I have been looking for a way to give specific arguments to the TeX engine tectonic uses when compiling my document. I tried looking at the tectonic --help output and searching the forums but I haven’t been able to find a way to do this.
It doesn’t look like there is a way currently – there’s an open issue on github for this.
Just to clarify for posterity — since Tectonic is a self-contained TeX implementation, it’s not like it is launching another executable to which it can pass classic-TeX command-line arguments such as -interaction-mode. The recently added support for “unstable” -Z options in version 0.2 gives a path to turning on certain options that might traditionally be enabled using some of the classic-TeX arguments.