Best practice for sharing ES6 code between a node server and an Ember client

finally including the file manually in the application HTML

You should be able to the app.import the “disted” file and therefore it ends up concatenated inside your vendor file.

As for the build step, I wish I had an answer… trying to solve this elegantly myself and ended up transpiling it down and wrapping it in a factory which spits out an export or invokes define depending on the environment.