This isn't technically true, the extension host we use is directly the one from VSCode, such that we can support their extensions (well...a subset as we fill in the gaps in for the Oni2 <-> ExtHost communication).

But the actual core editor is all seperate, written in ReasonML (or OCaml if you know that instead), with a bunch of C libs in the background we've wrapped (Skia/Harfbuzz/We wrap real vim etc).

So the core editing experience has no code sharing, but the extension side of things does!