diff --git a/ostp-client/src/bridge.rs b/ostp-client/src/bridge.rs
index 7cdaac8..d6e2d65 100644
--- a/ostp-client/src/bridge.rs
+++ b/ostp-client/src/bridge.rs
@@ -533,7 +533,7 @@ impl Bridge {
             psk,
             session_id,
             handshake_payload,
-            max_padding: 1400, // §7 FIX: Allow padding up to full MTU size to break traffic analysis fingerprints
+            max_padding: 1280, // Safe MTU size to avoid UDP fragmentation on Windows/PPPoE
             padding_strategy: PaddingStrategy::Profile(self.profile),
             obfuscation_key: obf_key,
             max_reorder: 262144,
diff --git a/ostp-client/src/tunnel/linux_handler.rs b/ostp-client/src/tunnel/linux_handler.rs
index f1cf2f7..71bd549 100644
--- a/ostp-client/src/tunnel/linux_handler.rs
+++ b/ostp-client/src/tunnel/linux_handler.rs
@@ -138,6 +138,7 @@ pub async fn run_linux_tunnel(
     // 4. Setup commands (Using standard /1 routing trick for fail-proof overriding)
     let setup_script = format!(
         "ip tuntap add name ostp_tun mode tun || true; \
+         ip link set dev ostp_tun mtu 1300; \
          ip addr add 10.1.0.2/24 dev ostp_tun || true; \
          ip link set dev ostp_tun up; \
          ip route add {} via {} dev {}; \
diff --git a/ostp-client/src/tunnel/wintun_handler.rs b/ostp-client/src/tunnel/wintun_handler.rs
index e9fe31e..992dc92 100644
--- a/ostp-client/src/tunnel/wintun_handler.rs
+++ b/ostp-client/src/tunnel/wintun_handler.rs
@@ -137,6 +137,7 @@ pub async fn run_wintun_tunnel(
     // to the physical interface DNS servers, which are physically routed and work flawlessly.
     let net_setup = "\
         netsh interface ipv4 set address name=\"ostp_tun\" static 10.1.0.2 255.255.255.0 10.1.0.1\n\
+        netsh interface ipv4 set subinterface \"ostp_tun\" mtu=1300 store=persistent\n\
         netsh interface ipv4 set interface name=\"ostp_tun\" metric=5\n";
     
     let _ = Command::new("powershell")
diff --git a/ostp-core/src/framing/padding.rs b/ostp-core/src/framing/padding.rs
index b2001dc..20c1203 100644
--- a/ostp-core/src/framing/padding.rs
+++ b/ostp-core/src/framing/padding.rs
@@ -10,9 +10,9 @@ pub enum TrafficProfile {
 impl TrafficProfile {
     pub fn target_size(&self, current: usize) -> usize {
         match self {
-            TrafficProfile::JsonRpc => align_up(current.max(220), 64).min(1408),
-            TrafficProfile::HttpsBurst => align_up(current.max(1200), 128).min(1472),
-            TrafficProfile::VideoStream => align_up(current.max(900), 188).min(1472),
+            TrafficProfile::JsonRpc => align_up(current.max(220), 64).min(1280),
+            TrafficProfile::HttpsBurst => align_up(current.max(1200), 128).min(1280),
+            TrafficProfile::VideoStream => align_up(current.max(900), 188).min(1280),
         }
     }
 }