diff --git a/tests/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests/StatusCodeParityTests.cs b/tests/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests/StatusCodeParityTests.cs
index 02122ad1b..d617384be 100644
--- a/tests/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests/StatusCodeParityTests.cs
+++ b/tests/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests/StatusCodeParityTests.cs
@@ -47,9 +47,9 @@ public sealed class StatusCodeParityTests
     /// <summary>Every <c>Opc.Ua.StatusCodes</c> member, by name — the oracle this test checks against.</summary>
     private static readonly IReadOnlyDictionary<string, uint> SdkStatusCodes =
         typeof(Opc.Ua.StatusCodes)
-            .GetFields(BindingFlags.Public | BindingFlags.Static)
-            .Where(f => f.IsLiteral && f.FieldType == typeof(uint))
-            .ToDictionary(f => f.Name, f => (uint)f.GetRawConstantValue()!, StringComparer.Ordinal);
+            .GetProperties(BindingFlags.Public | BindingFlags.Static)
+            .Where(p => p.PropertyType == typeof(Opc.Ua.StatusCode))
+            .ToDictionary(p => p.Name, p => ((Opc.Ua.StatusCode)p.GetValue(null)!).Code, StringComparer.Ordinal);
 
     /// <summary>
     ///     Every status-shaped <c>const uint</c> declared anywhere in the deployed driver assemblies, as
diff --git a/tests/Drivers/Historian.Conformance/AtTimeConformance.cs b/tests/Drivers/Historian.Conformance/AtTimeConformance.cs
index 0379f484e..4061ce032 100644
--- a/tests/Drivers/Historian.Conformance/AtTimeConformance.cs
+++ b/tests/Drivers/Historian.Conformance/AtTimeConformance.cs
@@ -24,7 +24,7 @@ public abstract class AtTimeConformance : ConformanceBase
         var code = new Opc.Ua.StatusCode(GoodInterpolated);
         code.AggregateBits.ShouldBe(Opc.Ua.AggregateBits.Interpolated);
         Opc.Ua.StatusCode.IsGood(code).ShouldBeTrue();
-        new Opc.Ua.StatusCode(UncertainInterpolated).CodeBits.ShouldBe(Opc.Ua.StatusCodes.UncertainDataSubNormal);
+        new Opc.Ua.StatusCode(UncertainInterpolated).CodeBits.ShouldBe(Opc.Ua.StatusCodes.UncertainDataSubNormal.Code);
         await Task.CompletedTask;
     }
 
diff --git a/tests/Drivers/Historian.Conformance/ProcessedConformance.cs b/tests/Drivers/Historian.Conformance/ProcessedConformance.cs
index 5f51434a9..71858e26c 100644
--- a/tests/Drivers/Historian.Conformance/ProcessedConformance.cs
+++ b/tests/Drivers/Historian.Conformance/ProcessedConformance.cs
@@ -31,10 +31,10 @@ public abstract class ProcessedConformance : ConformanceBase
     {
         new Opc.Ua.StatusCode(GoodCalc).AggregateBits.ShouldBe(Opc.Ua.AggregateBits.Calculated);
         new Opc.Ua.StatusCode(UncertainCalc).AggregateBits.ShouldBe(Opc.Ua.AggregateBits.Calculated);
-        new Opc.Ua.StatusCode(UncertainCalc).CodeBits.ShouldBe(Opc.Ua.StatusCodes.UncertainDataSubNormal);
-        new Opc.Ua.StatusCode(NoDataCalc).CodeBits.ShouldBe(Opc.Ua.StatusCodes.BadNoData);
+        new Opc.Ua.StatusCode(UncertainCalc).CodeBits.ShouldBe(Opc.Ua.StatusCodes.UncertainDataSubNormal.Code);
+        new Opc.Ua.StatusCode(NoDataCalc).CodeBits.ShouldBe(Opc.Ua.StatusCodes.BadNoData.Code);
         new Opc.Ua.StatusCode(NoDataCalc).AggregateBits.ShouldBe(Opc.Ua.AggregateBits.Calculated);
-        new Opc.Ua.StatusCode(InvalidInputsCalc).CodeBits.ShouldBe(Opc.Ua.StatusCodes.BadAggregateInvalidInputs);
+        new Opc.Ua.StatusCode(InvalidInputsCalc).CodeBits.ShouldBe(Opc.Ua.StatusCodes.BadAggregateInvalidInputs.Code);
     }
 
     [Theory]
diff --git a/tests/Drivers/Historian.Conformance/SdkAggregateOracle.cs b/tests/Drivers/Historian.Conformance/SdkAggregateOracle.cs
index b7dd2f781..0be20dfd0 100644
--- a/tests/Drivers/Historian.Conformance/SdkAggregateOracle.cs
+++ b/tests/Drivers/Historian.Conformance/SdkAggregateOracle.cs
@@ -1,13 +1,14 @@
 using Opc.Ua;
 using Opc.Ua.Server;
+using ZB.MOM.WW.OtOpcUa.OpcUaServer.Compatibility.Aggregates;
 using Shouldly;
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 
 namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Conformance;
 
 /// <summary>
-///     Drives the pinned OPC UA SDK's own Part 13 aggregate calculators (<c>Opc.Ua.Server</c> — the classes the SDK's
-///     <c>AggregateManager</c> registers) in-process over a sample set, so our processed reads can be compared with the
+///     Drives the application's versioned 1.5.378.182 Part 13 compatibility calculators — the same factories
+///     the upgraded server registers for live aggregates in-process over a sample set, so our processed reads can be compared with the
 ///     reference implementation bucket by bucket (#677). The calculators run under the server's default
 ///     <see cref="AggregateConfiguration"/> (TreatUncertainAsBad = false, PercentDataBad = PercentDataGood = 100,
 ///     UseSlopedExtrapolation = false), sloped interpolation, source timestamps.
@@ -17,6 +18,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Conformance;
 /// </remarks>
 public static class SdkAggregateOracle
 {
+    private static readonly ITelemetryContext Telemetry = DefaultTelemetry.Create(_ => { });
     /// <summary>One processed value: value (double / int / null), full status code, timestamp.</summary>
     public readonly record struct Result(object? Value, uint StatusCode, DateTime Timestamp);
 
@@ -43,22 +45,7 @@ public static class SdkAggregateOracle
         var id = AggregateId(aggregate);
         var ms = interval.TotalMilliseconds;
         var cfg = DefaultConfiguration;
-        IAggregateCalculator calc = aggregate switch
-        {
-            HistoryAggregateType.Average or HistoryAggregateType.TimeAverage or HistoryAggregateType.TimeAverage2
-                or HistoryAggregateType.Total or HistoryAggregateType.Total2 =>
-                new AverageAggregateCalculator(id, start, end, ms, false, cfg, null),
-            HistoryAggregateType.Minimum or HistoryAggregateType.Maximum or HistoryAggregateType.Range
-                or HistoryAggregateType.MinimumActualTime or HistoryAggregateType.MaximumActualTime =>
-                new MinMaxAggregateCalculator(id, start, end, ms, false, cfg, null),
-            HistoryAggregateType.Count => new CountAggregateCalculator(id, start, end, ms, false, cfg, null),
-            HistoryAggregateType.PercentGood or HistoryAggregateType.PercentBad =>
-                new StatusAggregateCalculator(id, start, end, ms, false, cfg, null),
-            HistoryAggregateType.Start or HistoryAggregateType.End or HistoryAggregateType.Delta =>
-                new StartEndAggregateCalculator(id, start, end, ms, false, cfg, null),
-            HistoryAggregateType.Interpolative => new AggregateCalculator(id, start, end, ms, false, cfg, null),
-            _ => throw new ArgumentOutOfRangeException(nameof(aggregate), aggregate, "no SDK calculator mapped"),
-        };
+        IAggregateCalculator calc = CompatibilityAggregateFactory.Create(id, start, end, ms, false, cfg, Telemetry);
 
         // The SDK expects values in the direction of the read: ascending forward, descending reverse.
         var ordered = samples.OrderBy(s => s.Time).ToList();
@@ -68,9 +55,8 @@ public static class SdkAggregateOracle
         var results = new List<Result>();
         for (var guard = 0; guard < 100_000; guard++)
         {
-            var dv = calc.GetProcessedValue(true);
-            if (dv is null) break;
-            results.Add(new Result(dv.Value, dv.StatusCode.Code, DateTime.SpecifyKind(dv.SourceTimestamp, DateTimeKind.Utc)));
+            if (!calc.TryGetProcessedValue(true, out var dv)) break;
+            results.Add(new Result(dv.WrappedValue.AsBoxedObject(Variant.BoxingBehavior.Legacy), dv.StatusCode.Code, (DateTime)dv.SourceTimestamp));
         }
         return results;
     }
@@ -123,20 +109,16 @@ public static class SdkAggregateOracle
         problems.ShouldBeEmpty($"{label} differs from the SDK:\n" + string.Join("\n", problems));
     }
 
-    private static DataValue ToDataValue(DateTime t, HistorianValue v, uint status) => new()
-    {
-        WrappedValue = v.Kind switch
+    private static DataValue ToDataValue(DateTime t, HistorianValue v, uint status) => new(
+        v.Kind switch
         {
             HistorianValueKind.Empty => Variant.Null,
-            HistorianValueKind.Int64 => new Variant(v.Integer),
-            HistorianValueKind.Boolean => new Variant(v.Number != 0),
-            HistorianValueKind.String => new Variant(v.Text),
-            _ => new Variant(v.Number),
+            HistorianValueKind.Int64 => Variant.From(v.Integer),
+            HistorianValueKind.Boolean => Variant.From(v.Number != 0),
+            HistorianValueKind.String => v.Text is { } text ? Variant.From(text) : Variant.Null,
+            _ => Variant.From(v.Number),
         },
-        StatusCode = status,
-        SourceTimestamp = t,
-        ServerTimestamp = t,
-    };
+        status, t, t);
 
     private static NodeId AggregateId(HistoryAggregateType a) => a switch
     {
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests.csproj b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests.csproj
index de0bc2753..e814277ae 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests.csproj
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.IntegrationTests.csproj
@@ -23,6 +23,8 @@
     </ItemGroup>
 
     <ItemGroup>
+        <!-- Test the same preserved aggregate algorithms registered by the application server. -->
+        <ProjectReference Include="..\..\..\src\Server\ZB.MOM.WW.OtOpcUa.OpcUaServer\ZB.MOM.WW.OtOpcUa.OpcUaServer.csproj"/>
         <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb\ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb.csproj"/>
         <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common\ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.csproj"/>
     </ItemGroup>
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/StatusCodeOracleTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/StatusCodeOracleTests.cs
index a672a6211..c5638b19e 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/StatusCodeOracleTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/StatusCodeOracleTests.cs
@@ -9,7 +9,7 @@ public sealed class StatusCodeOracleTests
     [Fact]
     public void Calculated_bits_match_the_SDK()
     {
-        var sdk = new Opc.Ua.StatusCode(Opc.Ua.StatusCodes.Good).SetAggregateBits(Opc.Ua.AggregateBits.Calculated);
+        var sdk = Opc.Ua.StatusCodes.Good.WithAggregateBits(Opc.Ua.AggregateBits.Calculated);
         sdk.Code.ShouldBe(HistorianInfoBits.WithCalculated(HistorianStatusCodes.Good));
         ((uint)Opc.Ua.AggregateBits.Calculated).ShouldBe(HistorianInfoBits.HistorianCalculated);
     }
@@ -17,7 +17,7 @@ public sealed class StatusCodeOracleTests
     [Fact]
     public void Interpolated_bits_match_the_SDK()
     {
-        var sdk = new Opc.Ua.StatusCode(Opc.Ua.StatusCodes.Good).SetAggregateBits(Opc.Ua.AggregateBits.Interpolated);
+        var sdk = Opc.Ua.StatusCodes.Good.WithAggregateBits(Opc.Ua.AggregateBits.Interpolated);
         sdk.Code.ShouldBe(HistorianInfoBits.WithInterpolated(HistorianStatusCodes.Good));
         ((uint)Opc.Ua.AggregateBits.Interpolated).ShouldBe(HistorianInfoBits.HistorianInterpolated);
     }
@@ -25,7 +25,7 @@ public sealed class StatusCodeOracleTests
     /// <summary>
     ///     A stored status that already carries a historian bit (a sample written via HistoryUpdate with the Calculated
     ///     bit, say) must come back with ONE historian bit, never both: the existing pair is masked off first. The SDK
-    ///     agrees — <c>SetAggregateBits</c> replaces, it does not OR.
+    ///     agrees — <c>WithAggregateBits</c> replaces, it does not OR.
     /// </summary>
     [Fact]
     public void Setting_one_historian_bit_clears_the_other()
@@ -45,7 +45,7 @@ public sealed class StatusCodeOracleTests
 
     [Fact]
     public void Generic_bad_matches_the_SDK() =>
-        HistorianStatusCodes.Bad.ShouldBe(Opc.Ua.StatusCodes.Bad);
+        HistorianStatusCodes.Bad.ShouldBe(Opc.Ua.StatusCodes.Bad.Code);
 
     [Fact]
     public void Info_type_is_data_value() =>
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests.csproj b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests.csproj
index f52434f39..959a08849 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests.csproj
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests.csproj
@@ -28,6 +28,8 @@
     </ItemGroup>
 
     <ItemGroup>
+        <!-- Test the same preserved aggregate algorithms registered by the application server. -->
+        <ProjectReference Include="..\..\..\src\Server\ZB.MOM.WW.OtOpcUa.OpcUaServer\ZB.MOM.WW.OtOpcUa.OpcUaServer.csproj"/>
         <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common\ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.csproj"/>
     </ItemGroup>
 
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests.csproj b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests.csproj
index 732de3bb5..8f3d3b1d0 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests.csproj
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests.csproj
@@ -22,6 +22,8 @@
     </ItemGroup>
 
     <ItemGroup>
+        <!-- Test the same preserved aggregate algorithms registered by the application server. -->
+        <ProjectReference Include="..\..\..\src\Server\ZB.MOM.WW.OtOpcUa.OpcUaServer\ZB.MOM.WW.OtOpcUa.OpcUaServer.csproj"/>
         <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer\ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.csproj"/>
         <ProjectReference Include="..\..\..\src\Drivers\ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common\ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.csproj"/>
     </ItemGroup>