Hello I am testing new luahbtex and comparing it with luatex because I am considering to set OpTeX with luahbtex engine instead luatex in TeXlive 2025. I have found a difference between lautex and luahbtex behavior which I am unable to explain why. The difference is shown only when huge number of fonts are downloaded by luaotfload and only with selected fonts from internet saved to ~/texmf/fonts. And it manifests only as a little delay (with luahbtex) during dlownloading the fonts to PDF at the end of the document visible if you are watching at the terminal. The PDF result is equal, but I am worried that there is a hidden bug in luahbtex because the difference is unexpected. I teseted this with OpTeX macros, they never use mode=harf. So I expect the same behavior with both engines. The example for testing is somewhat more complicated and it is exactly described at https://tex.stackexchange.com/questions/735071/ The main question is: why luatex behaves correctly (with no delay during downolading fonts) but luahbtex presents a delay in given cases? Where is the difference? Can the luatex developers explain this? Thank you Petr Olsak