@TonyRoberts, Wrote: I still don't get the event being fired that I described originally, though.
As a first step, may you please check that you are not referring to a later jsdoc?
Note that "onStart" was introduced in Web Client Library quite recently (version 4.1 build 1261).
About the snapshot, note that, indeed, any update event for an item (let's call it ITEM) sent by the Data Adapter before ITEM is ever subscribed to (i.e. before the first client subscribes to ITEM) is ignored.
All updates for ITEM coming from the feed before the subscription should be kept by the Data Adapter; then, upon the subscription, they can be sent by the Data Adapter to the Server as the item snapshot.
Alternatively, the Data Adapter should, in turn, ask its feed for updates for ITEM only upon the subscription; at that moment, it could also ask the feed for the current item state and send it as the snapshot.
In both cases, the Server forwards this snapshot to the first client; then it takes care of managing the snapshot for the subsequent clients.
This requirement may complicate the Data Adapter somewhat. However, your tests already include a workaround for this. If you can subscribe to ITEM from a dummy client when the item state is still empty, then your Data Adapter can always send an empty snapshot and just forward the updates to the Server, which will produce suitable snapshots for ITEM for the real clients.
Dario