An auto-update from, say, version 3.x to 4.x would not work because the two machines wouldn't be able to communicate with each other. If the server and the client are running different versions of Presstore 4.x that are deemed compatible, then auto-update won't kick in either because the two versions are supposedly compatible and a customer may not want to update the client automatically in that case.
The only instance we would force an automatic update would be if, within the same major release (e.g. 4.x), the two versions are deemed incompatible because of some changes under the hood.

The client update works across platforms. The code for the different supported operating system is stored on the Presstore server and is being pushed out to clients based on their operating system. This means, a Presstore server running Solaris is capable of updating Mac, Linux or Windows clients - or any other combination of the four.