Post

New in Loro: Mergeable Containers! Concurrent Map child container creations no longer overwrite. This surprising overwrite issue existed in Loro, Yjs, and Automerge. Happy to finally ship a solution!

Loro

@loro.dev

Root cause: normal child Container IDs include an OpId. So if two peers create a child container concurrently, they get different IDs. When both write to the same LoroMap key, one child can overwrite the other.

9/6/26, 3:30 am0 reposts0 likes

Loro

@loro.dev

9 June

The fix: make the child ID independent of the creation OpId. We reuse Loro’s Root Container idea: identity from a unique string. For mergeable children, that string encodes the parent LoroMap + key, so both peers derive the same ID.

Loro

@loro.dev

9 June

Blog: loro.dev/blog/mergeab...

loro.devMergeable Containers: Fixing Concurrent Child Creation – LoroMergeable Containers let Loro peers concurrently create the same child container under a Map key and still merge into one shared child, by deriving identity from the logical parent/key/type instead of...