diff --git a/README.md b/README.md
index 449c579..0cc579f 100644
--- a/README.md
+++ b/README.md
@@ -147,7 +147,9 @@ Unknown unicast from a client is forwarded only to the gateway port; unknown
 unicast from the gateway is dropped instead of flooded to every remote client.
 When a peer joins or leaves, the relay sends a reliable lifecycle control event
 to peers that are still present in the room. Newly joined peers also receive
-`PeerJoined` events for peers that were already present.
+`PeerJoined` events for peers that were already present. Accepted joins notify
+existing peers before the joining peer receives its welcome, so gateways can
+seed client MAC state before a freshly accepted client starts sending frames.
 
 ### MVP Trust Model
 
diff --git a/crates/lanparty-relay/src/server.rs b/crates/lanparty-relay/src/server.rs
index 9aa9ca3..964a4b6 100644
--- a/crates/lanparty-relay/src/server.rs
+++ b/crates/lanparty-relay/src/server.rs
@@ -275,18 +275,27 @@ async fn accept_control_handshake(
     let (accepted, response) = build_handshake_response(rooms, connection, frame.as_slice()).await;
     if let Some(accepted) = &accepted {
         register_peer(sessions, accepted, connection.clone()).await;
+        // Seed existing peers before the joining peer can send Ethernet datagrams.
+        notify_peer_joined(sessions, accepted).await;
     }
 
     if let Err(error) = send_control_message(&mut send, &response).await {
         if let Some(accepted) = &accepted {
-            leave_peer(rooms, sessions, &accepted.room, accepted.peer.peer_id()).await?;
+            let leave =
+                leave_peer(rooms, sessions, &accepted.room, accepted.peer.peer_id()).await?;
+            notify_peer_left(
+                sessions,
+                &accepted.room,
+                leave.peer().peer_id(),
+                DisconnectReason::Normal,
+            )
+            .await;
         }
 
         return Err(error);
     }
 
     if let Some(accepted) = &accepted {
-        notify_peer_joined(sessions, accepted).await;
         notify_existing_peers_to_joined_peer(rooms, connection, accepted).await;
     }