I would like to give an update on "federation" on Bluesky.
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@mcc@mastodon.social amazing thread. so clear even explaining what you’re not clear about. but it does make me feel like it shouldn’t be this complicated. i haven’t looked at atproto but everything i read makes me not want to.
@ellyxir I honestly don't think their architecture is very good
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@mcc it's certainly possible! I didn't think they were running a separate appview yet but I could easily be wrong.
(blacksky.community is currently a fork of the Blluesky app-aka-client, it hasn't diverged much yet. not sure if and when they're planning on writing their own implementation of that)
@mcc mmmmkay it looks like Rudy is now in the process of "standing up an app.bsky.* API server" (aka appview) which "Is different from our community.blacksky.* API which is going on hold". So, my best guess is that his answer to you reflected the architecture (where the ommunity.blacksky,* API server is conceptually part of blacksky,.community) rather than the currently-available public implementation at the time.
(And no idea whether he's standing up an early implementation of their Rust appview or doing the off-the-shelf Bluesky appview or something else.)
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@mcc mmmmkay it looks like Rudy is now in the process of "standing up an app.bsky.* API server" (aka appview) which "Is different from our community.blacksky.* API which is going on hold". So, my best guess is that his answer to you reflected the architecture (where the ommunity.blacksky,* API server is conceptually part of blacksky,.community) rather than the currently-available public implementation at the time.
(And no idea whether he's standing up an early implementation of their Rust appview or doing the off-the-shelf Bluesky appview or something else.)
@jdp23 What's interesting to me here is, the bluesky line is "ha ha it's super good everyone is angry at us because it accelerates federation", but you're making it sound like Rudy is having to upend his software engineering schedule to do stuff he otherwise wouldn't have had to do at all early, because of this incident forcing him to protect his users
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@mcc what exactly is the benefit of migrating to a non bluesky PDS? I understand being on an entirely different vertical stack like Blacksky or Northsky but what does being on a PDS give you? Aren't you still (almost) entirely at bluesky's mercy?
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@jdp23 What's interesting to me here is, the bluesky line is "ha ha it's super good everyone is angry at us because it accelerates federation", but you're making it sound like Rudy is having to upend his software engineering schedule to do stuff he otherwise wouldn't have had to do at all early, because of this incident forcing him to protect his users
@mcc @jdp23 here guys this might help clarify why Rudy has to rearrange his epics in jira:
https://whtwnd.com/bnewbold.net/3m2j6ccx2bs2t
moderation can only be additive until/unless you pony up the CSAM/hashmatch API key money plus roll and run yr own mod sys at scale. thats the real Achilles heel of composable moderation-- replacing the bottom layer is incredibly expensive -
@anna @adrienne @eniko @mcc all the records in your PDS contain references to your identity (DID document), it's theoretically possible to modify the data to change that but requires rewriting your entire PDS for that account, so not particularly practical.
It's the DID that is moderated against in the higher layers, not your handle.
So it doesn't matter if you're @fred.example or @jason.example, if the DID used for one becomes the DID used for another handle.
It's kinda like how on ActivityPub, software has often encoded your username into the identifier for all your posts, meaning you can't change it without breaking everything.
(Though Mastodon is starting to fix this long-standing issue, there's fix only applies on new accounts, there's no protocol level way to fix it yet — it's kinda a weakness in JSON-LD)
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So. The thread above. An update.
We finally got a live test of the "Gertrude scenario", when a popular Blacksky user got permbanned by Bluesky. I, using my own PDS and blacksky's website, can't see him or his posts ( https://blacksky.community/profile/did:plc:2aebn3xk5t63net43eeepire/post/3m2iokicegs2b ). What gives?
A lot of people claim this is because Blacksky really is using Bluesky's appview, and gave me a way to verify this looking at headers. This seems to contradict Rudy's previous claims. I've asked Rudy for clarification: https://bsky.app/profile/did:plc:2aebn3xk5t63net43eeepire/post/3m2jve23cf22m
Follow up, 2025-12-27: Rudy here confirms the Blacksky appview is still being worked on (eg: blacksky uses bluesky's appview still)
Rudy wants revolution. (@rude1.blacksky.team)
Funding for Cash comes from CCI and the Cypherpunk Fellowship ($70K total). I am still working on the app-view. I hit storage limits on the previous server during backfill and needed to buy a $14K OVH Cloud instance.
Bluesky Social (bsky.app)
The sticking point, as he describes it, is "backfill". This alludes to the issue that makes me compare ATProto to blockchain: to get the features users expect, every node on the network must mirror the network's entire history. This is impractical, which is why bluesky is as of this moment a federated network with effectively only one node.
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Follow up, 2025-12-27: Rudy here confirms the Blacksky appview is still being worked on (eg: blacksky uses bluesky's appview still)
Rudy wants revolution. (@rude1.blacksky.team)
Funding for Cash comes from CCI and the Cypherpunk Fellowship ($70K total). I am still working on the app-view. I hit storage limits on the previous server during backfill and needed to buy a $14K OVH Cloud instance.
Bluesky Social (bsky.app)
The sticking point, as he describes it, is "backfill". This alludes to the issue that makes me compare ATProto to blockchain: to get the features users expect, every node on the network must mirror the network's entire history. This is impractical, which is why bluesky is as of this moment a federated network with effectively only one node.
@mcc its really weird for it to be controversial to compare ATProto to blockchain when it was an explicit selling point of the protocol before blockchains became embarrassing to develop for!!
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Follow up, 2025-12-27: Rudy here confirms the Blacksky appview is still being worked on (eg: blacksky uses bluesky's appview still)
Rudy wants revolution. (@rude1.blacksky.team)
Funding for Cash comes from CCI and the Cypherpunk Fellowship ($70K total). I am still working on the app-view. I hit storage limits on the previous server during backfill and needed to buy a $14K OVH Cloud instance.
Bluesky Social (bsky.app)
The sticking point, as he describes it, is "backfill". This alludes to the issue that makes me compare ATProto to blockchain: to get the features users expect, every node on the network must mirror the network's entire history. This is impractical, which is why bluesky is as of this moment a federated network with effectively only one node.
@mcc it's such a confusing aspect of the protocol. why does everything need the firehose? how do they expect it to scale/?
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@mcc it's such a confusing aspect of the protocol. why does everything need the firehose? how do they expect it to scale/?
@whitequark If hypothetically, just hypothetically, we imagine that a core design requirement of the protocol was "regardless of what happens in future, it must continue to be necessary that the company Bluesky LLC exists"… the decision becomes a lot less confusing.
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@whitequark If hypothetically, just hypothetically, we imagine that a core design requirement of the protocol was "regardless of what happens in future, it must continue to be necessary that the company Bluesky LLC exists"… the decision becomes a lot less confusing.
@whitequark (More charitably: If one considered fast, full-text search to be a highest priority feature, and it was merely *unimportant* to the designer whether a second full-service node could ever function… then one might make the decisions bluesky made here.
As for scaling, I assume when the day comes they need it to actually scale they'll either discontinue or break the externally-published linear event stream?)
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Follow up, 2025-12-27: Rudy here confirms the Blacksky appview is still being worked on (eg: blacksky uses bluesky's appview still)
Rudy wants revolution. (@rude1.blacksky.team)
Funding for Cash comes from CCI and the Cypherpunk Fellowship ($70K total). I am still working on the app-view. I hit storage limits on the previous server during backfill and needed to buy a $14K OVH Cloud instance.
Bluesky Social (bsky.app)
The sticking point, as he describes it, is "backfill". This alludes to the issue that makes me compare ATProto to blockchain: to get the features users expect, every node on the network must mirror the network's entire history. This is impractical, which is why bluesky is as of this moment a federated network with effectively only one node.
:frogsiren: BLUESKY HAS OFFICIALLY NETSPLIT :frogsiren:
There has always been more than one Fediverse. Different instances make different moderation decisions so some instances can't see posts by some users.
There has only ever been one Bluesky because every ATProto frontend uses the same Appview.
It is January 2026 and that's no longer true; Blacksky's Appview is available for beta use and there is at least 1 user banned on Bluesky but not Blacksky. And vice versa.
Rudy wants revolution. (@rude1.blacksky.team)
Bluesky runs an appview. Blacksky runs an appview. A complete appview is a several terabytes sized database of the >18 billion follows, likes and posts of all bsky users, ever and forever. To run a different appview is to make a fork in bsky’s timeline. One has new posts from Łink. One doesn’t.
Bluesky Social (bsky.app)
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:frogsiren: BLUESKY HAS OFFICIALLY NETSPLIT :frogsiren:
There has always been more than one Fediverse. Different instances make different moderation decisions so some instances can't see posts by some users.
There has only ever been one Bluesky because every ATProto frontend uses the same Appview.
It is January 2026 and that's no longer true; Blacksky's Appview is available for beta use and there is at least 1 user banned on Bluesky but not Blacksky. And vice versa.
Rudy wants revolution. (@rude1.blacksky.team)
Bluesky runs an appview. Blacksky runs an appview. A complete appview is a several terabytes sized database of the >18 billion follows, likes and posts of all bsky users, ever and forever. To run a different appview is to make a fork in bsky’s timeline. One has new posts from Łink. One doesn’t.
Bluesky Social (bsky.app)
@mcc for us tech noobies in the audience, could you explain what does this mean?
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:frogsiren: BLUESKY HAS OFFICIALLY NETSPLIT :frogsiren:
There has always been more than one Fediverse. Different instances make different moderation decisions so some instances can't see posts by some users.
There has only ever been one Bluesky because every ATProto frontend uses the same Appview.
It is January 2026 and that's no longer true; Blacksky's Appview is available for beta use and there is at least 1 user banned on Bluesky but not Blacksky. And vice versa.
Rudy wants revolution. (@rude1.blacksky.team)
Bluesky runs an appview. Blacksky runs an appview. A complete appview is a several terabytes sized database of the >18 billion follows, likes and posts of all bsky users, ever and forever. To run a different appview is to make a fork in bsky’s timeline. One has new posts from Łink. One doesn’t.
Bluesky Social (bsky.app)
The "portable identity" elements of Bluesky/ATProto make the netsplit just a tad odd. My account is hosted on a PDS server I run, so I'm beholden to no frontend. If I log in through the main Blacksky frontend (Bluesky appview) one user I'm following shows only an error message. Via the Staging Blacksky frontend (atproto.africa), I can see I'm following him and see his posts. I'm SO curious about the edge cases. I assume if I boost him it's hidden from the Bluesky appview. What if I reply to him?
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The "portable identity" elements of Bluesky/ATProto make the netsplit just a tad odd. My account is hosted on a PDS server I run, so I'm beholden to no frontend. If I log in through the main Blacksky frontend (Bluesky appview) one user I'm following shows only an error message. Via the Staging Blacksky frontend (atproto.africa), I can see I'm following him and see his posts. I'm SO curious about the edge cases. I assume if I boost him it's hidden from the Bluesky appview. What if I reply to him?
@mcc When you are suspended by bluesky corp, is the ban at the app view or PDS level?
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The "portable identity" elements of Bluesky/ATProto make the netsplit just a tad odd. My account is hosted on a PDS server I run, so I'm beholden to no frontend. If I log in through the main Blacksky frontend (Bluesky appview) one user I'm following shows only an error message. Via the Staging Blacksky frontend (atproto.africa), I can see I'm following him and see his posts. I'm SO curious about the edge cases. I assume if I boost him it's hidden from the Bluesky appview. What if I reply to him?
Oh and I can't get staging.blacksky on my phone app. So imagine if you were using Mastodon, but you saw a slightly different list of posters, *and potentially a different set of your own posts*, depending on whether you were using your PC or your phone. This is great if there's a banned user you want to follow— you get an *option* to follow them. Mastodon.social can deny me the *option* to follow someone, on Fediverse. But except in this edge case that *might* not be a fantastic user experience!
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@mcc for us tech noobies in the audience, could you explain what does this mean?
@coracinho Does this help? https://mastodon.social/@mcc/115918101156654032
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@mcc When you are suspended by bluesky corp, is the ban at the app view or PDS level?
@fabrice This is a VERY interesting question, as the answer appears to be "all of them". And when Link got banned, *that answer appeared to be surprising even to Bluesky employees*. The original messaging from Bluesky suggested you'd get banned only by the "labeler"— a third thing altogether. But there's obvious problems with that answer, it's never what Bluesky implemented. After Link got banned Bluesky said they were reviewing this, but I don't think *changed* anything.
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Oh and I can't get staging.blacksky on my phone app. So imagine if you were using Mastodon, but you saw a slightly different list of posters, *and potentially a different set of your own posts*, depending on whether you were using your PC or your phone. This is great if there's a banned user you want to follow— you get an *option* to follow them. Mastodon.social can deny me the *option* to follow someone, on Fediverse. But except in this edge case that *might* not be a fantastic user experience!
Oh, and let's consider, for a moment, the downsides of an individual user being able to "opt out" of moderation decisions. The problem with misbehavior on social media is force multipliers. One person harassing you is no problem; one person and their 3000 friends is a big problem. Imagine Bluesky and Blacksky ban user X but Trumpsky lets X keep posting. Now their 3000 friends— still in Bluesky's good graces— can see their posts calling to harass you, AND can zero-friction zip over to yell at you
