diff --git a/crates/adapters/postgres/src/remote_actor.rs b/crates/adapters/postgres/src/remote_actor.rs
index ab3bd22..1e9425f 100644
--- a/crates/adapters/postgres/src/remote_actor.rs
+++ b/crates/adapters/postgres/src/remote_actor.rs
@@ -44,6 +44,6 @@ impl RemoteActorRepository for PgRemoteActorRepository {
             "SELECT url,handle,display_name,inbox_url,shared_inbox_url,public_key,last_fetched_at FROM remote_actors WHERE url=$1"
         ).bind(url).fetch_optional(&self.pool).await
         .map_err(|e| DomainError::Internal(e.to_string()))
-        .map(|o| o.map(|r| RemoteActor { url: r.url, handle: r.handle, display_name: r.display_name, inbox_url: r.inbox_url, shared_inbox_url: r.shared_inbox_url, public_key: r.public_key, last_fetched_at: r.last_fetched_at }))
+        .map(|o| o.map(|r| RemoteActor { url: r.url, handle: r.handle, display_name: r.display_name, inbox_url: r.inbox_url, shared_inbox_url: r.shared_inbox_url, public_key: r.public_key, avatar_url: None, last_fetched_at: r.last_fetched_at }))
     }
 }
diff --git a/crates/domain/src/errors.rs b/crates/domain/src/errors.rs
index f8a6af5..fb8ac55 100644
--- a/crates/domain/src/errors.rs
+++ b/crates/domain/src/errors.rs
@@ -12,6 +12,8 @@ pub enum DomainError {
     Conflict(String),
     #[error("invalid input: {0}")]
     InvalidInput(String),
+    #[error("external service error: {0}")]
+    ExternalService(String),
     #[error("internal error: {0}")]
     Internal(String),
 }
diff --git a/crates/domain/src/models/remote_actor.rs b/crates/domain/src/models/remote_actor.rs
index f8d439c..07c2fb6 100644
--- a/crates/domain/src/models/remote_actor.rs
+++ b/crates/domain/src/models/remote_actor.rs
@@ -8,5 +8,6 @@ pub struct RemoteActor {
     pub inbox_url: String,
     pub shared_inbox_url: Option<String>,
     pub public_key: String,
+    pub avatar_url: Option<String>,
     pub last_fetched_at: DateTime<Utc>,
 }
diff --git a/crates/domain/src/ports.rs b/crates/domain/src/ports.rs
index 6ffc407..86d6ff3 100644
--- a/crates/domain/src/ports.rs
+++ b/crates/domain/src/ports.rs
@@ -194,6 +194,12 @@ pub trait RemoteActorRepository: Send + Sync {
     async fn find_by_url(&self, url: &str) -> Result<Option<RemoteActor>, DomainError>;
 }
 
+#[async_trait]
+pub trait FederationActionPort: Send + Sync {
+    async fn lookup_actor(&self, handle: &str) -> Result<RemoteActor, DomainError>;
+    async fn follow_remote(&self, local_user_id: &UserId, handle: &str) -> Result<(), DomainError>;
+}
+
 #[async_trait]
 pub trait FeedRepository: Send + Sync {
     async fn home_feed(
diff --git a/crates/domain/src/testing.rs b/crates/domain/src/testing.rs
index 38078ec..c0d81fe 100644
--- a/crates/domain/src/testing.rs
+++ b/crates/domain/src/testing.rs
@@ -534,6 +534,21 @@ impl RemoteActorRepository for TestStore {
     }
 }
 
+#[async_trait]
+impl FederationActionPort for TestStore {
+    async fn lookup_actor(&self, _handle: &str) -> Result<RemoteActor, DomainError> {
+        Err(DomainError::NotFound)
+    }
+
+    async fn follow_remote(
+        &self,
+        _local_user_id: &UserId,
+        _handle: &str,
+    ) -> Result<(), DomainError> {
+        Ok(())
+    }
+}
+
 #[async_trait]
 impl FeedRepository for TestStore {
     async fn home_feed(
@@ -767,6 +782,32 @@ mod ap_repo_tests {
     }
 }
 
+#[cfg(test)]
+mod federation_port_tests {
+    use super::*;
+    use crate::value_objects::UserId;
+
+    fn uid() -> UserId {
+        UserId::new()
+    }
+
+    #[tokio::test]
+    async fn test_store_lookup_returns_not_found() {
+        let store = TestStore::default();
+        let err = store.lookup_actor("@alice@example.com").await.unwrap_err();
+        assert!(matches!(err, DomainError::NotFound));
+    }
+
+    #[tokio::test]
+    async fn test_store_follow_remote_is_noop_ok() {
+        let store = TestStore::default();
+        store
+            .follow_remote(&uid(), "@alice@example.com")
+            .await
+            .unwrap();
+    }
+}
+
 #[cfg(test)]
 mod search_tests {
     use super::*;
diff --git a/crates/presentation/src/errors.rs b/crates/presentation/src/errors.rs
index 9b320bf..db1ec41 100644
--- a/crates/presentation/src/errors.rs
+++ b/crates/presentation/src/errors.rs
@@ -28,6 +28,9 @@ impl IntoResponse for ApiError {
             Self::Domain(DomainError::Forbidden) => (StatusCode::FORBIDDEN, "forbidden".into()),
             Self::Domain(DomainError::Conflict(m)) => (StatusCode::CONFLICT, m),
             Self::Domain(DomainError::InvalidInput(m)) => (StatusCode::UNPROCESSABLE_ENTITY, m),
+            Self::Domain(DomainError::ExternalService(_)) => {
+                (StatusCode::BAD_GATEWAY, "external service error".into())
+            }
             Self::Domain(DomainError::Internal(_)) => (
                 StatusCode::INTERNAL_SERVER_ERROR,
                 "internal server error".into(),