diff --git a/README.md b/README.md
index a022c5c..0c88a19 100644
--- a/README.md
+++ b/README.md
@@ -98,6 +98,7 @@ Public relay binary and relay-owned room state:
 - one gateway per room, duplicate client MAC rejection, and room limits
 - stable effective room MTU chosen before Ethernet datagrams flow
 - live Ethernet datagram forwarding with no ingress reflection
+- per-peer egress budget checks against the negotiated datagram size
 - reliable `PeerJoined`/`PeerLeft` notifications to existing room peers
 - L2 safety filters for invalid-source, jumbo, switch-control, DHCP-server,
   and IPv6-RA frames
diff --git a/crates/lanparty-relay/src/server.rs b/crates/lanparty-relay/src/server.rs
index 11a87c5..a99af70 100644
--- a/crates/lanparty-relay/src/server.rs
+++ b/crates/lanparty-relay/src/server.rs
@@ -762,6 +762,7 @@ async fn build_handshake_response(
         Ok(hello) => hello,
         Err(reject) => return (None, ControlMessage::Reject(reject)),
     };
+    let peer_max_datagram_size = usize::from(hello.max_datagram_size());
     let join = rooms.lock().await.join(hello);
 
     match join {
@@ -771,7 +772,7 @@ async fn build_handshake_response(
                 welcome: join.welcome().clone(),
                 peer: join.peer().clone(),
                 remote_addr: connection.remote_address(),
-                max_datagram_size: connection_max_datagram_size,
+                max_datagram_size: peer_max_datagram_size,
             };
 
             (
@@ -950,10 +951,15 @@ mod tests {
             .unwrap()
             .await
             .unwrap();
+        let advertised_datagram_size = 1000;
+        assert!(
+            connection.max_datagram_size().unwrap() > usize::from(advertised_datagram_size),
+            "test must advertise less than the QUIC transport budget"
+        );
         let hello = EndpointHello::client(
             RoomCode::new("TESTROOM").unwrap(),
             MacAddr::new([0x02, 0, 0, 0, 0, 1]),
-            1400,
+            advertised_datagram_size,
         )
         .unwrap();
         let response = request_control_message(&connection, ControlMessage::Hello(hello))
@@ -966,7 +972,7 @@ mod tests {
 
         assert_eq!(welcome.room_id(), 1);
         assert_eq!(welcome.peer_id(), 1);
-        assert!(welcome.effective_tap_mtu() <= 1400);
+        assert!(welcome.effective_tap_mtu() <= advertised_datagram_size);
 
         connection.close(0_u32.into(), b"test complete");
         client.wait_idle().await;
@@ -978,6 +984,10 @@ mod tests {
         assert_eq!(accepted.room.as_str(), "TESTROOM");
         assert_eq!(accepted.peer.peer_id(), 1);
         assert_eq!(accepted.welcome, welcome);
+        assert_eq!(
+            accepted.max_datagram_size,
+            usize::from(advertised_datagram_size)
+        );
         assert_eq!(rooms.lock().await.room_count(), 0);
     }