diff --git a/src/GameCult.Mesh/CultMeshClient.cs b/src/GameCult.Mesh/CultMeshClient.cs
index 230ce55b..5db03ca5 100644
--- a/src/GameCult.Mesh/CultMeshClient.cs
+++ b/src/GameCult.Mesh/CultMeshClient.cs
@@ -587,7 +587,7 @@ namespace GameCult.Mesh
             using var snapshot = await CultMeshSnapshotSession.ConnectAsync(
                     _sessions,
                     target,
-                    CultMeshProtocols.Content,
+                    CultMeshProtocols.Documents,
                     new CultMeshSnapshotRequestOptions
                     {
                         ConnectTimeout = TimeSpan.FromSeconds(5),
diff --git a/src/GameCult.Mesh/CultMeshSessionIdentity.cs b/src/GameCult.Mesh/CultMeshSessionIdentity.cs
index 43a49162..3fad99f9 100644
--- a/src/GameCult.Mesh/CultMeshSessionIdentity.cs
+++ b/src/GameCult.Mesh/CultMeshSessionIdentity.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.Linq;
 using System.Security.Cryptography;
 using System.Threading;
@@ -70,7 +71,9 @@ namespace GameCult.Mesh
         private readonly HashSet<string> _protocolIds;
         private readonly HashSet<string> _routeGenerations;
         private readonly Dictionary<string, CultMeshSessionProofSigner> _proofSigners;
+        private readonly ConcurrentDictionary<ICultNetSchemaServerPeer, string> _acceptedPeers = new();
         private readonly Func<CultMeshSessionOpenMessage, ICultNetSchemaServerPeer, Task> _handler;
+        private readonly ICultNetSchemaServerPeerLifecycle? _peerLifecycle;
         private bool _disposed;
 
         public CultMeshSessionIdentityServer(
@@ -90,18 +93,33 @@ namespace GameCult.Mesh
                 .ToDictionary(signer => signer.Route.Generation, StringComparer.Ordinal);
             _handler = HandleAsync;
             _server.OnCultNet(_handler);
+            _peerLifecycle = server as ICultNetSchemaServerPeerLifecycle;
+            if (_peerLifecycle != null)
+                _peerLifecycle.PeerDisconnected += ForgetPeer;
         }
 
+        /// <summary>
+        /// Resolves the runtime identity established by this peer's accepted session-open handshake.
+        /// Application ingress must use this transport-bound value instead of trusting payload identity fields.
+        /// </summary>
+        public bool TryGetSourceRuntimeId(ICultNetSchemaServerPeer peer, out string sourceRuntimeId) =>
+            _acceptedPeers.TryGetValue(peer, out sourceRuntimeId!);
+
         public void Dispose()
         {
             if (_disposed) return;
             _disposed = true;
             _server.RemoveCultNetMessageListener<CultMeshSessionOpenMessage>(_handler);
+            if (_peerLifecycle != null)
+                _peerLifecycle.PeerDisconnected -= ForgetPeer;
+            _acceptedPeers.Clear();
         }
 
         private Task HandleAsync(CultMeshSessionOpenMessage request, ICultNetSchemaServerPeer peer)
         {
             var error = Validate(request);
+            if (error == null)
+                error = BindPeer(peer, request.SourceRuntimeId);
             _proofSigners.TryGetValue(request.RouteGeneration ?? string.Empty, out var signer);
             peer.SendCultNet(new CultMeshSessionAcceptedMessage
             {
@@ -119,6 +137,19 @@ namespace GameCult.Mesh
             return Task.CompletedTask;
         }
 
+        private void ForgetPeer(ICultNetSchemaServerPeer peer) => _acceptedPeers.TryRemove(peer, out _);
+
+        private string? BindPeer(ICultNetSchemaServerPeer peer, string sourceRuntimeId)
+        {
+            if (_acceptedPeers.TryGetValue(peer, out var established))
+                return string.Equals(established, sourceRuntimeId, StringComparison.Ordinal)
+                    ? null
+                    : "session-source-runtime-rebind-forbidden";
+            return _acceptedPeers.TryAdd(peer, sourceRuntimeId)
+                ? null
+                : BindPeer(peer, sourceRuntimeId);
+        }
+
         private string? Validate(CultMeshSessionOpenMessage request)
         {
             if (string.IsNullOrWhiteSpace(request.MessageId)) return "session-message-id-required";
diff --git a/tests/GameCult.Mesh.Tests/CultMeshTransportModularityTests.cs b/tests/GameCult.Mesh.Tests/CultMeshTransportModularityTests.cs
index 979c7230..e5d3867e 100644
--- a/tests/GameCult.Mesh.Tests/CultMeshTransportModularityTests.cs
+++ b/tests/GameCult.Mesh.Tests/CultMeshTransportModularityTests.cs
@@ -29,7 +29,9 @@ public sealed class CultMeshTransportModularityTests
             new[] { RouteGeneration });
         server.OnCultNet<CultNetHelloMessage>((message, peer) =>
         {
-            peer.SendCultNet(new CultNetErrorMessage { Error = "tcp:" + message.RuntimeId });
+            identity.TryGetSourceRuntimeId(peer, out var sourceRuntimeId).Should().BeTrue(
+                "application ingress must only trust a runtime identity bound by the session-open handshake");
+            peer.SendCultNet(new CultNetErrorMessage { Error = $"tcp:{message.RuntimeId}:{sourceRuntimeId}" });
             return Task.CompletedTask;
         });
         var tcpEndpoint = $"cultnet+tcp://127.0.0.1:{server.LocalEndPoint.Port}";
@@ -55,7 +57,7 @@ public sealed class CultMeshTransportModularityTests
         var received = await response.Task.WaitAsync(TimeSpan.FromSeconds(5));
 
         session.State.Path!.Endpoint.Should().Be(tcpEndpoint);
-        received.Error.Should().Be("tcp:eve-unity");
+        received.Error.Should().Be("tcp:eve-unity:cultmesh-client");
         legacy.ConnectCount.Should().Be(0,
             "a lower transport tier is fallback, not a race against the preferred TCP tier");
     }
diff --git a/tests/GameCult.Mesh.Tests/GameCult.Mesh.Tests.csproj b/tests/GameCult.Mesh.Tests/GameCult.Mesh.Tests.csproj
index 14e99d63..292e42df 100644
--- a/tests/GameCult.Mesh.Tests/GameCult.Mesh.Tests.csproj
+++ b/tests/GameCult.Mesh.Tests/GameCult.Mesh.Tests.csproj
@@ -15,7 +15,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="NUnit" Version="4.*" />
+    <PackageReference Include="NUnit" Version="4.6.1" />
     <PackageReference Include="NUnit3TestAdapter" Version="6.2.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.4.0" />
     <PackageReference Include="FluentAssertions" Version="8.9.0" />
diff --git a/unity/org.gamecult.cultlib/package.json b/unity/org.gamecult.cultlib/package.json
index b957b18c..cae02b50 100644
--- a/unity/org.gamecult.cultlib/package.json
+++ b/unity/org.gamecult.cultlib/package.json
@@ -1,7 +1,7 @@
 {
   "name": "org.gamecult.cultlib",
   "displayName": "CultLib",
-  "version": "1.0.49",
+  "version": "1.0.50",
   "unity": "2021.3",
   "description": "CultCache, CultNet, and CultMesh managed runtime assemblies for Unity.",
   "license": "MIT",