1. A method comprising: instantiating, in an application server of a computer system, a first user interface (UI) session in communication through a first UI connection with a corresponding first UI agent instantiated in a first client computing device and a second UI session in communication through a second UI connection with a corresponding second UI agent instantiated in a second client computing device, wherein the first UI session handles transactions for information from a data source for the first UI agent to display on the first client computing device a first UI comprising the information from the data source, wherein the second UI session handles transactions for information from the data source for the second UI agent to display on the second client computing device a second UI comprising the information from the data source; associating, in the computer system, the first and second UI connections with an application messaging channel (AMC), the AMC comprising an interface for communicating between the first UI session and the second UI session, wherein associating the first UI connection with the AMC comprises storing a UI connection identifier for the UI connection and an AMC identifier for the AMC in an AMC registry comprising a plurality of AMC definitions, wherein each AMC definition in the plurality of AMC definitions comprises an AMC identifier associated with at least one UI connection identifier or a corresponding UI agent identifier; receiving, in the computer system, on the AMC a notification of an event in the data source from the second UI session, wherein the event is caused by the second UI agent in the second client computing device; and sending the notification of the event from the computer system to the first UI agent through the first UI connection.