Introduction

In the Livelymerge project, Dan Ingalls, Peter Van Hardenberg, and I (Alex Warth) are building a Lively Kernel-like system whose heap — every object, class, and method — is an Automerge document. The pitch, from the first note in this series, was that this would give us merges “for free”: multiple users share the same object memory, work on it concurrently (even offline), and Automerge reconciles everything.

I also wrote that merging the state of a live system is a nontrivial problem, and that there’s no way to guarantee that objects’ invariants won’t be violated. This note looks that problem straight in the eye, with a concrete example. We don’t have a solution yet — this is an acknowledgment, not a victory lap — but I’ll sketch one possible solution that we find promising, and we’d love to hear your ideas, too.

Exhibit A: a linked list

Automerge’s promise is convergence : after two clients exchange their changes, they are guaranteed to arrive at the same state.…