I haven't started implementing plugins yet, so details are still vague. General thoughts, they communicate with the core through a simple JSON-based protocol, so can be written in any language you like. I imagine Python will be one of the popular choices. Among other things, they'll be able to annotate the text with rich-text spans, for things like syntax coloring. Also, I'm planning for them to be async, so they won't slow typing even when they're busy computing.