> I don't think you get the idea of extensions in XMPP

I don't think you read the other comments I linked to. My fault for not copy-pasting the entire thing every time the "y u not be exactly XMPP" train comes on HN again...

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> - unique message IDs? Absent. XEPs kind of provide; but I can't tell you which of the three or for relevant ones are the most relevant (AMP IDs from XEP 0079? Stream Management from XEP 0198? Acking from XEP 0184? Something from Carbons or MAM in 0313 or 0280? You know, if you wanted some light reading...).

> - multi device? Oh. My. God. It's bananas. The spec behavior is that whenever a client sends a message, the server is supposed to consider that one the most alive, and then route all future messages exclusively to that one. So you send a message on your phone? Yeah, your desktop is just going to silently stop receiving messages.

> - there's a concept of "message carbons" to deal with this. This involves re-sending all your messages back to the server after you receive them, with special instructions to send them back again to your other clients. The amount of redundantly redundant XML involved is eyewatering.

> Combine that multidevice behavior (messages can get randomly routed anywhere at any time) with the wild-west nature of message delivery acks, and you can see how ridiculously difficult this makes the basic idea of "all clients should see the same picture".

> Overall, the XEP process, conceptually, is a great example of open extensibility. The trouble is, so much of this stuff is core to sane message delivery semantics that it really, practically speaking, causes huge problems when it's all considered "extensions". Stuff like message IDs fundamentally shouldn't be an extension because it's just too critical that all minimum-viable clients agree. You just can't build higher level stuff without that. XEPs are great. A community process for extensions should exist. It just needs to exist for extensions, not subsume the total set of realistic minimum viable features.

(All of this is a shameless repost from https://news.ycombinator.com/item?id=9772968 ; please forgive my humble attempt to save the dear reader from the need to traverse any links.)

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I get the idea of extensions in XMPP. I have tried to implement them. It is based on this first-hand experience that I am now arguing that the XEPs are a swamp. It is time to move on.

Yes, even with Compliance Profiles. It's too late. The horses have left the barn, developed tools, formed their own complex civilizations, invented light speed travel, and in fact left the galaxy. That's how far out of the barn they are.

Message ID and multi-device messaging is in fact fundamentally broken in such a unique, fascinating way in XMPP that all other clients will cease to operate correctly in the presence of a single bad client.

That's right. Any bad client can cause other clients which are following the spec to the letter to begin to drop messages, forward them incorrectly, and generally lose history and form desynchronized views of the world. I'm not kidding. If you haven't read the XEPs, and don't believe me, go read the XEPs. The only way to implement a reasonably correct multi-device behavior requires ignoring significant parts of XMPP because it is wrong.

Start. Over. XMPP is not your savior.