I believe Andre himself isn't a big fan of JSX so doesn't make a big number of introducing it in the documentation, but you can totally use it.

It used to be that you couldn't just plug in Cycle.js to JSX by default, because the function used for virtual-dom node creation had a signature that slightly differed from what JSX expects. These days @cycle/dom exports hJSX [0], which is compatible.

[0]: https://github.com/cyclejs/cycle-dom/blob/master/docs/api.md...

JSX worked quite well last time I tried it: https://github.com/killercup/cycle-webpack-starter