Replication is a fundamental idea in collaborative editing systems
Sub-problem 1: Source of Truth
Offline-mode support is unachievable if we don’t keep a local copy of the data that the client can operate on while offline.
The basic idea is that we let the server maintain the source of truth for the conversation thread and we make a copy (replica) of that conversation thread on each client.
Each client operates on their replica based on events from the server or the user but only the server is allowed to make updates to the source of truth.
The clients collaborate on making changes to the source of truth by sending update requests to the server and syncing server states with their respective replica states.