diff --git a/crates/adapters/activitypub-base/src/service.rs b/crates/adapters/activitypub-base/src/service.rs
index f2c185f..d01e953 100644
--- a/crates/adapters/activitypub-base/src/service.rs
+++ b/crates/adapters/activitypub-base/src/service.rs
@@ -1278,6 +1278,8 @@ impl ActivityPubService {
 
 #[async_trait::async_trait]
 impl domain::ports::OutboundFederationPort for ActivityPubService {
+    // Actor identity (ap_id, followers_url) comes from federation config via get_local_actor.
+    // author_username is provided by the caller but not needed here.
     async fn broadcast_create(
         &self,
         author_user_id: &domain::value_objects::UserId,
@@ -1328,6 +1330,8 @@ impl domain::ports::OutboundFederationPort for ActivityPubService {
             .map_err(|e| domain::errors::DomainError::Internal(e.to_string()))
     }
 
+    // Actor identity (ap_id, followers_url) comes from federation config via get_local_actor.
+    // author_username is provided by the caller but not needed here.
     async fn broadcast_update(
         &self,
         author_user_id: &domain::value_objects::UserId,
@@ -1340,10 +1344,11 @@ impl domain::ports::OutboundFederationPort for ActivityPubService {
             .await
             .map_err(|e| domain::errors::DomainError::Internal(e.to_string()))?;
 
-        let ap_id = format!("{}/thoughts/{}", self.base_url, thought.id);
+        let ap_id = url::Url::parse(&format!("{}/thoughts/{}", self.base_url, thought.id))
+            .map_err(|e| domain::errors::DomainError::Internal(e.to_string()))?;
         let mut note = serde_json::json!({
             "type": "Note",
-            "id": ap_id,
+            "id": ap_id.to_string(),
             "attributedTo": local_actor.ap_id.to_string(),
             "content": thought.content.as_str(),
             "published": thought.created_at.to_rfc3339(),
@@ -1357,6 +1362,9 @@ impl domain::ports::OutboundFederationPort for ActivityPubService {
         if let Some(ref reply_url) = thought.in_reply_to_url {
             note["inReplyTo"] = serde_json::json!(reply_url);
         }
+        if let Some(updated_at) = thought.updated_at {
+            note["updated"] = serde_json::json!(updated_at.to_rfc3339());
+        }
 
         self.broadcast_update_to_followers(user_uuid, note)
             .await