XSLT 3.0 streaming with Saxon requires Saxon-EE (closed-source Enterprise Edition), see https://www.saxonica.com/html/documentation/sourcedocs/strea...
Are there Open source xstl 3.0 processors with streaming support?
Are there Open source xstl 3.0 processors with streaming support?
There is also Exselt http://exselt.net (appears to be down at the moment), I don't think this is Open Source, but it was freely available for download previously.