diff --git a/include/lnl/net_manager.h b/include/lnl/net_manager.h
index c1ec872..e96dbf5 100644
--- a/include/lnl/net_manager.h
+++ b/include/lnl/net_manager.h
@@ -4,6 +4,8 @@
 #include <optional>
 #include <thread>
 #include <unordered_map>
+#include <functional>
+#include <vector>
 
 #ifdef WIN32
 
@@ -80,6 +82,13 @@ namespace lnl {
         bool disconnect_on_unreachable = false;
         std::string name;
 
+        // Optional datagram transform layers (a generic hook, equivalent to the C# PacketLayerBase).
+        // outbound_layer: given the packet about to be sent, fill `out` with the bytes to put on the
+        //   wire and return their length. inbound_layer: mutate a freshly received datagram in place
+        //   and return the new length, or 0 to drop it. Used by Tachyon for the RecRoom 0x11 marker.
+        std::function<size_t(const uint8_t* data, size_t length, std::vector<uint8_t>& out)> outbound_layer;
+        std::function<size_t(uint8_t* data, size_t length)> inbound_layer;
+
         explicit net_manager(net_event_listener* listener);
 
         ~net_manager();
diff --git a/src/lnl/net_manager.cpp b/src/lnl/net_manager.cpp
index 0cfe2a7..fa23eef 100644
--- a/src/lnl/net_manager.cpp
+++ b/src/lnl/net_manager.cpp
@@ -219,6 +219,15 @@ void lnl::net_manager::receive_logic() {
 
         packet->resize(size);
 
+        if (inbound_layer) {
+            size_t newLen = inbound_layer(packet->data(), (size_t) size);
+            if (newLen == 0) {          // layer dropped the datagram (unknown/undecryptable marker)
+                pool_recycle(packet);
+                continue;
+            }
+            packet->resize(newLen);
+        }
+
         on_message_received(packet, addr);
     }
 }
@@ -517,8 +526,16 @@ int32_t lnl::net_manager::send_raw(const uint8_t* data, size_t offset, size_t le
         return 0;
     }
 
+    const uint8_t* sendData = &data[offset];
+    size_t sendLen = length;
+    if (outbound_layer) {
+        thread_local std::vector<uint8_t> layerBuf;
+        sendLen = outbound_layer(&data[offset], length, layerBuf);
+        sendData = layerBuf.data();
+    }
+
     auto result = sendto(m_socket,
-                         (const char*) &data[offset], (int) length,
+                         (const char*) sendData, (int) sendLen,
                          0,
                          (sockaddr*) &endpoint.raw, sizeof(sockaddr_in));