diff --git a/src/GameCult.Geometry/CultGeometryDocuments.cs b/src/GameCult.Geometry/CultGeometryDocuments.cs
index 306b5849..1ce73bdb 100644
--- a/src/GameCult.Geometry/CultGeometryDocuments.cs
+++ b/src/GameCult.Geometry/CultGeometryDocuments.cs
@@ -153,8 +153,8 @@ namespace GameCult.Geometry
         public string RequestId { get; set; } = string.Empty;
 
         [Key(1)]
-        [CultReference(typeof(CultGeometryDomainDocument))]
-        public string DomainKey { get; set; } = string.Empty;
+        [MessagePackFormatter(typeof(CultRecordRefFormatter<CultGeometryDomainDocument>))]
+        public CultRecordRef<CultGeometryDomainDocument> DomainKey { get; set; }
 
         [Key(2)]
         [CultIndex]
@@ -200,7 +200,7 @@ namespace GameCult.Geometry
         {
             if (request == null) throw new ArgumentNullException(nameof(request));
             return new CultRecordKey("geometry:request:" + StableHash(
-                request.DomainKey,
+                request.DomainKey.Key.Value,
                 request.WorkerGroup,
                 StableVector(request.CameraPosition),
                 StableVector(request.FrustumMin),
@@ -228,8 +228,8 @@ namespace GameCult.Geometry
         public string CutId { get; set; } = string.Empty;
 
         [Key(1)]
-        [CultReference(typeof(CultGeometryBuildRequest))]
-        public string RequestKey { get; set; } = string.Empty;
+        [MessagePackFormatter(typeof(CultRecordRefFormatter<CultGeometryBuildRequest>))]
+        public CultRecordRef<CultGeometryBuildRequest> RequestKey { get; set; }
 
         [Key(2)]
         public string[] SelectedNodes { get; set; } = Array.Empty<string>();
@@ -247,7 +247,7 @@ namespace GameCult.Geometry
         {
             if (cut == null) throw new ArgumentNullException(nameof(cut));
             return new CultRecordKey("geometry:cut:" + StableHash(
-                cut.RequestKey,
+                cut.RequestKey.Key.Value,
                 cut.CutId,
                 StableArray(cut.SelectedNodes),
                 StableArray(cut.DeferredChildRequests),
@@ -313,8 +313,8 @@ namespace GameCult.Geometry
         public string ChunkId { get; set; } = string.Empty;
 
         [Key(1)]
-        [CultReference(typeof(CultGeometrySelectedCutManifest))]
-        public string CutKey { get; set; } = string.Empty;
+        [MessagePackFormatter(typeof(CultRecordRefFormatter<CultGeometrySelectedCutManifest>))]
+        public CultRecordRef<CultGeometrySelectedCutManifest> CutKey { get; set; }
 
         [Key(2)]
         [CultIndex]
@@ -357,7 +357,7 @@ namespace GameCult.Geometry
         {
             if (chunk == null) throw new ArgumentNullException(nameof(chunk));
             return new CultRecordKey("geometry:chunk:" + StableHash(
-                chunk.CutKey,
+                chunk.CutKey.Key.Value,
                 chunk.ChunkId,
                 chunk.SelectedCutId,
                 StableArray(chunk.SourceDomainKeys),
diff --git a/src/GameCult.Geometry/GameCult.Geometry.csproj b/src/GameCult.Geometry/GameCult.Geometry.csproj
index c10c2ecf..cc66cba9 100644
--- a/src/GameCult.Geometry/GameCult.Geometry.csproj
+++ b/src/GameCult.Geometry/GameCult.Geometry.csproj
@@ -10,6 +10,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\packages\cultmath\src\CultMath\CultMath.csproj" />
     <ProjectReference Include="..\GameCult.Caching\GameCult.Caching.csproj" />
+    <ProjectReference Include="..\GameCult.Caching.MessagePack\GameCult.Caching.MessagePack.csproj" />
     <PackageReference Include="MessagePack" Version="3.1.7" />
     <PackageReference Include="System.Text.Json" Version="9.0.10" />
   </ItemGroup>
diff --git a/tests/GameCult.Geometry.Tests/GeometryDocumentTests.cs b/tests/GameCult.Geometry.Tests/GeometryDocumentTests.cs
index 8741f891..b5f63775 100644
--- a/tests/GameCult.Geometry.Tests/GeometryDocumentTests.cs
+++ b/tests/GameCult.Geometry.Tests/GeometryDocumentTests.cs
@@ -10,6 +10,7 @@ using R3;
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Text.Json;
 using System.Threading.Tasks;
 
@@ -104,7 +105,7 @@ namespace GameCult.Geometry.Tests
             var domainKey = CultGeometryDomainDocument.CreateRecordKey(domain);
             var request = new CultGeometryBuildRequest
             {
-                DomainKey = domainKey.Value,
+                DomainKey = new CultRecordRef<CultGeometryDomainDocument>(domainKey),
                 WorkerGroup = "ragnarok-column-workers",
                 CameraPosition = [36f, -42f, 30f],
                 FrustumMin = [-75f, -75f, -30f],
@@ -129,6 +130,26 @@ namespace GameCult.Geometry.Tests
             first.Value.Should().StartWith("geometry:request:");
         }
 
+        // The geometry documents reference each other by record key. The reference members are
+        // CultRecordRef<T> so the cache can walk them, and they stay a bare msgpack string on the wire.
+        [Test]
+        public void GeometryReferences_AreWalkableByTheCache_AndStayStringsOnTheWire()
+        {
+            var cache = new CultCache();
+            var descriptor = cache.Registry.GetRequired<CultGeometryBuildRequest>();
+            descriptor.DeclaredMembers.Should().Contain(m => m.MemberName == "DomainKey" && m.IsReference && !m.IsMany);
+
+            var chunk = SampleChunk();
+            var references = cache.Registry.GetRequired<CultGeometryChunkArtifact>().ReferencesOf(chunk, "CutKey").ToArray();
+            references.Should().ContainSingle().Which.Target.Value.Should().Be("geometry:cut:test");
+
+            var payload = CultDocumentMessagePackSerialization.SerializeUntyped(chunk, typeof(CultGeometryChunkArtifact));
+            var reader = new MessagePackReader(payload);
+            reader.ReadArrayHeader();
+            reader.ReadString().Should().Be(chunk.ChunkId);
+            reader.ReadString().Should().Be("geometry:cut:test");
+        }
+
         [Test]
         public void ChunkArtifact_RoundTrips_ThroughCultCacheMessagePack()
         {
@@ -382,7 +403,7 @@ namespace GameCult.Geometry.Tests
             return new CultGeometryChunkArtifact
             {
                 ChunkId = "chunk/ragnarok-column/column-00",
-                CutKey = "geometry:cut:test",
+                CutKey = new CultRecordRef<CultGeometrySelectedCutManifest>(new CultRecordKey("geometry:cut:test")),
                 SelectedCutId = "cut-test",
                 BoundsMin = [-1f, -1f, 0f],
                 BoundsMax = [1f, 1f, 1f],