Taking a peek at the repo and the local first data layer issue (https://github.com/bartblast/hologram/issues/940) I get the sense that you aren't (and not planning to) using any off-the-shelf CRDT or the like, am I right in that assumption?

How will conflict resolution be handled? Or is it a last-write-wins type setup? It would be amazing to have this build on top of automerge or something like that! It could compile to and use the automerge js libs in the browser, and deal with automerge through a NIF server side? Ok, not knowing your implementation and plans, I have to confess I am talking a bit out of my arse here...

I don't think CRDTs are needed and they come with some significant downsides. Bart's plan has the right idea using server reconciliation.