I've got module loading working. Its a combination of a few pieces I worked on. programmatic import + modules as panels + mutable fileattachments. Its a little different to observable where you only import via an import statement. Now you add a module to the bundle, which better in the multi-module UI world as a module can be useful without being directly linked (e.g. it can just implement a useful tool). The list of modules is recorded in a JSON file attachment. This list of extra modules is programatically imported on startup. The programatic import first tries to load the module from the bundle local-first, if it can't find it it falls back to the Observable API. So this mechanism allows you to initialize from the Observable ecosystem, but once loaded into the runtime, subsequent exports include it in the bundle and it becomes a vendored local-first dependancy.