Tools and techniques for synchronizing metadata and document content across client systems using different communication channels are provided. These tools may define logical communication channels between client software components, and may allocate one of these channels to synchronizing updates to the contents of documents shared between these client components. These tools may allocate another one of the communication channels to synchronizing metadata between the client components, with the metadata describing activity pertaining to the shared documents. The client components may receive indications of activity made by users to the document contents, and may create metadata representing the activity. These client components may then transmit this metadata, using the further communication channel, to any number of other client components automatically in real time with the updates.