crates/adapters/activitypub-base/src/service.rs

@@ -1561,6 +1561,15 @@ impl domain::ports::OutboundFederationPort for ActivityPubService {
             .await
             .map_err(|e| domain::errors::DomainError::Internal(e.to_string()))
     }
+
+    async fn broadcast_actor_update(
+        &self,
+        user_id: &domain::value_objects::UserId,
+    ) -> Result<(), domain::errors::DomainError> {
+        self.broadcast_actor_update(user_id.as_uuid())
+            .await
+            .map_err(|e| domain::errors::DomainError::Internal(e.to_string()))
+    }
 }
 
 #[async_trait::async_trait]

crates/adapters/event-payload/src/lib.rs

@@ -68,6 +68,9 @@ pub enum EventPayload {
     UserRegistered {
         user_id: String,
     },
+    ProfileUpdated {
+        user_id: String,
+    },
     FetchRemoteActorPosts {
         actor_ap_url: String,
         outbox_url: String,
@@ -98,6 +101,7 @@ impl EventPayload {
             Self::UserBlocked { .. } => "users.blocked",
             Self::UserUnblocked { .. } => "users.unblocked",
             Self::UserRegistered { .. } => "users.registered",
+            Self::ProfileUpdated { .. } => "users.profile_updated",
             Self::FetchRemoteActorPosts { .. } => "federation.fetch_outbox",
             Self::FetchActorConnections { .. } => "federation.fetch_connections",
         }
@@ -209,6 +213,9 @@ impl From<&DomainEvent> for EventPayload {
             DomainEvent::UserRegistered { user_id } => Self::UserRegistered {
                 user_id: user_id.to_string(),
             },
+            DomainEvent::ProfileUpdated { user_id } => Self::ProfileUpdated {
+                user_id: user_id.to_string(),
+            },
             DomainEvent::FetchRemoteActorPosts {
                 actor_ap_url,
                 outbox_url,
@@ -345,6 +352,9 @@ impl TryFrom<EventPayload> for DomainEvent {
             EventPayload::UserRegistered { user_id } => DomainEvent::UserRegistered {
                 user_id: UserId::from_uuid(parse_uuid(&user_id, "user_id")?),
             },
+            EventPayload::ProfileUpdated { user_id } => DomainEvent::ProfileUpdated {
+                user_id: UserId::from_uuid(parse_uuid(&user_id, "user_id")?),
+            },
             EventPayload::FetchRemoteActorPosts {
                 actor_ap_url,
                 outbox_url,

crates/application/src/services/federation_event.rs

@@ -277,6 +277,10 @@ impl FederationEventService {
                     .await
             }
 
+            DomainEvent::ProfileUpdated { user_id } => {
+                self.ap.broadcast_actor_update(user_id).await
+            }
+
             _ => Ok(()),
         }
     }
@@ -308,6 +312,7 @@ mod tests {
         undo_announced: Mutex<Vec<String>>,
         liked: Mutex<Vec<String>>,
         undo_liked: Mutex<Vec<String>>,
+        actor_updated: Mutex<Vec<UserId>>,
     }
 
     #[async_trait]
@@ -366,6 +371,11 @@ mod tests {
             self.undo_liked.lock().unwrap().push(ap_id.to_string());
             Ok(())
         }
+
+        async fn broadcast_actor_update(&self, user_id: &UserId) -> Result<(), DomainError> {
+            self.actor_updated.lock().unwrap().push(user_id.clone());
+            Ok(())
+        }
     }
 
     fn alice() -> User {

crates/application/src/use_cases/profile.rs

@@ -1,7 +1,8 @@
 use domain::{
     errors::DomainError,
+    events::DomainEvent,
     models::{top_friend::TopFriend, user::User},
-    ports::{TopFriendRepository, UserRepository},
+    ports::{EventPublisher, TopFriendRepository, UserRepository},
     value_objects::{UserId, Username},
 };
 
@@ -38,8 +39,10 @@ pub async fn get_user_by_id_or_username(
     }
 }
 
+#[allow(clippy::too_many_arguments)]
 pub async fn update_profile(
     users: &dyn UserRepository,
+    events: &dyn EventPublisher,
     user_id: &UserId,
     display_name: Option<String>,
     bio: Option<String>,
@@ -56,6 +59,11 @@ pub async fn update_profile(
             header_url,
             custom_css,
         )
+        .await?;
+    events
+        .publish(&DomainEvent::ProfileUpdated {
+            user_id: user_id.clone(),
+        })
         .await
 }
 

crates/domain/src/events.rs

@@ -60,6 +60,9 @@ pub enum DomainEvent {
     UserRegistered {
         user_id: UserId,
     },
+    ProfileUpdated {
+        user_id: UserId,
+    },
     FetchRemoteActorPosts {
         actor_ap_url: String,
         outbox_url: String,

crates/domain/src/ports.rs

@@ -471,4 +471,7 @@ pub trait OutboundFederationPort: Send + Sync {
         object_ap_id: &str,
         author_inbox_url: &str,
     ) -> Result<(), DomainError>;
+
+    /// Fan out an Update(Actor) to all accepted followers after a profile change.
+    async fn broadcast_actor_update(&self, user_id: &UserId) -> Result<(), DomainError>;
 }

crates/presentation/src/handlers/users.rs

@@ -72,6 +72,7 @@ pub async fn patch_profile(
 ) -> Result<Json<UserResponse>, ApiError> {
     update_profile(
         &*s.users,
+        &*s.events,
         &uid,
         body.display_name,
         body.bio,