Do have any pointers to javascript libraries that work this way? All the libs I've looked at (not recently) require the server to keep a running log of updates

Do have any pointers to javascript libraries that work this way? All the libs I've looked at (not recently) require the server to keep a running log of updates for the life of the document. For example, the automerge library linked elsewhere on this thread requires it. My understanding (flawed) is that you need to keep all the changes on the server because you never know how long it's been since a client has pulled/pushed changes to a document. I guess arbitrary limits based on number of updates or time can be imposed, but I haven't seen libraries that do that. Thanks.