Hi--- Here's another apparent change on the MP side---for keyword functions, string parameters no longer accept string variables directly. They do seem to register them (hasparameter => true) but don't capture the value (getparameter => 0). Thus: system > ConTeXt ver: 2021.07.16 22:03 LMTX fmt: 2021.7.21 int: english/english metapost > trace > This is MPLIB for LuaMetaTeX, version 3.11, running in scaled mode. metapost > trace > metapost > trace > loading metafun for lmtx, including the plain 1.004 base definitions metapost > trace > metapost > trace > >> "string constant fuschia ..." metapost > trace > >> true metapost > trace > >> "fuschia" metapost > trace > >> "string variable fuschia = fuschia ..." metapost > trace > >> true metapost > trace > >> 0 metapost > trace > >> "expression containing string variable fuschia = fuschia ..." metapost > trace > >> true metapost > trace > >> "fuschia" String constant: succeeds String variable: fails String expression with string variable: succeeds Here's the MWE: %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % system > ConTeXt ver: 2021.07.16 22:03 LMTX fmt: 2021.7.21 int: english/english \startMPdefinitions presetparameters "parameters_Test" [ ] def Test = applyparameters "parameters_Test" "do_Test" enddef; def do_Test = pushparameters "parameters_Test"; show hasparameter "color"; show getparameter "color"; enddef; \stopMPdefinitions \starttext hello \startalignment[center] \startplacefigure \startMPcode string fuschia; fuschia = "fuschia"; show "string constant fuschia ..."; Test [ color = "fuschia" ]; show "string variable fuschia = " & fuschia & " ..."; Test [ color = fuschia ]; show "expression containing string variable fuschia = " & fuschia & " ..."; Test [ color = "" & fuschia ]; \stopMPcode \stopplacefigure \stopalignment goodbye \stoptext %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Kevin W. Rudd, Ph.D. CAPT, USN (Ret) Computer Architecture & Computer Engineering Advanced Computing Systems (ACS) Research Program Laboratory for Physical Sciences (LPS) 443-654-7878 kevin@lps.umd.edumailto:kevin@lps.umd.edu Visiting Research Professor United States Naval Academy rudd@usna.edumailto:rudd@usna.edu