The answer is you won't have to. I asked in the Replicache discord if there was any more public info on Zero and the creator linked to this notion document https://replicache.notion.site/Introducing-Zero-8ce1b1f184aa...

Basically Zero will run in the browser and has it's own server which will exist next your database. So you can do all your database management through Rails and there is a section about Custom Mutators where if you need to pipe data through to AR to have it run callbacks, that is possible.