Resolve C# shard catalog filters by schema alias

src/GameCult.Networking/CultNetDatabase.cs

@@ -1509,15 +1509,12 @@ namespace GameCult.Networking
                 "not_primary");
         }
 
-        private static bool MatchesCatalogFilter(
+        private bool MatchesCatalogFilter(
             CultNetShardDescriptor shard,
             IReadOnlyList<string>? schemaIds,
             IReadOnlyList<CultRecordKey>? recordKeys)
         {
-            var schemaMatches = schemaIds == null ||
-                                schemaIds.Count == 0 ||
-                                shard.SchemaIds.Count == 0 ||
-                                schemaIds.Any(schemaId => shard.SchemaIds.Contains(schemaId, StringComparer.Ordinal));
+            var schemaMatches = SchemaMatchesCatalogFilter(shard, schemaIds);
             var keyMatches = recordKeys == null ||
                              recordKeys.Count == 0 ||
                              recordKeys.Any(key => string.IsNullOrEmpty(shard.KeyPrefix) ||
@@ -1525,6 +1522,33 @@ namespace GameCult.Networking
             return schemaMatches && keyMatches;
         }
 
+        private bool SchemaMatchesCatalogFilter(
+            CultNetShardDescriptor shard,
+            IReadOnlyList<string>? schemaIds)
+        {
+            if (schemaIds == null || schemaIds.Count == 0 || shard.SchemaIds.Count == 0)
+                return true;
+
+            var requestedSchemaIds = schemaIds.ToHashSet(StringComparer.Ordinal);
+            if (shard.SchemaIds.Any(requestedSchemaIds.Contains))
+                return true;
+
+            foreach (var shardSchemaId in shard.SchemaIds)
+            {
+                try
+                {
+                    if (MatchesRequestedSchema(_cache.Registry.GetRequiredBySchemaId(shardSchemaId), requestedSchemaIds))
+                        return true;
+                }
+                catch (InvalidOperationException)
+                {
+                    // Shards can advertise schemas that are not loaded in this process.
+                }
+            }
+
+            return false;
+        }
+
         private static bool MatchesRequestedSchema(
             CultDocumentDescriptor descriptor,
             ISet<string> requestedSchemaIds)

tests/GameCult.Networking.Tests/NetworkingTests.cs

@@ -1955,6 +1955,16 @@ namespace GameCult.Networking.Tests
             Assert.That(response.Shards[0].Epoch, Is.EqualTo(3));
             Assert.That(response.Shards[0].PrimaryEndpoints, Is.EqualTo(["cultnet://runtime-a:3075"]));
             Assert.That(response.Shards[0].ReadReplicaEndpoints, Is.EqualTo(["cultnet://edge-a:3075"]));
+
+            var aliasResponse = databaseServer.CreateShardCatalogResponse(new CultNetShardCatalogRequestMessage
+            {
+                MessageId = "catalog-players-alias",
+                SchemaIds = ["gamecult.player_data.v2"],
+                RecordKeys = ["player:one"]
+            });
+
+            Assert.That(aliasResponse.Shards, Has.Length.EqualTo(1));
+            Assert.That(aliasResponse.Shards[0].ShardId, Is.EqualTo("players"));
         }
 
         [Test]