The same thing happens when the app sees an input text in a language that the developer didn’t consider. Even if the input file is made for LuaLaTeX, using style files specific to that engine, it auto senses to xelatex and requires manually stopping auto-sense and then specify the correct engine, each time a new file is opened. Any situation that is not known to the developer and their auto sense rules will most likely default in xelatex, and that happens VERY often. One thing I dislike about Texpad is their faulty “auto-sense” algorithm and the developer insists on not providing manually setting the default engine.
