diff --git a/src/transport/middle_proxy/handshake.rs b/src/transport/middle_proxy/handshake.rs
index 251c911..1016c6b 100644
--- a/src/transport/middle_proxy/handshake.rs
+++ b/src/transport/middle_proxy/handshake.rs
@@ -38,6 +38,22 @@ use super::MePool;
 
 const ME_KDF_DRIFT_STRICT: bool = false;
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+enum KdfClientPortSource {
+    LocalSocket = 0,
+    SocksBound = 1,
+}
+
+impl KdfClientPortSource {
+    fn from_socks_bound_port(socks_bound_port: Option<u16>) -> Self {
+        if socks_bound_port.is_some() {
+            Self::SocksBound
+        } else {
+            Self::LocalSocket
+        }
+    }
+}
+
 /// Result of a successful ME handshake with timings.
 pub(crate) struct HandshakeOutput {
     pub rd: ReadHalf<TcpStream>,
@@ -52,18 +68,18 @@ pub(crate) struct HandshakeOutput {
 
 impl MePool {
     fn kdf_material_fingerprint(
-        local_addr_nat: SocketAddr,
+        local_ip_nat: IpAddr,
         peer_addr_nat: SocketAddr,
-        client_port_for_kdf: u16,
-        reflected: Option<SocketAddr>,
-        socks_bound_addr: Option<SocketAddr>,
+        reflected_ip: Option<IpAddr>,
+        socks_bound_ip: Option<IpAddr>,
+        client_port_source: KdfClientPortSource,
     ) -> u64 {
         let mut hasher = DefaultHasher::new();
-        local_addr_nat.hash(&mut hasher);
+        local_ip_nat.hash(&mut hasher);
         peer_addr_nat.hash(&mut hasher);
-        client_port_for_kdf.hash(&mut hasher);
-        reflected.hash(&mut hasher);
-        socks_bound_addr.hash(&mut hasher);
+        reflected_ip.hash(&mut hasher);
+        socks_bound_ip.hash(&mut hasher);
+        client_port_source.hash(&mut hasher);
         hasher.finish()
     }
 
@@ -359,35 +375,48 @@ impl MePool {
 
         let ts_bytes = crypto_ts.to_le_bytes();
         let server_port_bytes = peer_addr_nat.port().to_le_bytes();
-        let client_port_for_kdf = socks_bound_addr
+        let socks_bound_port = socks_bound_addr
             .map(|bound| bound.port())
-            .filter(|port| *port != 0)
-            .unwrap_or(local_addr_nat.port());
+            .filter(|port| *port != 0);
+        let client_port_for_kdf = socks_bound_port.unwrap_or(local_addr_nat.port());
+        let client_port_source = KdfClientPortSource::from_socks_bound_port(socks_bound_port);
         let kdf_fingerprint = Self::kdf_material_fingerprint(
-            local_addr_nat,
+            local_addr_nat.ip(),
             peer_addr_nat,
-            client_port_for_kdf,
-            reflected,
-            socks_bound_addr,
+            reflected.map(|value| value.ip()),
+            socks_bound_addr.map(|value| value.ip()),
+            client_port_source,
         );
         let mut kdf_fingerprint_guard = self.kdf_material_fingerprint.lock().await;
-        if let Some(prev_fingerprint) = kdf_fingerprint_guard.get(&peer_addr_nat).copied()
-            && prev_fingerprint != kdf_fingerprint
+        if let Some((prev_fingerprint, prev_client_port)) =
+            kdf_fingerprint_guard.get(&peer_addr_nat).copied()
         {
-            self.stats.increment_me_kdf_drift_total();
-            warn!(
-                %peer_addr_nat,
-                %local_addr_nat,
-                client_port_for_kdf,
-                "ME KDF input drift detected for endpoint"
-            );
-            if ME_KDF_DRIFT_STRICT {
-                return Err(ProxyError::InvalidHandshake(
-                    "ME KDF input drift detected (strict mode)".to_string(),
-                ));
+            if prev_fingerprint != kdf_fingerprint {
+                self.stats.increment_me_kdf_drift_total();
+                warn!(
+                    %peer_addr_nat,
+                    %local_addr_nat,
+                    client_port_for_kdf,
+                    client_port_source = ?client_port_source,
+                    "ME KDF material drift detected for endpoint"
+                );
+                if ME_KDF_DRIFT_STRICT {
+                    return Err(ProxyError::InvalidHandshake(
+                        "ME KDF material drift detected (strict mode)".to_string(),
+                    ));
+                }
+            } else if prev_client_port != client_port_for_kdf {
+                self.stats.increment_me_kdf_port_only_drift_total();
+                debug!(
+                    %peer_addr_nat,
+                    previous_client_port_for_kdf = prev_client_port,
+                    client_port_for_kdf,
+                    client_port_source = ?client_port_source,
+                    "ME KDF client port changed with stable material"
+                );
             }
         }
-        kdf_fingerprint_guard.insert(peer_addr_nat, kdf_fingerprint);
+        kdf_fingerprint_guard.insert(peer_addr_nat, (kdf_fingerprint, client_port_for_kdf));
         drop(kdf_fingerprint_guard);
 
         let client_port_bytes = client_port_for_kdf.to_le_bytes();
diff --git a/src/transport/middle_proxy/health.rs b/src/transport/middle_proxy/health.rs
index c07ec4f..192bf1b 100644
--- a/src/transport/middle_proxy/health.rs
+++ b/src/transport/middle_proxy/health.rs
@@ -395,6 +395,19 @@ async fn maybe_rotate_single_endpoint_shadow(
     }
 
     let endpoint = endpoints[0];
+    if pool.is_endpoint_quarantined(endpoint).await {
+        pool.stats
+            .increment_me_single_endpoint_shadow_rotate_skipped_quarantine_total();
+        shadow_rotate_deadline.insert(key, now + Duration::from_secs(SHADOW_ROTATE_RETRY_SECS));
+        debug!(
+            dc = %dc,
+            ?family,
+            %endpoint,
+            "Single-endpoint shadow rotation skipped: endpoint is quarantined"
+        );
+        return;
+    }
+
     let Some(writer_ids) = live_writer_ids_by_addr.get(&endpoint) else {
         shadow_rotate_deadline.insert(key, now + Duration::from_secs(SHADOW_ROTATE_RETRY_SECS));
         return;
diff --git a/src/transport/middle_proxy/pool_refill.rs b/src/transport/middle_proxy/pool_refill.rs
index 92071bd..6e14617 100644
--- a/src/transport/middle_proxy/pool_refill.rs
+++ b/src/transport/middle_proxy/pool_refill.rs
@@ -37,7 +37,7 @@ impl MePool {
         );
     }
 
-    async fn is_endpoint_quarantined(&self, addr: SocketAddr) -> bool {
+    pub(super) async fn is_endpoint_quarantined(&self, addr: SocketAddr) -> bool {
         let mut guard = self.endpoint_quarantine.lock().await;
         let now = Instant::now();
         guard.retain(|_, expiry| *expiry > now);