I think maybe I assumed that the error from a query wouldn't be enough as what would differentiate this failed query from a regular one?

In the current direction we are going if a query is onlineOnly then we just call forward(operation). If we do this then the query just fails. However my understanding was that we need to provide the client with some way to track this. Maybe we don't and maybe the fact that we are now exposing the network interface will cover us?
e.g.

if (online) {

  client.mutate(...)

} else {

  this.showNotification("Go online first")

}