We’re interested in adding a TypeScript cell mode, probably first with type stripping rather than validating types. I was hoping for a pure JavaScript implementation; maybe we’ll try https://github.com/bloomberg/ts-blank-space? I’ve also been looking at https://github.com/val-town/codemirror-ts for the editor, but it’s a lot of machinery.

I would only expect type stripping, although it seems you already have the TypeScript language server hanging out in the editor for completion and docs and such, it’s not much extra challenge to get the VFS hooked up enough to show red squiggles in CodeMirror. I built a CodeMirror + typescript for the React docs site and it’s definitely machinery but not too bad maybe 600-800 LoC (never got merged, sad)