I can't speak for latexmk, but Tectonic has, if I may say so myself, some quite sophisticated logic for managing reruns and figuring out which intermediate file

I can't speak for latexmk, but Tectonic has, if I may say so myself, some quite sophisticated logic for managing reruns and figuring out which intermediate files can't be written to disk. That being said, I wouldn't say that the `latexmk`-type functionality is the thing that is going to make Tectonic unique. Hopefully that will be the HTML output, but I have to implement that first ...