The latest commit to NodeBB's activitypub branch updates the post handler so that the replies property returns either an empty array (i.e. []) if it has no direct replies, or a resolvable URL to a replies collection.

This step completes the two-way traversal options for any given object. Given any object (e.g. an as:Note or otherwise), you can traverse up through parent objects via inReplyTo, and down through child objects via replies.

However, neither of these options are ideal for building out a reliable context around any given object. For a variety of reasons, somewhere along the parent or child chain you could run into issues retrieving the object (outages, timeouts, DNS, etc.), which is problematic when you're hoping to completely traverse a linked list.

What we need is to move past the uni-dimensional movement of inReplyTo/replies, and to the next dimension: the ability to see the entire context at once!

Luckily, one of the ForumWG's goals has been working towards a more reliable implementation using the rather aptly named context property, resolvable to an OrderedCollection. NodeBB already does provide this, Discourse is going to build out this capability, and I am interested in seeing if any other AP impementers are open to building out implementations against it.

Short-to-medium term, we're hoping to draft an FEP to codify this behaviour, but I'd love to see some working implementations first!