feat: add broadcast_move to ActivityPubService; bump to v0.1.9

Threads serves actors at threads.net but their id field uses www.threads.net.
Extract apex_domain() helper and fall back to apex comparison when the
strict verify_domains_match check fails.

Cargo.lock

@@ -1368,7 +1368,7 @@ dependencies = [
 
 [[package]]
 name = "k-ap"
-version = "0.1.0"
+version = "0.1.9"
 dependencies = [
  "activitypub_federation",
  "anyhow",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "k-ap"
-version = "0.1.0"
+version = "0.1.9"
 edition = "2024"
 description = "Generic ActivityPub protocol layer"
 license = "MIT"

src/activities.rs

@@ -65,12 +65,20 @@ impl Activity for FollowActivity {
                 )));
             }
         };
-        if target_domain != data.domain {
-            return Err(Error::bad_request(anyhow::anyhow!(
-                "follow target is not a local actor"
-            )));
+        if target_domain == data.domain {
+            return Ok(());
         }
-        Ok(())
+        // Domain mismatch — still accept if the UUID resolves to a local user.
+        // This handles domain migrations where remote servers have cached the old actor URL.
+        if let Some(uuid) = crate::urls::extract_user_id_from_url(target_url) {
+            if data.user_repo.find_by_id(uuid).await.ok().flatten().is_some() {
+                tracing::debug!(target = %target_url, local_domain = %data.domain, "accepting follow for migrated actor URL");
+                return Ok(());
+            }
+        }
+        Err(Error::bad_request(anyhow::anyhow!(
+            "follow target is not a local actor"
+        )))
     }
 
     async fn receive(self, data: &Data<Self::DataType>) -> Result<(), Self::Error> {
@@ -829,10 +837,86 @@ impl Activity for MoveActivity {
         if data.federation_repo.is_domain_blocked(domain).await? {
             return Ok(());
         }
+
+        // Fetch the target actor via signed request.
+        let target = ObjectId::<DbActor>::from(self.target.clone())
+            .dereference(data)
+            .await
+            .map_err(|e| Error::from(anyhow::anyhow!("{e}")))?;
+
+        // Verify the new actor claims the old identity via alsoKnownAs.
+        let old_url = self.object.as_str();
+        if target.also_known_as.as_deref() != Some(old_url) {
+            return Err(Error::bad_request(anyhow::anyhow!(
+                "Move target alsoKnownAs does not reference old actor"
+            )));
+        }
+
+        // Migrate DB records; get user IDs that need a re-follow.
+        let affected = data
+            .federation_repo
+            .migrate_follower_actor(old_url, self.target.as_str())
+            .await
+            .map_err(|e| Error::from(anyhow::anyhow!("{e}")))?;
+
+        let affected_count = affected.len();
+
+        // Re-follow on behalf of each affected local user.
+        for local_user_id in &affected {
+            let local_actor = match crate::actors::get_local_actor(*local_user_id, data).await {
+                Ok(a) => a,
+                Err(e) => {
+                    tracing::warn!(error = %e, %local_user_id, "Move: failed to load local actor for re-follow");
+                    continue;
+                }
+            };
+
+            let follow_id = match crate::urls::activity_url(&data.base_url) {
+                Ok(u) => u,
+                Err(e) => {
+                    tracing::warn!(error = %e, "Move: failed to generate follow activity URL");
+                    continue;
+                }
+            };
+
+            let follow = FollowActivity {
+                id: follow_id,
+                kind: Default::default(),
+                actor: activitypub_federation::fetch::object_id::ObjectId::from(
+                    local_actor.ap_id.clone(),
+                ),
+                object: activitypub_federation::fetch::object_id::ObjectId::from(
+                    self.target.clone(),
+                ),
+            };
+
+            let sends = match activitypub_federation::activity_sending::SendActivityTask::prepare(
+                &activitypub_federation::protocol::context::WithContext::new_default(follow),
+                &local_actor,
+                vec![target.inbox_url.clone()],
+                data,
+            )
+            .await
+            {
+                Ok(s) => s,
+                Err(e) => {
+                    tracing::warn!(error = %e, "Move: failed to prepare re-follow");
+                    continue;
+                }
+            };
+
+            for send in sends {
+                if let Err(e) = send.sign_and_send(data).await {
+                    tracing::warn!(error = %e, %local_user_id, "Move: re-follow delivery failed");
+                }
+            }
+        }
+
         tracing::info!(
             actor = %self.actor.inner(),
             target = %self.target,
-            "received Move (account migration) — target noted"
+            affected = affected_count,
+            "received Move — migrated follower relationships"
         );
         Ok(())
     }

src/actors.rs

@@ -2,7 +2,6 @@ use activitypub_federation::{
     config::Data,
     fetch::object_id::ObjectId,
     http_signatures::generate_actor_keypair,
-    kinds::actor::PersonType,
     protocol::{public_key::PublicKey, verification::verify_domains_match},
     traits::{Actor, Object},
 };
@@ -19,6 +18,7 @@ use crate::user::ApProfileField;
 pub struct DbActor {
     pub user_id: uuid::Uuid,
     pub username: String,
+    pub display_name: Option<String>,
     pub public_key_pem: String,
     pub private_key_pem: Option<String>,
     pub inbox_url: Url,
@@ -57,18 +57,39 @@ pub struct ProfileFieldObject {
     pub value: String,
 }
 
+/// Accepts any AP actor type on inbound JSON; always serializes as "Person" for local actors.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum ApActorType {
+    Person,
+    Service,
+    Application,
+    Organization,
+    Group,
+}
+
+impl Default for ApActorType {
+    fn default() -> Self {
+        Self::Person
+    }
+}
+
 #[derive(Debug, Clone, Deserialize, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct Person {
     #[serde(rename = "type")]
-    kind: PersonType,
+    kind: ApActorType,
     id: ObjectId<DbActor>,
+    #[serde(default)]
     preferred_username: String,
     inbox: Url,
-    outbox: Url,
-    followers: Url,
-    following: Url,
-    public_key: PublicKey,
+    #[serde(default)]
+    outbox: Option<Url>,
+    #[serde(default)]
+    followers: Option<Url>,
+    #[serde(default)]
+    following: Option<Url>,
+    pub public_key: PublicKey,
+    #[serde(default)]
     name: Option<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
     summary: Option<String>,
@@ -78,6 +99,7 @@ pub struct Person {
     url: Option<Url>,
     #[serde(skip_serializing_if = "Option::is_none")]
     discoverable: Option<bool>,
+    #[serde(default)]
     manually_approves_followers: bool,
     #[serde(skip_serializing_if = "Option::is_none", default)]
     updated: Option<DateTime<Utc>>,
@@ -152,6 +174,7 @@ pub async fn get_local_actor(
     Ok(DbActor {
         user_id,
         username: user.username,
+        display_name: None,
         public_key_pem: public_key,
         private_key_pem: Some(private_key),
         inbox_url,
@@ -170,6 +193,11 @@ pub async fn get_local_actor(
     })
 }
 
+fn apex_domain(url: &Url) -> String {
+    let host = url.host_str().unwrap_or("");
+    host.strip_prefix("www.").unwrap_or(host).to_owned()
+}
+
 #[async_trait::async_trait]
 impl Object for DbActor {
     type DataType = FederationData;
@@ -219,6 +247,7 @@ impl Object for DbActor {
         Ok(Some(DbActor {
             user_id,
             username: user.username,
+            display_name: None,
             public_key_pem: public_key,
             private_key_pem: private_key,
             inbox_url,
@@ -272,9 +301,9 @@ impl Object for DbActor {
             id: self.ap_id.clone().into(),
             preferred_username: self.username.clone(),
             inbox: self.inbox_url.clone(),
-            outbox: self.outbox_url.clone(),
-            followers: self.followers_url.clone(),
-            following: self.following_url.clone(),
+            outbox: Some(self.outbox_url.clone()),
+            followers: Some(self.followers_url.clone()),
+            following: Some(self.following_url.clone()),
             public_key,
             name: Some(self.username.clone()),
             summary: self.bio.clone(),
@@ -295,11 +324,26 @@ impl Object for DbActor {
         expected_domain: &Url,
         _data: &Data<Self::DataType>,
     ) -> Result<(), Self::Error> {
-        verify_domains_match(json.id.inner(), expected_domain)?;
-        Ok(())
+        if verify_domains_match(json.id.inner(), expected_domain).is_ok() {
+            return Ok(());
+        }
+        if apex_domain(json.id.inner()) == apex_domain(expected_domain) {
+            tracing::debug!(
+                actor_id = %json.id.inner(),
+                expected = %expected_domain,
+                "domain verified via www-apex equivalence"
+            );
+            return Ok(());
+        }
+        verify_domains_match(json.id.inner(), expected_domain).map_err(Error::from)
     }
 
     async fn from_json(json: Self::Kind, data: &Data<Self::DataType>) -> Result<Self, Self::Error> {
+        tracing::debug!(
+            actor_id = %json.id.inner(),
+            username = %json.preferred_username,
+            "ingesting remote actor"
+        );
         let shared_inbox_url = json.endpoints.as_ref().map(|e| e.shared_inbox.to_string());
         let actor = RemoteActor {
             url: json.id.inner().to_string(),
@@ -308,7 +352,7 @@ impl Object for DbActor {
             shared_inbox_url,
             display_name: json.name.clone(),
             avatar_url: json.icon.as_ref().map(|i| i.url.to_string()),
-            outbox_url: Some(json.outbox.to_string()),
+            outbox_url: json.outbox.as_ref().map(|u| u.to_string()),
         };
         data.federation_repo.upsert_remote_actor(actor).await?;
 
@@ -320,13 +364,17 @@ impl Object for DbActor {
             .endpoints
             .as_ref()
             .and_then(|e| Url::parse(e.shared_inbox.as_str()).ok());
-        let outbox_url = json.outbox.clone();
-        let followers_url = json.followers.clone();
-        let following_url = json.following.clone();
+        let fallback = |suffix: &str| {
+            Url::parse(&format!("{}{}", ap_id, suffix)).unwrap_or_else(|_| ap_id.clone())
+        };
+        let outbox_url = json.outbox.clone().unwrap_or_else(|| fallback("/outbox"));
+        let followers_url = json.followers.clone().unwrap_or_else(|| fallback("/followers"));
+        let following_url = json.following.clone().unwrap_or_else(|| fallback("/following"));
 
         Ok(DbActor {
             user_id,
             username: json.preferred_username.clone(),
+            display_name: json.name.clone(),
             public_key_pem: json.public_key.public_key_pem,
             private_key_pem: None,
             inbox_url,

src/lib.rs

@@ -25,4 +25,4 @@ pub use repository::{
     BlockedDomain, FederationRepository, Follower, FollowerStatus, FollowingStatus, RemoteActor,
 };
 pub use service::ActivityPubService;
-pub use user::{ApProfileField, ApUser, ApUserRepository};
+pub use user::{ApProfileField, ApUser, ApUserRepository, LookedUpActor};

src/repository.rs

@@ -131,4 +131,12 @@ pub trait FederationRepository: Send + Sync {
     async fn remove_blocked_actor(&self, local_user_id: uuid::Uuid, actor_url: &str) -> Result<()>;
     async fn get_blocked_actors(&self, local_user_id: uuid::Uuid) -> Result<Vec<String>>;
     async fn is_actor_blocked(&self, local_user_id: uuid::Uuid, actor_url: &str) -> Result<bool>;
+    /// Migrate all local following records from old_actor_url to new_actor_url.
+    /// Returns the local user IDs whose records were migrated (excludes users
+    /// already following the new actor — they need no re-follow).
+    async fn migrate_follower_actor(
+        &self,
+        old_actor_url: &str,
+        new_actor_url: &str,
+    ) -> Result<Vec<uuid::Uuid>>;
 }

src/service.rs

@@ -330,6 +330,36 @@ impl ActivityPubService {
         Ok(serde_json::to_string(&WithContext::new_default(person))?)
     }
 
+    /// Resolve a `@user@domain` handle to actor data using a signed HTTP request.
+    /// Unlike a plain unauthenticated fetch, this works with instances (e.g. Threads)
+    /// that require HTTP signatures before returning full actor JSON.
+    pub async fn lookup_actor_by_handle(
+        &self,
+        handle: &str,
+    ) -> anyhow::Result<crate::user::LookedUpActor> {
+        tracing::info!(handle, "looking up remote actor");
+        let data = self.federation_config.to_request_data();
+        let actor = Self::webfinger_https(handle, &data).await
+            .inspect_err(|e| tracing::warn!(handle, error = %e, "actor lookup failed"))?;
+        let domain = actor.ap_id.host_str().unwrap_or("").to_string();
+        let handle = format!("{}@{}", actor.username, domain);
+        tracing::info!(handle, ap_url = %actor.ap_id, "remote actor resolved");
+        Ok(crate::user::LookedUpActor {
+            handle,
+            display_name: actor.display_name,
+            bio: actor.bio,
+            avatar_url: actor.avatar_url,
+            banner_url: actor.banner_url,
+            ap_url: actor.ap_id,
+            outbox_url: Some(actor.outbox_url),
+            followers_url: Some(actor.followers_url),
+            following_url: Some(actor.following_url),
+            also_known_as: actor.also_known_as,
+            profile_url: actor.profile_url,
+            attachment: actor.attachment,
+        })
+    }
+
     /// Returns the ActivityPub router compatible with any outer state `S`.
     /// Handlers only use `Data<FederationData>` injected by the middleware layer,
     /// so the router is independent of the application state type.
@@ -570,6 +600,7 @@ impl ActivityPubService {
             "https://{}/.well-known/webfinger?resource=acct:{}@{}",
             domain_str, user, domain_str
         );
+        tracing::debug!(handle, wf_url, "resolving webfinger");
         let wf: serde_json::Value = reqwest::Client::new()
             .get(&wf_url)
             .header("Accept", "application/jrd+json, application/json")
@@ -588,6 +619,7 @@ impl ActivityPubService {
             .and_then(|l| l["href"].as_str())
             .ok_or_else(|| anyhow::anyhow!("no self link in WebFinger response"))?
             .to_owned();
+        tracing::debug!(handle, self_href, "webfinger resolved, fetching actor with signature");
         let self_url = url::Url::parse(&self_href)?;
         let actor: DbActor = ObjectId::from(self_url)
             .dereference(data)
@@ -1171,6 +1203,74 @@ impl ActivityPubService {
         Ok(())
     }
 
+    /// Broadcast a Move activity to all accepted followers, signalling that this
+    /// actor is migrating to `new_actor_url`.
+    ///
+    /// **Pre-condition (caller's responsibility):**
+    /// Before calling this, the application must persist `also_known_as = [new_actor_url]`
+    /// in the local actor's row so the old actor JSON already advertises the new URL
+    /// when remote servers fetch it to verify the cross-reference.
+    pub async fn broadcast_move(
+        &self,
+        user_id: uuid::Uuid,
+        new_actor_url: url::Url,
+    ) -> anyhow::Result<()> {
+        let data = self.federation_config.to_request_data();
+        let local_actor = get_local_actor(user_id, &data)
+            .await
+            .map_err(|e| anyhow::anyhow!("{e}"))?;
+
+        let followers = data.federation_repo.get_followers(user_id).await?;
+        let accepted: Vec<_> = followers
+            .into_iter()
+            .filter(|f| f.status == FollowerStatus::Accepted)
+            .collect();
+
+        if accepted.is_empty() {
+            tracing::info!(
+                %user_id,
+                "broadcast_move: no accepted followers, nothing to send"
+            );
+            return Ok(());
+        }
+
+        let inboxes = collect_inboxes(&accepted);
+
+        let move_id =
+            crate::urls::activity_url(&self.base_url).map_err(|e| anyhow::anyhow!("{e}"))?;
+
+        let move_activity = crate::activities::MoveActivity {
+            id: move_id,
+            kind: Default::default(),
+            actor: ObjectId::from(local_actor.ap_id.clone()),
+            object: local_actor.ap_id.clone(),
+            target: new_actor_url.clone(),
+        };
+
+        let sends = SendActivityTask::prepare(
+            &WithContext::new_default(move_activity),
+            &local_actor,
+            inboxes,
+            &data,
+        )
+        .await?;
+
+        let failures = send_with_retry(sends, &data).await;
+        if !failures.is_empty() {
+            tracing::warn!(
+                count = failures.len(),
+                "some Move deliveries failed permanently"
+            );
+        }
+
+        tracing::info!(
+            %user_id,
+            target = %new_actor_url,
+            "broadcast_move: delivered to all accepted followers"
+        );
+        Ok(())
+    }
+
     pub async fn block_actor(
         &self,
         local_user_id: uuid::Uuid,

src/user.rs

@@ -7,6 +7,24 @@ pub struct ApProfileField {
     pub value: String,
 }
 
+/// Resolved actor data returned by [`crate::service::ActivityPubService::lookup_actor_by_handle`].
+/// Fetched via a signed HTTP request so strict instances (e.g. Threads) return full data.
+#[derive(Debug, Clone)]
+pub struct LookedUpActor {
+    pub handle: String,
+    pub display_name: Option<String>,
+    pub bio: Option<String>,
+    pub avatar_url: Option<Url>,
+    pub banner_url: Option<Url>,
+    pub ap_url: Url,
+    pub outbox_url: Option<Url>,
+    pub followers_url: Option<Url>,
+    pub following_url: Option<Url>,
+    pub also_known_as: Option<String>,
+    pub profile_url: Option<Url>,
+    pub attachment: Vec<ApProfileField>,
+}
+
 #[derive(Debug, Clone)]
 pub struct ApUser {
     pub id: uuid::Uuid,