diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/OpcUaClientDriver.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/OpcUaClientDriver.cs
index d81ed3b7..bf9cb5ab 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/OpcUaClientDriver.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/OpcUaClientDriver.cs
@@ -1675,6 +1675,91 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         _ => throw new ArgumentOutOfRangeException(nameof(aggregate), aggregate, null),
     };
 
+    // Canonical BaseEventType select-clause order — MapHistoryEvents maps by these indices.
+    private static readonly string[] EventFieldBrowseNames =
+    [
+        BrowseNames.EventId,      // 0
+        BrowseNames.SourceName,   // 1
+        BrowseNames.Time,         // 2
+        BrowseNames.ReceiveTime,  // 3
+        BrowseNames.Message,      // 4
+        BrowseNames.Severity,     // 5
+    ];
+
+    /// <summary>
+    ///     Builds the fixed canonical EventFilter the driver sends upstream for HistoryReadEvents —
+    ///     the six BaseEventType fields the OtOpcUa server projects (<see cref="HistoricalEvent"/>).
+    ///     The clause order is load-bearing: <see cref="MapHistoryEvents"/> reads results by index.
+    /// </summary>
+    /// <returns>An EventFilter with six SimpleAttributeOperand value clauses.</returns>
+    internal static EventFilter BuildBaseEventFilter()
+    {
+        var filter = new EventFilter();
+        foreach (var browseName in EventFieldBrowseNames)
+        {
+            filter.SelectClauses.Add(new SimpleAttributeOperand
+            {
+                TypeDefinitionId = ObjectTypeIds.BaseEventType,
+                BrowsePath = new QualifiedNameCollection { new QualifiedName(browseName) },
+                AttributeId = Attributes.Value,
+            });
+        }
+        return filter;
+    }
+
+    /// <summary>
+    ///     Maps an upstream <see cref="HistoryEvent"/> (field arrays ordered to match
+    ///     <see cref="BuildBaseEventFilter"/>) onto <see cref="HistoricalEvent"/> records. Defensive:
+    ///     short / null / wrong-typed fields degrade to null/default rather than throwing.
+    /// </summary>
+    /// <param name="historyEvent">The upstream history-event payload.</param>
+    /// <returns>The mapped historical events in upstream order.</returns>
+    internal static IReadOnlyList<Core.Abstractions.HistoricalEvent> MapHistoryEvents(HistoryEvent historyEvent)
+    {
+        if (historyEvent?.Events is not { Count: > 0 } rows) return [];
+        var result = new List<Core.Abstractions.HistoricalEvent>(rows.Count);
+        foreach (var row in rows)
+        {
+            var fields = row?.EventFields;
+            result.Add(new Core.Abstractions.HistoricalEvent(
+                EventId: CoerceEventId(FieldAt(fields, 0)),
+                SourceName: CoerceString(FieldAt(fields, 1)),
+                EventTimeUtc: CoerceDateTime(FieldAt(fields, 2)),
+                ReceivedTimeUtc: CoerceDateTime(FieldAt(fields, 3)),
+                Message: CoerceString(FieldAt(fields, 4)),
+                Severity: CoerceSeverity(FieldAt(fields, 5))));
+        }
+        return result;
+    }
+
+    private static object? FieldAt(VariantCollection? fields, int index)
+        => fields is not null && index < fields.Count ? fields[index].Value : null;
+
+    private static string CoerceEventId(object? value) => value switch
+    {
+        byte[] bytes => Convert.ToBase64String(bytes),
+        string s => s,
+        null => string.Empty,
+        _ => value.ToString() ?? string.Empty,
+    };
+
+    private static string? CoerceString(object? value) => value switch
+    {
+        LocalizedText lt => lt.Text,
+        string s => s,
+        null => null,
+        _ => value.ToString(),
+    };
+
+    private static DateTime CoerceDateTime(object? value)
+        => value is DateTime dt ? dt : DateTime.MinValue;
+
+    private static ushort CoerceSeverity(object? value)
+    {
+        try { return value is null ? (ushort)0 : Convert.ToUInt16(value); }
+        catch (Exception ex) when (ex is FormatException or InvalidCastException or OverflowException) { return 0; }
+    }
+
     // ReadEventsAsync stays at the interface default (throws NotSupportedException) per
     // IHistoryProvider contract -- the OPC UA Client driver CAN forward HistoryReadEvents,
     // but the call-site needs an EventFilter SelectClauses surface which the interface
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientHistoryTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientHistoryTests.cs
index 381e99ce..4207fa74 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientHistoryTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientHistoryTests.cs
@@ -96,4 +96,75 @@ public sealed class OpcUaClientHistoryTests
                 maxEvents: 100,
                 cancellationToken: TestContext.Current.CancellationToken));
     }
+
+    /// <summary>BuildBaseEventFilter emits the six canonical BaseEventType select clauses in order.</summary>
+    [Fact]
+    public void BuildBaseEventFilter_has_six_canonical_BaseEventType_value_clauses()
+    {
+        var filter = OpcUaClientDriver.BuildBaseEventFilter();
+
+        filter.SelectClauses.Count.ShouldBe(6);
+        string[] expected = ["EventId", "SourceName", "Time", "ReceiveTime", "Message", "Severity"];
+        for (var i = 0; i < expected.Length; i++)
+        {
+            var clause = filter.SelectClauses[i];
+            clause.TypeDefinitionId.ShouldBe(ObjectTypeIds.BaseEventType);
+            clause.AttributeId.ShouldBe(Attributes.Value);
+            clause.BrowsePath.Count.ShouldBe(1);
+            clause.BrowsePath[0].Name.ShouldBe(expected[i]);
+        }
+    }
+
+    /// <summary>MapHistoryEvents maps every field by its canonical select-clause index.</summary>
+    [Fact]
+    public void MapHistoryEvents_maps_all_six_fields_by_canonical_index()
+    {
+        var eventTime = new DateTime(2026, 6, 18, 10, 0, 0, DateTimeKind.Utc);
+        var recvTime = eventTime.AddSeconds(1);
+        var he = new HistoryEvent();
+        var fields = new HistoryEventFieldList();
+        fields.EventFields.Add(new Variant(new byte[] { 1, 2, 3 }));            // 0 EventId
+        fields.EventFields.Add(new Variant("Pump17"));                          // 1 SourceName
+        fields.EventFields.Add(new Variant(eventTime));                         // 2 Time
+        fields.EventFields.Add(new Variant(recvTime));                          // 3 ReceiveTime
+        fields.EventFields.Add(new Variant(new LocalizedText("High temp")));    // 4 Message
+        fields.EventFields.Add(new Variant((ushort)700));                       // 5 Severity
+        he.Events.Add(fields);
+
+        var mapped = OpcUaClientDriver.MapHistoryEvents(he);
+
+        mapped.Count.ShouldBe(1);
+        var e = mapped[0];
+        e.EventId.ShouldBe(Convert.ToBase64String(new byte[] { 1, 2, 3 }));
+        e.SourceName.ShouldBe("Pump17");
+        e.EventTimeUtc.ShouldBe(eventTime);
+        e.ReceivedTimeUtc.ShouldBe(recvTime);
+        e.Message.ShouldBe("High temp");
+        e.Severity.ShouldBe((ushort)700);
+    }
+
+    /// <summary>MapHistoryEvents returns empty for a HistoryEvent with no rows.</summary>
+    [Fact]
+    public void MapHistoryEvents_with_no_events_returns_empty()
+    {
+        OpcUaClientDriver.MapHistoryEvents(new HistoryEvent()).ShouldBeEmpty();
+    }
+
+    /// <summary>MapHistoryEvents tolerates a field list shorter than six without throwing.</summary>
+    [Fact]
+    public void MapHistoryEvents_tolerates_short_field_list_without_throwing()
+    {
+        var he = new HistoryEvent();
+        var fields = new HistoryEventFieldList();
+        fields.EventFields.Add(new Variant(new byte[] { 9 })); // only EventId present
+        he.Events.Add(fields);
+
+        var mapped = OpcUaClientDriver.MapHistoryEvents(he);
+
+        mapped.Count.ShouldBe(1);
+        mapped[0].EventId.ShouldBe(Convert.ToBase64String(new byte[] { 9 }));
+        mapped[0].SourceName.ShouldBeNull();
+        mapped[0].EventTimeUtc.ShouldBe(DateTime.MinValue);
+        mapped[0].Severity.ShouldBe((ushort)0);
+    }
 }