I have been trying to figure out how to send a DM using #ActivityPub but I have still not found any clear instructions on what the message should contain for it to be a proper DM.

I believe it's a list of actors in the to field and these actors being included as a mention in tags.

But not 100% certain. It's all very awkward and very specific to how one writes one's front end code. I would expect that if someone were to write a messenger app for the Fediverse, e.g. something to talk with other people using DMs, its behavior would be different from the current implementations.

@helge are you replying for Mastodon specifically, or for ActivityPub in general. For the later, I don't think that in plain ActivityPub you need to do anything with the tags or mentions.

@nuekaze

DMs are AFAIK a Mastodon feature, so I'm of course talking about Mastodon.

@helge @nuekaze @mariusor How it is a Mastodon feature? Direct message is just a Note with a single actor in to, it is one of the simplest possible AP objects

@silverpill@mitra.social @helge@mymath.rocks NodeBB sends DMs. A mention is not required, just the addressing.

Mastodon conflating addressing with notifications is annoying and is the reason mention spam exists.

@julian

Please upvote https://github.com/mastodon/mastodon/issues/32242 (funny detail: the "bug" label was removed)

@helge @nuekaze @mariusor

@silverpill@mitra.social looks like the label was removed because GitHub introduced issue types.