First of all, very nice work - the API and storage model very much "just make sense".
I've encountered an issue where [Model].arrange is not properly nesting the 1st level of child nodes -> they appear at the to level of the hash along with the root nodes. Lower nodes are nested as expected.
I see the same behavior with [Model]find([node_id]).subtree.arrange
I have depth caching applied (and rebuilt), and verifying/restoring integrity checking finds no issues to fix.
I'm using v1.1.0 of the gem - any thoughts?
Fixed in 1.1.1