I do love the way to share code using specifications.
However, if you want to share constants between server and client for example, specifications can’t help you. So there is another way for it.
In the folder where entities are generated in the server (WAQS.Northwind in my case), you can add some files which ends by .shared.cs.
Then WAQS duplicates them in the client in client entities generation process with a namespace transformation in order to use the client one.