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Why do only SOME updates reach Lemmy from Mastodon?
(mastodon.social)
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this post was submitted on 15 Jul 2026
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Mastodon sends the replies directly and only to the instance of each individual you reply to. However lemmy expects that all replies will be sent to the community instance which will then forward them to all subscribers to that community on other instances . So when mastodon interacts with a comment from an instance that is not the one hosting the community, those comments do not replicate
@db0 Thanks! Based on your explanation:
- My original post from Mastodon was to a Lemmy community hosted on the lemmy.ml instance: https://lemmy.ml/c/asklemmy
- My reply to @gary_host_laptop showed in that community because their Fediverse account is ALSO on the lemmy.ml instance.
- My reply to @sem did not show in that community because their Fediverse account is NOT on the lemmy.ml instance.
BUT
Why then did my later reply to @grandel NOT show at !asklemmy@lemmy.ml ? https://mastodon.social/@modem/_down/116907056512323326
Hm, maybe federation failed?
@db0 Yes, looks like it did fail. It would be good to figure out how/why, in order to learn what users or devs should do to avoid those failures.
Another reason your initial explanation seems not to be correct (though I'm still grateful for it!) is that even though your Fediverse account is NOT hosted on the Lemmy.ml instance, my reply to you from Mastodon DID show up on Lemmy.ml: https://lemmy.ml/post/50110148
No it doesn't seem to have reached lemmy.ml on my end
Ah wait, you mean my first reply. This might be because you pinged lemmy.ml users in it. Also note that embedded images are also broken (i.e you won't see the image I embedded on my previous reply)
@db0 Thanks, let me test whether mentioning a Lemmy.ml user (Hello, @lemmy_support !) causes this message to show up at Lemmy.ml
It would explain why even though my first reply to in this thread DID show up on Lemmy.ml, ~~my reply to your second message in this thread did NOT show up there~~.
UPDATE: my reply to your 2nd message HAS now shown up on lemmy.ml . I guess it got caught in a random federation delay. So, now we still don't know why my message to Grandel didn't show there. 🤔
If the update showed after you pinged/mentioned the .ml community, I would suspect that it's the mention that reinforced the missing federation.
@db0 You mean that pinging a user from the target Lemmy instance might force that instance to pull in intermediate messages from the same thread? Yes, that could be a factor.
Still doesn't explain why my reply to Grendel didn't reach Lemmy.ml, though.
I'm not pinging anyone from Lemmy.ml this time, so see what happens.
Also, you didn't just ping just any user. You pinged the community handle.
@db0 but the following replies that I sent from Mastodon did NOT ping the community handle, yet still reached Lemmy.ml:
- My first reply to you in this thread.
- My reply to @gary_host_laptop on my original "can you see this message?" thread.
There's some apub unseen metadata which is not visible to us which might cause any of these. I can't investigate it though, I just know that while federation is working, it's notoriously flakey between the two apub services.
@db0 do you have a GitHub account?
If so, would you mind opening an issue there, asking the Lemmy devs to take a look at this thread so investigate why my reply to Grendel didn't reach lemmy.ml even though it should have done. Thank you again.
It does seem like there must have been some kind of federation bug involved.
I'm afraid that's entirely more effort than I'm willing to do atm.