@raf - Currently the CHT is set up for a server ↔ client architecture in which the after client has synchronized the first time, the client can then operate for minutes to months with out Internet. This is what we mean by “Offline First”.
While the CHT does not support client ↔ client sync, we have experimented with a fully offline server set up. In this configuration, a remote outpost would have the minimum equipment to deploy a viable CHT server, but would not need the Internet to work. When ever the client, a tablet in your case, comes with in range of the outpost, sync could occur. Otherwise, both the client tablet and the server could continue to operate independently until sync happens.
Please review our documentation on this topic as well as a proof of concept forum post. However, please note that this is at an experimental stage and not supported for a production environment:
This is not meant for a production CHT instance. Support may be added in the future an offline CHT server in a production environment.