablo Rodriguez (oinos@gmx.es) escribió:

Dear list,

this sample cannot be compiled with latest LMTX (2021.01.29 19:44).

  \enableexperiments[fonts.compact]

  \definefontfamily
      [mainface]
      [rm]
      [TeX Gyre Pagella]

  \definefontfamily
      [mainface]
      [mm]
      [TeX Gyre Pagella Math]

  \setupbodyfont
      [mainface, 12pt]

  \starttext
    \input zapf
  \stoptext

I get the following error message:

  I was looking for a control sequence whose current meaning
  has been defined by \font or a valid font id number.
  mtx-context     | fatal error: return code: 256

Previous latest from compiles the sample perfectly fine.

Could anyone confirm this bug?

Mamy thanks for your help,

Pablo
--
http://www.ousia.tk
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