test: verify SDK 2 driver boundaries and lifecycle contracts

src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Commands/HistoryReadCommand.cs

@@ -1,4 +1,3 @@
-using ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
 using System.Globalization;
 using CliFx.Attributes;
 using CliFx.Exceptions;
@@ -211,7 +210,7 @@ public class HistoryReadCommand : CommandBase
                         : StatusCode.IsBad(dv.StatusCode) ? "Bad"
                         : "Uncertain";
                     await console.Output.WriteLineAsync(
-                        $"{dv.SourceTimestamp.ToString("O"),-35} {ValueConverter.ToClrObject(dv.WrappedValue)?.ToString() ?? "(none)",-15} {status,-10} " +
+                        $"{dv.SourceTimestamp.ToString("O"),-35} {dv.Value?.ToString() ?? "(none)",-15} {status,-10} " +
                         $"{e.UpdateType,-8} {e.UserName ?? "",-20} {e.ModificationTime:O}");
                 }
 
@@ -245,7 +244,7 @@ public class HistoryReadCommand : CommandBase
                     : StatusCode.IsBad(dv.StatusCode) ? "Bad"
                     : "Uncertain";
                 await console.Output.WriteLineAsync(
-                    $"{dv.SourceTimestamp.ToString("O"),-35} {ValueConverter.ToClrObject(dv.WrappedValue),-15} {status}");
+                    $"{dv.SourceTimestamp.ToString("O"),-35} {dv.Value,-15} {status}");
             }
 
             await console.Output.WriteLineAsync();
@@ -277,25 +276,23 @@ public class HistoryReadCommand : CommandBase
     internal static EventFilter BuildEventFilter(IReadOnlyList<string> fields, NodeId? ofType)
     {
         var filter = new EventFilter();
-        var clauses = new List<SimpleAttributeOperand>();
         foreach (var field in fields)
         {
             var type = string.Equals(field, "ConditionName", StringComparison.Ordinal)
                 ? ObjectTypeIds.ConditionType
                 : ObjectTypeIds.BaseEventType;
-            clauses.Add(new SimpleAttributeOperand(type, new QualifiedName(field)) { AttributeId = Attributes.Value });
+            filter.SelectClauses.Add(new SimpleAttributeOperand(type, new QualifiedName(field)) { AttributeId = Attributes.Value });
         }
 
-        filter.SelectClauses = clauses.ToArrayOf();
         if (ofType is not null)
-            filter.WhereClause.Push(FilterOperator.OfType, Variant.From(ofType.Value));
+            filter.WhereClause.Push(FilterOperator.OfType, new LiteralOperand(new Variant(ofType)));
         return filter;
     }
 
     /// <summary>Formats one projected event field for the console: byte strings as hex, times as ISO 8601, null as <c>-</c>.</summary>
     /// <param name="field">The field value.</param>
     /// <returns>Its display text.</returns>
-    private static string FormatEventField(Variant field) => ValueConverter.ToClrObject(field) switch
+    private static string FormatEventField(Variant field) => field.Value switch
     {
         null => "-",
         byte[] bytes => Convert.ToHexString(bytes),

src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Commands/HistoryUpdateCommand.cs

@@ -1,4 +1,3 @@
-using ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
 using System.Globalization;
 using CliFx.Attributes;
 using CliFx.Exceptions;
@@ -90,11 +89,11 @@ public class HistoryUpdateCommand : CommandBase
                     throw new CommandException(
                         $"--value and --time must be supplied in pairs ({values.Count} value(s), {times.Count} time(s)).");
 
-                var updates = new List<DataValue>();
+                var updates = new DataValueCollection();
                 for (var i = 0; i < values.Count; i++)
                 {
                     var ts = ParseTime(times[i], "--time");
-                    updates.Add(new DataValue(ValueConverter.ToVariant(ParseValue(values[i], Type)), StatusCodes.Good, ts, ts));
+                    updates.Add(new DataValue(new Variant(ParseValue(values[i], Type)), StatusCodes.Good, ts, ts));
                 }
 
                 return new UpdateDataDetails
@@ -106,7 +105,7 @@ public class HistoryUpdateCommand : CommandBase
                         "replace" => PerformUpdateType.Replace,
                         _ => PerformUpdateType.Update
                     },
-                    UpdateValues = updates.ToArrayOf()
+                    UpdateValues = updates
                 };
             }
             case "delete-raw":
@@ -135,9 +134,9 @@ public class HistoryUpdateCommand : CommandBase
                     throw new CommandException("--mode delete-at-time takes --time only; --value is not allowed.");
                 if (times.Count == 0)
                     throw new CommandException("--mode delete-at-time requires at least one --time.");
-                var req = new List<DateTimeUtc>();
+                var req = new DateTimeCollection();
                 foreach (var t in times) req.Add(ParseTime(t, "--time"));
-                return new DeleteAtTimeDetails { NodeId = nodeId, ReqTimes = req.ToArrayOf() };
+                return new DeleteAtTimeDetails { NodeId = nodeId, ReqTimes = req };
             }
         }
     }
@@ -239,8 +238,8 @@ public class HistoryUpdateCommand : CommandBase
     /// <returns>The status name, or <c>0xXXXXXXXX</c>.</returns>
     private static string StatusName(StatusCode code)
     {
-        var name = code.SymbolicId;
-        if (string.IsNullOrEmpty(name)) name = new StatusCode(code.Code & 0xFFFF0000u).SymbolicId;
+        var name = StatusCodes.GetBrowseName(code.Code);
+        if (string.IsNullOrEmpty(name)) name = StatusCodes.GetBrowseName(code.Code & 0xFFFF0000u);
         return string.IsNullOrEmpty(name) ? $"0x{code.Code:X8}" : name;
     }
 
@@ -248,8 +247,8 @@ public class HistoryUpdateCommand : CommandBase
     {
         return details switch
         {
-            UpdateDataDetails u => (u.UpdateValues.ToArray() ?? []).Select(v => v.SourceTimestamp.ToString("O")).ToList(),
-            DeleteAtTimeDetails d => (d.ReqTimes.ToArray() ?? []).Select(t => t.ToString("O")).ToList(),
+            UpdateDataDetails u => u.UpdateValues.Select(v => v.SourceTimestamp.ToString("O")).ToList(),
+            DeleteAtTimeDetails d => d.ReqTimes.Select(t => t.ToString("O")).ToList(),
             DeleteRawModifiedDetails r => [$"{r.StartTime:O}..{r.EndTime:O}"],
             _ => []
         };

src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Commands/ReadCommand.cs

@@ -1,4 +1,3 @@
-using ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
 using CliFx.Attributes;
 using CliFx.Exceptions;
 using CliFx.Infrastructure;
@@ -60,12 +59,12 @@ public class ReadCommand : CommandBase
                 // not crash with a stack trace — session-level failures still propagate.
                 await console.Output.WriteLineAsync($"Node:        {NodeId}");
                 await console.Output.WriteLineAsync($"Value:       ");
-                await console.Output.WriteLineAsync($"Status:      {(StatusCode)ex.StatusCode} ({ex.StatusCode.SymbolicId})");
+                await console.Output.WriteLineAsync($"Status:      {(StatusCode)ex.StatusCode} ({StatusCodes.GetBrowseName(ex.StatusCode)})");
                 return;
             }
 
             await console.Output.WriteLineAsync($"Node:        {NodeId}");
-            await console.Output.WriteLineAsync($"Value:       {ValueConverter.ToClrObject(value.WrappedValue)}");
+            await console.Output.WriteLineAsync($"Value:       {value.Value}");
             await console.Output.WriteLineAsync($"Status:      {value.StatusCode}");
             await console.Output.WriteLineAsync($"Source Time: {value.SourceTimestamp:O}");
             await console.Output.WriteLineAsync($"Server Time: {value.ServerTimestamp:O}");

src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Commands/SubscribeCommand.cs

@@ -1,4 +1,3 @@
-using ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
 using System.Collections.Concurrent;
 using System.Threading.Channels;
 using CliFx.Attributes;
@@ -124,14 +123,14 @@ public class SubscribeCommand : CommandBase
                 try
                 {
                     var key = e.NodeId.ToString();
-                    lastStatus[key] = (e.Value.StatusCode, DateTime.UtcNow, ValueConverter.ToClrObject(e.Value.WrappedValue));
+                    lastStatus[key] = (e.Value.StatusCode, DateTime.UtcNow, e.Value.Value);
                     updateCount.AddOrUpdate(key, 1, (_, v) => v + 1);
                     if (!StatusCode.IsGood(e.Value.StatusCode))
                         everBad.TryAdd(key, 0);
                     if (!Quiet)
                     {
                         var line =
-                            $"[{e.Value.SourceTimestamp:O}] {displayNameByNodeId.GetValueOrDefault(key, key)} = {ValueConverter.ToClrObject(e.Value.WrappedValue)} ({e.Value.StatusCode})";
+                            $"[{e.Value.SourceTimestamp:O}] {displayNameByNodeId.GetValueOrDefault(key, key)} = {e.Value.Value} ({e.Value.StatusCode})";
                         outputChannel.Writer.TryWrite(line);
                     }
                 }
@@ -272,7 +271,7 @@ public class SubscribeCommand : CommandBase
             var childPath = $"{parentPath}/{child.DisplayName}";
             if (child.NodeClass == "Variable")
             {
-                into.Add((nodeId.Value, childPath));
+                into.Add((nodeId, childPath));
             }
             if (child.HasChildren)
             {

src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Commands/WriteCommand.cs

@@ -54,7 +54,7 @@ public class WriteCommand : CommandBase
 
             // Read current value to determine type for conversion
             var currentValue = await service.ReadValueAsync(nodeId, ct);
-            var typedValue = ValueConverter.ConvertValue(Value, ValueConverter.ToClrObject(currentValue.WrappedValue));
+            var typedValue = ValueConverter.ConvertValue(Value, currentValue.Value);
 
             var statusCode = await service.WriteValueAsync(nodeId, typedValue, ct);
 

src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Helpers/NodeIdParser.cs

@@ -52,6 +52,6 @@ public static class NodeIdParser
         var result = Parse(nodeIdString);
         if (result == null)
             throw new ArgumentException("Node ID is required but was not provided.");
-        return result.Value;
+        return result;
     }
 }

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Adapters/DefaultApplicationConfigurationFactory.cs

@@ -58,26 +58,20 @@ internal sealed class DefaultApplicationConfigurationFactory : IApplicationConfi
             }
         };
 
-        try
-        {
-            await config.ValidateAsync(ApplicationType.Client, ct);
+        await config.ValidateAsync(ApplicationType.Client, ct);
 
-            if (settings.SecurityMode != SecurityMode.None)
-            {
-                var app = new ApplicationInstance(ClientTelemetry.Context)
-                {
-                    ApplicationName = "OtOpcUaClient",
-                    ApplicationType = ApplicationType.Client,
-                    ApplicationConfiguration = config
-                };
-                await app.CheckApplicationInstanceCertificatesAsync(false, lifeTimeInMonths: 2048, ct: ct);
-            }
-        }
-        catch
+        if (settings.AutoAcceptCertificates)
+            config.CertificateValidator.CertificateValidation += (_, e) => e.Accept = true;
+
+        if (settings.SecurityMode != SecurityMode.None)
         {
-            try { (config.CertificateManager as IDisposable)?.Dispose(); }
-            catch (Exception ex) { Logger.Warning(ex, "Disposing certificate manager after configuration failure"); }
-            throw;
+            var app = new ApplicationInstance(ClientTelemetry.Context)
+            {
+                ApplicationName = "OtOpcUaClient",
+                ApplicationType = ApplicationType.Client,
+                ApplicationConfiguration = config
+            };
+            await app.CheckApplicationInstanceCertificatesAsync(false, 2048);
         }
 
         Logger.Debug("ApplicationConfiguration created for {EndpointUrl}", settings.EndpointUrl);

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Adapters/DefaultEndpointDiscovery.cs

@@ -19,9 +19,9 @@ internal sealed class DefaultEndpointDiscovery : IEndpointDiscovery
         // obsolete synchronous CoreClientUtils.SelectEndpoint, which does the same filter + rewrite.)
         using var client = await DiscoveryClient.CreateAsync(
             config, new Uri(endpointUrl), DiagnosticsMasks.None, ct).ConfigureAwait(false);
-        var allEndpoints = await client.GetEndpointsAsync(default, ct).ConfigureAwait(false);
+        var allEndpoints = await client.GetEndpointsAsync(null, ct).ConfigureAwait(false);
 
-        return EndpointSelector.SelectBest(allEndpoints.ToArray() ?? [], endpointUrl, requestedMode);
+        return EndpointSelector.SelectBest(allEndpoints, endpointUrl, requestedMode);
     }
 }
 
@@ -90,7 +90,7 @@ internal static class EndpointSelector
         // advertises its own host:port (docker-dev containers all say :4840); following that would
         // open the session on a different server and fail the secure-channel certificate check.
         // Only when the scheme matches: a different scheme (https vs opc.tcp) is a different transport.
-        var serverUri = new Uri(best.EndpointUrl ?? throw new InvalidOperationException("Endpoint has no URL."));
+        var serverUri = new Uri(best.EndpointUrl);
         var requestedUri = new Uri(endpointUrl);
         // A URL typed without a port (opc.tcp has no registered default, so Port is -1) keeps the advertised port.
         var port = requestedUri.Port > 0 ? requestedUri.Port : serverUri.Port;

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Adapters/DefaultSessionAdapter.cs

@@ -12,25 +12,21 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
 {
     private static readonly ILogger Logger = Log.ForContext<DefaultSessionAdapter>();
     private readonly Session _session;
-    private readonly IDisposable? _certificateManager;
-    private int _disposed;
 
     /// <summary>
     /// Wraps a live OPC UA session so the shared client can issue runtime operations through a testable adapter surface.
     /// </summary>
     /// <param name="session">The connected OPC UA session used for browsing, reads, writes, history, and subscriptions.</param>
-    /// <param name="certificateManager">The per-connection certificate manager owned until session disposal.</param>
-    public DefaultSessionAdapter(Session session, IDisposable? certificateManager = null)
+    public DefaultSessionAdapter(Session session)
     {
         _session = session;
-        _certificateManager = certificateManager;
     }
 
     /// <inheritdoc />
     public bool Connected => _session.Connected;
 
     /// <inheritdoc />
-    public string SessionId => _session.SessionId.IsNull ? string.Empty : _session.SessionId.ToString();
+    public string SessionId => _session.SessionId?.ToString() ?? string.Empty;
 
     /// <inheritdoc />
     public string SessionName => _session.SessionName ?? string.Empty;
@@ -39,7 +35,7 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
     public string EndpointUrl => _session.Endpoint?.EndpointUrl ?? string.Empty;
 
     /// <inheritdoc />
-    public string ServerName => _session.Endpoint?.Server?.ApplicationName.Text ?? string.Empty;
+    public string ServerName => _session.Endpoint?.Server?.ApplicationName?.Text ?? string.Empty;
 
     /// <inheritdoc />
     public string SecurityMode => _session.Endpoint?.SecurityMode.ToString() ?? string.Empty;
@@ -76,13 +72,13 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
             Value = value
         };
 
-        ArrayOf<WriteValue> writeCollection = [writeValue];
+        var writeCollection = new WriteValueCollection { writeValue };
         var response = await _session.WriteAsync(null, writeCollection, ct);
         // A malformed or service-level-faulted response can come back with an empty
         // Results collection alongside a service fault. Surface the service result
         // (or BadUnexpectedError) rather than letting Results[0] throw
         // IndexOutOfRangeException upstream.
-        if (response.Results.Count == 0)
+        if (response.Results == null || response.Results.Count == 0)
         {
             var serviceResult = response.ResponseHeader?.ServiceResult.Code ?? StatusCodes.BadUnexpectedError;
             throw new ServiceResultException(serviceResult,
@@ -93,7 +89,7 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
     }
 
     /// <inheritdoc />
-    public async Task<(byte[]? ContinuationPoint, ArrayOf<ReferenceDescription> References)> BrowseAsync(
+    public async Task<(byte[]? ContinuationPoint, ReferenceDescriptionCollection References)> BrowseAsync(
         NodeId nodeId, uint nodeClassMask, CancellationToken ct)
     {
         var (_, continuationPoint, references) = await _session.BrowseAsync(
@@ -104,25 +100,19 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
             BrowseDirection.Forward,
             ReferenceTypeIds.HierarchicalReferences,
             true,
-            nodeClassMask, ct);
+            nodeClassMask);
 
-        return (continuationPoint.IsNull ? null : continuationPoint.ToArray(), references);
+        return (continuationPoint, references ?? []);
     }
 
     /// <inheritdoc />
-    public async Task<(byte[]? ContinuationPoint, ArrayOf<ReferenceDescription> References)> BrowseNextAsync(
+    public async Task<(byte[]? ContinuationPoint, ReferenceDescriptionCollection References)> BrowseNextAsync(
         byte[] continuationPoint, CancellationToken ct)
     {
         // Pass the caller's token so a cancelled browse does not block on the continuation
         // round-trip.
-        var (_, nextCp, nextRefs) = await _session.BrowseNextAsync(null, false, ByteString.From(continuationPoint), ct);
-        return (nextCp.IsNull ? null : nextCp.ToArray(), nextRefs);
-    }
-
-    /// <inheritdoc />
-    public async Task ReleaseBrowseContinuationPointAsync(byte[] continuationPoint, CancellationToken ct)
-    {
-        await _session.BrowseNextAsync(null, true, ByteString.From(continuationPoint), ct).ConfigureAwait(false);
+        var (_, nextCp, nextRefs) = await _session.BrowseNextAsync(null, false, continuationPoint, ct);
+        return (nextCp, nextRefs ?? []);
     }
 
     /// <inheritdoc />
@@ -130,16 +120,16 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
     {
         var response = await _session.HistoryUpdateAsync(
             null,
-            [new ExtensionObject(details)],
+            new ExtensionObjectCollection { new ExtensionObject(details) },
             ct).ConfigureAwait(false);
 
         var statuses = new List<StatusCode>();
         var ops = new List<IReadOnlyList<StatusCode>>();
-        if (!response.Results.IsEmpty)
+        if (response.Results != null)
             foreach (var r in response.Results)
             {
                 statuses.Add(r.StatusCode);
-                ops.Add(r.OperationResults.ToArray() ?? []);
+                ops.Add(r.OperationResults?.ToArray() ?? Array.Empty<StatusCode>());
             }
 
         return new Models.HistoryUpdateOutcome(response.ResponseHeader.ServiceResult, statuses, ops);
@@ -162,10 +152,10 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
         // by the cap releases the server's cursor (HistoryReadPaging). This path used to pass
         // `releaseContinuationPoints: continuationPoint != null`, which RELEASED the second page instead of reading it,
         // silently truncating every raw read to its first server page.
-        return await HistoryReadPaging.ReadAllAsync<DataValue>(
+        return await HistoryReadPaging.ReadAllAsync(
             (cp, release, token) => ReadHistoryPageAsync(details, nodeId, cp, release, TimestampsToReturn.Source, token),
-            result => result.HistoryData.TryGetValue(out HistoryData? historyData)
-                ? historyData.DataValues.ToArray() ?? []
+            result => result.HistoryData is ExtensionObject { Body: HistoryData historyData }
+                ? historyData.DataValues
                 : [],
             maxValues, nodeId, ct).ConfigureAwait(false);
     }
@@ -203,21 +193,21 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
 
         return await HistoryReadPaging.ReadAllAsync(
             (cp, release, token) => ReadHistoryPageAsync(details, nodeId, cp, release, TimestampsToReturn.Both, token),
-            result => result.HistoryData.TryGetValue(out HistoryEvent? historyEvent)
-                ? (historyEvent.Events.ToArray() ?? []).Select(e => new Models.HistoryEventEntry(e.EventFields.ToArray() ?? []))
+            result => result.HistoryData is ExtensionObject { Body: HistoryEvent historyEvent }
+                ? historyEvent.Events.Select(e => new Models.HistoryEventEntry(e.EventFields?.ToArray() ?? []))
                 : [],
             maxEvents, nodeId, ct).ConfigureAwait(false);
     }
 
     private static IEnumerable<Models.HistoryModifiedEntry> ToModifiedEntries(HistoryReadResult result)
     {
-        if (!result.HistoryData.TryGetValue(out HistoryModifiedData? modified)) yield break;
+        if (result.HistoryData is not ExtensionObject { Body: HistoryModifiedData modified }) yield break;
         for (var i = 0; i < modified.DataValues.Count; i++)
         {
             var info = i < modified.ModificationInfos.Count ? modified.ModificationInfos[i] : null;
             yield return new Models.HistoryModifiedEntry(
                 modified.DataValues[i],
-                info?.ModificationTime.ToDateTime() ?? DateTime.MinValue,
+                info?.ModificationTime ?? DateTime.MinValue,
                 info?.UpdateType ?? default,
                 info?.UserName);
         }
@@ -228,10 +218,10 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
         HistoryReadDetails details, NodeId nodeId, byte[]? continuationPoint, bool release,
         TimestampsToReturn timestamps, CancellationToken ct)
     {
-        ArrayOf<HistoryReadValueId> nodesToRead =
-        [
-            new HistoryReadValueId { NodeId = nodeId, ContinuationPoint = ByteString.From(continuationPoint) }
-        ];
+        var nodesToRead = new HistoryReadValueIdCollection
+        {
+            new HistoryReadValueId { NodeId = nodeId, ContinuationPoint = continuationPoint }
+        };
 
         // The async overload honours the token and does not block the caller's thread (the UI dispatcher for
         // client.ui consumers).
@@ -254,7 +244,10 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
             AggregateType = [aggregateId]
         };
 
-        ArrayOf<HistoryReadValueId> nodesToRead = [new HistoryReadValueId { NodeId = nodeId }];
+        var nodesToRead = new HistoryReadValueIdCollection
+        {
+            new HistoryReadValueId { NodeId = nodeId }
+        };
 
         // Use the async overload so the method honors the cancellation token and
         // does not block on a synchronous service round-trip.
@@ -269,23 +262,13 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
         var results = response.Results;
         var allValues = new List<DataValue>();
 
-        if (results.Count > 0)
+        if (results != null && results.Count > 0)
         {
             var result = results[0];
-            try
-            {
-                HistoryReadStatus.ThrowIfRefused(result.StatusCode, nodeId);
-                if (result.HistoryData.TryGetValue(out HistoryData? historyData))
-                    allValues.AddRange(historyData.DataValues);
-            }
-            finally
-            {
-                // Keep the existing one-shot processed read; it owns no outstanding server cursor on return.
-                if (!result.ContinuationPoint.IsEmpty)
-                    await HistoryReadPaging.ReleaseAsync(
-                        (cp, release, token) => ReadHistoryPageAsync(details, nodeId, cp, release, TimestampsToReturn.Source, token),
-                        result.ContinuationPoint.ToArray(), nodeId).ConfigureAwait(false);
-            }
+            HistoryReadStatus.ThrowIfRefused(result.StatusCode, nodeId);
+            if (result.HistoryData is ExtensionObject ext &&
+                ext.Body is HistoryData historyData)
+                allValues.AddRange(historyData.DataValues);
         }
 
         return allValues;
@@ -339,7 +322,6 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
     /// </summary>
     public void Dispose()
     {
-        if (Interlocked.Exchange(ref _disposed, 1) != 0) return;
         try
         {
             if (_session.Connected) DisposeBridge.Run(ct => _session.CloseAsync(ct));
@@ -348,8 +330,7 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
         {
         }
 
-        try { _session.Dispose(); }
-        finally { _certificateManager?.Dispose(); }
+        _session.Dispose();
     }
 
     /// <inheritdoc />
@@ -358,20 +339,20 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
     {
         var result = await _session.CallAsync(
             null,
-            new CallMethodRequest[]
+            new CallMethodRequestCollection
             {
                 new()
                 {
                     ObjectId = objectId,
                     MethodId = methodId,
-                    InputArguments = inputArguments.Select(ValueConverter.ToVariant).ToArrayOf()
+                    InputArguments = new VariantCollection(inputArguments.Select(a => new Variant(a)))
                 }
             },
             ct);
 
         // An empty Results collection paired with a service fault must surface as
         // a ServiceResultException, not an IndexOutOfRangeException from Results[0].
-        if (result.Results.Count == 0)
+        if (result.Results == null || result.Results.Count == 0)
         {
             var serviceResult = result.ResponseHeader?.ServiceResult.Code ?? StatusCodes.BadUnexpectedError;
             throw new ServiceResultException(serviceResult,
@@ -382,7 +363,6 @@ internal sealed class DefaultSessionAdapter : ISessionAdapter
         if (StatusCode.IsBad(callResult.StatusCode))
             throw new ServiceResultException(callResult.StatusCode);
 
-        return callResult.OutputArguments.IsNull ? null
-            : (callResult.OutputArguments.ToArray() ?? []).Select(v => ValueConverter.ToClrObject(v)!).ToList();
+        return callResult.OutputArguments?.Select(v => v.Value).ToList();
     }
 }

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Adapters/DefaultSessionFactory.cs

@@ -30,13 +30,13 @@ internal sealed class DefaultSessionFactory : ISessionFactory
             sessionName,
             sessionTimeoutMs,
             identity,
-            default,
+            null,
             ct);
         var session = created as Session
             ?? throw new InvalidOperationException(
                 $"Session factory returned {created.GetType().Name}, expected {nameof(Session)}.");
 
         Logger.Information("Session created: {SessionName} -> {EndpointUrl}", sessionName, endpoint.EndpointUrl);
-        return new DefaultSessionAdapter(session, config.CertificateManager as IDisposable);
+        return new DefaultSessionAdapter(session);
     }
 }

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Adapters/DefaultSubscriptionAdapter.cs

@@ -14,8 +14,6 @@ internal sealed class DefaultSubscriptionAdapter : ISubscriptionAdapter
     private readonly Subscription _subscription;
     private readonly Func<Subscription, CancellationToken, Task>? _detach;
     private int _detached;
-    private int _finishing;
-    private readonly TaskCompletionSource _finished = new(TaskCreationOptions.RunContinuationsAsynchronously);
 
     /// <summary>
     /// Wraps a live OPC UA subscription so client code can manage monitored items through a testable abstraction.
@@ -49,7 +47,7 @@ internal sealed class DefaultSubscriptionAdapter : ISubscriptionAdapter
 
         item.Notification += (_, e) =>
         {
-            if (Volatile.Read(ref _finishing) == 0 && e.NotificationValue is MonitoredItemNotification notification)
+            if (e.NotificationValue is MonitoredItemNotification notification)
                 onDataChange(nodeId.ToString(), notification.Value);
         };
 
@@ -92,7 +90,7 @@ internal sealed class DefaultSubscriptionAdapter : ISubscriptionAdapter
 
         item.Notification += (_, e) =>
         {
-            if (Volatile.Read(ref _finishing) == 0 && e.NotificationValue is EventFieldList eventFields) onEvent(eventFields);
+            if (e.NotificationValue is EventFieldList eventFields) onEvent(eventFields);
         };
 
         _subscription.AddItem(item);
@@ -114,28 +112,19 @@ internal sealed class DefaultSubscriptionAdapter : ISubscriptionAdapter
     /// <inheritdoc />
     public async Task DeleteAsync(CancellationToken ct)
     {
-        if (Interlocked.Exchange(ref _finishing, 1) != 0)
-        {
-            await _finished.Task.WaitAsync(ct).ConfigureAwait(false);
-            return;
-        }
         try
         {
-            try { await _subscription.DeleteAsync(true, ct).ConfigureAwait(false); }
-            catch (Exception ex) { Logger.Warning(ex, "Error deleting subscription"); }
-
-            // A cancelled delete still has local resources to release. Cleanup gets its own bounded token.
-            using var cleanup = new CancellationTokenSource(TimeSpan.FromSeconds(5));
-            try { await DetachAsync(cleanup.Token).WaitAsync(cleanup.Token).ConfigureAwait(false); }
-            catch (Exception ex) { Logger.Warning(ex, "Error detaching subscription"); }
-            finally
-            {
-                _monitoredItems.Clear();
-                try { await Task.Run(_subscription.Dispose).WaitAsync(cleanup.Token).ConfigureAwait(false); }
-                catch (Exception ex) { Logger.Warning(ex, "Error disposing subscription resources"); }
-            }
+            // Forward the caller's token so the delete can be cancelled.
+            await _subscription.DeleteAsync(true, ct);
         }
-        finally { _finished.TrySetResult(); }
+        catch (Exception ex)
+        {
+            Logger.Warning(ex, "Error deleting subscription");
+        }
+
+        // Detach whether or not the server-side delete succeeded: the adapter is finished with it either way.
+        await DetachAsync(ct);
+        _monitoredItems.Clear();
     }
 
     private async Task DetachAsync(CancellationToken ct)
@@ -156,6 +145,21 @@ internal sealed class DefaultSubscriptionAdapter : ISubscriptionAdapter
     /// </summary>
     public void Dispose()
     {
-        DisposeBridge.Run(DeleteAsync);
+        // One bounded bridge (5 s) for delete + detach, so a dispose never blocks longer than before (review m6).
+        // DetachAsync swallows its own failures; a failed delete must not skip the detach.
+        try
+        {
+            DisposeBridge.Run(async ct =>
+            {
+                try { await _subscription.DeleteAsync(true, ct); }
+                catch (Exception ex) { Logger.Warning(ex, "Error deleting subscription"); }
+                await DetachAsync(ct);
+            });
+        }
+        catch
+        {
+        }
+
+        _monitoredItems.Clear();
     }
 }

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Adapters/ISessionAdapter.cs

@@ -78,7 +78,7 @@ internal interface ISessionAdapter : IDisposable
     /// <param name="nodeClassMask">The node classes that should be returned to the caller.</param>
     /// <param name="ct">The cancellation token that aborts the browse request.</param>
     /// <returns>A continuation point (or <c>null</c> when complete) and the references found.</returns>
-    Task<(byte[]? ContinuationPoint, ArrayOf<ReferenceDescription> References)> BrowseAsync(
+    Task<(byte[]? ContinuationPoint, ReferenceDescriptionCollection References)> BrowseAsync(
         NodeId nodeId, uint nodeClassMask = 0, CancellationToken ct = default);
 
     /// <summary>
@@ -87,15 +87,9 @@ internal interface ISessionAdapter : IDisposable
     /// <param name="continuationPoint">The continuation token returned by a prior browse result page.</param>
     /// <param name="ct">The cancellation token that aborts the browse-next request.</param>
     /// <returns>The next continuation point (or <c>null</c> when exhausted) and the additional references.</returns>
-    Task<(byte[]? ContinuationPoint, ArrayOf<ReferenceDescription> References)> BrowseNextAsync(
+    Task<(byte[]? ContinuationPoint, ReferenceDescriptionCollection References)> BrowseNextAsync(
         byte[] continuationPoint, CancellationToken ct = default);
 
-    /// <summary>Releases a browse cursor that the caller stops following.</summary>
-    /// <param name="continuationPoint">The cursor owned by this session.</param>
-    /// <param name="ct">A bounded cleanup token independent of the cancelled browse.</param>
-    /// <returns>The completion of the release request.</returns>
-    Task ReleaseBrowseContinuationPointAsync(byte[] continuationPoint, CancellationToken ct);
-
     /// <summary>
     ///     Reads raw historical data.
     /// </summary>

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Helpers/HistoryReadPaging.cs

@@ -56,15 +56,15 @@ internal static class HistoryReadPaging
                 HistoryReadStatus.ThrowIfRefused(result.StatusCode, nodeId);
                 all.AddRange(extract(result));
 
-                continuationPoint = result.ContinuationPoint.IsNull ? null : result.ContinuationPoint.ToArray();
+                continuationPoint = result.ContinuationPoint;
                 if (continuationPoint is not { Length: > 0 }) return Trim(all, maxValues);
                 if (all.Count >= maxValues) break;
             }
         }
-        catch
+        catch (OperationCanceledException)
         {
-            // A refused/failed/cancelled continuation still leaves the last cursor owned by this read.
-            // Best-effort release must preserve the original operation failure.
+            // Cancelled between pages (or during page N+1) with a cursor outstanding: release it rather than leave it
+            // occupying one of the session's continuation-point slots, then surface the cancellation.
             if (continuationPoint is { Length: > 0 }) await ReleaseAsync(readPage, continuationPoint, nodeId);
             throw;
         }
@@ -81,12 +81,12 @@ internal static class HistoryReadPaging
         return all;
     }
 
-    internal static async Task ReleaseAsync(PageReader readPage, byte[] continuationPoint, NodeId nodeId)
+    private static async Task ReleaseAsync(PageReader readPage, byte[] continuationPoint, NodeId nodeId)
     {
         try
         {
             using var cts = new CancellationTokenSource(ReleaseTimeout);
-            await readPage(continuationPoint, true, cts.Token).WaitAsync(cts.Token).ConfigureAwait(false);
+            await readPage(continuationPoint, true, cts.Token).ConfigureAwait(false);
         }
         catch (Exception ex)
         {

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Helpers/HistoryReadStatus.cs

@@ -19,6 +19,6 @@ internal static class HistoryReadStatus
     {
         if (!StatusCode.IsBad(status) || status.Code == StatusCodes.BadNoData) return;
         throw new ServiceResultException(status.Code,
-            $"HistoryRead of {nodeId} failed: {status.ToString()} (0x{status.Code:X8}).");
+            $"HistoryRead of {nodeId} failed: {StatusCodes.GetBrowseName(status.Code)} (0x{status.Code:X8}).");
     }
 }

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/Helpers/ValueConverter.cs

@@ -1,5 +1,3 @@
-using Opc.Ua;
-
 namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
 
 /// <summary>
@@ -8,49 +6,6 @@ namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
 /// </summary>
 public static class ValueConverter
 {
-    /// <summary>Converts a supported client payload to an SDK value, detaching caller-owned buffers.</summary>
-    /// <param name="value">The existing CLR or SDK payload.</param>
-    /// <returns>The corresponding OPC UA value.</returns>
-    /// <exception cref="ServiceResultException">The payload shape is unsupported.</exception>
-    public static Variant ToVariant(object? value)
-    {
-        // Historically a CLR byte[] supplied to a client write/method was a scalar ByteString.
-        if (value is byte[] bytes && bytes.GetType() == typeof(byte[])) return Variant.From(ByteString.From(bytes.AsSpan()));
-        if (value is ByteString byteString) return Variant.From(byteString.IsNull ? default : byteString.Copy());
-        if (!VariantHelper.TryCastFrom(value, out Variant variant))
-            throw new ServiceResultException(StatusCodes.BadTypeMismatch, "Unsupported client value type or shape.");
-        if (variant.TypeInfo.IsMatrix)
-            throw new ServiceResultException(StatusCodes.BadTypeMismatch, "Unsupported client matrix shape.");
-        if (variant.TypeInfo.IsArray && variant.TryGetValue(out ArrayOf<ByteString> buffers))
-            return Variant.From(buffers.IsNull ? default : buffers.ConvertAll(b => b.IsNull ? default : b.Copy()));
-        // ArrayOf is read-only, but can wrap externally owned ReadOnlyMemory. Detach it too.
-        if (value is not Array && variant.TypeInfo.IsArray && variant.AsBoxedObject(Variant.BoxingBehavior.Legacy) is Array array)
-        {
-            if (!VariantHelper.TryCastFrom(array, out variant))
-                throw new ServiceResultException(StatusCodes.BadTypeMismatch, "Unsupported client array type.");
-        }
-        else if (variant.TypeInfo.IsScalar && variant.TryGetValue(out ByteString retainedBytes))
-            variant = Variant.From(retainedBytes.IsNull ? default : retainedBytes.Copy());
-        return variant;
-    }
-
-    /// <summary>Returns the CLR representation expected by existing client object consumers.</summary>
-    /// <param name="value">The SDK value to inspect.</param>
-    /// <returns>A CLR scalar or array, preserving null versus empty values.</returns>
-    public static object? ToClrObject(Variant value)
-    {
-        return value.AsBoxedObject(Variant.BoxingBehavior.Legacy) switch
-        {
-            ByteString bytes => bytes.IsNull ? null : bytes.ToArray(),
-            DateTimeUtc timestamp => timestamp.ToDateTime(),
-            Uuid guid => (Guid)guid,
-            DateTimeUtc[] timestamps => timestamps.Select(t => t.ToDateTime()).ToArray(),
-            Uuid[] guids => guids.Select(g => (Guid)g).ToArray(),
-            ByteString[] buffers => buffers.Select(b => b.IsNull ? null : b.ToArray()).ToArray(),
-            var payload => payload
-        };
-    }
-
     /// <summary>
     ///     Converts a raw string value into the runtime type expected by the target node.
     /// </summary>

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/OpcUaClientService.cs

@@ -221,13 +221,13 @@ public sealed class OpcUaClientService : IOpcUaClientService
         if (value is string rawString)
         {
             var currentDataValue = await _session!.ReadValueAsync(nodeId, ct);
-            if (!StatusCode.IsGood(currentDataValue.StatusCode) || ValueConverter.ToClrObject(currentDataValue.WrappedValue) == null)
+            if (!StatusCode.IsGood(currentDataValue.StatusCode) || currentDataValue.Value == null)
                 throw new InvalidOperationException(
                     $"Cannot infer target type for node {nodeId}: read returned status {currentDataValue.StatusCode} with no value. Provide a typed value instead of a string.");
-            typedValue = ValueConverter.ConvertValue(rawString, ValueConverter.ToClrObject(currentDataValue.WrappedValue));
+            typedValue = ValueConverter.ConvertValue(rawString, currentDataValue.Value);
         }
 
-        var dataValue = new DataValue(ValueConverter.ToVariant(typedValue));
+        var dataValue = new DataValue(new Variant(typedValue));
         return await _session!.WriteValueAsync(nodeId, dataValue, ct);
     }
 
@@ -242,39 +242,22 @@ public sealed class OpcUaClientService : IOpcUaClientService
         var nodeClassMask = (uint)NodeClass.Object | (uint)NodeClass.Variable | (uint)NodeClass.Method;
         var results = new List<BrowseResult>();
 
-        // A cursor belongs to the session that issued it, including while failover swaps _session.
-        var session = _session!;
-        byte[]? continuationPoint = null;
-        try
-        {
-            ArrayOf<ReferenceDescription> references;
-            (continuationPoint, references) = await session.BrowseAsync(startNode, nodeClassMask, ct);
-            while (references.Count > 0)
-            {
-                foreach (var reference in references)
-                    results.Add(new BrowseResult(
-                        reference.NodeId.ToString(),
-                        reference.DisplayName.Text ?? string.Empty,
-                        reference.NodeClass.ToString(),
-                        reference.NodeClass == NodeClass.Object));
+        var (continuationPoint, references) = await _session!.BrowseAsync(startNode, nodeClassMask, ct);
 
-                if (continuationPoint is not { Length: > 0 } pending) break;
-                ct.ThrowIfCancellationRequested();
-                (continuationPoint, references) = await session.BrowseNextAsync(pending, ct);
-            }
-        }
-        finally
+        while (references.Count > 0)
         {
-            if (continuationPoint is { Length: > 0 })
-            {
-                try
-                {
-                    using var release = new CancellationTokenSource(HistoryReadPaging.ReleaseTimeout);
-                    await session.ReleaseBrowseContinuationPointAsync(continuationPoint, release.Token)
-                        .WaitAsync(release.Token).ConfigureAwait(false);
-                }
-                catch (Exception ex) { Logger.Warning(ex, "Releasing browse continuation point failed"); }
-            }
+            // Child detection is lazy: an Object MAY have children and is confirmed when the caller expands or
+            // recurses into it. Probing each Object child with its own Browse made one level of N folders cost N + 1
+            // round trips, and a recursive subscribe over a 50k-node tree ~50k extra Browse calls.
+            foreach (var reference in references)
+                results.Add(new BrowseResult(
+                    reference.NodeId.ToString(),
+                    reference.DisplayName?.Text ?? string.Empty,
+                    reference.NodeClass.ToString(),
+                    reference.NodeClass == NodeClass.Object));
+
+            if (continuationPoint is not { Length: > 0 } pending) break;
+            (continuationPoint, references) = await _session.BrowseNextAsync(pending, ct);
         }
 
         return results;
@@ -310,7 +293,7 @@ public sealed class OpcUaClientService : IOpcUaClientService
             }
 
             var handle = await subscription.AddDataChangeMonitoredItemAsync(
-                nodeId, intervalMs, DataCallback(session, subscription), ct);
+                nodeId, intervalMs, OnDataChangeNotification, ct);
 
             lock (_subscriptionLock)
             {
@@ -394,7 +377,7 @@ public sealed class OpcUaClientService : IOpcUaClientService
 
             var filter = CreateAlarmEventFilter();
             await subscription.AddEventMonitoredItemAsync(
-                monitorNode, intervalMs, filter, AlarmCallback(session, subscription), ct);
+                monitorNode, intervalMs, filter, OnAlarmEventNotification, ct);
 
             lock (_subscriptionLock)
             {
@@ -700,15 +683,15 @@ public sealed class OpcUaClientService : IOpcUaClientService
         var redundancySupportValue =
             await _session!.ReadValueAsync(VariableIds.Server_ServerRedundancy_RedundancySupport, ct);
         RedundancySupport redundancySupport;
-        if (StatusCode.IsGood(redundancySupportValue.StatusCode) && ValueConverter.ToClrObject(redundancySupportValue.WrappedValue) != null)
-            redundancySupport = (RedundancySupport)Convert.ToInt32(ValueConverter.ToClrObject(redundancySupportValue.WrappedValue));
+        if (StatusCode.IsGood(redundancySupportValue.StatusCode) && redundancySupportValue.Value != null)
+            redundancySupport = (RedundancySupport)Convert.ToInt32(redundancySupportValue.Value);
         else
             redundancySupport = RedundancySupport.None;
         var redundancyMode = redundancySupport.ToString();
 
         var serviceLevelValue = await _session.ReadValueAsync(VariableIds.Server_ServiceLevel, ct);
-        var serviceLevel = StatusCode.IsGood(serviceLevelValue.StatusCode) && ValueConverter.ToClrObject(serviceLevelValue.WrappedValue) != null
-            ? Convert.ToByte(ValueConverter.ToClrObject(serviceLevelValue.WrappedValue))
+        var serviceLevel = StatusCode.IsGood(serviceLevelValue.StatusCode) && serviceLevelValue.Value != null
+            ? Convert.ToByte(serviceLevelValue.Value)
             : (byte)0;
 
         string[] serverUris = [];
@@ -716,7 +699,7 @@ public sealed class OpcUaClientService : IOpcUaClientService
         {
             var serverUriArrayValue =
                 await _session.ReadValueAsync(VariableIds.Server_ServerRedundancy_ServerUriArray, ct);
-            if (ValueConverter.ToClrObject(serverUriArrayValue.WrappedValue) is string[] uris)
+            if (serverUriArrayValue.Value is string[] uris)
                 serverUris = uris;
         }
         catch
@@ -728,7 +711,7 @@ public sealed class OpcUaClientService : IOpcUaClientService
         try
         {
             var serverArrayValue = await _session.ReadValueAsync(VariableIds.Server_ServerArray, ct);
-            if (ValueConverter.ToClrObject(serverArrayValue.WrappedValue) is string[] serverArray && serverArray.Length > 0)
+            if (serverArrayValue.Value is string[] serverArray && serverArray.Length > 0)
                 applicationUri = serverArray[0];
         }
         catch
@@ -783,26 +766,16 @@ public sealed class OpcUaClientService : IOpcUaClientService
         };
 
         var config = await _configFactory.CreateAsync(effectiveSettings, ct);
-        try
-        {
-            var requestedMode = SecurityModeMapper.ToMessageSecurityMode(settings.SecurityMode);
-            var endpoint = await _endpointDiscovery.SelectEndpointAsync(config, endpointUrl, requestedMode, ct);
+        var requestedMode = SecurityModeMapper.ToMessageSecurityMode(settings.SecurityMode);
+        var endpoint = await _endpointDiscovery.SelectEndpointAsync(config, endpointUrl, requestedMode, ct);
 
-            var identity = settings.Username != null
-                ? new UserIdentity(settings.Username, Encoding.UTF8.GetBytes(settings.Password ?? ""))
-                : new UserIdentity();
+        var identity = settings.Username != null
+            ? new UserIdentity(settings.Username, Encoding.UTF8.GetBytes(settings.Password ?? ""))
+            : new UserIdentity();
 
-            var sessionTimeoutMs = (uint)(settings.SessionTimeoutSeconds * 1000);
-            return await _sessionFactory.CreateSessionAsync(config, endpoint, "OtOpcUaClient", sessionTimeoutMs, identity,
-                ct);
-        }
-        catch
-        {
-            // The session adapter owns it after successful creation; a failed attempt has no adapter owner.
-            try { (config.CertificateManager as IDisposable)?.Dispose(); }
-            catch (Exception ex) { Logger.Warning(ex, "Disposing certificate manager after connection failure"); }
-            throw;
-        }
+        var sessionTimeoutMs = (uint)(settings.SessionTimeoutSeconds * 1000);
+        return await _sessionFactory.CreateSessionAsync(config, endpoint, "OtOpcUaClient", sessionTimeoutMs, identity,
+            ct);
     }
 
     /// <summary>A bad keep-alive from the session of connection <paramref name="epoch"/>.</summary>
@@ -989,7 +962,7 @@ public sealed class OpcUaClientService : IOpcUaClientService
                 }
 
                 var handle = await dataSubscription.AddDataChangeMonitoredItemAsync(
-                    nodeId, intervalMs, DataCallback(session, dataSubscription), CancellationToken.None);
+                    nodeId, intervalMs, OnDataChangeNotification, CancellationToken.None);
 
                 lock (_subscriptionLock)
                 {
@@ -1012,7 +985,7 @@ public sealed class OpcUaClientService : IOpcUaClientService
                 lock (_subscriptionLock) _alarmSubscription = replayedAlarms;
                 var filter = CreateAlarmEventFilter();
                 await replayedAlarms.AddEventMonitoredItemAsync(
-                    monitorNode, intervalMs, filter, AlarmCallback(session, replayedAlarms), CancellationToken.None);
+                    monitorNode, intervalMs, filter, OnAlarmEventNotification, CancellationToken.None);
 
                 lock (_subscriptionLock)
                 {
@@ -1026,25 +999,6 @@ public sealed class OpcUaClientService : IOpcUaClientService
         }
     }
 
-    private bool IsCurrentNotification(ISessionAdapter session, ISubscriptionAdapter subscription, bool alarm)
-    {
-        lock (_subscriptionLock)
-            return !_disposed && _state == ConnectionState.Connected && ReferenceEquals(_session, session)
-                && ReferenceEquals(alarm ? _alarmSubscription : _dataSubscription, subscription);
-    }
-
-    private Action<string, DataValue> DataCallback(ISessionAdapter session, ISubscriptionAdapter subscription) =>
-        (nodeId, value) =>
-        {
-            if (IsCurrentNotification(session, subscription, false)) OnDataChangeNotification(nodeId, value);
-        };
-
-    private Action<EventFieldList> AlarmCallback(ISessionAdapter session, ISubscriptionAdapter subscription) =>
-        fields =>
-        {
-            if (IsCurrentNotification(session, subscription, true)) OnAlarmEventNotification(fields);
-        };
-
     private void OnDataChangeNotification(string nodeId, DataValue value)
     {
         DataChanged?.Invoke(this, new DataChangedEventArgs(nodeId, value));
@@ -1053,28 +1007,28 @@ public sealed class OpcUaClientService : IOpcUaClientService
     private void OnAlarmEventNotification(EventFieldList eventFields)
     {
         var fields = eventFields.EventFields;
-        if (fields.Count < 1)
+        if (fields == null || fields.Count < 1)
             return;
 
-        var eventId = fields.Count > 0 ? ValueConverter.ToClrObject(fields[0]) as byte[] : null;
-        var sourceName = fields.Count > 2 ? ValueConverter.ToClrObject(fields[2]) as string ?? string.Empty : string.Empty;
+        var eventId = fields.Count > 0 ? fields[0].Value as byte[] : null;
+        var sourceName = fields.Count > 2 ? fields[2].Value as string ?? string.Empty : string.Empty;
         var time = DateTime.MinValue;
-        if (fields.Count > 3 && ValueConverter.ToClrObject(fields[3]) != null)
+        if (fields.Count > 3 && fields[3].Value != null)
         {
-            if (ValueConverter.ToClrObject(fields[3]) is DateTime dt)
+            if (fields[3].Value is DateTime dt)
                 time = dt;
-            else if (DateTime.TryParse(ValueConverter.ToClrObject(fields[3])?.ToString(), out var parsed))
+            else if (DateTime.TryParse(fields[3].Value.ToString(), out var parsed))
                 time = parsed;
         }
-        var message = fields.Count > 4 ? (fields[4].TryGetValue(out LocalizedText text) ? text.Text : null) ?? string.Empty : string.Empty;
-        var severity = fields.Count > 5 ? Convert.ToUInt16(ValueConverter.ToClrObject(fields[5])) : (ushort)0;
-        var conditionName = fields.Count > 6 ? ValueConverter.ToClrObject(fields[6]) as string ?? string.Empty : string.Empty;
-        var retain = fields.Count > 7 && ParseBool(ValueConverter.ToClrObject(fields[7]));
-        var conditionNodeId = fields.Count > 12 ? ValueConverter.ToClrObject(fields[12])?.ToString() : null;
+        var message = fields.Count > 4 ? (fields[4].Value as LocalizedText)?.Text ?? string.Empty : string.Empty;
+        var severity = fields.Count > 5 ? Convert.ToUInt16(fields[5].Value) : (ushort)0;
+        var conditionName = fields.Count > 6 ? fields[6].Value as string ?? string.Empty : string.Empty;
+        var retain = fields.Count > 7 && ParseBool(fields[7].Value);
+        var conditionNodeId = fields.Count > 12 ? fields[12].Value?.ToString() : null;
 
         // Try standard OPC UA ActiveState/AckedState fields first
-        bool? ackedField = fields.Count > 8 && ValueConverter.ToClrObject(fields[8]) != null ? ParseBool(ValueConverter.ToClrObject(fields[8])) : null;
-        bool? activeField = fields.Count > 9 && ValueConverter.ToClrObject(fields[9]) != null ? ParseBool(ValueConverter.ToClrObject(fields[9])) : null;
+        bool? ackedField = fields.Count > 8 && fields[8].Value != null ? ParseBool(fields[8].Value) : null;
+        bool? activeField = fields.Count > 9 && fields[9].Value != null ? ParseBool(fields[9].Value) : null;
 
         var ackedState = ackedField ?? false;
         var activeState = activeField ?? false;
@@ -1099,25 +1053,39 @@ public sealed class OpcUaClientService : IOpcUaClientService
     /// <returns>The populated <see cref="EventFilter"/>.</returns>
     internal static EventFilter CreateAlarmEventFilter()
     {
-        var filter = new EventFilter
-        {
-            SelectClauses =
-            [
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.BaseEventType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("EventId")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.BaseEventType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("EventType")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.BaseEventType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("SourceName")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.BaseEventType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("Time")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.BaseEventType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("Message")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.BaseEventType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("Severity")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.ConditionType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("ConditionName")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.ConditionType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("Retain")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.AcknowledgeableConditionType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("AckedState"), new QualifiedName("Id")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.AlarmConditionType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("ActiveState"), new QualifiedName("Id")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.ConditionType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("EnabledState"), new QualifiedName("Id")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.AlarmConditionType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("SuppressedOrShelved")] },
-                new SimpleAttributeOperand { TypeDefinitionId = ObjectTypeIds.BaseEventType, AttributeId = Attributes.Value, BrowsePath = [new QualifiedName("SourceNode")] },
-            ]
-        };
+        var filter = new EventFilter();
+        // 0: EventId
+        filter.AddSelectClause(ObjectTypeIds.BaseEventType, BrowseNames.EventId);
+        // 1: EventType
+        filter.AddSelectClause(ObjectTypeIds.BaseEventType, BrowseNames.EventType);
+        // 2: SourceName
+        filter.AddSelectClause(ObjectTypeIds.BaseEventType, BrowseNames.SourceName);
+        // 3: Time
+        filter.AddSelectClause(ObjectTypeIds.BaseEventType, BrowseNames.Time);
+        // 4: Message
+        filter.AddSelectClause(ObjectTypeIds.BaseEventType, BrowseNames.Message);
+        // 5: Severity
+        filter.AddSelectClause(ObjectTypeIds.BaseEventType, BrowseNames.Severity);
+        // 6: ConditionName
+        filter.AddSelectClause(ObjectTypeIds.ConditionType, BrowseNames.ConditionName);
+        // 7: Retain
+        filter.AddSelectClause(ObjectTypeIds.ConditionType, BrowseNames.Retain);
+        // 8-10: the two-state /Id booleans. Each browse path is TWO QualifiedNames. Passing "AckedState/Id" as a
+        // string to AddSelectClause does not split it — it selects one element NAMED "AckedState/Id", which no
+        // event carries, so all three arrived null and every alarm read inactive + unacknowledged.
+        // 8: AckedState/Id
+        filter.SelectClauses.Add(new SimpleAttributeOperand(
+            ObjectTypeIds.AcknowledgeableConditionType, [BrowseNames.AckedState, BrowseNames.Id]));
+        // 9: ActiveState/Id
+        filter.SelectClauses.Add(new SimpleAttributeOperand(
+            ObjectTypeIds.AlarmConditionType, [BrowseNames.ActiveState, BrowseNames.Id]));
+        // 10: EnabledState/Id
+        filter.SelectClauses.Add(new SimpleAttributeOperand(
+            ObjectTypeIds.ConditionType, [BrowseNames.EnabledState, BrowseNames.Id]));
+        // 11: SuppressedOrShelved
+        filter.AddSelectClause(ObjectTypeIds.AlarmConditionType, "SuppressedOrShelved");
+        // 12: SourceNode (ConditionId for acknowledgment)
+        filter.AddSelectClause(ObjectTypeIds.BaseEventType, BrowseNames.SourceNode);
         return filter;
     }
 

src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/ZB.MOM.WW.OtOpcUa.Client.Shared.csproj

@@ -8,6 +8,7 @@
     </PropertyGroup>
 
     <ItemGroup>
+        <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.MigrationAnalyzer" PrivateAssets="all" IncludeAssets="analyzers;build;buildtransitive" />
         <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.Client"/>
         <PackageReference Include="Serilog"/>
     </ItemGroup>

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Helpers/StatusCodeFormatter.cs

@@ -16,7 +16,7 @@ internal static class StatusCodeFormatter
         var hex = $"0x{code:X8}";
 
         // Try the SDK's browse name lookup first
-        var name = statusCode.SymbolicId;
+        var name = StatusCodes.GetBrowseName(code);
         if (!string.IsNullOrEmpty(name))
             return $"{hex} ({name})";
 
@@ -24,7 +24,7 @@ internal static class StatusCodeFormatter
         var mainCode = code & 0xFFFF0000;
         if (mainCode != code)
         {
-            name = new StatusCode(mainCode).SymbolicId;
+            name = StatusCodes.GetBrowseName(mainCode);
             if (!string.IsNullOrEmpty(name))
                 return $"{hex} ({name})";
         }

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/AlarmsViewModel.cs

@@ -109,7 +109,7 @@ public partial class AlarmsViewModel : ObservableObject
     {
         try
         {
-            NodeId? sourceNodeId = string.IsNullOrWhiteSpace(MonitoredNodeIdText)
+            var sourceNodeId = string.IsNullOrWhiteSpace(MonitoredNodeIdText)
                 ? null
                 : NodeId.Parse(MonitoredNodeIdText);
 
@@ -275,7 +275,7 @@ public partial class AlarmsViewModel : ObservableObject
 
         try
         {
-            NodeId? nodeId = string.IsNullOrWhiteSpace(sourceNodeId)
+            var nodeId = string.IsNullOrWhiteSpace(sourceNodeId)
                 ? null
                 : NodeId.Parse(sourceNodeId);
 

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/HistoryViewModel.cs

@@ -1,4 +1,3 @@
-using ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
 using System.Collections.ObjectModel;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
@@ -98,7 +97,7 @@ public partial class HistoryViewModel : ObservableObject
             {
                 foreach (var dv in values)
                     Results.Add(new HistoryValueViewModel(
-                        Helpers.ValueFormatter.Format(ValueConverter.ToClrObject(dv.WrappedValue)),
+                        Helpers.ValueFormatter.Format(dv.Value),
                         Helpers.StatusCodeFormatter.Format(dv.StatusCode),
                         dv.SourceTimestamp.ToString("O"),
                         dv.ServerTimestamp.ToString("O")));

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/ReadWriteViewModel.cs

@@ -1,4 +1,3 @@
-using ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
 using Opc.Ua;
@@ -77,7 +76,7 @@ public partial class ReadWriteViewModel : ObservableObject
 
             _dispatcher.Post(() =>
             {
-                CurrentValue = Helpers.ValueFormatter.Format(ValueConverter.ToClrObject(dataValue.WrappedValue));
+                CurrentValue = Helpers.ValueFormatter.Format(dataValue.Value);
                 CurrentStatus = Helpers.StatusCodeFormatter.Format(dataValue.StatusCode);
                 SourceTimestamp = dataValue.SourceTimestamp.ToString("O");
                 ServerTimestamp = dataValue.ServerTimestamp.ToString("O");

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/SubscriptionsViewModel.cs

@@ -1,4 +1,3 @@
-using ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using CommunityToolkit.Mvvm.ComponentModel;
@@ -76,7 +75,7 @@ public partial class SubscriptionsViewModel : ObservableObject
             if (!_rowsByNodeId.TryGetValue(e.NodeId, out var rows)) return;
             foreach (var item in rows)
             {
-                item.Value = Helpers.ValueFormatter.Format(ValueConverter.ToClrObject(e.Value.WrappedValue));
+                item.Value = Helpers.ValueFormatter.Format(e.Value.Value);
                 item.Status = Helpers.StatusCodeFormatter.Format(e.Value.StatusCode);
                 item.Timestamp = e.Value.SourceTimestamp.ToString("O");
             }
@@ -282,7 +281,7 @@ public partial class SubscriptionsViewModel : ObservableObject
 
             // Read current value to determine target type
             var currentDataValue = await _service.ReadValueAsync(nodeId);
-            var currentValue = ValueConverter.ToClrObject(currentDataValue.WrappedValue);
+            var currentValue = currentDataValue.Value;
 
             // Try parsing to the target type before writing
             try

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser/OpcUaClientBrowseSession.cs

@@ -17,7 +17,7 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
     private readonly NodeId _rootNodeId;
     private readonly SemaphoreSlim _gate = new(1, 1);
     private volatile bool _disposed;
-    private readonly IDisposable? _ownedCredential;
+    private readonly IAsyncDisposable? _ownedApplication;
 
     /// <summary>
     ///     Construct a browse session bound to an already-connected <paramref name="session"/>.
@@ -26,10 +26,10 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
     /// <param name="nsMap">Namespace snapshot taken at connect time; used to render outbound
     ///     NodeIds in the server-stable <c>nsu=…</c> form.</param>
     /// <param name="rootNodeId">The node under which <see cref="RootAsync"/> browses one level.</param>
-    /// <param name="ownedCredential">A credential (the user certificate) this session owns and disposes with itself.</param>
-    internal OpcUaClientBrowseSession(ISession session, NamespaceMap nsMap, NodeId rootNodeId, IDisposable? ownedCredential = null)
+    /// <param name="ownedApplication">The SDK application whose certificate manager this session owns.</param>
+    internal OpcUaClientBrowseSession(ISession session, NamespaceMap nsMap, NodeId rootNodeId, IAsyncDisposable? ownedApplication = null)
     {
-        _ownedCredential = ownedCredential;
+        _ownedApplication = ownedApplication;
         _session = session;
         _nsMap = nsMap;
         _rootNodeId = rootNodeId;
@@ -73,10 +73,10 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
             Attributes.NodeClass, Attributes.DisplayName, Attributes.DataType, Attributes.ValueRank,
             Attributes.UserAccessLevel,
         ];
-        var toRead = new ReadValueIdCollection(attributeIds.Length);
+        var toRead = new List<ReadValueId>(attributeIds.Length);
         foreach (var id in attributeIds) toRead.Add(new ReadValueId { NodeId = resolved, AttributeId = id });
 
-        DataValueCollection values;
+        ArrayOf<DataValue> values;
         await _gate.WaitAsync(cancellationToken).ConfigureAwait(false);
         try
         {
@@ -97,15 +97,15 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
         DataValue? At(int i) => i < values.Count && StatusCode.IsGood(values[i].StatusCode)
             ? values[i] : null;
 
-        var nodeClass = At(0)?.Value is int nc ? (NodeClass)nc : NodeClass.Unspecified;
+        var nodeClass = At(0)?.WrappedValue.AsBoxedObject() is int nc ? (NodeClass)nc : NodeClass.Unspecified;
         if (nodeClass != NodeClass.Variable) return Array.Empty<AttributeInfo>();
 
-        var name = (At(1)?.Value as LocalizedText)?.Text ?? resolved.ToString() ?? nodeId;
-        var dataType = At(2)?.Value is NodeId dt
+        var name = (At(1)?.WrappedValue.AsBoxedObject() as LocalizedText?)?.Text ?? resolved.ToString() ?? nodeId;
+        var dataType = At(2)?.WrappedValue.AsBoxedObject() is NodeId dt
             ? UpstreamAttributeMapping.MapDataType(dt)
             : ZB.MOM.WW.OtOpcUa.Core.Abstractions.DriverDataType.String;
-        var valueRank = At(3)?.Value is int vr ? vr : ValueRanks.Scalar;
-        var access = At(4)?.Value is byte ab ? ab : (byte)0;
+        var valueRank = At(3)?.WrappedValue.AsBoxedObject() is int vr ? vr : ValueRanks.Scalar;
+        var access = At(4)?.WrappedValue.AsBoxedObject() is byte ab ? ab : (byte)0;
 
         return
         [
@@ -126,7 +126,7 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
         await _gate.WaitAsync(ct).ConfigureAwait(false);
         try
         {
-            var descriptions = new BrowseDescriptionCollection
+            var descriptions = new List<BrowseDescription>
             {
                 new()
                 {
@@ -154,7 +154,7 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
             }
 
             var result = resp.Results[0];
-            var refs = result.References;
+            var refs = result.References.ToList();
 
             // Follow browse continuation points so folders larger than the server's per-call
             // cap aren't silently truncated.
@@ -177,11 +177,12 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
                     // Best-effort — mirrors OpcUaClientDriver's pagination loop.
                     try
                     {
+                        using var release = new CancellationTokenSource(TimeSpan.FromSeconds(5));
                         await _session.BrowseNextAsync(
                             requestHeader: null,
                             releaseContinuationPoints: true,
                             continuationPoints: [cp],
-                            ct: CancellationToken.None).ConfigureAwait(false);
+                            ct: release.Token).AsTask().WaitAsync(release.Token).ConfigureAwait(false);
                     }
                     catch { /* best-effort — server may have already cleaned up */ }
                     throw;
@@ -190,7 +191,7 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
                 if (next.Results.Count == 0) break;
                 var nextResult = next.Results[0];
                 if (nextResult.References is { Count: > 0 })
-                    refs.AddRange(nextResult.References);
+                    refs.AddRange(nextResult.References.ToList());
                 cp = nextResult.ContinuationPoint;
             }
 
@@ -214,8 +215,8 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
     {
         var childId = ExpandedNodeId.ToNodeId(rf.NodeId, _session.NamespaceUris);
         var isObject = rf.NodeClass == NodeClass.Object;
-        var displayName = rf.DisplayName?.Text
-                          ?? rf.BrowseName?.Name
+        var displayName = rf.DisplayName.Text
+                          ?? rf.BrowseName.Name
                           ?? childId.ToString()
                           ?? "(unnamed)";
         return new BrowseNode(
@@ -246,7 +247,9 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
         try { _gate.Dispose(); }
         catch { /* best-effort */ }
 
-        try { _ownedCredential?.Dispose(); }
-        catch { /* best-effort */ }
+        if (_ownedApplication is not null)
+        {
+            try { await _ownedApplication.DisposeAsync().ConfigureAwait(false); } catch { /* best-effort */ }
+        }
     }
 }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser/OpcUaClientDriverBrowser.cs

@@ -69,9 +69,10 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
         // R06:O-5 — Certificate auth is supported: the identity is built (and any secret: credential resolved) by the
         // same factory the runtime driver uses, BEFORE any network I/O, so a bad certificate path / password fails fast
         // with its own message.
-        var (identity, ownedCertificate) = await BuildBrowseCredentialAsync(opts, _secretResolver, cancellationToken)
+        var identity = await BuildBrowseUserIdentityAsync(opts, _secretResolver, cancellationToken)
             .ConfigureAwait(false);
 
+        ApplicationInstance? ownedApplication = null;
         try
         {
             if (opts.AutoAcceptCertificates)
@@ -81,7 +82,9 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
                     "driver's PKI store instead.",
                     endpoint);
 
-            var appConfig = await BuildBrowseAppConfigurationAsync(cancellationToken).ConfigureAwait(false);
+            var app = await BuildBrowseAppConfigurationAsync(cancellationToken).ConfigureAwait(false);
+            ownedApplication = app;
+            var appConfig = app.ApplicationConfiguration!;
 
             var perEndpointBudget = TimeSpan.FromSeconds(
                 Math.Clamp(opts.PerEndpointConnectTimeout.TotalSeconds, 5, 30));
@@ -101,11 +104,12 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
                 sessionName: "OtOpcUa AdminUI Browse",
                 (uint)opts.SessionTimeout.TotalMilliseconds,
                 identity,
-                preferredLocales: null,
+                preferredLocales: default,
                 connectCts.Token).ConfigureAwait(false);
 
             try
             {
+                connectCts.Token.ThrowIfCancellationRequested();
                 var nsMap = NamespaceMap.FromSession(session);
                 var rootNodeId = string.IsNullOrEmpty(opts.BrowseRoot)
                     ? ObjectIds.ObjectsFolder
@@ -115,7 +119,9 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
                     "AdminUI OPC UA browse session opened against {Endpoint} (policy {Policy}, mode {Mode})",
                     endpoint, opts.SecurityPolicy, opts.SecurityMode);
 
-                return new OpcUaClientBrowseSession(session, nsMap, rootNodeId, ownedCertificate);
+                var browse = new OpcUaClientBrowseSession(session, nsMap, rootNodeId, ownedApplication);
+                ownedApplication = null;
+                return browse;
             }
             catch
             {
@@ -126,9 +132,8 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
         }
         catch
         {
-            // Review m9: the certificate (and its private-key handle) is owned by the browse session once handed
-            // over; any failure before that releases it here instead of leaving it to the GC.
-            ownedCertificate?.Dispose();
+            // The SDK application owns its certificate manager until the browse session takes it.
+            if (ownedApplication is not null) await ownedApplication.DisposeAsync().ConfigureAwait(false);
             throw;
         }
     }
@@ -139,7 +144,7 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
     ///     trust decisions don't leak into the deployed driver's cert store.
     /// </summary>
     /// <param name="ct">Cancellation token for the configuration build.</param>
-    private static async Task<ApplicationConfiguration> BuildBrowseAppConfigurationAsync(CancellationToken ct)
+    private static async Task<ApplicationInstance> BuildBrowseAppConfigurationAsync(CancellationToken ct)
     {
         // The ITelemetryContext overload is the non-obsolete ctor; an empty builder keeps SDK
         // internals off any logging provider.
@@ -153,7 +158,7 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
             Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
             "OtOpcUa", "adminui-browse-pki");
 
-        var config = new ApplicationConfiguration
+        var config = new ApplicationConfiguration(BrowseTelemetry.Context)
         {
             ApplicationName = "OtOpcUa AdminUI Browse",
             ApplicationType = ApplicationType.Client,
@@ -187,11 +192,19 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
             ClientConfiguration = new ClientConfiguration { DefaultSessionTimeout = 60_000 },
             DisableHiResClock = true,
         };
-        await config.ValidateAsync(ApplicationType.Client, ct).ConfigureAwait(false);
         app.ApplicationConfiguration = config;
-        await app.CheckApplicationInstanceCertificatesAsync(silent: true, lifeTimeInMonths: null, ct)
-            .ConfigureAwait(false);
-        return config;
+        try
+        {
+            await config.ValidateAsync(ApplicationType.Client, ct).ConfigureAwait(false);
+            await app.CheckApplicationInstanceCertificatesAsync(silent: true, lifeTimeInMonths: null, ct)
+                .ConfigureAwait(false);
+            return app;
+        }
+        catch
+        {
+            await app.DisposeAsync().ConfigureAwait(false);
+            throw;
+        }
     }
 
     /// <summary>
@@ -203,29 +216,11 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
     /// <param name="ct">Cancellation token for the secret resolution.</param>
     /// <returns>The identity the browse session activates with.</returns>
     internal static async Task<UserIdentity> BuildBrowseUserIdentityAsync(
-        OpcUaClientDriverOptions opts, ISecretResolver? secretResolver, CancellationToken ct) =>
-        (await BuildBrowseCredentialAsync(opts, secretResolver, ct).ConfigureAwait(false)).Identity;
-
-    /// <summary>
-    ///     As <see cref="BuildBrowseUserIdentityAsync"/>, also handing back the user certificate a Certificate-auth
-    ///     identity holds, so the browse session that uses it can dispose it (review m9: the browse opens one per picker
-    ///     session, and an undisposed <c>X509Certificate2</c> pins a private-key handle until GC).
-    /// </summary>
-    /// <param name="opts">Driver options carrying the form's auth fields.</param>
-    /// <param name="secretResolver">The secret store, or null when none is available.</param>
-    /// <param name="ct">Cancellation token for the secret resolution.</param>
-    /// <returns>The identity, and the certificate it owns (null for Anonymous / Username).</returns>
-    internal static async Task<(UserIdentity Identity, System.Security.Cryptography.X509Certificates.X509Certificate2? Certificate)>
-        BuildBrowseCredentialAsync(OpcUaClientDriverOptions opts, ISecretResolver? secretResolver, CancellationToken ct)
+        OpcUaClientDriverOptions opts, ISecretResolver? secretResolver, CancellationToken ct)
     {
+        ct.ThrowIfCancellationRequested();
         var resolved = await OpcUaUserIdentityFactory.ResolveSecretRefsAsync(opts, secretResolver, ct).ConfigureAwait(false);
-        if (resolved.AuthType != OpcUaAuthType.Certificate)
-        {
-            return (OpcUaUserIdentityFactory.Build(resolved), null);
-        }
-
-        var certificate = OpcUaUserIdentityFactory.LoadCertificate(resolved);
-        return (new UserIdentity(certificate), certificate);
+        return OpcUaUserIdentityFactory.Build(resolved);
     }
 
     /// <summary>Select the endpoint matching the requested SecurityPolicy + SecurityMode pair.</summary>
@@ -240,7 +235,7 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
     {
         using var client = await DiscoveryClient.CreateAsync(
             appConfig, new Uri(url), DiagnosticsMasks.None, ct).ConfigureAwait(false);
-        var all = await client.GetEndpointsAsync(null, ct).ConfigureAwait(false);
+        var all = await client.GetEndpointsAsync(default, ct).ConfigureAwait(false);
 
         var wantedPolicy = MapPolicy(policy);
         var wantedMode = mode switch
@@ -250,11 +245,11 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
             OpcUaSecurityMode.SignAndEncrypt => MessageSecurityMode.SignAndEncrypt,
             _ => throw new ArgumentOutOfRangeException(nameof(mode)),
         };
-        var match = all.FirstOrDefault(e =>
+        var match = all.ToList().FirstOrDefault(e =>
             e.SecurityPolicyUri == wantedPolicy && e.SecurityMode == wantedMode);
         if (match is null)
         {
-            var advertised = string.Join(", ", all.Select(e =>
+            var advertised = string.Join(", ", all.ToList().Select(e =>
                 $"{ShortName(e.SecurityPolicyUri)}/{e.SecurityMode}"));
             throw new InvalidOperationException(
                 $"No endpoint at '{url}' matches SecurityPolicy={policy} + SecurityMode={mode}. " +
@@ -278,7 +273,7 @@ public sealed class OpcUaClientDriverBrowser : IDriverBrowser
 
     /// <summary>Render an OPC UA security-policy URI as its short suffix for diag messages.</summary>
     /// <param name="uri">Full policy URI to shorten.</param>
-    private static string ShortName(string uri) =>
+    private static string ShortName(string? uri) =>
         uri?.Substring(uri.LastIndexOf('#') + 1) ?? "(null)";
 }
 

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser.csproj

@@ -13,7 +13,6 @@
         <ProjectReference Include="..\ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Session\ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Session.csproj" />
     </ItemGroup>
     <ItemGroup>
-        <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.MigrationAnalyzer" PrivateAssets="all" IncludeAssets="analyzers;build;buildtransitive" />
         <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.Client" />
         <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.Configuration" />
         <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" />

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Session/NamespaceMap.cs

@@ -196,7 +196,6 @@ public sealed class NamespaceMap
     /// <returns>The server-stable reference string for <paramref name="nodeId"/>.</returns>
     public string ToStableReference(NodeId nodeId)
     {
-        ArgumentNullException.ThrowIfNull(nodeId);
         // Namespace 0 is fixed by the spec — the compact form is already stable.
         if (nodeId.NamespaceIndex == 0)
             return nodeId.ToString() ?? string.Empty;
@@ -238,7 +237,7 @@ public sealed class NamespaceMap
             // reorder since the reference was captured resolves correctly. Plain ns=N forms
             // resolve directly.
             nodeId = NodeId.Parse(currentSession.MessageContext, reference);
-            return !NodeId.IsNull(nodeId);
+            return !nodeId.IsNull;
         }
         catch
         {
@@ -249,10 +248,10 @@ public sealed class NamespaceMap
     /// <summary>Render just the identifier portion (<c>s=…</c>, <c>i=…</c>, <c>g=…</c>, <c>b=…</c>) of a NodeId.</summary>
     private static string IdentifierPart(NodeId nodeId) => nodeId.IdType switch
     {
-        IdType.Numeric => $"i={nodeId.Identifier}",
-        IdType.String => $"s={nodeId.Identifier}",
-        IdType.Guid => $"g={nodeId.Identifier}",
-        IdType.Opaque => $"b={Convert.ToBase64String((byte[])nodeId.Identifier)}",
-        _ => $"s={nodeId.Identifier}",
+        IdType.Numeric => $"i={nodeId.IdentifierAsString}",
+        IdType.String => $"s={nodeId.IdentifierAsString}",
+        IdType.Guid => $"g={nodeId.IdentifierAsString}",
+        IdType.Opaque => $"b={nodeId.IdentifierAsString}",
+        _ => throw new ArgumentOutOfRangeException(nameof(nodeId)),
     };
 }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Session/OpcUaUserIdentityFactory.cs

@@ -1,4 +1,5 @@
 using Opc.Ua;
+using Opc.Ua.Security.Certificates;
 using ZB.MOM.WW.Secrets.Abstractions;
 
 namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient;
@@ -37,7 +38,37 @@ public static class OpcUaUserIdentityFactory
     /// </summary>
     /// <param name="options">Driver options containing certificate configuration.</param>
     /// <returns>The certificate-backed <see cref="UserIdentity"/>.</returns>
-    public static UserIdentity FromCertificate(OpcUaClientDriverOptions options) => new(LoadCertificate(options));
+    public static UserIdentity FromCertificate(OpcUaClientDriverOptions options)
+    {
+        using var certificate = LoadCertificate(options);
+        var identifier = new CertificateIdentifier { Thumbprint = certificate.Thumbprint };
+        return new UserIdentity(new X509IdentityTokenHandler(identifier,
+            new CertificatePasswordProvider(), new FileCertificateProvider(options, certificate.Thumbprint)));
+    }
+
+    // The configured credential is a PFX file, rather than an SDK certificate store. SDK 2 resolves
+    // signing keys on demand and disposes each returned Certificate. Pin the public identity for this
+    // lifecycle; a file/secret rotation is picked up only by the next initialise/open.
+    private sealed class FileCertificateProvider(OpcUaClientDriverOptions options, string thumbprint) : ICertificateProvider
+    {
+        public Certificate? TryGetPrivateKeyCertificate(string requestedThumbprint) => null;
+
+        public ValueTask<Certificate?> GetPrivateKeyCertificateAsync(CertificateIdentifier identifier,
+            ICertificatePasswordProvider? passwordProvider = null, string? applicationUri = null,
+            CancellationToken ct = default)
+        {
+            ct.ThrowIfCancellationRequested();
+            var certificate = LoadCertificate(options);
+            if (!string.Equals(certificate.Thumbprint, thumbprint, StringComparison.OrdinalIgnoreCase)
+                || !string.Equals(identifier.Thumbprint, thumbprint, StringComparison.OrdinalIgnoreCase))
+            {
+                certificate.Dispose();
+                throw new ServiceResultException(StatusCodes.BadIdentityTokenInvalid,
+                    "The user certificate changed; reopen the session to use the rotated credential.");
+            }
+            return ValueTask.FromResult<Certificate?>(Certificate.From(certificate));
+        }
+    }
 
     /// <summary>
     ///     Loads (and validates) the user-authentication certificate <see cref="FromCertificate"/> wraps. The caller owns

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Session/UpstreamValueMapping.cs

@@ -0,0 +1,32 @@
+using Opc.Ua;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient;
+
+/// <summary>Detaches SDK values at the driver boundary while preserving deployed CLR payload types.</summary>
+public static class UpstreamValueMapping
+{
+    /// <summary>Materializes scalar and one-dimensional array values without flattening matrices.</summary>
+    /// <param name="value">The upstream value.</param>
+    /// <returns>The independent CLR payload.</returns>
+    public static object? ToClr(Variant value)
+    {
+        if (value.TypeInfo.IsMatrix)
+            throw new NotSupportedException("Matrix payloads are not supported by the OPC UA driver.");
+        return Detach(value.AsBoxedObject(Variant.BoxingBehavior.Legacy));
+    }
+
+    private static object? Detach(object? value) => value switch
+    {
+        ByteString bytes => bytes.IsNull ? null : bytes.ToArray(),
+        DateTimeUtc time => time.ToDateTime(),
+        Uuid uuid => (Guid)uuid,
+        ByteString[] bytes => bytes.Select(b => b.IsNull ? null : b.ToArray()).ToArray(),
+        DateTimeUtc[] times => times.Select(t => t.ToDateTime()).ToArray(),
+        Uuid[] uuids => uuids.Select(u => (Guid)u).ToArray(),
+        Variant[] variants => variants.Select(ToClr).ToArray(),
+        byte[][] bytes => bytes.Select(b => b?.ToArray()).ToArray(),
+        object?[] objects when objects.GetType() == typeof(object[]) => objects.Select(Detach).ToArray(),
+        Array array => array.Clone(),
+        _ => value,
+    };
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Session/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Session.csproj

@@ -34,7 +34,6 @@
         ContractsIsDependencyLightTests in Driver.OpcUaClient.Tests.
     -->
     <ItemGroup>
-        <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.MigrationAnalyzer" PrivateAssets="all" IncludeAssets="analyzers;build;buildtransitive" />
         <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.Client" />
         <!-- OpcUaUserIdentityFactory: the secret: resolution of the credential fields feeding the SDK UserIdentity is
              shared by the driver and the AdminUI browse (review 2026-10-21 O-5), so the browse presents exactly the

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/OpcUaClientDriver.cs

@@ -274,12 +274,13 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
     /// <summary>
     ///     Cert-validation delegate wired when <see cref="OpcUaClientDriverOptions.AutoAcceptCertificates"/>
     ///     is <c>true</c>. Stored so <see cref="Dispose"/> / <see cref="DisposeAsync"/> can
-    ///     detach it from the (potentially process-shared) <see cref="CertificateValidator"/>
+    ///     detach it from the (potentially process-shared) <see cref="ICertificateManager"/>
     ///     and avoid leaking the closure.
     /// </summary>
-    private CertificateValidationEventHandler? _certValidationHandler;
-    /// <summary>The <see cref="CertificateValidator"/> that owns <see cref="_certValidationHandler"/>.</summary>
-    private CertificateValidator? _certValidatorRef;
+    private Func<Opc.Ua.Security.Certificates.Certificate, ServiceResult, bool>? _certValidationHandler;
+    /// <summary>The <see cref="ICertificateManager"/> that owns <see cref="_certValidationHandler"/>.</summary>
+    private ICertificateManager? _certValidatorRef;
+    private ApplicationInstance? _ownedApplication;
     /// <summary>
     ///     1 while the CURRENT session's keep-alive is bad (an outage is in progress), else 0. The
     ///     0→1 edge publishes the outage once (Bad per subscribed ref + a quality-only alarm annotation); the 1→0
@@ -547,7 +548,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             // G-2b: resolve any secret:-prefixed Password / UserCertificatePassword through the
             // shared secret store ONCE, here in the async connect flow, just before the credentials
             // are consumed. _options stays the raw config (with secret: refs) — only this
-            // connect-scoped local carries plaintext, and only for the duration of the connect.
+            // session identity carries the resolved credential while activation/signing needs it.
             // Resolving on every InitializeAsync (a full reconnect calls it) picks up rotations.
             // Both credential consumers — the Username password below and the Certificate password
             // in BuildCertificateIdentity — flow through BuildUserIdentity(resolvedOptions), so a
@@ -565,6 +566,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             string? connectedUrl = null;
             foreach (var url in candidates)
             {
+                cancellationToken.ThrowIfCancellationRequested();
                 try
                 {
                     session = OpenSessionForTest is { } open
@@ -572,9 +574,11 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
                         : await OpenSessionOnEndpointAsync(
                             appConfig, url, _options.SecurityPolicy, _options.SecurityMode,
                             identity, cancellationToken).ConfigureAwait(false);
+                    cancellationToken.ThrowIfCancellationRequested();
                     connectedUrl = url;
                     break;
                 }
+                catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested) { throw; }
                 catch (Exception ex)
                 {
                     attemptErrors.Add($"{url} -> {ex.GetType().Name}: {ex.Message}");
@@ -622,6 +626,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
                     DetachCertValidation(_certValidatorRef, _certValidationHandler);
                     _certValidationHandler = certValidation.Handler;
                     _certValidatorRef = certValidation.Validator;
+                    _ownedApplication = certValidation.Application;
                     installed = true;
                 }
             }
@@ -642,7 +647,12 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             // superseded check) does not orphan it and its keep-alive timer until GC.
             if (session is not null && !installed)
                 await DiscardSessionAsync(session, keepAliveHandler).ConfigureAwait(false);
-            if (!installed) DetachCertValidation(certValidation.Validator, certValidation.Handler);
+            if (!installed)
+            {
+                DetachCertValidation(certValidation.Validator, certValidation.Handler);
+                if (certValidation.Application is { } application)
+                    await application.DisposeAsync().ConfigureAwait(false);
+            }
             if (Volatile.Read(ref _lifecycleGeneration) == generation)
             {
                 if (installed)
@@ -657,14 +667,15 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
     /// <summary>The auto-accept certificate-validation handler one initialise attached, handed back to it (review m2).</summary>
     private sealed class CertValidationHook
     {
-        public CertificateValidationEventHandler? Handler { get; set; }
-        public CertificateValidator? Validator { get; set; }
+        public Func<Opc.Ua.Security.Certificates.Certificate, ServiceResult, bool>? Handler { get; set; }
+        public ICertificateManager? Validator { get; set; }
+        public ApplicationInstance? Application { get; set; }
     }
 
-    private static void DetachCertValidation(CertificateValidator? validator, CertificateValidationEventHandler? handler)
+    private static void DetachCertValidation(ICertificateManager? validator, Func<Opc.Ua.Security.Certificates.Certificate, ServiceResult, bool>? handler)
     {
         if (validator is null || handler is null) return;
-        try { validator.CertificateValidation -= handler; } catch { /* best-effort */ }
+        try { if (ReferenceEquals(validator.AcceptError, handler)) validator.AcceptError = null; } catch { /* best-effort */ }
     }
 
     /// <summary>
@@ -735,11 +746,12 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             ApplicationType = ApplicationType.Client,
         };
 
+        certValidation.Application = app;
         var pkiRoot = Path.Combine(
             Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
             "OtOpcUa", "pki");
 
-        var config = new ApplicationConfiguration
+        var config = new ApplicationConfiguration(_sdkTelemetry)
         {
             ApplicationName = _options.SessionName,
             ApplicationType = ApplicationType.Client,
@@ -782,6 +794,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             DisableHiResClock = true,
         };
 
+        app.ApplicationConfiguration = config;
         await config.ValidateAsync(ApplicationType.Client, ct).ConfigureAwait(false);
 
         // AutoAccept=true is a dev-only escape hatch. Emit a prominent warning so a
@@ -801,28 +814,26 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             // the latter would silently fail for those certs. A REVOKED certificate is the one
             // exception: auto-accept is for dev self-signed certs, never for a cert its issuer
             // has explicitly withdrawn.
-            CertificateValidationEventHandler handler = (_, e) =>
+            Func<Opc.Ua.Security.Certificates.Certificate, ServiceResult, bool> handler = (certificate, error) =>
             {
-                if (IsRevocationFailure(e.Error.StatusCode))
+                if (IsRevocationFailure(error.StatusCode))
                 {
                     _logger.LogWarning(
                         "OpcUaClientDriver '{DriverInstanceId}': REVOKED server certificate rejected " +
                         "(subject={Subject}, status=0x{Status:X8}) — AutoAcceptCertificates does not apply to revoked certs.",
-                        _driverInstanceId, e.Certificate?.Subject, e.Error.StatusCode.Code);
-                    e.Accept = false;
-                    return;
+                        _driverInstanceId, certificate.Subject, error.StatusCode.Code);
+                    return false;
                 }
-                e.Accept = true;
+                return true;
             };
-            config.CertificateValidator.CertificateValidation += handler;
+            config.CertificateManager.AcceptError = handler;
             // Handed back to the caller, which stores the refs (so ShutdownAsync + Dispose can detach the delegate)
             // only while its initialise is the current lifecycle generation.
             certValidation.Handler = handler;
-            certValidation.Validator = config.CertificateValidator;
+            certValidation.Validator = config.CertificateManager;
         }
 
         // Ensure an application certificate exists. The SDK auto-generates one if missing.
-        app.ApplicationConfiguration = config;
         await app.CheckApplicationInstanceCertificatesAsync(silent: true, lifeTimeInMonths: null, ct)
             .ConfigureAwait(false);
 
@@ -888,31 +899,31 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         var wantedPolicyUri = MapSecurityPolicy(policy);
         var wantedMode = ToMessageSecurityMode(mode);
 
-        ApplicationDescriptionCollection servers;
+        ArrayOf<ApplicationDescription> servers;
         using (var lds = await DiscoveryClient.CreateAsync(
                    appConfig, new Uri(discoveryUrl), Opc.Ua.DiagnosticsMasks.None, ct).ConfigureAwait(false))
         {
-            servers = await lds.FindServersAsync(null, ct).ConfigureAwait(false);
+            servers = await lds.FindServersAsync(default, ct).ConfigureAwait(false);
         }
 
         var found = new List<DiscoveredEndpoint>();
-        foreach (var server in servers)
+        foreach (var server in servers.ToList())
         {
-            if (server.DiscoveryUrls is null) continue;
-            foreach (var serverDiscoveryUrl in server.DiscoveryUrls)
+            if (server.DiscoveryUrls.IsNull) continue;
+            foreach (var serverDiscoveryUrl in server.DiscoveryUrls.ToList())
             {
                 if (string.IsNullOrWhiteSpace(serverDiscoveryUrl)) continue;
-                EndpointDescriptionCollection endpoints;
+                ArrayOf<EndpointDescription> endpoints;
                 try
                 {
                     using var ep = await DiscoveryClient.CreateAsync(
                         appConfig, new Uri(serverDiscoveryUrl), Opc.Ua.DiagnosticsMasks.None, ct).ConfigureAwait(false);
-                    endpoints = await ep.GetEndpointsAsync(null, ct).ConfigureAwait(false);
+                    endpoints = await ep.GetEndpointsAsync(default, ct).ConfigureAwait(false);
                 }
                 catch (OperationCanceledException) when (ct.IsCancellationRequested) { throw; }
                 catch { continue; }
 
-                found.AddRange(FilterEndpointUrls(endpoints, wantedPolicyUri, wantedMode)
+                found.AddRange(FilterEndpointUrls(endpoints.ToList(), wantedPolicyUri, wantedMode)
                     .Select(u => new DiscoveredEndpoint(server.ApplicationUri ?? string.Empty, u)));
             }
         }
@@ -965,7 +976,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         endpoints
             .Where(e => e.SecurityPolicyUri == wantedPolicyUri && e.SecurityMode == wantedMode
                         && !string.IsNullOrWhiteSpace(e.EndpointUrl))
-            .Select(e => e.EndpointUrl);
+            .Select(e => e.EndpointUrl!);
 
     private static MessageSecurityMode ToMessageSecurityMode(OpcUaSecurityMode mode) => mode switch
     {
@@ -1052,7 +1063,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             _options.SessionName,
             (uint)_options.SessionTimeout.TotalMilliseconds,
             identity,
-            null,                                               // preferredLocales
+            default,                                            // preferredLocales
             cts.Token).ConfigureAwait(false);
 
         session.KeepAliveInterval = (int)_options.KeepAliveInterval.TotalMilliseconds;
@@ -1080,17 +1091,17 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         // all deprecated.
         using var client = await DiscoveryClient.CreateAsync(
             appConfig, new Uri(endpointUrl), Opc.Ua.DiagnosticsMasks.None, ct).ConfigureAwait(false);
-        var all = await client.GetEndpointsAsync(null, ct).ConfigureAwait(false);
+        var all = await client.GetEndpointsAsync(default, ct).ConfigureAwait(false);
 
         var wantedPolicyUri = MapSecurityPolicy(policy);
         var wantedMode = ToMessageSecurityMode(mode);
 
-        var match = all.FirstOrDefault(e =>
+        var match = all.ToList().FirstOrDefault(e =>
             e.SecurityPolicyUri == wantedPolicyUri && e.SecurityMode == wantedMode);
 
         if (match is null)
         {
-            var advertised = string.Join(", ", all
+            var advertised = string.Join(", ", all.ToList()
                 .Select(e => $"{ShortPolicyName(e.SecurityPolicyUri)}/{e.SecurityMode}"));
             throw new InvalidOperationException(
                 $"No endpoint at '{endpointUrl}' matches SecurityPolicy={policy} + SecurityMode={mode}. " +
@@ -1157,7 +1168,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         _ => throw new ArgumentOutOfRangeException(nameof(policy), policy, null),
     };
 
-    private static string ShortPolicyName(string policyUri) =>
+    private static string ShortPolicyName(string? policyUri) =>
         policyUri?.Substring(policyUri.LastIndexOf('#') + 1) ?? "(null)";
 
     /// <inheritdoc />
@@ -1182,10 +1193,13 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         // Take the session reference under _probeLock and clear Session to null so any concurrent caller that
         // checks inside _gate sees null immediately after release begins.
         ISession? sessionToClose;
+        ApplicationInstance? applicationToDispose;
         lock (_probeLock)
         {
             if (Volatile.Read(ref _lifecycleGeneration) != generation) return;
             sessionToClose = Session;
+            applicationToDispose = _ownedApplication;
+            _ownedApplication = null;
             if (_keepAliveHandler is not null && sessionToClose is not null)
             {
                 try { sessionToClose.KeepAlive -= _keepAliveHandler; } catch { }
@@ -1210,6 +1224,10 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         }
         catch { /* best-effort */ }
         try { sessionToClose?.Dispose(); } catch { }
+        if (applicationToDispose is not null)
+        {
+            try { await applicationToDispose.DisposeAsync().ConfigureAwait(false); } catch { }
+        }
         Interlocked.Exchange(ref _sessionLost, 0);
         Interlocked.Exchange(ref _subscriptionLost, 0);
         Interlocked.Exchange(ref _publishingStoppedSinceTicks, 0);
@@ -1347,7 +1365,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
                 _namespaceMap = null;
                 _connectedEndpointUrl = null;
 
-                // Detach the cert-validation handler so the (potentially process-shared) CertificateValidator doesn't
+                // Detach the cert-validation handler so the (potentially process-shared) ICertificateManager doesn't
                 // hold a delegate to a shutting-down driver — generation-checked like the map (r1 N-3): a newer init
                 // that installed its own handler meanwhile keeps it.
                 DetachCertValidation(_certValidatorRef, _certValidationHandler);
@@ -1424,7 +1442,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             // A RawPath the authored RawTags table doesn't know — or a node id that won't parse —
             // gets BadNodeIdInvalid and is omitted from the wire request, saving a round-trip for a
             // fault the driver can detect locally.
-            var toSend = new ReadValueIdCollection();
+            var toSend = new List<ReadValueId>();
             var indexMap = new List<int>(fullReferences.Count); // maps wire-index -> results-index
             for (var i = 0; i < fullReferences.Count; i++)
             {
@@ -1456,11 +1474,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
                     // Preserve the upstream StatusCode verbatim — including Bad codes per
                     // §8's cascading-quality rule. Also preserve SourceTimestamp so downstream
                     // clients can detect stale upstream data.
-                    results[r] = new DataValueSnapshot(
-                        Value: dv.Value,
-                        StatusCode: dv.StatusCode.Code,
-                        SourceTimestampUtc: dv.SourceTimestamp == DateTime.MinValue ? null : dv.SourceTimestamp,
-                        ServerTimestampUtc: dv.ServerTimestamp == DateTime.MinValue ? now : dv.ServerTimestamp);
+                    results[r] = ToSnapshot(dv, now);
                 }
                 RecordDeviceAnswered(generation, now);
             }
@@ -1506,7 +1520,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             return results;
         }
 
-        var toSend = new WriteValueCollection();
+        var toSend = new List<WriteValue>();
         var indexMap = new List<int>(writes.Count);
         for (var i = 0; i < writes.Count; i++)
         {
@@ -1515,11 +1529,16 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
                 results[i] = new WriteResult(StatusBadNodeIdInvalid);
                 continue;
             }
+            if (!VariantHelper.TryCastFrom(writes[i].Value, out Variant value))
+            {
+                results[i] = new WriteResult(StatusCodes.BadTypeMismatch.Code);
+                continue;
+            }
             toSend.Add(new WriteValue
             {
                 NodeId = nodeId,
                 AttributeId = Attributes.Value,
-                Value = new DataValue(new Variant(writes[i].Value)),
+                Value = new DataValue(value),
             });
             indexMap.Add(i);
         }
@@ -1674,7 +1693,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         if (discovered() >= _options.MaxDiscoveredNodes) return;
         if (!visited.Add(node)) return;
 
-        var browseDescriptions = new BrowseDescriptionCollection
+        var browseDescriptions = new List<BrowseDescription>
         {
             new()
             {
@@ -1688,7 +1707,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             }
         };
 
-        ReferenceDescriptionCollection refs;
+        List<ReferenceDescription> refs;
         try
         {
             var resp = await session.BrowseAsync(
@@ -1700,7 +1719,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
 
             if (resp.Results.Count == 0) return;
             var result = resp.Results[0];
-            refs = result.References;
+            refs = result.References.ToList();
 
             // Follow browse continuation points. OPC UA servers cap the references returned
             // per node in a single response; when a folder has more children than the cap,
@@ -1728,11 +1747,12 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
                     // the release fails silently and the cursor times out server-side anyway.
                     try
                     {
+                        using var release = new CancellationTokenSource(TimeSpan.FromSeconds(5));
                         await session.BrowseNextAsync(
                             requestHeader: null,
                             releaseContinuationPoints: true,
                             continuationPoints: [continuationPoint],
-                            ct: CancellationToken.None).ConfigureAwait(false);
+                            ct: release.Token).AsTask().WaitAsync(release.Token).ConfigureAwait(false);
                     }
                     catch { /* best-effort — server may have already cleaned up */ }
                     throw;
@@ -1741,7 +1761,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
                 if (next.Results.Count == 0) break;
                 var nextResult = next.Results[0];
                 if (nextResult.References is { Count: > 0 })
-                    refs.AddRange(nextResult.References);
+                    refs.AddRange(nextResult.References.ToList());
                 continuationPoint = nextResult.ContinuationPoint;
             }
         }
@@ -1764,10 +1784,10 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             if (discovered() >= _options.MaxDiscoveredNodes) break;
 
             var childId = ExpandedNodeId.ToNodeId(rf.NodeId, session.NamespaceUris);
-            if (NodeId.IsNull(childId)) continue;
+            if (childId.IsNull) continue;
 
-            var browseName = rf.BrowseName?.Name ?? childId.ToString();
-            var displayName = rf.DisplayName?.Text ?? browseName;
+            var browseName = rf.BrowseName.Name ?? childId.ToString();
+            var displayName = rf.DisplayName.Text ?? browseName;
 
             if (rf.NodeClass == NodeClass.Object)
             {
@@ -1812,7 +1832,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         if (pending.Count == 0) return;
 
         // 4 attributes per variable: DataType, ValueRank, UserAccessLevel, Historizing.
-        var nodesToRead = new ReadValueIdCollection(pending.Count * 4);
+        var nodesToRead = new List<ReadValueId>(pending.Count * 4);
         foreach (var pv in pending)
         {
             nodesToRead.Add(new ReadValueId { NodeId = pv.NodeId, AttributeId = Attributes.DataType });
@@ -1821,7 +1841,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             nodesToRead.Add(new ReadValueId { NodeId = pv.NodeId, AttributeId = Attributes.Historizing });
         }
 
-        DataValueCollection values;
+        ArrayOf<DataValue> values;
         try
         {
             var resp = await session.ReadAsync(
@@ -1851,10 +1871,10 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             var accessDv = values[baseIdx + 2];
             var histDv = values[baseIdx + 3];
 
-            var dataType = StatusCode.IsGood(dataTypeDv.StatusCode) && dataTypeDv.Value is NodeId dtId
+            var dataType = StatusCode.IsGood(dataTypeDv.StatusCode) && UpstreamValueMapping.ToClr(dataTypeDv.WrappedValue) is NodeId dtId
                 ? MapUpstreamDataType(dtId)
                 : DriverDataType.Int32;
-            var valueRank = StatusCode.IsGood(valueRankDv.StatusCode) && valueRankDv.Value is int vr ? vr : -1;
+            var valueRank = StatusCode.IsGood(valueRankDv.StatusCode) && UpstreamValueMapping.ToClr(valueRankDv.WrappedValue) is int vr ? vr : -1;
             // OPC UA Part 3 ValueRank constants: -3 = ScalarOrOneDimension, -2 = Any,
             // -1 = Scalar, 0 = OneOrMoreDimensions, 1 = OneDimension, >1 = N specific dimensions.
             // Deliberate choice: treat anything >= 0 as an array (the spec guarantees -3/-2/-1
@@ -1863,9 +1883,9 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             // as scalar — array-of-one is exposed as scalar to the local address space until
             // the upstream variable carries a concrete dimensioned rank.
             var isArray = UpstreamAttributeMapping.IsArray(valueRank);
-            var access = StatusCode.IsGood(accessDv.StatusCode) && accessDv.Value is byte ab ? ab : (byte)0;
+            var access = StatusCode.IsGood(accessDv.StatusCode) && UpstreamValueMapping.ToClr(accessDv.WrappedValue) is byte ab ? ab : (byte)0;
             var securityClass = MapAccessLevelToSecurityClass(access);
-            var historizing = StatusCode.IsGood(histDv.StatusCode) && histDv.Value is bool b && b;
+            var historizing = StatusCode.IsGood(histDv.StatusCode) && UpstreamValueMapping.ToClr(histDv.WrappedValue) is bool b && b;
 
             pv.ParentFolder.Variable(pv.BrowseName, pv.DisplayName, new DriverAttributeInfo(
                 FullName: StableReference(pv.NodeId),
@@ -2077,10 +2097,22 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         // subscriptions; extract its DataValue. The Handle property carries our tag string.
         if (args.NotificationValue is not MonitoredItemNotification mn) return;
         var dv = mn.Value;
-        if (dv is null) return;
         PublishNotification(handle, RefOf(item), dv);
     }
 
+    private static DataValueSnapshot ToSnapshot(DataValue value, DateTime now)
+    {
+        // Matrix payloads have no driver-domain contract. SDK 2's Legacy boxing materializes
+        // them into CLR matrices, so refuse that unsupported shape before boxing. 1D arrays
+        // retain their deployed pass-through behavior, including scalar-shaped authored tags.
+        var unsupportedShape = value.WrappedValue.TypeInfo.IsMatrix;
+        return new DataValueSnapshot(
+            Value: unsupportedShape ? null : UpstreamValueMapping.ToClr(value.WrappedValue),
+            StatusCode: unsupportedShape ? StatusCodes.BadTypeMismatch.Code : value.StatusCode.Code,
+            SourceTimestampUtc: value.SourceTimestamp == DateTimeUtc.MinValue ? null : value.SourceTimestamp.ToDateTime(),
+            ServerTimestampUtc: value.ServerTimestamp == DateTimeUtc.MinValue ? now : value.ServerTimestamp.ToDateTime());
+    }
+
     private static string RefOf(MonitoredItem item) => (item.Handle as string) ?? item.DisplayName ?? string.Empty;
 
     private void PublishNotification(OpcUaSubscriptionHandle handle, string fullRef, DataValue dv)
@@ -2090,11 +2122,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         // a delivered notification is liveness evidence — the subscription path never calls ReadAsync, so
         // without this a busy subscription-only driver's LastSuccessfulRead stayed at its connect time.
         RecordLivenessEvidence();
-        var snapshot = new DataValueSnapshot(
-            Value: dv.Value,
-            StatusCode: dv.StatusCode.Code,
-            SourceTimestampUtc: dv.SourceTimestamp == DateTime.MinValue ? null : dv.SourceTimestamp,
-            ServerTimestampUtc: dv.ServerTimestamp == DateTime.MinValue ? DateTime.UtcNow : dv.ServerTimestamp);
+        var snapshot = ToSnapshot(dv, DateTime.UtcNow);
         // Review of 3b88056f: the replay check and the publish are one critical section shared with the recovery and
         // trailing reads, so an older value can never be delivered after a newer one (see _deliveryLock).
         lock (_deliveryLock)
@@ -2415,7 +2443,8 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         // constants so the notification handler indexes in O(1) without re-examining the
         // QualifiedName BrowsePaths.
         var filter = new EventFilter();
-        void AddField(string browseName) => filter.SelectClauses.Add(new SimpleAttributeOperand
+        var selectClauses = new List<SimpleAttributeOperand>();
+        void AddField(string browseName) => selectClauses.Add(new SimpleAttributeOperand
         {
             TypeDefinitionId = ObjectTypeIds.BaseEventType,
             BrowsePath = [new QualifiedName(browseName)],
@@ -2429,7 +2458,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         AddField("Time");
         // ConditionId on ConditionType nodes is the branch identifier for
         // acknowledgeable conditions. Not a BaseEventType field — reach it via the typed path.
-        filter.SelectClauses.Add(new SimpleAttributeOperand
+        selectClauses.Add(new SimpleAttributeOperand
         {
             TypeDefinitionId = ObjectTypeIds.ConditionType,
             BrowsePath = [], // empty path = the condition node itself
@@ -2437,13 +2466,13 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         });
         // the host derives Active/Acked solely from AlarmEventArgs.Kind, so the condition state
         // must be selected. TWO-element browse paths — a single "ActiveState/Id" QualifiedName names nothing.
-        filter.SelectClauses.Add(new SimpleAttributeOperand
+        selectClauses.Add(new SimpleAttributeOperand
         {
             TypeDefinitionId = ObjectTypeIds.AlarmConditionType,
             BrowsePath = [new QualifiedName(BrowseNames.ActiveState), new QualifiedName(BrowseNames.Id)],
             AttributeId = Attributes.Value,
         });
-        filter.SelectClauses.Add(new SimpleAttributeOperand
+        selectClauses.Add(new SimpleAttributeOperand
         {
             TypeDefinitionId = ObjectTypeIds.AcknowledgeableConditionType,
             BrowsePath = [new QualifiedName(BrowseNames.AckedState), new QualifiedName(BrowseNames.Id)],
@@ -2451,13 +2480,15 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         });
         // BranchId — a non-null one marks a condition BRANCH event (a previous state, with its own
         // EventId). Only the trunk (null BranchId) is the condition's current state.
-        filter.SelectClauses.Add(new SimpleAttributeOperand
+        selectClauses.Add(new SimpleAttributeOperand
         {
             TypeDefinitionId = ObjectTypeIds.ConditionType,
             BrowsePath = [new QualifiedName(BrowseNames.BranchId)],
             AttributeId = Attributes.Value,
         });
 
+        filter.SelectClauses = selectClauses;
+
         // Set by CreateAlarmEventItemAsync so a failure after the handler is attached can detach it.
         MonitoredItem? eventItem = null;
         MonitoredItemNotificationEventHandler? notifHandler = null;
@@ -2598,7 +2629,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             // OPC UA A&C: call the AcknowledgeableConditionType.Acknowledge method on each
             // condition node with EventId + Comment arguments. CallAsync accepts a batch —
             // one CallMethodRequest per ack.
-            var callRequests = new CallMethodRequestCollection();
+            var callRequests = new List<CallMethodRequest>();
             foreach (var ack in acknowledgements)
             {
                 // the host acks by RawPath; Acknowledge must hit the upstream CONDITION node.
@@ -2624,7 +2655,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
                     ObjectId = conditionId,
                     MethodId = MethodIds.AcknowledgeableConditionType_Acknowledge,
                     InputArguments = [
-                        new Variant(eventId),  // Part 9 §5.7.3: the EventId being acknowledged (empty only when none seen)
+                        Variant.From(eventId.ToByteString()),  // Part 9 §5.7.3: the EventId being acknowledged (empty only when none seen)
                         new Variant(new LocalizedText(ack.Comment ?? string.Empty)),
                     ],
                 });
@@ -2711,7 +2742,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         // without this it would feed RouteAlarmEvent alongside the real one.
         if (!_alarmSubscriptions.ContainsKey(handle.Id)) return;
         RecordLivenessEvidence();
-        RouteAlarmEvent(efl.EventFields, sourceFilter, handle);
+        RouteAlarmEvent(efl.EventFields.ToList(), sourceFilter, handle);
     }
 
     /// <summary>
@@ -2805,7 +2836,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
     /// <param name="fields">The event's fields.</param>
     /// <returns>Whether the event is a RefreshRequired marker.</returns>
     internal static bool IsRefreshRequired(IReadOnlyList<Variant> fields) =>
-        fields.Count > AlarmFieldEventType && fields[AlarmFieldEventType].Value is NodeId t
+        fields.Count > AlarmFieldEventType && UpstreamValueMapping.ToClr(fields[AlarmFieldEventType]) is NodeId t
         && t == ObjectTypeIds.RefreshRequiredEventType;
 
     /// <summary>True for the three ConditionRefresh marker event types — never alarms.</summary>
@@ -3017,21 +3048,21 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         state = null;
         if (fields.Count <= AlarmFieldConditionId) return null;
         // ConditionRefresh brackets its re-delivery with RefreshStart/RefreshEnd — markers, never alarms.
-        if (IsRefreshMarker(fields[AlarmFieldEventType].Value)) return null;
+        if (IsRefreshMarker(UpstreamValueMapping.ToClr(fields[AlarmFieldEventType]))) return null;
         // A condition BRANCH event reports a previous state with its own EventId: projecting it would flip the
         // trunk's state, remembering it would make Acknowledge ack the branch.
-        if (fields.Count > AlarmFieldBranchId && fields[AlarmFieldBranchId].Value is NodeId branch && !NodeId.IsNull(branch))
+        if (fields.Count > AlarmFieldBranchId && UpstreamValueMapping.ToClr(fields[AlarmFieldBranchId]) is NodeId branch && !branch.IsNull)
             return null;
         if (fields.Count > AlarmFieldAckedState
-            && fields[AlarmFieldActiveState].Value is bool active
-            && fields[AlarmFieldAckedState].Value is bool acked)
+            && UpstreamValueMapping.ToClr(fields[AlarmFieldActiveState]) is bool active
+            && UpstreamValueMapping.ToClr(fields[AlarmFieldAckedState]) is bool acked)
             state = (active, acked);
 
         // Pass-through (no authored refs) keeps the raw serialized ids; an authored index compares
         // server-stable keys (see AlarmIndexKey), matching the CONDITION node first — the only way to tell
         // several conditions on one source apart — and then the source node.
-        var sourceField = fields[AlarmFieldSourceNode].Value;
-        var conditionField = fields[AlarmFieldConditionId].Value;
+        var sourceField = UpstreamValueMapping.ToClr(fields[AlarmFieldSourceNode]);
+        var conditionField = UpstreamValueMapping.ToClr(fields[AlarmFieldConditionId]);
         string reported, upstreamCondition;
         if (sourceIndex.Count == 0)
         {
@@ -3040,23 +3071,23 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         }
         else
         {
-            upstreamCondition = conditionField is NodeId cn && !NodeId.IsNull(cn) ? keyOf(cn) : string.Empty;
-            var sourceKey = sourceField is NodeId sn && !NodeId.IsNull(sn) ? keyOf(sn) : string.Empty;
+            upstreamCondition = conditionField is NodeId cn && !cn.IsNull ? keyOf(cn) : string.Empty;
+            var sourceKey = sourceField is NodeId sn && !sn.IsNull ? keyOf(sn) : string.Empty;
             if (!(upstreamCondition.Length > 0 && sourceIndex.TryGetValue(upstreamCondition, out reported!))
                 && !(sourceKey.Length > 0 && sourceIndex.TryGetValue(sourceKey, out reported!)))
                 return null;
         }
 
-        var eventType = fields[AlarmFieldEventType].Value?.ToString() ?? "BaseEventType";
-        var message = (fields[AlarmFieldMessage].Value as LocalizedText)?.Text ?? string.Empty;
-        var severity = fields[AlarmFieldSeverity].Value is ushort sev ? sev : (ushort)0;
-        var time = fields[AlarmFieldTime].Value is DateTime t ? t : DateTime.UtcNow;
+        var eventType = UpstreamValueMapping.ToClr(fields[AlarmFieldEventType])?.ToString() ?? "BaseEventType";
+        var message = (UpstreamValueMapping.ToClr(fields[AlarmFieldMessage]) as LocalizedText?)?.Text ?? string.Empty;
+        var severity = UpstreamValueMapping.ToClr(fields[AlarmFieldSeverity]) is ushort sev ? sev : (ushort)0;
+        var time = UpstreamValueMapping.ToClr(fields[AlarmFieldTime]) is DateTime t ? t : DateTime.UtcNow;
 
         if (sourceIndex.Count != 0 && upstreamCondition.Length > 0)
             rememberCondition(reported, new AlarmAckTarget(
                 upstreamCondition,
                 // A copy: the decoded notification's array is not ours to alias for the ack's lifetime.
-                (fields[AlarmFieldEventId].Value as byte[])?.ToArray() ?? Array.Empty<byte>()));
+                (UpstreamValueMapping.ToClr(fields[AlarmFieldEventId]) as byte[])?.ToArray() ?? Array.Empty<byte>()));
 
         return new AlarmEventArgs(
             SubscriptionHandle: handle,
@@ -3166,10 +3197,10 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         catch { /* best-effort — SDK may have already cleared its invocation lists on session loss */ }
     }
 
-    private static int CountNotifications(ExtensionObject nd) => nd.Body switch
+    private static int CountNotifications(ExtensionObject nd) => (nd.TryGetValue(out IEncodeable? body) ? body : null) switch
     {
-        DataChangeNotification dc => dc.MonitoredItems?.Count ?? 0,
-        EventNotificationList ev => ev.Events?.Count ?? 0,
+        DataChangeNotification dc => dc.MonitoredItems.Count,
+        EventNotificationList ev => ev.Events.Count,
         StatusChangeNotification => 1,
         _ => 1,
     };
@@ -3268,7 +3299,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             PublishCommsLoss(now);
         }
         if (definitive)
-            RaiseConnectionLost($"upstream session keep-alive reported {StatusCodes.GetBrowseName(keepAliveCode.Code)}");
+            RaiseConnectionLost($"upstream session keep-alive reported {keepAliveCode.SymbolicId}");
     }
 
     /// <summary>
@@ -3696,8 +3727,8 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
     ///     hook synchronously (no async work on this hot path), then fires the cert-validation
     ///     handler detach. The async session-close is intentionally skipped — it requires a
     ///     live session + network round-trip and is unsafe to block-on from a potentially
-    ///     single-threaded context (OPC UA stack thread). The session will be cleaned up by
-    ///     the SDK's own finalizer on GC (no sync-over-async).
+    ///     single-threaded context (OPC UA stack thread). Local session and certificate-manager
+    ///     resources are disposed synchronously.
     /// </summary>
     public void Dispose()
     {
@@ -3715,15 +3746,20 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
                 try { Session.KeepAlive -= _keepAliveHandler; } catch { }
             }
             _keepAliveHandler = null;
+            var session = Session;
             Session = null;
+            if (session is not null) DetachDiagnostics(session);
+            try { session?.Dispose(); } catch { }
+            try { (_ownedApplication?.ApplicationConfiguration?.CertificateManager as IDisposable)?.Dispose(); } catch { }
+            _ownedApplication = null;
         }
 
         // Detach the cert-validation handler registered during InitializeAsync so the
-        // CertificateValidator (which may be process-shared) doesn't hold a reference to
+        // ICertificateManager (which may be process-shared) doesn't hold a reference to
         // a disposed driver.
         if (_certValidationHandler is not null && _certValidatorRef is not null)
         {
-            try { _certValidatorRef.CertificateValidation -= _certValidationHandler; } catch { }
+            try { if (ReferenceEquals(_certValidatorRef.AcceptError, _certValidationHandler)) _certValidatorRef.AcceptError = null; } catch { }
             _certValidationHandler = null;
             _certValidatorRef = null;
         }
@@ -3764,7 +3800,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
         // Detach the cert-validation handler.
         if (_certValidationHandler is not null && _certValidatorRef is not null)
         {
-            try { _certValidatorRef.CertificateValidation -= _certValidationHandler; } catch { }
+            try { if (ReferenceEquals(_certValidatorRef.AcceptError, _certValidationHandler)) _certValidatorRef.AcceptError = null; } catch { }
             _certValidationHandler = null;
             _certValidatorRef = null;
         }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/OpcUaClientDriverProbe.cs

@@ -85,7 +85,7 @@ public sealed class OpcUaClientDriverProbe : IDriverProbe
             var appConfig = BuildMinimalAppConfig();
             using var client = await DiscoveryClient.CreateAsync(
                 appConfig, new Uri(endpointUrl), DiagnosticsMasks.None, cts.Token).ConfigureAwait(false);
-            var endpoints = await client.GetEndpointsAsync(null, cts.Token).ConfigureAwait(false);
+            var endpoints = await client.GetEndpointsAsync(default, cts.Token).ConfigureAwait(false);
             sw.Stop();
 
             if (endpoints is { Count: > 0 })
@@ -130,7 +130,7 @@ public sealed class OpcUaClientDriverProbe : IDriverProbe
     ///     is plain-text and does not require a client certificate.
     /// </summary>
     private static ApplicationConfiguration BuildMinimalAppConfig() =>
-        new()
+        new(SdkTelemetry.Context)
         {
             ApplicationName = "OtOpcUa.Probe",
             ApplicationType = ApplicationType.Client,

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.csproj

@@ -21,7 +21,6 @@
     </ItemGroup>
 
     <ItemGroup>
-        <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.MigrationAnalyzer" PrivateAssets="all" IncludeAssets="analyzers;build;buildtransitive" />
         <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.Client"/>
         <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.Configuration"/>
         <PackageReference Include="ZB.MOM.WW.Secrets.Abstractions"/>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.CLI.Tests/AlarmsCommandTests.cs

@@ -54,7 +54,7 @@ public class AlarmsCommandTests
 
         fakeService.SubscribeAlarmsCalls.Count.ShouldBe(1);
         fakeService.SubscribeAlarmsCalls[0].SourceNodeId.ShouldNotBeNull();
-        fakeService.SubscribeAlarmsCalls[0].SourceNodeId!.Value.IdentifierAsString.ShouldBe("AlarmSource");
+        fakeService.SubscribeAlarmsCalls[0].SourceNodeId!.Identifier.ShouldBe("AlarmSource");
     }
 
     /// <summary>Verifies that Execute with refresh requests condition refresh.</summary>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.CLI.Tests/BrowseCommandTests.cs

@@ -56,7 +56,7 @@ public class BrowseCommandTests
 
         fakeService.BrowseNodeIds.Count.ShouldBe(1);
         fakeService.BrowseNodeIds[0].ShouldNotBeNull();
-        fakeService.BrowseNodeIds[0]!.Value.IdentifierAsString.ShouldBe("StartNode");
+        fakeService.BrowseNodeIds[0]!.Identifier.ShouldBe("StartNode");
     }
 
     /// <summary>Verifies that Execute browses from null node when not specified.</summary>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.CLI.Tests/HistoryReadCommandTests.cs

@@ -61,7 +61,7 @@ public class HistoryReadCommandTests
 
         fakeService.HistoryReadRawCalls.Count.ShouldBe(1);
         fakeService.HistoryReadRawCalls[0].MaxValues.ShouldBe(500);
-        fakeService.HistoryReadRawCalls[0].NodeId.IdentifierAsString.ShouldBe("HistNode");
+        fakeService.HistoryReadRawCalls[0].NodeId.Identifier.ShouldBe("HistNode");
     }
 
     /// <summary>Verifies AggregateRead execution calls HistoryReadAggregate.</summary>
@@ -211,11 +211,11 @@ public class HistoryReadCommandTests
 
         var call = fakeService.HistoryReadEventsCalls.ShouldHaveSingleItem();
         call.MaxEvents.ShouldBe(25);
-        call.Filter.SelectClauses.ToArray()!.Select(c => c.BrowsePath.ToArray()!.ShouldHaveSingleItem().Name)
+        call.Filter.SelectClauses.Select(c => c.BrowsePath.ShouldHaveSingleItem().Name)
             .ShouldBe(["EventId", "EventType", "Time", "SourceName", "Severity", "Message", "ConditionName", "SourceNode"]);
-        call.Filter.SelectClauses.ToArray()!.Single(c => c.BrowsePath[0].Name == "ConditionName").TypeDefinitionId
+        call.Filter.SelectClauses.Single(c => c.BrowsePath[0].Name == "ConditionName").TypeDefinitionId
             .ShouldBe(ObjectTypeIds.ConditionType);
-        call.Filter.WhereClause.Elements.ToArray()!.ShouldBeEmpty("no --of-type, no where-clause");
+        call.Filter.WhereClause.Elements.ShouldBeEmpty("no --of-type, no where-clause");
         fakeService.HistoryReadRawCalls.ShouldBeEmpty();
 
         var output = TestConsoleHelper.GetOutput(console);
@@ -243,10 +243,10 @@ public class HistoryReadCommandTests
         await command.ExecuteAsync(console);
 
         var filter = fakeService.HistoryReadEventsCalls.ShouldHaveSingleItem().Filter;
-        filter.SelectClauses.ToArray()!.Select(c => c.BrowsePath[0].Name).ShouldBe(["EventType", "Severity"]);
-        var element = filter.WhereClause.Elements.ToArray()!.ShouldHaveSingleItem();
+        filter.SelectClauses.Select(c => c.BrowsePath[0].Name).ShouldBe(["EventType", "Severity"]);
+        var element = filter.WhereClause.Elements.ShouldHaveSingleItem();
         element.FilterOperator.ShouldBe(FilterOperator.OfType);
-        (element.FilterOperands[0].TryGetValue(out LiteralOperand? literal) ? literal.Value : Variant.Null)
+        ((LiteralOperand)ExtensionObject.ToEncodeable(element.FilterOperands[0])).Value.Value
             .ShouldBe(ObjectTypeIds.LimitAlarmType);
         TestConsoleHelper.GetOutput(console).ShouldContain("0 events returned.");
     }

tests/Client/ZB.MOM.WW.OtOpcUa.Client.CLI.Tests/HistoryUpdateCommandTests.cs

@@ -33,9 +33,9 @@ public class HistoryUpdateCommandTests
             .BuildDetails().ShouldBeOfType<UpdateDataDetails>();
         d.PerformInsertReplace.ShouldBe(PerformUpdateType.Insert);
         d.UpdateValues.Count.ShouldBe(2);
-        d.UpdateValues[1].WrappedValue.ShouldBe(Variant.From(2.5));
+        d.UpdateValues[1].Value.ShouldBe(2.5);
         d.UpdateValues[0].SourceTimestamp.ShouldBe(new DateTime(2026, 1, 15, 8, 0, 0, DateTimeKind.Utc));
-        d.NodeId.IdentifierAsString.ShouldBe("HistNode");
+        d.NodeId.Identifier.ShouldBe("HistNode");
     }
 
     /// <summary>Replace and update map to their update types.</summary>
@@ -60,7 +60,7 @@ public class HistoryUpdateCommandTests
     {
         var d = Make(values: [value], times: ["2026-01-15T08:00:00Z"], type: type)
             .BuildDetails().ShouldBeOfType<UpdateDataDetails>();
-        ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers.ValueConverter.ToClrObject(d.UpdateValues[0].WrappedValue).ShouldBeOfType(expected);
+        d.UpdateValues[0].Value.ShouldBeOfType(expected);
     }
 
     /// <summary>delete-raw builds DeleteRawModifiedDetails with IsDeleteModified=false.</summary>
@@ -211,7 +211,7 @@ public class HistoryUpdateCommandTests
     public async Task Execute_UnnamedStatus_PrintsHex()
     {
         const uint unnamed = 0x8FFF0000u;
-        new StatusCode(unnamed).SymbolicId.ShouldBeNullOrEmpty(); // precondition: genuinely unnamed
+        StatusCodes.GetBrowseName(unnamed).ShouldBeNullOrEmpty(); // precondition: genuinely unnamed
         var svc = new FakeOpcUaClientService
         {
             HistoryUpdateResult = new HistoryUpdateOutcome(StatusCodes.Good, [StatusCodes.Good],

tests/Client/ZB.MOM.WW.OtOpcUa.Client.CLI.Tests/NodeIdParserTests.cs

@@ -34,8 +34,8 @@ public class NodeIdParserTests
     {
         var result = NodeIdParser.Parse("ns=2;s=MyNode");
         result.ShouldNotBeNull();
-        result.Value.NamespaceIndex.ShouldBe((ushort)2);
-        result.Value.IdentifierAsString.ShouldBe("MyNode");
+        result.NamespaceIndex.ShouldBe((ushort)2);
+        result.Identifier.ShouldBe("MyNode");
     }
 
     /// <summary>Verifies that Parse correctly parses numeric NodeId format (i=85).</summary>
@@ -44,7 +44,7 @@ public class NodeIdParserTests
     {
         var result = NodeIdParser.Parse("i=85");
         result.ShouldNotBeNull();
-        result.Value.IdType.ShouldBe(IdType.Numeric);
+        result.IdType.ShouldBe(IdType.Numeric);
     }
 
     /// <summary>Verifies that Parse treats bare numeric input as namespace 0 numeric NodeId.</summary>
@@ -53,9 +53,8 @@ public class NodeIdParserTests
     {
         var result = NodeIdParser.Parse("85");
         result.ShouldNotBeNull();
-        result.Value.NamespaceIndex.ShouldBe((ushort)0);
-        result.Value.TryGetValue(out uint identifier).ShouldBeTrue();
-        identifier.ShouldBe(85u);
+        result.NamespaceIndex.ShouldBe((ushort)0);
+        result.Identifier.ShouldBe((uint)85);
     }
 
     /// <summary>Verifies that Parse trims whitespace padding from input.</summary>
@@ -64,7 +63,7 @@ public class NodeIdParserTests
     {
         var result = NodeIdParser.Parse("  ns=2;s=MyNode  ");
         result.ShouldNotBeNull();
-        result.Value.IdentifierAsString.ShouldBe("MyNode");
+        result.Identifier.ShouldBe("MyNode");
     }
 
     /// <summary>Verifies that Parse throws FormatException for invalid input.</summary>
@@ -93,36 +92,7 @@ public class NodeIdParserTests
     public void ParseRequired_ValidInput_ReturnsNodeId()
     {
         var result = NodeIdParser.ParseRequired("ns=2;s=TestNode");
-        result.IsNull.ShouldBeFalse();
-        result.IdentifierAsString.ShouldBe("TestNode");
-    }
-
-    [Fact]
-    public void Parse_OpaqueIdentifier_PreservesBytes()
-    {
-        var node = NodeIdParser.ParseRequired("ns=3;b=AQID");
-        node.IdType.ShouldBe(IdType.Opaque);
-        node.NamespaceIndex.ShouldBe((ushort)3);
-        node.TryGetValue(out ByteString bytes).ShouldBeTrue();
-        bytes.ToArray().ShouldBe(new byte[] { 1, 2, 3 });
-    }
-
-    [Fact]
-    public void Parse_StringIdentifierContainingEncodedText_StaysLiteral()
-    {
-        var node = NodeIdParser.ParseRequired("ns=4;s=ns=2;b=AQID");
-        node.IdType.ShouldBe(IdType.String);
-        node.NamespaceIndex.ShouldBe((ushort)4);
-        node.TryGetValue(out string? identifier).ShouldBeTrue();
-        identifier.ShouldBe("ns=2;b=AQID");
-    }
-
-    [Theory]
-    [InlineData("ns=bad;i=1")]
-    [InlineData("ns=2;b=invalid!")]
-    [InlineData("ns=2;i=invalid")]
-    public void Parse_InvalidEncodedIdentifier_IsRejected(string input)
-    {
-        Should.Throw<FormatException>(() => NodeIdParser.ParseRequired(input));
+        result.ShouldNotBeNull();
+        result.Identifier.ShouldBe("TestNode");
     }
 }

tests/Client/ZB.MOM.WW.OtOpcUa.Client.CLI.Tests/ReadCommandTests.cs

@@ -56,7 +56,7 @@ public class ReadCommandTests
         await command.ExecuteAsync(console);
 
         fakeService.ReadNodeIds.Count.ShouldBe(1);
-        fakeService.ReadNodeIds[0].IdentifierAsString.ShouldBe("MyVariable");
+        fakeService.ReadNodeIds[0].Identifier.ShouldBe("MyVariable");
     }
 
     /// <summary>Verifies that execute disconnects in finally.</summary>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.CLI.Tests/SubscribeCommandSummaryTests.cs

@@ -222,8 +222,8 @@ public class SubscribeCommandSummaryTests
 
         // Both Variables (depth 1 + depth 2) should have been subscribed.
         fakeService.SubscribeCalls.Count.ShouldBeGreaterThanOrEqualTo(2);
-        fakeService.SubscribeCalls.ShouldContain(c => c.NodeId.IdentifierAsString.ToString() == "Tag1");
-        fakeService.SubscribeCalls.ShouldContain(c => c.NodeId.IdentifierAsString.ToString() == "Tag2");
+        fakeService.SubscribeCalls.ShouldContain(c => c.NodeId.Identifier.ToString() == "Tag1");
+        fakeService.SubscribeCalls.ShouldContain(c => c.NodeId.Identifier.ToString() == "Tag2");
 
         var output = TestConsoleHelper.GetOutput(console);
         output.ShouldContain("Browsing subtree of ns=2;s=Root");

tests/Client/ZB.MOM.WW.OtOpcUa.Client.CLI.Tests/SubscribeCommandTests.cs

@@ -33,7 +33,7 @@ public class SubscribeCommandTests
 
         fakeService.SubscribeCalls.Count.ShouldBe(1);
         fakeService.SubscribeCalls[0].IntervalMs.ShouldBe(500);
-        fakeService.SubscribeCalls[0].NodeId.IdentifierAsString.ShouldBe("TestVar");
+        fakeService.SubscribeCalls[0].NodeId.Identifier.ShouldBe("TestVar");
     }
 
     /// <summary>Verifies that ExecuteAsync unsubscribes when cancellation is requested.</summary>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Adapters/DefaultSubscriptionAdapterTests.cs

@@ -11,48 +11,6 @@ namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Tests.Adapters;
 /// </summary>
 public class DefaultSubscriptionAdapterTests
 {
-    private sealed class CountingSubscription() : Subscription(ClientTelemetry.Context)
-    {
-        public int DisposeCount;
-        protected override void Dispose(bool disposing)
-        {
-            if (disposing) Interlocked.Increment(ref DisposeCount);
-            base.Dispose(disposing);
-        }
-    }
-
-    [Fact]
-    public async Task DeleteAndDispose_ReleaseSdkResourcesExactlyOnce()
-    {
-        var subscription = new CountingSubscription();
-        var detached = 0;
-        var adapter = new DefaultSubscriptionAdapter(subscription, (_, _) =>
-        {
-            Interlocked.Increment(ref detached);
-            return Task.CompletedTask;
-        });
-        await adapter.DeleteAsync(TestContext.Current.CancellationToken);
-        adapter.Dispose();
-        adapter.Dispose();
-        detached.ShouldBe(1);
-        subscription.DisposeCount.ShouldBe(1);
-    }
-
-    [Fact]
-    public async Task ConcurrentTeardown_HasOneSdkResourceOwner()
-    {
-        var subscription = new CountingSubscription();
-        var detached = 0;
-        var adapter = new DefaultSubscriptionAdapter(subscription, (_, _) =>
-        {
-            Interlocked.Increment(ref detached);
-            return Task.CompletedTask;
-        });
-        await Task.WhenAll(Task.Run(adapter.Dispose, TestContext.Current.CancellationToken), adapter.DeleteAsync(TestContext.Current.CancellationToken));
-        detached.ShouldBe(1);
-        subscription.DisposeCount.ShouldBe(1);
-    }
-
     /// <summary>DeleteAsync detaches the wrapped subscription exactly once, even when Dispose follows.</summary>
     [Fact]
     public async Task DeleteAsync_detaches_the_subscription_from_its_session_once()

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Adapters/EndpointSelectorTests.cs

@@ -117,7 +117,7 @@ public class EndpointSelectorTests
         var best = EndpointSelector.SelectBest(endpoints, "opc.tcp://external-host:4840",
             MessageSecurityMode.Sign);
 
-        new Uri(best.EndpointUrl.ShouldNotBeNull()).Host.ShouldBe("external-host");
+        new Uri(best.EndpointUrl).Host.ShouldBe("external-host");
     }
 
     /// <summary>
@@ -169,7 +169,7 @@ public class EndpointSelectorTests
 
         var best = EndpointSelector.SelectBest(endpoints, "opc.tcp://localhost:4841", MessageSecurityMode.None);
 
-        var uri = new Uri(best.EndpointUrl.ShouldNotBeNull());
+        var uri = new Uri(best.EndpointUrl);
         uri.Host.ShouldBe("localhost");
         uri.Port.ShouldBe(4841);
         uri.AbsolutePath.ShouldBe("/OtOpcUa");
@@ -183,8 +183,8 @@ public class EndpointSelectorTests
 
         var best = EndpointSelector.SelectBest(endpoints, "opc.tcp://localhost:4841", MessageSecurityMode.None);
 
-        new Uri(best.EndpointUrl.ShouldNotBeNull()).Host.ShouldBe("internal-host");
-        new Uri(best.EndpointUrl.ShouldNotBeNull()).Port.ShouldBe(4843);
+        new Uri(best.EndpointUrl).Host.ShouldBe("internal-host");
+        new Uri(best.EndpointUrl).Port.ShouldBe(4843);
     }
 
     /// <summary>Identical host, port and scheme: nothing to rewrite.</summary>
@@ -206,7 +206,7 @@ public class EndpointSelectorTests
 
         var best = EndpointSelector.SelectBest(endpoints, "opc.tcp://localhost", MessageSecurityMode.None);
 
-        var uri = new Uri(best.EndpointUrl.ShouldNotBeNull());
+        var uri = new Uri(best.EndpointUrl);
         uri.Host.ShouldBe("localhost");
         uri.Port.ShouldBe(4840);
     }
@@ -219,7 +219,7 @@ public class EndpointSelectorTests
 
         var best = EndpointSelector.SelectBest(endpoints, "opc.tcp://[::1]:4841", MessageSecurityMode.None);
 
-        var uri = new Uri(best.EndpointUrl.ShouldNotBeNull());
+        var uri = new Uri(best.EndpointUrl);
         uri.Host.ShouldBe("[::1]");
         uri.Port.ShouldBe(4841);
     }

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/AlarmEventFilterTests.cs

@@ -18,7 +18,7 @@ public sealed class AlarmEventFilterTests
     {
         var filter = OpcUaClientService.CreateAlarmEventFilter();
 
-        filter.SelectClauses.ToArray()!.SelectMany(c => c.BrowsePath.ToArray()!).ShouldAllBe(q => !(q.Name ?? "").Contains('/'));
+        filter.SelectClauses.SelectMany(c => c.BrowsePath).ShouldAllBe(q => !q.Name.Contains('/'));
     }
 
     /// <summary>The two-state ids are selected by their two-element browse paths, at the indices the parser reads.</summary>
@@ -27,7 +27,7 @@ public sealed class AlarmEventFilterTests
     {
         var clauses = OpcUaClientService.CreateAlarmEventFilter().SelectClauses;
 
-        string Path(int i) => string.Join("/", clauses[i].BrowsePath.ToArray()!.Select(q => q.Name));
+        string Path(int i) => string.Join("/", clauses[i].BrowsePath.Select(q => q.Name));
         Path(8).ShouldBe("AckedState/Id");
         clauses[8].BrowsePath.Count.ShouldBe(2);
         Path(9).ShouldBe("ActiveState/Id");

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/FailoverEpochTests.cs

@@ -164,7 +164,7 @@ public sealed class FailoverEpochTests : IDisposable
         var sub = new FakeSubscriptionAdapter();
         _factory.EnqueueSession(new FakeSessionAdapter { NextSubscription = sub });
         await _service.ConnectAsync(Settings(), TestContext.Current.CancellationToken);
-        var node = Opc.Ua.NodeId.Parse("ns=2;s=X");
+        var node = new Opc.Ua.NodeId("ns=2;s=X");
         await _service.SubscribeAsync(node, ct: TestContext.Current.CancellationToken);
 
         sub.ThrowOnRemove = true;

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeEndpointDiscovery.cs

@@ -35,7 +35,7 @@ internal sealed class FakeEndpointDiscovery : IEndpointDiscovery
                 : SecurityPolicies.Basic256Sha256,
             Server = new ApplicationDescription
             {
-                ApplicationName = new LocalizedText("FakeServer"),
+                ApplicationName = "FakeServer",
                 ApplicationUri = "urn:localhost:FakeServer"
             }
         });

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeSessionAdapter.cs

@@ -48,15 +48,11 @@ internal sealed class FakeSessionAdapter : ISessionAdapter
     public bool ThrowOnBrowse { get; set; }
 
     /// <summary>Gets or sets the browse references returned by browse operations.</summary>
-    public ArrayOf<ReferenceDescription> BrowseResponse { get; set; } = [];
+    public ReferenceDescriptionCollection BrowseResponse { get; set; } = [];
     /// <summary>Gets or sets the continuation point for browse operations.</summary>
     public byte[]? BrowseContinuationPoint { get; set; }
-    public Func<CancellationToken, Task>? BeforeBrowseNext { get; set; }
-    public List<(byte[] Point, bool Cancelled)> BrowseReleases { get; } = [];
-    public bool ThrowOnBrowseRelease { get; set; }
-
     /// <summary>Gets or sets the browse references returned by browse-next operations.</summary>
-    public ArrayOf<ReferenceDescription> BrowseNextResponse { get; set; } = [];
+    public ReferenceDescriptionCollection BrowseNextResponse { get; set; } = [];
     /// <summary>Gets or sets the continuation point for browse-next operations.</summary>
     public byte[]? BrowseNextContinuationPoint { get; set; }
 
@@ -133,7 +129,7 @@ internal sealed class FakeSessionAdapter : ISessionAdapter
     }
 
     /// <inheritdoc />
-    public Task<(byte[]? ContinuationPoint, ArrayOf<ReferenceDescription> References)> BrowseAsync(
+    public Task<(byte[]? ContinuationPoint, ReferenceDescriptionCollection References)> BrowseAsync(
         NodeId nodeId, uint nodeClassMask, CancellationToken ct)
     {
         BrowseCount++;
@@ -143,19 +139,11 @@ internal sealed class FakeSessionAdapter : ISessionAdapter
     }
 
     /// <inheritdoc />
-    public async Task<(byte[]? ContinuationPoint, ArrayOf<ReferenceDescription> References)> BrowseNextAsync(
+    public Task<(byte[]? ContinuationPoint, ReferenceDescriptionCollection References)> BrowseNextAsync(
         byte[] continuationPoint, CancellationToken ct)
     {
         BrowseNextCount++;
-        if (BeforeBrowseNext != null) await BeforeBrowseNext(ct);
-        return (BrowseNextContinuationPoint, BrowseNextResponse);
-    }
-
-    public Task ReleaseBrowseContinuationPointAsync(byte[] continuationPoint, CancellationToken ct)
-    {
-        BrowseReleases.Add((continuationPoint, ct.IsCancellationRequested));
-        if (ThrowOnBrowseRelease) throw new ServiceResultException(StatusCodes.BadSessionClosed);
-        return Task.CompletedTask;
+        return Task.FromResult((BrowseNextContinuationPoint, BrowseNextResponse));
     }
 
     /// <inheritdoc />

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeSessionFactory.cs

@@ -40,7 +40,7 @@ internal sealed class FakeSessionFactory : ISessionFactory
         uint sessionTimeoutMs, UserIdentity identity, CancellationToken ct)
     {
         CreateCallCount++;
-        LastEndpointUrl = endpoint.EndpointUrl ?? string.Empty;
+        LastEndpointUrl = endpoint.EndpointUrl;
 
         // One-shot: the gate holds only the call that observed it, so a later call (e.g. a user's Connect while a
         // failover is held) runs freely.
@@ -60,14 +60,14 @@ internal sealed class FakeSessionFactory : ISessionFactory
         else
             session = new FakeSessionAdapter
             {
-                EndpointUrl = endpoint.EndpointUrl ?? string.Empty,
-                ServerName = endpoint.Server?.ApplicationName.Text ?? "FakeServer",
+                EndpointUrl = endpoint.EndpointUrl,
+                ServerName = endpoint.Server?.ApplicationName?.Text ?? "FakeServer",
                 SecurityMode = endpoint.SecurityMode.ToString(),
                 SecurityPolicyUri = endpoint.SecurityPolicyUri ?? string.Empty
             };
 
         // Ensure endpoint URL matches
-        session.EndpointUrl = endpoint.EndpointUrl ?? string.Empty;
+        session.EndpointUrl = endpoint.EndpointUrl;
         _createdSessions.Add(session);
         return session;
     }

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeSubscriptionAdapter.cs

@@ -129,16 +129,6 @@ internal sealed class FakeSubscriptionAdapter : ISubscriptionAdapter
         lock (_itemsLock) _items.Clear();
     }
 
-    public Action<string, DataValue> CaptureDataCallback(uint handle)
-    {
-        lock (_itemsLock) return _items[handle].DataCallback!;
-    }
-
-    public Action<EventFieldList> CaptureEventCallback(uint handle)
-    {
-        lock (_itemsLock) return _items[handle].EventCallback!;
-    }
-
     /// <summary>
     ///     Simulates a data change notification for testing.
     /// </summary>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Helpers/AggregateTypeMapperTests.cs

@@ -26,7 +26,8 @@ public class AggregateTypeMapperTests
     public void ToNodeId_ReturnsNonNullForAllValues(AggregateType aggregate)
     {
         var nodeId = AggregateTypeMapper.ToNodeId(aggregate);
-        nodeId.IsNull.ShouldBeFalse();
+        nodeId.ShouldNotBeNull();
+        nodeId.IsNullNodeId.ShouldBeFalse();
     }
 
     /// <summary>Verifies that Average aggregate type maps to the correct OPC UA node ID.</summary>
@@ -108,9 +109,9 @@ public class AggregateTypeMapperTests
     [MemberData(nameof(AllAggregates))]
     public void ToNodeId_maps_to_the_same_named_AggregateFunction(AggregateType aggregate)
     {
-        var property = typeof(ObjectIds).GetProperty("AggregateFunction_" + aggregate);
-        property.ShouldNotBeNull();
-        AggregateTypeMapper.ToNodeId(aggregate).ShouldBe((NodeId)property.GetValue(null)!);
+        var field = typeof(ObjectIds).GetField("AggregateFunction_" + aggregate);
+        field.ShouldNotBeNull();
+        AggregateTypeMapper.ToNodeId(aggregate).ShouldBe((NodeId)field.GetValue(null)!);
     }
 
     /// <summary>Every client aggregate.</summary>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Helpers/HistoryReadPagingTests.cs

@@ -29,18 +29,19 @@ public class HistoryReadPagingTests
             Calls.Add(new Call(cp, release));
             if (release) return Task.FromResult<HistoryReadResult?>(new HistoryReadResult { StatusCode = StatusCodes.Good });
             var (count, next) = _pages.Dequeue();
-            var data = new HistoryData { DataValues = Enumerable.Range(0, count).Select(i => new DataValue(Variant.From(i))).ToArrayOf() };
+            var data = new HistoryData();
+            for (var i = 0; i < count; i++) data.DataValues.Add(new DataValue(new Variant(i)));
             return Task.FromResult<HistoryReadResult?>(new HistoryReadResult
             {
                 StatusCode = StatusCodes.Good,
-                ContinuationPoint = ByteString.From(next),
+                ContinuationPoint = next,
                 HistoryData = new ExtensionObject(data)
             });
         }
     }
 
     private static IEnumerable<DataValue> Values(HistoryReadResult r) =>
-        r.HistoryData.TryGetValue(out HistoryData? d) ? d.DataValues.ToArray() ?? [] : [];
+        r.HistoryData?.Body is HistoryData d ? d.DataValues : [];
 
     /// <summary>
     /// A server page limit below the caller's cap hands back a continuation point: the follow-up must READ the next
@@ -135,7 +136,8 @@ public class HistoryReadPagingTests
             calls.Add((cp, release, ct.IsCancellationRequested));
             if (release) return Task.FromResult<HistoryReadResult?>(new HistoryReadResult { StatusCode = StatusCodes.Good });
             if (cp != null) { cts.Cancel(); ct.ThrowIfCancellationRequested(); }
-            var data = new HistoryData { DataValues = [new DataValue(Variant.From(1))] };
+            var data = new HistoryData();
+            data.DataValues.Add(new DataValue(new Variant(1)));
             return Task.FromResult<HistoryReadResult?>(new HistoryReadResult
             {
                 StatusCode = StatusCodes.Good, ContinuationPoint = [5], HistoryData = new ExtensionObject(data)
@@ -163,7 +165,8 @@ public class HistoryReadPagingTests
                 releaseSawCancelled = ct.IsCancellationRequested;
                 return Task.FromResult<HistoryReadResult?>(new HistoryReadResult { StatusCode = StatusCodes.Good });
             }
-            var data = new HistoryData { DataValues = [new DataValue(Variant.From(1))] };
+            var data = new HistoryData();
+            data.DataValues.Add(new DataValue(new Variant(1)));
             cts.Cancel(); // the caller gives up right as the capped page arrives
             return Task.FromResult<HistoryReadResult?>(new HistoryReadResult
             {
@@ -186,7 +189,8 @@ public class HistoryReadPagingTests
         {
             calls++;
             if (release) throw new ServiceResultException(StatusCodes.BadSessionClosed);
-            var data = new HistoryData { DataValues = [new DataValue(Variant.From(1))] };
+            var data = new HistoryData();
+            data.DataValues.Add(new DataValue(new Variant(1)));
             return Task.FromResult<HistoryReadResult?>(new HistoryReadResult
             {
                 StatusCode = StatusCodes.Good, ContinuationPoint = [9], HistoryData = new ExtensionObject(data)
@@ -212,24 +216,4 @@ public class HistoryReadPagingTests
         await Should.ThrowAsync<ServiceResultException>(() =>
             HistoryReadPaging.ReadAllAsync(Read, Values, maxValues: 10, Node, CancellationToken.None));
     }
-    [Fact]
-    public async Task RefusedContinuationPage_ReleasesCursorAndPreservesStatus()
-    {
-        var releases = new List<byte[]>();
-        Task<HistoryReadResult?> Read(byte[]? cp, bool release, CancellationToken ct)
-        {
-            if (release)
-            {
-                releases.Add(cp!);
-                throw new ServiceResultException(StatusCodes.BadSessionClosed);
-            }
-            return Task.FromResult<HistoryReadResult?>(cp == null
-                ? new HistoryReadResult { StatusCode = StatusCodes.Good, ContinuationPoint = [7] }
-                : new HistoryReadResult { StatusCode = StatusCodes.BadUserAccessDenied });
-        }
-        var exception = await Should.ThrowAsync<ServiceResultException>(() =>
-            HistoryReadPaging.ReadAllAsync(Read, Values, 10, Node, TestContext.Current.CancellationToken));
-        exception.StatusCode.ShouldBe(StatusCodes.BadUserAccessDenied);
-        releases.ShouldHaveSingleItem().ShouldBe(new byte[] { 7 });
-    }
 }

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Helpers/HistoryReadStatusTests.cs

@@ -7,29 +7,32 @@ namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Tests.Helpers;
 
 public class HistoryReadStatusTests
 {
-    public static IEnumerable<object[]> Refusals() => new[] { StatusCodes.BadHistoryOperationUnsupported,
-        StatusCodes.BadUserAccessDenied, StatusCodes.BadNodeIdUnknown, StatusCodes.BadTimeout }.Select(s => new object[] { s });
-    public static IEnumerable<object[]> NonRefusals() => new[] { StatusCodes.Good, StatusCodes.GoodNoData,
-        StatusCodes.GoodMoreData, StatusCodes.UncertainNoCommunicationLastUsableValue, StatusCodes.BadNoData }.Select(s => new object[] { s });
     /// <summary>A refused read must surface, carrying the status code, rather than read as an empty result.</summary>
     /// <param name="code">The Bad per-node status code.</param>
     [Theory]
-    [MemberData(nameof(Refusals))]
-    public void Bad_status_throws_ServiceResultException_with_the_code(StatusCode code)
+    [InlineData(StatusCodes.BadHistoryOperationUnsupported)]
+    [InlineData(StatusCodes.BadUserAccessDenied)]
+    [InlineData(StatusCodes.BadNodeIdUnknown)]
+    [InlineData(StatusCodes.BadTimeout)]
+    public void Bad_status_throws_ServiceResultException_with_the_code(uint code)
     {
         var ex = Should.Throw<ServiceResultException>(
-            () => HistoryReadStatus.ThrowIfRefused(code, new NodeId("n", 2)));
+            () => HistoryReadStatus.ThrowIfRefused(new StatusCode(code), new NodeId("n", 2)));
 
-        ex.StatusCode.ShouldBe(code.Code);
+        ex.StatusCode.ShouldBe(code);
         ex.Message.ShouldContain("ns=2;s=n");
     }
 
     /// <summary>Good, GoodNoData, Uncertain and BadNoData are all non-refusals (the window may simply be empty).</summary>
     /// <param name="code">The non-refusal status code.</param>
     [Theory]
-    [MemberData(nameof(NonRefusals))]
-    public void Non_refusal_status_does_not_throw(StatusCode code)
+    [InlineData(StatusCodes.Good)]
+    [InlineData(StatusCodes.GoodNoData)]
+    [InlineData(StatusCodes.GoodMoreData)]
+    [InlineData(StatusCodes.UncertainNoCommunicationLastUsableValue)]
+    [InlineData(StatusCodes.BadNoData)]
+    public void Non_refusal_status_does_not_throw(uint code)
     {
-        Should.NotThrow(() => HistoryReadStatus.ThrowIfRefused(code, new NodeId("n", 2)));
+        Should.NotThrow(() => HistoryReadStatus.ThrowIfRefused(new StatusCode(code), new NodeId("n", 2)));
     }
 }

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Helpers/VariantBoundaryTests.cs

@@ -1,126 +0,0 @@
-using Opc.Ua;
-using Shouldly;
-using Xunit;
-using ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
-
-namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Tests.Helpers;
-
-public class VariantBoundaryTests
-{
-    public static IEnumerable<object?[]> Payloads()
-    {
-        foreach (var value in new object?[] { null, true, (sbyte)-1, (byte)1, (short)-2, (ushort)2,
-                     -3, 3u, -4L, 4UL, 1.25f, 2.5, "", "text", Guid.Parse("de305d54-75b4-431b-adb2-eb6b9e546014"),
-                     new DateTime(2026, 11, 10, 0, 0, 0, DateTimeKind.Utc), Array.Empty<byte>(), new byte[] { 1, 2 },
-                     Array.Empty<int>(), new[] { 1 }, new[] { 1, 2 }, Array.Empty<string>(), new[] { "", "text" } })
-            yield return [value];
-        foreach (var value in new object[] { true, (sbyte)-1, (byte)1, (short)-2, (ushort)2,
-                     -3, 3u, -4L, 4UL, 1.25f, 2.5, "text", Guid.Empty,
-                     new DateTime(2026, 11, 10, 0, 0, 0, DateTimeKind.Utc) })
-        {
-            foreach (var count in new[] { 0, 1, 3 })
-            {
-                var array = Array.CreateInstance(value.GetType(), count);
-                for (var i = 0; i < count; i++) array.SetValue(value, i);
-                yield return [array];
-            }
-        }
-    }
-
-    [Theory]
-    [MemberData(nameof(Payloads))]
-    public void RoundTrip_PreservesClrTypeAndValue(object? expected)
-    {
-        var actual = ValueConverter.ToClrObject(ValueConverter.ToVariant(expected));
-        if (expected == null) actual.ShouldBeNull();
-        else
-        {
-            actual.ShouldNotBeNull();
-            actual.GetType().ShouldBe(expected.GetType());
-            actual.ShouldBe(expected);
-        }
-    }
-
-    [Fact]
-    public void RetainedArrays_AreDetachedFromCaller()
-    {
-        var bytes = new byte[] { 1, 2 };
-        var numbers = new[] { 3, 4 };
-        var byteValue = ValueConverter.ToVariant(bytes);
-        var numericValue = ValueConverter.ToVariant(numbers);
-        bytes[0] = 99;
-        numbers[0] = 99;
-        ValueConverter.ToClrObject(byteValue).ShouldBe(new byte[] { 1, 2 });
-        ValueConverter.ToClrObject(numericValue).ShouldBe(new[] { 3, 4 });
-    }
-
-    [Fact]
-    public void ByteString_NullAndEmptyRemainDistinct()
-    {
-        ValueConverter.ToClrObject(Variant.From(default(ByteString))).ShouldBeNull();
-        ValueConverter.ToClrObject(Variant.From(ByteString.Empty)).ShouldBe(Array.Empty<byte>());
-        ValueConverter.ToClrObject(Variant.Null).ShouldBeNull();
-        ValueConverter.ToClrObject(Variant.From(0)).ShouldBe(0);
-    }
-
-    [Fact]
-    public void NullWrapperInputs_RemainNullAfterRetention()
-    {
-        ValueConverter.ToClrObject(ValueConverter.ToVariant(default(ByteString))).ShouldBeNull();
-        ValueConverter.ToClrObject(ValueConverter.ToVariant(default(ArrayOf<int>))).ShouldBeNull();
-        ValueConverter.ToVariant(default(ArrayOf<byte>)).TypeInfo.ValueRank.ShouldBe(ValueRanks.OneDimension);
-        ValueConverter.ToClrObject(ValueConverter.ToVariant(Variant.From(default(ByteString)))).ShouldBeNull();
-    }
-
-    [Fact]
-    public void ReadOnlyWrappers_AreDetachedFromMutableBackingBuffers()
-    {
-        var bytes = new byte[] { 1, 2 };
-        var numbers = new[] { 3, 4 };
-        var retainedBytes = ValueConverter.ToVariant(new ByteString(bytes));
-        var retainedNumbers = ValueConverter.ToVariant(new ArrayOf<int>(numbers));
-        bytes[0] = 99;
-        numbers[0] = 99;
-        ValueConverter.ToClrObject(retainedBytes).ShouldBe(new byte[] { 1, 2 });
-        ValueConverter.ToClrObject(retainedNumbers).ShouldBe(new[] { 3, 4 });
-    }
-
-    [Fact]
-    public void RetainedByteStringArray_CopiesElementBuffersAndPreservesNullEmpty()
-    {
-        var bytes = new byte[] { 1, 2 };
-        var value = ValueConverter.ToVariant(new ByteString[] { default, ByteString.Empty, new(bytes) });
-        bytes[0] = 99;
-        var actual = ValueConverter.ToClrObject(value).ShouldBeOfType<byte[][]>();
-        actual[0].ShouldBeNull();
-        actual[1].ShouldBeEmpty();
-        actual[2].ShouldBe(new byte[] { 1, 2 });
-    }
-
-    [Fact]
-    public void ByteArrayAndByteString_KeepWireRank()
-    {
-        ValueConverter.ToVariant(new byte[] { 1 }).TypeInfo.BuiltInType.ShouldBe(BuiltInType.ByteString);
-        ValueConverter.ToVariant(new ArrayOf<byte>(new byte[] { 1 })).TypeInfo.BuiltInType.ShouldBe(BuiltInType.Byte);
-        ValueConverter.ToVariant(new ArrayOf<byte>(new byte[] { 1 })).TypeInfo.ValueRank.ShouldBe(ValueRanks.OneDimension);
-    }
-
-    [Fact]
-    public void NodeIds_KeepOpaqueBytesAndLiteralStringIdentifiers()
-    {
-        var opaque = NodeId.Parse("ns=2;b=AQID");
-        ValueConverter.ToClrObject(ValueConverter.ToVariant(opaque)).ShouldBe(opaque);
-        var literal = new NodeId("ns=2;s=literal", 4);
-        var result = ValueConverter.ToClrObject(ValueConverter.ToVariant(literal)).ShouldBeOfType<NodeId>();
-        result.NamespaceIndex.ShouldBe((ushort)4);
-        result.TryGetValue(out string? identifier).ShouldBeTrue();
-        identifier.ShouldBe("ns=2;s=literal");
-    }
-
-    [Fact]
-    public void UnsupportedShape_IsRejected()
-    {
-        Should.Throw<ServiceResultException>(() => ValueConverter.ToVariant(new int[2, 2]));
-        Should.Throw<ServiceResultException>(() => ValueConverter.ToVariant(new object()));
-    }
-}

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Models/ModelConstructionTests.cs

@@ -76,7 +76,7 @@ public class ModelConstructionTests
 
         args.NodeId.ShouldBe("ns=2;s=Temp");
         args.Value.ShouldBe(value);
-        args.Value.WrappedValue.ShouldBe(Variant.From(42));
+        args.Value.Value.ShouldBe(42);
     }
 
     /// <summary>Verifies that ConnectionStateChangedEventArgs constructs correctly with all properties.</summary>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/OpcUaClientServiceTests.cs

@@ -197,9 +197,9 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        var result = await _service.ReadValueAsync(NodeId.Parse("ns=2;s=MyNode"), TestContext.Current.CancellationToken);
+        var result = await _service.ReadValueAsync(new NodeId("ns=2;s=MyNode"), TestContext.Current.CancellationToken);
 
-        result.WrappedValue.ShouldBe(Variant.From(42));
+        result.Value.ShouldBe(42);
         session.ReadCount.ShouldBe(1);
     }
 
@@ -210,7 +210,7 @@ public class OpcUaClientServiceTests : IDisposable
     public async Task ReadValueAsync_WhenDisconnected_Throws()
     {
         await Should.ThrowAsync<InvalidOperationException>(() =>
-            _service.ReadValueAsync(NodeId.Parse("ns=2;s=MyNode")));
+            _service.ReadValueAsync(new NodeId("ns=2;s=MyNode")));
     }
 
     /// <summary>
@@ -224,7 +224,7 @@ public class OpcUaClientServiceTests : IDisposable
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
         await Should.ThrowAsync<ServiceResultException>(() =>
-            _service.ReadValueAsync(NodeId.Parse("ns=2;s=MyNode")));
+            _service.ReadValueAsync(new NodeId("ns=2;s=MyNode")));
     }
 
     // --- Write tests ---
@@ -243,7 +243,7 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        var result = await _service.WriteValueAsync(NodeId.Parse("ns=2;s=MyNode"), 42, TestContext.Current.CancellationToken);
+        var result = await _service.WriteValueAsync(new NodeId("ns=2;s=MyNode"), 42, TestContext.Current.CancellationToken);
 
         result.ShouldBe(StatusCodes.Good);
         session.WriteCount.ShouldBe(1);
@@ -262,7 +262,7 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        await _service.WriteValueAsync(NodeId.Parse("ns=2;s=MyNode"), "42", TestContext.Current.CancellationToken);
+        await _service.WriteValueAsync(new NodeId("ns=2;s=MyNode"), "42", TestContext.Current.CancellationToken);
 
         session.WriteCount.ShouldBe(1);
         session.ReadCount.ShouldBe(1); // Read for type inference
@@ -278,7 +278,7 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        await _service.WriteValueAsync(NodeId.Parse("ns=2;s=MyNode"), 42, TestContext.Current.CancellationToken);
+        await _service.WriteValueAsync(new NodeId("ns=2;s=MyNode"), 42, TestContext.Current.CancellationToken);
 
         session.WriteCount.ShouldBe(1);
         session.ReadCount.ShouldBe(0); // No read for non-string values
@@ -291,7 +291,7 @@ public class OpcUaClientServiceTests : IDisposable
     public async Task WriteValueAsync_WhenDisconnected_Throws()
     {
         await Should.ThrowAsync<InvalidOperationException>(() =>
-            _service.WriteValueAsync(NodeId.Parse("ns=2;s=MyNode"), 42));
+            _service.WriteValueAsync(new NodeId("ns=2;s=MyNode"), 42));
     }
 
     /// <summary>
@@ -303,13 +303,13 @@ public class OpcUaClientServiceTests : IDisposable
     {
         var session = new FakeSessionAdapter
         {
-            ReadResponse = DataValue.FromStatusCode(StatusCodes.BadNodeIdUnknown) // Bad status, null Value
+            ReadResponse = new DataValue(StatusCodes.BadNodeIdUnknown) // Bad status, null Value
         };
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
         var ex = await Should.ThrowAsync<InvalidOperationException>(() =>
-            _service.WriteValueAsync(NodeId.Parse("ns=2;s=MyNode"), "42"));
+            _service.WriteValueAsync(new NodeId("ns=2;s=MyNode"), "42"));
 
         ex.Message.ShouldContain("Cannot infer target type");
     }
@@ -323,90 +323,17 @@ public class OpcUaClientServiceTests : IDisposable
     {
         var session = new FakeSessionAdapter
         {
-            ReadResponse = DataValue.FromStatusCode(StatusCodes.BadNotReadable)
+            ReadResponse = new DataValue(StatusCodes.BadNotReadable)
         };
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
         var ex = await Should.ThrowAsync<InvalidOperationException>(() =>
-            _service.WriteValueAsync(NodeId.Parse("ns=2;s=MyNode"), "42"));
+            _service.WriteValueAsync(new NodeId("ns=2;s=MyNode"), "42"));
 
         ex.Message.ShouldContain("ns=2;s=MyNode");
     }
 
-    [Theory]
-    [InlineData(false)]
-    [InlineData(true)]
-    public async Task BrowseCancellation_ReleasesOwnedCursor_WithoutMaskingCancellation(bool releaseFails)
-    {
-        using var cts = new CancellationTokenSource();
-        var session = new FakeSessionAdapter
-        {
-            BrowseResponse = [new ReferenceDescription { NodeId = new ExpandedNodeId("child", 2) }],
-            BrowseContinuationPoint = [7],
-            ThrowOnBrowseRelease = releaseFails,
-            BeforeBrowseNext = token => { cts.Cancel(); token.ThrowIfCancellationRequested(); return Task.CompletedTask; }
-        };
-        _sessionFactory.EnqueueSession(session);
-        await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
-        await Should.ThrowAsync<OperationCanceledException>(() => _service.BrowseAsync(ct: cts.Token));
-        var release = session.BrowseReleases.ShouldHaveSingleItem();
-        release.Point.ShouldBe(new byte[] { 7 });
-        release.Cancelled.ShouldBeFalse();
-    }
-
-    [Fact]
-    public async Task BrowseEmptyPage_ReleasesRemainingCursor()
-    {
-        var session = new FakeSessionAdapter { BrowseContinuationPoint = [8] };
-        _sessionFactory.EnqueueSession(session);
-        await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
-        (await _service.BrowseAsync(ct: TestContext.Current.CancellationToken)).ShouldBeEmpty();
-        session.BrowseReleases.ShouldHaveSingleItem().Point.ShouldBe(new byte[] { 8 });
-    }
-
-    [Fact]
-    public async Task ReadValue_PreservesSdkStatusTimestampsAndPicoseconds()
-    {
-        var source = new DateTime(2026, 11, 10, 12, 0, 0, DateTimeKind.Utc);
-        var value = new DataValue(Variant.From(12.5), StatusCodes.UncertainLastUsableValue,
-            source, source.AddSeconds(1), 12, 34);
-        var session = new FakeSessionAdapter { ReadResponse = value };
-        _sessionFactory.EnqueueSession(session);
-        await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
-        var actual = await _service.ReadValueAsync(new NodeId("tag", 2), TestContext.Current.CancellationToken);
-        actual.ShouldBe(value);
-        actual.StatusCode.ShouldBe(StatusCodes.UncertainLastUsableValue);
-        actual.SourcePicoseconds.ShouldBe((ushort)12);
-        actual.ServerPicoseconds.ShouldBe((ushort)34);
-    }
-
-    [Fact]
-    public async Task AlarmMapping_PreservesTimeEmptyTextAndRetainedEventId()
-    {
-        var session = new FakeSessionAdapter();
-        _sessionFactory.EnqueueSession(session);
-        await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
-        await _service.SubscribeAlarmsAsync(ct: TestContext.Current.CancellationToken);
-        var timestamp = new DateTime(2026, 11, 10, 12, 0, 0, DateTimeKind.Utc);
-        var bytes = new byte[] { 1, 2, 3 };
-        AlarmEventArgs? received = null;
-        _service.AlarmEvent += (_, e) => received = e;
-        var subscription = session.CreatedSubscriptions.Single();
-        subscription.SimulateEvent(subscription.ActiveHandles.Single(), new EventFieldList
-        {
-            EventFields = [Variant.From(new ByteString(bytes)), Variant.From(ObjectTypeIds.AlarmConditionType),
-                Variant.From("source"), Variant.From((DateTimeUtc)timestamp), Variant.From(LocalizedText.Null),
-                Variant.From((ushort)321), Variant.From("condition"), Variant.From(true)]
-        });
-        bytes[0] = 99;
-        received.ShouldNotBeNull();
-        received.Time.ShouldBe(timestamp);
-        received.Message.ShouldBe("");
-        received.EventId.ShouldBe(new byte[] { 1, 2, 3 });
-        received.Severity.ShouldBe((ushort)321);
-    }
-
     // --- Browse tests ---
 
     /// <summary>
@@ -421,7 +348,7 @@ public class OpcUaClientServiceTests : IDisposable
             [
                 new ReferenceDescription
                 {
-                    NodeId = ExpandedNodeId.Parse("ns=2;s=Child1"),
+                    NodeId = new ExpandedNodeId("ns=2;s=Child1"),
                     DisplayName = new LocalizedText("Child1"),
                     NodeClass = NodeClass.Variable
                 }
@@ -470,19 +397,19 @@ public class OpcUaClientServiceTests : IDisposable
             [
                 new ReferenceDescription
                 {
-                    NodeId = ExpandedNodeId.Parse("ns=2;s=Folder1"),
+                    NodeId = new ExpandedNodeId("ns=2;s=Folder1"),
                     DisplayName = new LocalizedText("Folder1"),
                     NodeClass = NodeClass.Object
                 },
                 new ReferenceDescription
                 {
-                    NodeId = ExpandedNodeId.Parse("ns=2;s=Folder2"),
+                    NodeId = new ExpandedNodeId("ns=2;s=Folder2"),
                     DisplayName = new LocalizedText("Folder2"),
                     NodeClass = NodeClass.Object
                 },
                 new ReferenceDescription
                 {
-                    NodeId = ExpandedNodeId.Parse("ns=2;s=Tag"),
+                    NodeId = new ExpandedNodeId("ns=2;s=Tag"),
                     DisplayName = new LocalizedText("Tag"),
                     NodeClass = NodeClass.Variable
                 }
@@ -510,7 +437,7 @@ public class OpcUaClientServiceTests : IDisposable
             [
                 new ReferenceDescription
                 {
-                    NodeId = ExpandedNodeId.Parse("ns=2;s=A"),
+                    NodeId = new ExpandedNodeId("ns=2;s=A"),
                     DisplayName = new LocalizedText("A"),
                     NodeClass = NodeClass.Variable
                 }
@@ -520,7 +447,7 @@ public class OpcUaClientServiceTests : IDisposable
             [
                 new ReferenceDescription
                 {
-                    NodeId = ExpandedNodeId.Parse("ns=2;s=B"),
+                    NodeId = new ExpandedNodeId("ns=2;s=B"),
                     DisplayName = new LocalizedText("B"),
                     NodeClass = NodeClass.Variable
                 }
@@ -557,7 +484,7 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        await _service.SubscribeAsync(NodeId.Parse("ns=2;s=MyNode"), 500, TestContext.Current.CancellationToken);
+        await _service.SubscribeAsync(new NodeId("ns=2;s=MyNode"), 500, TestContext.Current.CancellationToken);
 
         session.CreatedSubscriptions.Count.ShouldBe(1);
         session.CreatedSubscriptions[0].AddDataChangeCount.ShouldBe(1);
@@ -573,8 +500,8 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        await _service.SubscribeAsync(NodeId.Parse("ns=2;s=MyNode"), ct: TestContext.Current.CancellationToken);
-        await _service.SubscribeAsync(NodeId.Parse("ns=2;s=MyNode"), ct: TestContext.Current.CancellationToken); // duplicate
+        await _service.SubscribeAsync(new NodeId("ns=2;s=MyNode"), ct: TestContext.Current.CancellationToken);
+        await _service.SubscribeAsync(new NodeId("ns=2;s=MyNode"), ct: TestContext.Current.CancellationToken); // duplicate
 
         session.CreatedSubscriptions[0].AddDataChangeCount.ShouldBe(1);
     }
@@ -593,7 +520,7 @@ public class OpcUaClientServiceTests : IDisposable
         DataChangedEventArgs? received = null;
         _service.DataChanged += (_, e) => received = e;
 
-        await _service.SubscribeAsync(NodeId.Parse("ns=2;s=MyNode"), 500, TestContext.Current.CancellationToken);
+        await _service.SubscribeAsync(new NodeId("ns=2;s=MyNode"), 500, TestContext.Current.CancellationToken);
 
         // Simulate data change
         var handle = fakeSub.ActiveHandles.First();
@@ -601,7 +528,7 @@ public class OpcUaClientServiceTests : IDisposable
 
         received.ShouldNotBeNull();
         received!.NodeId.ShouldBe("ns=2;s=MyNode");
-        received.Value.WrappedValue.ShouldBe(Variant.From(99));
+        received.Value.Value.ShouldBe(99);
     }
 
     /// <summary>
@@ -615,8 +542,8 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        await _service.SubscribeAsync(NodeId.Parse("ns=2;s=MyNode"), ct: TestContext.Current.CancellationToken);
-        await _service.UnsubscribeAsync(NodeId.Parse("ns=2;s=MyNode"), TestContext.Current.CancellationToken);
+        await _service.SubscribeAsync(new NodeId("ns=2;s=MyNode"), ct: TestContext.Current.CancellationToken);
+        await _service.UnsubscribeAsync(new NodeId("ns=2;s=MyNode"), TestContext.Current.CancellationToken);
 
         fakeSub.RemoveCount.ShouldBe(1);
     }
@@ -631,7 +558,7 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        await _service.UnsubscribeAsync(NodeId.Parse("ns=2;s=NotSubscribed"), TestContext.Current.CancellationToken);
+        await _service.UnsubscribeAsync(new NodeId("ns=2;s=NotSubscribed"), TestContext.Current.CancellationToken);
         // Should not throw
     }
 
@@ -642,7 +569,7 @@ public class OpcUaClientServiceTests : IDisposable
     public async Task SubscribeAsync_WhenDisconnected_Throws()
     {
         await Should.ThrowAsync<InvalidOperationException>(() =>
-            _service.SubscribeAsync(NodeId.Parse("ns=2;s=MyNode")));
+            _service.SubscribeAsync(new NodeId("ns=2;s=MyNode")));
     }
 
     // --- Alarm subscription tests ---
@@ -815,7 +742,7 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        var results = await _service.HistoryReadRawAsync(NodeId.Parse("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow, ct: TestContext.Current.CancellationToken);
+        var results = await _service.HistoryReadRawAsync(new NodeId("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow, ct: TestContext.Current.CancellationToken);
 
         results.Count.ShouldBe(2);
         session.HistoryReadRawCount.ShouldBe(1);
@@ -828,7 +755,7 @@ public class OpcUaClientServiceTests : IDisposable
     public async Task HistoryReadRawAsync_WhenDisconnected_Throws()
     {
         await Should.ThrowAsync<InvalidOperationException>(() =>
-            _service.HistoryReadRawAsync(NodeId.Parse("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow));
+            _service.HistoryReadRawAsync(new NodeId("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow));
     }
 
     /// <summary>
@@ -842,7 +769,7 @@ public class OpcUaClientServiceTests : IDisposable
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
         await Should.ThrowAsync<ServiceResultException>(() =>
-            _service.HistoryReadRawAsync(NodeId.Parse("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow));
+            _service.HistoryReadRawAsync(new NodeId("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow));
     }
 
     /// <summary>
@@ -859,7 +786,7 @@ public class OpcUaClientServiceTests : IDisposable
         _sessionFactory.EnqueueSession(session);
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
-        var results = await _service.HistoryReadAggregateAsync(NodeId.Parse("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow, AggregateType.Average, ct: TestContext.Current.CancellationToken);
+        var results = await _service.HistoryReadAggregateAsync(new NodeId("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow, AggregateType.Average, ct: TestContext.Current.CancellationToken);
 
         results.Count.ShouldBe(1);
         session.HistoryReadAggregateCount.ShouldBe(1);
@@ -873,7 +800,7 @@ public class OpcUaClientServiceTests : IDisposable
     {
         await Should.ThrowAsync<InvalidOperationException>(() =>
             _service.HistoryReadAggregateAsync(
-                NodeId.Parse("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow,
+                new NodeId("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow,
                 AggregateType.Average));
     }
 
@@ -889,7 +816,7 @@ public class OpcUaClientServiceTests : IDisposable
 
         await Should.ThrowAsync<ServiceResultException>(() =>
             _service.HistoryReadAggregateAsync(
-                NodeId.Parse("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow,
+                new NodeId("ns=2;s=Temp"), DateTime.UtcNow.AddHours(-1), DateTime.UtcNow,
                 AggregateType.Average));
     }
 
@@ -913,7 +840,7 @@ public class OpcUaClientServiceTests : IDisposable
                     return new DataValue(new Variant(["urn:server1", "urn:server2"]), StatusCodes.Good);
                 if (nodeId == VariableIds.Server_ServerArray)
                     return new DataValue(new Variant(["urn:server1"]), StatusCodes.Good);
-                return DataValue.FromStatusCode(StatusCodes.BadNodeIdUnknown);
+                return new DataValue(StatusCodes.BadNodeIdUnknown);
             }
         };
         _sessionFactory.EnqueueSession(session);
@@ -1006,9 +933,9 @@ public class OpcUaClientServiceTests : IDisposable
             ReadResponseFunc = nodeId =>
             {
                 if (nodeId == VariableIds.Server_ServerRedundancy_RedundancySupport)
-                    return DataValue.FromStatusCode(StatusCodes.BadNotReadable); // bad status, null Value
+                    return new DataValue(StatusCodes.BadNotReadable); // bad status, null Value
                 if (nodeId == VariableIds.Server_ServiceLevel)
-                    return DataValue.FromStatusCode(StatusCodes.BadNotReadable);
+                    return new DataValue(StatusCodes.BadNotReadable);
                 throw new ServiceResultException(StatusCodes.BadNodeIdUnknown);
             }
         };
@@ -1119,7 +1046,7 @@ public class OpcUaClientServiceTests : IDisposable
         var result = await _service.AcknowledgeAlarmAsync("ns=2;s=Cond", new byte[] { 1, 2 }, "acked", TestContext.Current.CancellationToken);
 
         StatusCode.IsBad(result).ShouldBeTrue();
-        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyEnabled.Code);
+        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyEnabled);
     }
 
     /// <summary>
@@ -1178,7 +1105,7 @@ public class OpcUaClientServiceTests : IDisposable
         var result = await _service.ConfirmAlarmAsync("ns=2;s=Cond", new byte[] { 1, 2 }, "confirmed", TestContext.Current.CancellationToken);
 
         StatusCode.IsBad(result).ShouldBeTrue();
-        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyEnabled.Code);
+        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyEnabled);
     }
 
     // --- ShelveAlarm tests ---
@@ -1259,7 +1186,7 @@ public class OpcUaClientServiceTests : IDisposable
         var result = await _service.ShelveAlarmAsync("ns=2;s=Cond", ShelveKind.OneShot, ct: TestContext.Current.CancellationToken);
 
         StatusCode.IsBad(result).ShouldBeTrue();
-        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyShelved.Code);
+        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyShelved);
     }
 
     // --- Enable / Disable tests (H4 client path) ---
@@ -1322,7 +1249,7 @@ public class OpcUaClientServiceTests : IDisposable
         var result = await _service.EnableAsync("ns=2;s=Cond", TestContext.Current.CancellationToken);
 
         StatusCode.IsBad(result).ShouldBeTrue();
-        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyEnabled.Code);
+        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyEnabled);
     }
 
     /// <summary>
@@ -1343,7 +1270,7 @@ public class OpcUaClientServiceTests : IDisposable
         var result = await _service.DisableAsync("ns=2;s=Cond", TestContext.Current.CancellationToken);
 
         StatusCode.IsBad(result).ShouldBeTrue();
-        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyDisabled.Code);
+        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyDisabled);
     }
 
     // --- Missing standard alarm fields (#598: the Galaxy-era supplemental reads are gone) ---
@@ -1557,7 +1484,7 @@ public class OpcUaClientServiceTests : IDisposable
 
         var gate = new TaskCompletionSource();
         session1.CreateSubscriptionGate = gate;
-        var subscribe = _service.SubscribeAsync(NodeId.Parse("ns=2;s=Racer"), 1000, TestContext.Current.CancellationToken);
+        var subscribe = _service.SubscribeAsync(new NodeId("ns=2;s=Racer"), 1000, TestContext.Current.CancellationToken);
         await session1.CreateSubscriptionEntered.Task.WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken);
 
         session1.SimulateKeepAlive(false);
@@ -1572,7 +1499,7 @@ public class OpcUaClientServiceTests : IDisposable
         replayed.AddDataChangeCount.ShouldBe(1);
 
         // And it is the live subscription: unsubscribing removes it from session2's subscription, not session1's.
-        await _service.UnsubscribeAsync(NodeId.Parse("ns=2;s=Racer"), TestContext.Current.CancellationToken);
+        await _service.UnsubscribeAsync(new NodeId("ns=2;s=Racer"), TestContext.Current.CancellationToken);
         replayed.RemoveCount.ShouldBe(1);
         replayed.ActiveHandles.ShouldBeEmpty();
     }
@@ -1621,7 +1548,7 @@ public class OpcUaClientServiceTests : IDisposable
         var tasks = new List<Task>();
         for (var i = 0; i < 50; i++)
         {
-            var nodeId = NodeId.Parse($"ns=2;s=Node{i}");
+            var nodeId = new NodeId($"ns=2;s=Node{i}");
             tasks.Add(Task.Run(async () =>
             {
                 await _service.SubscribeAsync(nodeId);
@@ -1633,55 +1560,6 @@ public class OpcUaClientServiceTests : IDisposable
         await Should.NotThrowAsync(() => Task.WhenAll(tasks));
     }
 
-    [Fact]
-    public async Task QueuedCallbacks_AfterDisposal_AreIgnored()
-    {
-        var session = new FakeSessionAdapter();
-        _sessionFactory.EnqueueSession(session);
-        await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
-        await _service.SubscribeAsync(new NodeId("tag", 2), ct: TestContext.Current.CancellationToken);
-        await _service.SubscribeAlarmsAsync(ct: TestContext.Current.CancellationToken);
-        var data = session.CreatedSubscriptions[0];
-        var alarm = session.CreatedSubscriptions[1];
-        var queuedData = data.CaptureDataCallback(data.ActiveHandles.Single());
-        var queuedAlarm = alarm.CaptureEventCallback(alarm.ActiveHandles.Single());
-        var dataCount = 0;
-        var alarmCount = 0;
-        _service.DataChanged += (_, _) => dataCount++;
-        _service.AlarmEvent += (_, _) => alarmCount++;
-        queuedData("ns=2;s=tag", new DataValue(Variant.From(1)));
-        queuedAlarm(new EventFieldList { EventFields = [Variant.From(ByteString.Empty)] });
-        dataCount.ShouldBe(1);
-        alarmCount.ShouldBe(1);
-        _service.Dispose();
-        queuedData("ns=2;s=tag", new DataValue(Variant.From(2)));
-        queuedAlarm(new EventFieldList { EventFields = [Variant.From(ByteString.Empty)] });
-        dataCount.ShouldBe(1);
-        alarmCount.ShouldBe(1);
-    }
-
-    [Fact]
-    public async Task QueuedCallbacks_FromPreviousSession_AreIgnoredAfterFailover()
-    {
-        var first = new FakeSessionAdapter();
-        var second = new FakeSessionAdapter();
-        _sessionFactory.EnqueueSession(first);
-        _sessionFactory.EnqueueSession(second);
-        await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
-        await _service.SubscribeAsync(new NodeId("tag", 2), ct: TestContext.Current.CancellationToken);
-        var firstSubscription = first.CreatedSubscriptions.Single();
-        var queued = firstSubscription.CaptureDataCallback(firstSubscription.ActiveHandles.Single());
-        var received = new List<DataValue>();
-        _service.DataChanged += (_, e) => received.Add(e.Value);
-        first.SimulateKeepAlive(false);
-        await _service.LastFailover!.WaitAsync(TestContext.Current.CancellationToken);
-        queued("ns=2;s=tag", new DataValue(Variant.From(1)));
-        received.ShouldBeEmpty();
-        var current = second.CreatedSubscriptions.Single();
-        current.SimulateDataChange(current.ActiveHandles.Single(), new DataValue(Variant.From(2)));
-        received.ShouldHaveSingleItem().WrappedValue.ShouldBe(Variant.From(2));
-    }
-
     // --- Dispose tests ---
 
     /// <summary>
@@ -1720,7 +1598,7 @@ public class OpcUaClientServiceTests : IDisposable
         await Should.ThrowAsync<ObjectDisposedException>(() =>
             _service.ConnectAsync(ValidSettings()));
         await Should.ThrowAsync<ObjectDisposedException>(() =>
-            _service.ReadValueAsync(NodeId.Parse("ns=2;s=X")));
+            _service.ReadValueAsync(new NodeId("ns=2;s=X")));
     }
 
     // --- Factory tests ---
@@ -1765,7 +1643,7 @@ public class OpcUaClientServiceTests : IDisposable
         await _service.ConnectAsync(ValidSettings(), TestContext.Current.CancellationToken);
 
         // Subscribe data (uses dataFakeSub from session.NextSubscription).
-        await _service.SubscribeAsync(NodeId.Parse("ns=2;s=Node1"), ct: TestContext.Current.CancellationToken);
+        await _service.SubscribeAsync(new NodeId("ns=2;s=Node1"), ct: TestContext.Current.CancellationToken);
 
         // Now set NextSubscription on the session so SubscribeAlarmsAsync gets the alarm fake.
         session.NextSubscription = alarmFakeSub;

tests/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/Fakes/FakeOpcUaClientService.cs

@@ -191,7 +191,7 @@ public sealed class FakeOpcUaClientService : IOpcUaClientService
         LastBrowseParentNodeId = parentNodeId;
         if (BrowseException != null) throw BrowseException;
 
-        if (parentNodeId != null && BrowseResultsByParent.TryGetValue(parentNodeId.Value.ToString(), out var perParent))
+        if (parentNodeId != null && BrowseResultsByParent.TryGetValue(parentNodeId.ToString(), out var perParent))
             return Task.FromResult(perParent);
 
         return Task.FromResult(BrowseResults);

tests/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/ReadWriteViewModelTests.cs

@@ -23,26 +23,6 @@ public class ReadWriteViewModelTests
         _vm = new ReadWriteViewModel(_service, dispatcher);
     }
 
-    [Fact]
-    public async Task ReadCommand_FormatsSdkArraysByteStringsAndEmptyText()
-    {
-        _vm.IsConnected = true;
-        _vm.SelectedNodeId = "ns=2;s=SomeNode";
-        foreach (var (value, expected) in new (Variant Value, string Expected)[]
-        {
-            (Variant.From(new int[] { 1, 2 }.ToArrayOf()), "[1,2]"),
-            (Variant.From(ArrayOf<int>.Empty), "[]"),
-            (Variant.From(ByteString.From(new byte[] { 3, 4 })), "[3,4]"),
-            (Variant.From(LocalizedText.Null), ""),
-            (Variant.Null, "(null)")
-        })
-        {
-            _service.ReadResult = new DataValue(value, StatusCodes.Good);
-            await _vm.ReadCommand.ExecuteAsync(null);
-            _vm.CurrentValue.ShouldBe(expected);
-        }
-    }
-
     /// <summary>Verifies that the read command cannot execute when disconnected.</summary>
     [Fact]
     public void ReadCommand_CannotExecute_WhenDisconnected()

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser.Tests/OpcUaClientBrowseSessionAttributesTests.cs

@@ -20,23 +20,23 @@ public sealed class OpcUaClientBrowseSessionAttributesTests
     private static Mock<ISession> SessionReturning(NodeClass nodeClass, NodeId dataType, int valueRank, byte userAccess)
     {
         var mock = new Mock<ISession>(MockBehavior.Loose);
-        mock.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(BrowseTelemetry.Context));
+        mock.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(BrowseTelemetry.Context));
         mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         mock.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
-            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, CancellationToken _) =>
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ArrayOf<ReadValueId> nodes, CancellationToken _) =>
                 new ReadResponse
                 {
                     ResponseHeader = new ResponseHeader(),
-                    Results = [.. nodes.Select(n => n.AttributeId switch
+                    Results = [.. nodes.ToList().Select(n => n.AttributeId switch
                     {
                         Attributes.NodeClass => new DataValue(new Variant((int)nodeClass)),
                         Attributes.DisplayName => new DataValue(new Variant(new LocalizedText("Speed"))),
                         Attributes.DataType => new DataValue(new Variant(dataType)),
                         Attributes.ValueRank => new DataValue(new Variant(valueRank)),
                         Attributes.UserAccessLevel => new DataValue(new Variant(userAccess)),
-                        _ => new DataValue(StatusCodes.BadAttributeIdInvalid),
+                        _ => DataValue.FromStatusCode(StatusCodes.BadAttributeIdInvalid),
                     })],
                     DiagnosticInfos = [],
                 });
@@ -101,19 +101,19 @@ public sealed class OpcUaClientBrowseSessionAttributesTests
             session.AttributesAsync("nsu=urn:not-in-table;s=X", TestContext.Current.CancellationToken));
     }
 
-    private sealed class TrackingCredential : IDisposable
+    private sealed class TrackingApplication : IAsyncDisposable
     {
         public int Disposed { get; private set; }
 
-        public void Dispose() => Disposed++;
+        public ValueTask DisposeAsync() { Disposed++; return ValueTask.CompletedTask; }
     }
 
-    /// <summary>Review m9: the browse session disposes the user certificate it was handed, with itself.</summary>
+    /// <summary>Review m9: the browse session disposes the SDK application it was handed, with itself.</summary>
     [Fact]
-    public async Task The_session_disposes_the_credential_it_owns()
+    public async Task The_session_disposes_the_application_it_owns()
     {
         var mock = SessionReturning(NodeClass.Variable, DataTypeIds.Int32, -1, 1);
-        var credential = new TrackingCredential();
+        var credential = new TrackingApplication();
         var session = new OpcUaClientBrowseSession(
             mock.Object, NamespaceMap.FromTable(new NamespaceTable()), ObjectIds.ObjectsFolder, credential);
 

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser.Tests/OpcUaClientBrowseSessionPaginationTests.cs

@@ -20,7 +20,7 @@ public sealed class OpcUaClientBrowseSessionPaginationTests
     private static Mock<ISession> BuildSession(bool cancelNext)
     {
         var mock = new Mock<ISession>(MockBehavior.Loose);
-        mock.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(BrowseTelemetry.Context));
+        mock.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(BrowseTelemetry.Context));
         mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
 
         var firstRef = new ReferenceDescription
@@ -32,44 +32,44 @@ public sealed class OpcUaClientBrowseSessionPaginationTests
         };
         mock.Setup(s => s.BrowseAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<ViewDescription>(), It.IsAny<uint>(),
-                It.IsAny<BrowseDescriptionCollection>(), It.IsAny<CancellationToken>()))
+                It.IsAny<ArrayOf<BrowseDescription>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(new BrowseResponse
             {
                 ResponseHeader = new ResponseHeader(),
-                Results = new BrowseResultCollection
+                Results = new List<BrowseResult>
                 {
                     new BrowseResult
                     {
-                        ContinuationPoint = FakeContinuationPoint,
-                        References = new ReferenceDescriptionCollection { firstRef },
+                        ContinuationPoint = FakeContinuationPoint.ToByteString(),
+                        References = new List<ReferenceDescription> { firstRef },
                     },
                 },
-                DiagnosticInfos = new DiagnosticInfoCollection(),
+                DiagnosticInfos = new List<DiagnosticInfo>(),
             });
 
         var emptyPage = new BrowseNextResponse
         {
             ResponseHeader = new ResponseHeader(),
-            Results = new BrowseResultCollection
+            Results = new List<BrowseResult>
             {
                 new BrowseResult
                 {
-                    ContinuationPoint = Array.Empty<byte>(),
-                    References = new ReferenceDescriptionCollection(),
+                    ContinuationPoint = ByteString.Empty,
+                    References = new List<ReferenceDescription>(),
                 },
             },
-            DiagnosticInfos = new DiagnosticInfoCollection(),
+            DiagnosticInfos = new List<DiagnosticInfo>(),
         };
 
         var pageSetup = mock.Setup(s => s.BrowseNextAsync(
             It.IsAny<RequestHeader>(), It.Is<bool>(r => !r),
-            It.IsAny<ByteStringCollection>(), It.IsAny<CancellationToken>()));
+            It.IsAny<ArrayOf<ByteString>>(), It.IsAny<CancellationToken>()));
         if (cancelNext) pageSetup.ThrowsAsync(new OperationCanceledException("cancelled mid-page"));
         else pageSetup.ReturnsAsync(emptyPage);
 
         mock.Setup(s => s.BrowseNextAsync(
                 It.IsAny<RequestHeader>(), It.Is<bool>(r => r),
-                It.IsAny<ByteStringCollection>(), It.IsAny<CancellationToken>()))
+                It.IsAny<ArrayOf<ByteString>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(emptyPage);
         return mock;
     }
@@ -89,7 +89,7 @@ public sealed class OpcUaClientBrowseSessionPaginationTests
 
         mock.Verify(s => s.BrowseNextAsync(
             It.IsAny<RequestHeader>(), It.Is<bool>(r => r),
-            It.IsAny<ByteStringCollection>(), It.IsAny<CancellationToken>()), Times.Once);
+            It.IsAny<ArrayOf<ByteString>>(), It.IsAny<CancellationToken>()), Times.Once);
     }
 
     /// <summary>Positive control: an uncancelled pagination never issues a release call.</summary>
@@ -104,9 +104,9 @@ public sealed class OpcUaClientBrowseSessionPaginationTests
         nodes.Count.ShouldBe(1);
         mock.Verify(s => s.BrowseNextAsync(
             It.IsAny<RequestHeader>(), It.Is<bool>(r => !r),
-            It.IsAny<ByteStringCollection>(), It.IsAny<CancellationToken>()), Times.Once);
+            It.IsAny<ArrayOf<ByteString>>(), It.IsAny<CancellationToken>()), Times.Once);
         mock.Verify(s => s.BrowseNextAsync(
             It.IsAny<RequestHeader>(), It.Is<bool>(r => r),
-            It.IsAny<ByteStringCollection>(), It.IsAny<CancellationToken>()), Times.Never);
+            It.IsAny<ArrayOf<ByteString>>(), It.IsAny<CancellationToken>()), Times.Never);
     }
 }

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser.Tests/OpcUaClientDriverBrowserTests.cs

@@ -120,7 +120,7 @@ public sealed class OpcUaClientDriverBrowserTests
         // A loose mock answers the attribute read with no response, so nothing is known about the node.
         var mockSession = new Mock<ISession>(MockBehavior.Loose);
         mockSession.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
-        mockSession.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(BrowseTelemetry.Context));
+        mockSession.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(BrowseTelemetry.Context));
         var nsMap = NamespaceMap.FromTable(new NamespaceTable());
         var sut = new OpcUaClientBrowseSession(mockSession.Object, nsMap, ObjectIds.ObjectsFolder);
 

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientAcknowledgeFailureTests.cs

@@ -21,7 +21,7 @@ public sealed class OpcUaClientAcknowledgeFailureTests
     private static Mock<ISession> NewSession()
     {
         var mock = new Mock<ISession>(MockBehavior.Loose);
-        mock.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(SdkTelemetry.Context));
+        mock.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         return mock;
     }
@@ -34,7 +34,7 @@ public sealed class OpcUaClientAcknowledgeFailureTests
     {
         using var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions(), "opcua-o8");
         var session = NewSession();
-        session.Setup(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<CallMethodRequestCollection>(), It.IsAny<CancellationToken>()))
+        session.Setup(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()))
             .ThrowsAsync(new ServiceResultException(StatusCodes.BadConnectionClosed));
         drv.SetSessionForTest(session.Object);
 
@@ -50,7 +50,7 @@ public sealed class OpcUaClientAcknowledgeFailureTests
     {
         using var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions(), "opcua-o8-ok");
         var session = NewSession();
-        session.Setup(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<CallMethodRequestCollection>(), It.IsAny<CancellationToken>()))
+        session.Setup(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(new CallResponse
             {
                 ResponseHeader = new ResponseHeader(),
@@ -61,10 +61,30 @@ public sealed class OpcUaClientAcknowledgeFailureTests
 
         await drv.AcknowledgeAsync(Ack(), TestContext.Current.CancellationToken);
 
-        session.Verify(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<CallMethodRequestCollection>(), It.IsAny<CancellationToken>()),
+        session.Verify(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()),
             Times.Once);
     }
 
+    [Fact]
+    public async Task Acknowledge_encodes_EventId_as_scalar_ByteString_and_never_retries_a_transport_failure()
+    {
+        using var driver = new OpcUaClientDriver(new OpcUaClientDriverOptions(), "opcua-ack-types");
+        var session = NewSession();
+        ArrayOf<CallMethodRequest> sent = default;
+        session.Setup(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()))
+            .Callback<RequestHeader, ArrayOf<CallMethodRequest>, CancellationToken>((_, calls, _) => sent = calls)
+            .ThrowsAsync(new ServiceResultException(StatusCodes.BadConnectionClosed));
+        driver.SetSessionForTest(session.Object);
+        await Should.ThrowAsync<ServiceResultException>(() => driver.AcknowledgeAsync(Ack(), TestContext.Current.CancellationToken));
+        var arguments = sent[0].InputArguments;
+        arguments[0].TypeInfo.BuiltInType.ShouldBe(BuiltInType.ByteString);
+        arguments[0].TypeInfo.ValueRank.ShouldBe(ValueRanks.Scalar);
+        arguments[0].GetByteString().IsEmpty.ShouldBeTrue();
+        arguments[1].TypeInfo.BuiltInType.ShouldBe(BuiltInType.LocalizedText);
+        arguments[1].GetLocalizedText().Text.ShouldBe("operator ack");
+        session.Verify(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()), Times.Once);
+    }
+
     /// <summary>A session lost while the ack queued on the gate fails the ack rather than reporting it applied.</summary>
     [Fact]
     public async Task A_session_lost_while_queued_fails_the_ack()
@@ -110,7 +130,7 @@ public sealed class OpcUaClientAcknowledgeFailureTests
 
         await drv.AcknowledgeAsync(Unresolvable(), TestContext.Current.CancellationToken);
 
-        session.Verify(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<CallMethodRequestCollection>(), It.IsAny<CancellationToken>()),
+        session.Verify(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()),
             Times.Never);
         lock (logger.Entries)
             logger.Entries.ShouldContain(e => e.Level == Microsoft.Extensions.Logging.LogLevel.Warning && e.Message.Contains("resolved none"));
@@ -127,7 +147,7 @@ public sealed class OpcUaClientAcknowledgeFailureTests
         var ct = TestContext.Current.CancellationToken;
         using var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions(), "opcua-n1");
         var session = NewSession();
-        session.Setup(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<CallMethodRequestCollection>(), It.IsAny<CancellationToken>()))
+        session.Setup(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(new CallResponse
             {
                 ResponseHeader = new ResponseHeader(),
@@ -154,7 +174,7 @@ public sealed class OpcUaClientAcknowledgeFailureTests
         await invoker.ExecuteAsync(DriverCapability.AlarmAcknowledge, "host",
             async c => await drv.AcknowledgeAsync(Ack(), c), ct);
 
-        session.Verify(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<CallMethodRequestCollection>(), It.IsAny<CancellationToken>()),
+        session.Verify(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()),
             Times.Once, "the genuine ack must still reach the server");
     }
 
@@ -166,7 +186,7 @@ public sealed class OpcUaClientAcknowledgeFailureTests
         var stamp = new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc);
         drv.SetHealthForTest(new DriverHealth(DriverState.Healthy, stamp, null));
         var session = NewSession();
-        session.Setup(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<CallMethodRequestCollection>(), It.IsAny<CancellationToken>()))
+        session.Setup(s => s.CallAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()))
             .ThrowsAsync(new ServiceResultException(StatusCodes.BadConnectionClosed));
         drv.SetSessionForTest(session.Object);
 

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientAlarmTests.cs

@@ -76,9 +76,9 @@ public sealed class OpcUaClientAlarmTests
 
     // ---- #619: v3 RawPath <-> upstream-source translation on the native-alarm path ----
 
-    private static VariantCollection EventFields(string sourceNode, string conditionNode) =>
+    private static List<Variant> EventFields(string sourceNode, string conditionNode) =>
     [
-        new Variant(new byte[] { 1 }),                       // EventId
+        Variant.From(new byte[] { 1 }.ToByteString()),       // scalar ByteString EventId
         new Variant(new NodeId("TripAlarmType", 3)),         // EventType
         new Variant(NodeId.Parse(sourceNode)),               // SourceNode
         new Variant(new LocalizedText("tripped")),           // Message
@@ -310,18 +310,18 @@ public sealed class OpcUaClientAlarmTests
         }
     }
 
-    private static VariantCollection ConditionFields(
+    private static List<Variant> ConditionFields(
         bool active, bool acked, string message = "tripped", ushort severity = 700, byte[]? eventId = null,
         NodeId? branchId = null, NodeId? eventType = null)
     {
         var f = EventFields("ns=3;s=Alarms.Trip1", "ns=3;s=Alarms.Trip1.Cond");
-        f[0] = new Variant(eventId ?? new byte[] { 1 });
-        if (eventType is not null) f[1] = new Variant(eventType);
+        f[0] = Variant.From(new ByteString((eventId ?? new byte[] { 1 }).AsMemory()));
+        if (eventType is not null) f[1] = Variant.From(eventType.Value);
         f[3] = new Variant(new LocalizedText(message));
         f[4] = new Variant(severity);
         f.Add(new Variant(active));
         f.Add(new Variant(acked));
-        f.Add(branchId is null ? Variant.Null : new Variant(branchId));
+        f.Add(branchId is null ? Variant.Null : Variant.From(branchId.Value));
         return f;
     }
 
@@ -382,7 +382,7 @@ public sealed class OpcUaClientAlarmTests
         OpcUaClientDriver.IsRefreshRequired(EventFieldsOfType(ObjectTypeIds.RefreshEndEventType)).ShouldBeFalse();
     }
 
-    private static VariantCollection EventFieldsOfType(NodeId type)
+    private static List<Variant> EventFieldsOfType(NodeId type)
     {
         var f = EventFields("i=2253", "i=0");
         f[1] = new Variant(type);

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientCertAuthTests.cs

@@ -65,4 +65,49 @@ public sealed class OpcUaClientCertAuthTests
             try { File.Delete(tmpPath); } catch { /* best-effort */ }
         }
     }
+    [Fact]
+    public async Task Certificate_identity_signs_repeatedly_and_requires_reopen_after_file_rotation()
+    {
+        var path = Path.Combine(Path.GetTempPath(), $"opcua-cert-rotation-{Guid.NewGuid():N}.pfx");
+        try
+        {
+            using var key = RSA.Create(2048);
+            var request = new CertificateRequest("CN=OpcUaSdk2Signing", key, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
+            using var original = request.CreateSelfSigned(DateTimeOffset.UtcNow.AddMinutes(-5), DateTimeOffset.UtcNow.AddHours(1));
+            File.WriteAllBytes(path, original.Export(X509ContentType.Pfx, "test-password"));
+            var options = new OpcUaClientDriverOptions { AuthType = OpcUaAuthType.Certificate,
+                UserCertificatePath = path, UserCertificatePassword = "test-password" };
+            var identity = OpcUaClientDriver.BuildCertificateIdentity(options);
+            byte[] challenge = [1, 2, 3, 4];
+            for (var i = 0; i < 2; i++)
+            {
+                var signature = await identity.TokenHandler.SignAsync(challenge, Opc.Ua.SecurityPolicies.Basic256Sha256,
+                    TestContext.Current.CancellationToken);
+                using var publicKey = original.GetRSAPublicKey();
+                publicKey.ShouldNotBeNull().VerifyData(challenge, signature.Signature.Span,
+                    HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1).ShouldBeTrue();
+            }
+            using var cancelled = new CancellationTokenSource();
+            cancelled.Cancel();
+            await Should.ThrowAsync<OperationCanceledException>(async () =>
+                await identity.TokenHandler.SignAsync(challenge, Opc.Ua.SecurityPolicies.Basic256Sha256, cancelled.Token));
+
+            using var rotatedKey = RSA.Create(2048);
+            var rotatedRequest = new CertificateRequest("CN=OpcUaSdk2Signing", rotatedKey, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
+            using var rotated = rotatedRequest.CreateSelfSigned(DateTimeOffset.UtcNow.AddMinutes(-5), DateTimeOffset.UtcNow.AddHours(1));
+            File.WriteAllBytes(path, rotated.Export(X509ContentType.Pfx, "test-password"));
+            var error = await Should.ThrowAsync<Opc.Ua.ServiceResultException>(async () =>
+                await identity.TokenHandler.SignAsync(challenge, Opc.Ua.SecurityPolicies.Basic256Sha256,
+                    TestContext.Current.CancellationToken));
+            error.StatusCode.ShouldBe(Opc.Ua.StatusCodes.BadIdentityTokenInvalid);
+            var fresh = OpcUaClientDriver.BuildCertificateIdentity(options);
+            var freshSignature = await fresh.TokenHandler.SignAsync(challenge, Opc.Ua.SecurityPolicies.Basic256Sha256,
+                TestContext.Current.CancellationToken);
+            using var rotatedPublicKey = rotated.GetRSAPublicKey();
+            rotatedPublicKey.ShouldNotBeNull().VerifyData(challenge, freshSignature.Signature.Span,
+                HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1).ShouldBeTrue();
+        }
+        finally { File.Delete(path); }
+    }
+
 }

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientConnectionLossSignalTests.cs

@@ -59,7 +59,7 @@ public sealed class OpcUaClientConnectionLossSignalTests
     private static Mock<ISession> NewSession()
     {
         var mock = new Mock<ISession>(MockBehavior.Loose);
-        mock.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(SdkTelemetry.Context));
+        mock.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         return mock;
     }
@@ -77,18 +77,18 @@ public sealed class OpcUaClientConnectionLossSignalTests
         return (drv, session, clock, log);
     }
 
-    private static DataValue Good(object value, DateTime ts) => new(new Variant(value), StatusCodes.Good, ts, ts);
+    private static DataValue Good(object value, DateTime ts) => new(VariantHelper.CastFrom(value), StatusCodes.Good, ts, ts);
 
     /// <summary>Every read returns <paramref name="values"/> (one per requested node, in order) at <paramref name="at"/>.</summary>
     private static void SetupRead(Mock<ISession> session, Func<DateTime> at, params object[] values) =>
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
-            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, CancellationToken _) =>
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ArrayOf<ReadValueId> nodes, CancellationToken _) =>
                 new ReadResponse
                 {
                     ResponseHeader = new ResponseHeader(),
-                    Results = [.. nodes.Select((_, i) => Good(values[i], at()))],
+                    Results = [.. nodes.ToList().Select((_, i) => Good(values[i], at()))],
                     DiagnosticInfos = [],
                 });
 
@@ -96,18 +96,18 @@ public sealed class OpcUaClientConnectionLossSignalTests
 
     public static TheoryData<uint> DefinitiveStatuses =>
     [
-        StatusCodes.BadSessionIdInvalid,
-        StatusCodes.BadSessionClosed,
-        StatusCodes.BadSessionNotActivated,
-        StatusCodes.BadServerHalted,
+        StatusCodes.BadSessionIdInvalid.Code,
+        StatusCodes.BadSessionClosed.Code,
+        StatusCodes.BadSessionNotActivated.Code,
+        StatusCodes.BadServerHalted.Code,
     ];
 
     public static TheoryData<uint> AmbiguousStatuses =>
     [
-        StatusCodes.BadNoCommunication,
-        StatusCodes.BadNotConnected,
-        StatusCodes.BadRequestTimeout,
-        StatusCodes.BadTimeout,
+        StatusCodes.BadNoCommunication.Code,
+        StatusCodes.BadNotConnected.Code,
+        StatusCodes.BadRequestTimeout.Code,
+        StatusCodes.BadTimeout.Code,
     ];
 
     [Theory]
@@ -127,7 +127,7 @@ public sealed class OpcUaClientConnectionLossSignalTests
         drv.RaiseKeepAliveForTest(StatusCodes.BadSessionIdInvalid);
 
         raised.ShouldHaveSingleItem("once per session, however many definitive keep-alives follow")
-            .Reason.ShouldContain(StatusCodes.GetBrowseName(status));
+            .Reason.ShouldContain(new StatusCode(status).SymbolicId!);
         order.ShouldBe([$"bad:{BadNoCommunication:X8}", "lost"], "subscribers see the Bad before the host tears down");
     }
 
@@ -404,7 +404,7 @@ public sealed class OpcUaClientConnectionLossSignalTests
         var reads = 0;
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(() =>
             {
                 var trailing = Interlocked.Increment(ref reads) > 1;
@@ -447,7 +447,7 @@ public sealed class OpcUaClientConnectionLossSignalTests
         var reads = 0;
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
             .Returns(async () =>
             {
                 if (Interlocked.Increment(ref reads) > 1) await gate.Task; // hold the trailing read
@@ -495,7 +495,7 @@ public sealed class OpcUaClientConnectionLossSignalTests
 
         session.Verify(s => s.ReadAsync(
             It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-            It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()), Times.Once,
+            It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()), Times.Once,
             "only the recovery read — the trailing read must not run against a session that is no longer current");
     }
 
@@ -506,7 +506,7 @@ public sealed class OpcUaClientConnectionLossSignalTests
         var reads = 0;
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(() => new ReadResponse
             {
                 ResponseHeader = new ResponseHeader(),
@@ -559,7 +559,7 @@ public sealed class OpcUaClientConnectionLossSignalTests
         var handle = drv.AddSubscriptionForTest([SpeedRef]);
         var t0 = clock.Now.UtcDateTime;
         DataValue NoSource(object v, DateTime server) =>
-            new(new Variant(v), StatusCodes.Good, DateTime.MinValue, server);
+            new(VariantHelper.CastFrom(v), StatusCodes.Good, DateTime.MinValue, server);
         drv.DeliverNotificationForTest(handle, SpeedRef, NoSource(10f, t0));
         var reads = SetupRecoveryThenTrailing(session, NoSource(10f, t0.AddSeconds(1)), NoSource(40f, t0.AddSeconds(9)));
 
@@ -587,7 +587,7 @@ public sealed class OpcUaClientConnectionLossSignalTests
         var reads = 0;
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(() => new ReadResponse
             {
                 ResponseHeader = new ResponseHeader(),
@@ -677,12 +677,12 @@ public sealed class OpcUaClientConnectionLossSignalTests
         drv.PostRecoveryReconcileDelay = () => TimeSpan.Zero;
         var handle = drv.AddSubscriptionForTest([SpeedRef]);
         var t0 = clock.Now.UtcDateTime;
-        DataValue NoSource(object v, DateTime server) => new(new Variant(v), StatusCodes.Good, DateTime.MinValue, server);
+        DataValue NoSource(object v, DateTime server) => new(VariantHelper.CastFrom(v), StatusCodes.Good, DateTime.MinValue, server);
         drv.DeliverNotificationForTest(handle, SpeedRef, NoSource(10f, t0));
         var reads = 0;
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(() =>
             {
                 DataValue result;

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientContinuationPointReleaseTests.cs

@@ -37,7 +37,7 @@ public sealed class OpcUaClientContinuationPointReleaseTests
     private static Mock<ISession> BuildCancellingSessionMock()
     {
         var mock = new Mock<ISession>(MockBehavior.Loose);
-        mock.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.SdkTelemetry.Context));
+        mock.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.SdkTelemetry.Context));
         mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
 
         // BrowseAsync — return one Object child plus a non-empty continuation point so
@@ -52,20 +52,20 @@ public sealed class OpcUaClientContinuationPointReleaseTests
         };
         var browseResult = new BrowseResult
         {
-            ContinuationPoint = FakeContinuationPoint,
-            References = new ReferenceDescriptionCollection { firstRef },
+            ContinuationPoint = FakeContinuationPoint.ToByteString(),
+            References = new List<ReferenceDescription> { firstRef },
         };
         var browseResp = new BrowseResponse
         {
             ResponseHeader = new ResponseHeader(),
-            Results = new BrowseResultCollection { browseResult },
-            DiagnosticInfos = new DiagnosticInfoCollection(),
+            Results = new List<BrowseResult> { browseResult },
+            DiagnosticInfos = new List<DiagnosticInfo>(),
         };
         mock.Setup(s => s.BrowseAsync(
                 It.IsAny<RequestHeader>(),
                 It.IsAny<ViewDescription>(),
                 It.IsAny<uint>(),
-                It.IsAny<BrowseDescriptionCollection>(),
+                It.IsAny<ArrayOf<BrowseDescription>>(),
                 It.IsAny<CancellationToken>()))
             .ReturnsAsync(browseResp);
 
@@ -73,7 +73,7 @@ public sealed class OpcUaClientContinuationPointReleaseTests
         mock.Setup(s => s.BrowseNextAsync(
                 It.IsAny<RequestHeader>(),
                 It.Is<bool>(release => !release),
-                It.IsAny<ByteStringCollection>(),
+                It.IsAny<ArrayOf<ByteString>>(),
                 It.IsAny<CancellationToken>()))
             .ThrowsAsync(new OperationCanceledException("ct cancelled during BrowseNext"));
 
@@ -82,19 +82,19 @@ public sealed class OpcUaClientContinuationPointReleaseTests
         // there is no separate BrowseNextResult type in the OPC UA SDK.
         var emptyReleaseResult = new BrowseResult
         {
-            ContinuationPoint = Array.Empty<byte>(),
-            References = new ReferenceDescriptionCollection(),
+            ContinuationPoint = ByteString.Empty,
+            References = new List<ReferenceDescription>(),
         };
         var releaseResp = new BrowseNextResponse
         {
             ResponseHeader = new ResponseHeader(),
-            Results = new BrowseResultCollection { emptyReleaseResult },
-            DiagnosticInfos = new DiagnosticInfoCollection(),
+            Results = new List<BrowseResult> { emptyReleaseResult },
+            DiagnosticInfos = new List<DiagnosticInfo>(),
         };
         mock.Setup(s => s.BrowseNextAsync(
                 It.IsAny<RequestHeader>(),
                 It.Is<bool>(release => release),
-                It.IsAny<ByteStringCollection>(),
+                It.IsAny<ArrayOf<ByteString>>(),
                 It.IsAny<CancellationToken>()))
             .ReturnsAsync(releaseResp);
 
@@ -127,7 +127,7 @@ public sealed class OpcUaClientContinuationPointReleaseTests
         sessionMock.Verify(s => s.BrowseNextAsync(
             It.IsAny<RequestHeader>(),
             It.Is<bool>(release => release),
-            It.IsAny<ByteStringCollection>(),
+            It.IsAny<ArrayOf<ByteString>>(),
             It.IsAny<CancellationToken>()),
             Times.Once,
             "DiscoverAsync must release the server-side continuation point on cancellation " +
@@ -148,7 +148,7 @@ public sealed class OpcUaClientContinuationPointReleaseTests
         using var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions(), "opcua-cp-norelease");
 
         var mock = new Mock<ISession>(MockBehavior.Loose);
-        mock.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.SdkTelemetry.Context));
+        mock.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.SdkTelemetry.Context));
         mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
 
         // BrowseAsync — return a result with a continuation point so the loop is entered.
@@ -161,27 +161,27 @@ public sealed class OpcUaClientContinuationPointReleaseTests
         };
         var browseResult = new BrowseResult
         {
-            ContinuationPoint = FakeContinuationPoint,
-            References = new ReferenceDescriptionCollection { firstRef },
+            ContinuationPoint = FakeContinuationPoint.ToByteString(),
+            References = new List<ReferenceDescription> { firstRef },
         };
         mock.Setup(s => s.BrowseAsync(
                 It.IsAny<RequestHeader>(),
                 It.IsAny<ViewDescription>(),
                 It.IsAny<uint>(),
-                It.IsAny<BrowseDescriptionCollection>(),
+                It.IsAny<ArrayOf<BrowseDescription>>(),
                 It.IsAny<CancellationToken>()))
             .ReturnsAsync(new BrowseResponse
             {
                 ResponseHeader = new ResponseHeader(),
-                Results = new BrowseResultCollection { browseResult },
-                DiagnosticInfos = new DiagnosticInfoCollection(),
+                Results = new List<BrowseResult> { browseResult },
+                DiagnosticInfos = new List<DiagnosticInfo>(),
             });
 
         // BrowseNextAsync — throw a non-cancellation transport error.
         mock.Setup(s => s.BrowseNextAsync(
                 It.IsAny<RequestHeader>(),
                 It.Is<bool>(release => !release),
-                It.IsAny<ByteStringCollection>(),
+                It.IsAny<ArrayOf<ByteString>>(),
                 It.IsAny<CancellationToken>()))
             .ThrowsAsync(new ServiceResultException(StatusCodes.BadCommunicationError));
 
@@ -195,7 +195,7 @@ public sealed class OpcUaClientContinuationPointReleaseTests
         mock.Verify(s => s.BrowseNextAsync(
             It.IsAny<RequestHeader>(),
             It.Is<bool>(release => release),
-            It.IsAny<ByteStringCollection>(),
+            It.IsAny<ArrayOf<ByteString>>(),
             It.IsAny<CancellationToken>()),
             Times.Never,
             "A transient transport failure must not trigger a release BrowseNext call");

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientGateSplitTests.cs

@@ -28,16 +28,16 @@ public sealed class OpcUaClientGateSplitTests
     {
         var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions { RawTags = Tags }, "opcua-o6");
         var session = new Mock<ISession>(MockBehavior.Loose);
-        session.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(SdkTelemetry.Context));
+        session.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         session.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
-            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, CancellationToken _) =>
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ArrayOf<ReadValueId> nodes, CancellationToken _) =>
                 new ReadResponse
                 {
                     ResponseHeader = new ResponseHeader(),
-                    Results = [.. nodes.Select(_ => new DataValue(new Variant(42), StatusCodes.Good, DateTime.UtcNow, DateTime.UtcNow))],
+                    Results = [.. nodes.ToList().Select(_ => new DataValue(new Variant(42), StatusCodes.Good, DateTime.UtcNow, DateTime.UtcNow))],
                     DiagnosticInfos = [],
                 });
         drv.SetSessionForTest(session.Object);
@@ -60,15 +60,15 @@ public sealed class OpcUaClientGateSplitTests
         using var _ = drv;
         var writeOnWire = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
         var releaseWrite = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
-        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<WriteValueCollection>(), It.IsAny<CancellationToken>()))
-            .Returns(async (RequestHeader _, WriteValueCollection nodes, CancellationToken _) =>
+        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()))
+            .Returns(async (RequestHeader _, ArrayOf<WriteValue> nodes, CancellationToken _) =>
             {
                 writeOnWire.TrySetResult();
                 await releaseWrite.Task;
                 return new WriteResponse
                 {
                     ResponseHeader = new ResponseHeader(),
-                    Results = [.. nodes.Select(_ => (StatusCode)StatusCodes.Good)],
+                    Results = [.. nodes.ToList().Select(_ => (StatusCode)StatusCodes.Good)],
                     DiagnosticInfos = [],
                 };
             });
@@ -111,8 +111,8 @@ public sealed class OpcUaClientGateSplitTests
         var releaseBrowse = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
         session.Setup(s => s.BrowseAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<ViewDescription>(), It.IsAny<uint>(),
-                It.IsAny<BrowseDescriptionCollection>(), It.IsAny<CancellationToken>()))
-            .Returns(async (RequestHeader _, ViewDescription _, uint _, BrowseDescriptionCollection _, CancellationToken _) =>
+                It.IsAny<ArrayOf<BrowseDescription>>(), It.IsAny<CancellationToken>()))
+            .Returns(async (RequestHeader _, ViewDescription _, uint _, ArrayOf<BrowseDescription> _, CancellationToken _) =>
             {
                 browseOnWire.TrySetResult();
                 await releaseBrowse.Task;

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientIdlePublishErrorTests.cs

@@ -28,7 +28,7 @@ public sealed class OpcUaClientIdlePublishErrorTests
     {
         var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions { RawTags = Tags }, instance);
         var session = new Mock<ISession>(MockBehavior.Loose);
-        session.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(SdkTelemetry.Context));
+        session.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         session.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         drv.SetSessionForTest(session.Object);
         drv.SetNamespaceMapForTest(NamespaceMap.FromTable(new NamespaceTable(), Tags));

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientLifecycleGenerationTests.cs

@@ -29,15 +29,15 @@ public sealed class OpcUaClientLifecycleGenerationTests
     private static Mock<ISession> NewSession()
     {
         var mock = new Mock<ISession>(MockBehavior.Loose);
-        mock.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(SdkTelemetry.Context));
+        mock.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         return mock;
     }
 
-    private static ReadResponse GoodRead(ReadValueIdCollection nodes) => new()
+    private static ReadResponse GoodRead(ArrayOf<ReadValueId> nodes) => new()
     {
         ResponseHeader = new ResponseHeader(),
-        Results = [.. nodes.Select(_ => new DataValue(new Variant(1), StatusCodes.Good, DateTime.UtcNow, DateTime.UtcNow))],
+        Results = [.. nodes.ToList().Select(_ => new DataValue(new Variant(1), StatusCodes.Good, DateTime.UtcNow, DateTime.UtcNow))],
         DiagnosticInfos = [],
     };
 
@@ -118,6 +118,26 @@ public sealed class OpcUaClientLifecycleGenerationTests
         drv.GetHealth().State.ShouldBe(DriverState.Unknown, "the abandoned init must not overwrite the newer health");
     }
 
+    [Fact]
+    public async Task Cancellation_at_session_ownership_transfer_discards_session_without_failover_or_install()
+    {
+        var session = NewSession();
+        using var cancellation = new CancellationTokenSource();
+        using var driver = new OpcUaClientDriver(new OpcUaClientDriverOptions
+            { EndpointUrls = ["opc.tcp://first:4840", "opc.tcp://second:4840"] }, "sdk2-cancel-open");
+        var opens = 0;
+        driver.OpenSessionForTest = (_, _) =>
+        {
+            opens++;
+            cancellation.Cancel();
+            return Task.FromResult(session.Object);
+        };
+        await Should.ThrowAsync<OperationCanceledException>(() => driver.InitializeAsync("{}", cancellation.Token));
+        opens.ShouldBe(1);
+        driver.Session.ShouldBeNull();
+        session.Verify(s => s.Dispose(), Times.Once);
+    }
+
     /// <summary>A read whose response arrives after a shutdown does not write Healthy over the shutdown.</summary>
     [Fact]
     public async Task A_read_that_outlives_a_shutdown_does_not_overwrite_the_shutdown_health()
@@ -160,8 +180,8 @@ public sealed class OpcUaClientLifecycleGenerationTests
         var respond = new System.Collections.Concurrent.ConcurrentQueue<TaskCompletionSource>();
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
-            .Returns(async (RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, CancellationToken _) =>
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
+            .Returns(async (RequestHeader _, double _, TimestampsToReturn _, ArrayOf<ReadValueId> nodes, CancellationToken _) =>
             {
                 var gate = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
                 respond.Enqueue(gate);

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientNamespaceTests.cs

@@ -74,6 +74,35 @@ public sealed class OpcUaClientNamespaceTests
         NamespaceMap.TryResolve(null!, "ns=1;s=X", out _).ShouldBeFalse();
     }
 
+    public static TheoryData<NodeId> IdentifierKinds =>
+    [
+        new NodeId(123u, 1),
+        new NodeId("literal;i=123", 1),
+        new NodeId(Guid.Parse("db8d57c4-316f-4517-819f-194c3a6db955"), 1),
+        new NodeId(new byte[] { 0, 1, 127, 255 }.ToByteString(), 1),
+    ];
+
+    [Theory]
+    [MemberData(nameof(IdentifierKinds))]
+    public void Stable_reference_rebinds_namespace_without_changing_identifier_type(NodeId original)
+    {
+        var stable = TestMap("http://opcfoundation.org/UA/", "urn:remote:server").ToStableReference(original);
+        var context = ServiceMessageContext.Create(SdkTelemetry.Context);
+        context.NamespaceUris.Append("urn:other");
+        context.NamespaceUris.Append("urn:remote:server");
+        var session = new Moq.Mock<Opc.Ua.Client.ISession>();
+        session.SetupGet(s => s.MessageContext).Returns(context);
+        NamespaceMap.TryResolve(session.Object, stable, out var rebound).ShouldBeTrue();
+        rebound.NamespaceIndex.ShouldBe((ushort)2);
+        rebound.IdType.ShouldBe(original.IdType);
+        rebound.IdentifierAsString.ShouldBe(original.IdentifierAsString);
+        if (original.IdType == IdType.Opaque)
+        {
+            rebound.TryGetValue(out ByteString identifier).ShouldBeTrue();
+            identifier.ToArray().ShouldBe(new byte[] { 0, 1, 127, 255 });
+        }
+    }
+
     // ---- v3: RawPath → upstream node id resolution table ----
 
     /// <summary>Verifies a RawPath resolves to the upstream node id authored in its TagConfig.nodeId.</summary>

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientSdkValueBoundaryTests.cs

@@ -0,0 +1,173 @@
+using Moq;
+using Opc.Ua;
+using Opc.Ua.Client;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
+
+[Trait("Category", "Unit")]
+public sealed class OpcUaClientSdkValueBoundaryTests
+{
+    private const string Reference = "Plant/Upstream/Value";
+    private static readonly RawTagEntry[] Tags = [new(Reference, """{"nodeId":"i=2258"}""", false)];
+
+    private static (OpcUaClientDriver Driver, Mock<ISession> Session) Connected()
+    {
+        var session = new Mock<ISession>();
+        session.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
+        session.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
+        var driver = new OpcUaClientDriver(new OpcUaClientDriverOptions { RawTags = Tags }, "sdk2-values");
+        driver.SetSessionForTest(session.Object);
+        driver.SetNamespaceMapForTest(NamespaceMap.FromTable(new NamespaceTable(), Tags));
+        return (driver, session);
+    }
+
+    public static TheoryData<Variant, object?> Payloads =>
+    [
+        new(Variant.From((sbyte)-3), (sbyte)-3),
+        new(Variant.From((byte)250), (byte)250),
+        new(Variant.From((short)-30), (short)-30),
+        new(Variant.From((ushort)60000), (ushort)60000),
+        new(Variant.From(-100), -100),
+        new(Variant.From(uint.MaxValue), uint.MaxValue),
+        new(Variant.From(long.MinValue), long.MinValue),
+        new(Variant.From(ulong.MaxValue), ulong.MaxValue),
+        new(Variant.From(1.5f), 1.5f),
+        new(Variant.From(1.5d), 1.5d),
+        new(Variant.From(true), true),
+        new(Variant.From("text"), "text"),
+        new(Variant.Null, null),
+        new(Variant.From(new DateTimeUtc(new DateTime(2026, 11, 10, 1, 2, 3, DateTimeKind.Utc))), new DateTime(2026, 11, 10, 1, 2, 3, DateTimeKind.Utc)),
+        new(Variant.From(new Uuid(Guid.Parse("db8d57c4-316f-4517-819f-194c3a6db955"))), Guid.Parse("db8d57c4-316f-4517-819f-194c3a6db955")),
+        new(Variant.From(new byte[] { 1, 2 }.ToByteString()), new byte[] { 1, 2 }),
+        new(Variant.From(default(ByteString)), null),
+        new(Variant.From(ByteString.Empty), Array.Empty<byte>()),
+        new(Variant.From((ArrayOf<bool>)[true, false]), new[] { true, false }),
+        new(Variant.From((ArrayOf<sbyte>)[-1, 2]), new sbyte[] { -1, 2 }),
+        new(Variant.From((ArrayOf<byte>)[1, 250]), new byte[] { 1, 250 }),
+        new(Variant.From((ArrayOf<short>)[1, 2]), new short[] { 1, 2 }),
+        new(Variant.From((ArrayOf<ushort>)[1, 60000]), new ushort[] { 1, 60000 }),
+        new(Variant.From((ArrayOf<int>)[-1, 2]), new int[] { -1, 2 }),
+        new(Variant.From((ArrayOf<long>)[long.MinValue, long.MaxValue]), new long[] { long.MinValue, long.MaxValue }),
+        new(Variant.From((ArrayOf<ulong>)[0, ulong.MaxValue]), new ulong[] { 0, ulong.MaxValue }),
+        new(Variant.From((ArrayOf<double>)[1, 2]), new double[] { 1, 2 }),
+        new(Variant.From((ArrayOf<uint>)[1, 2]), new uint[] { 1, 2 }),
+        new(Variant.From((ArrayOf<float>)[1, 2]), new float[] { 1, 2 }),
+        new(Variant.From((ArrayOf<string>)["a", "b"]), new[] { "a", "b" }),
+        new(Variant.From((ArrayOf<DateTimeUtc>)[new DateTimeUtc(new DateTime(2026, 11, 10, 1, 2, 3, DateTimeKind.Utc))]), new[] { new DateTime(2026, 11, 10, 1, 2, 3, DateTimeKind.Utc) }),
+        new(Variant.From((ArrayOf<Uuid>)[new Uuid(Guid.Empty)]), new[] { Guid.Empty }),
+        new(Variant.From((ArrayOf<ByteString>)[new byte[] { 3 }.ToByteString(), ByteString.Empty]), new byte[][] { [3], [] }),
+        new(Variant.From(default(ArrayOf<short>)), null),
+        new(Variant.From((ArrayOf<short>)[]), Array.Empty<short>()),
+    ];
+
+    [Theory]
+    [MemberData(nameof(Payloads))]
+    public async Task Read_and_notification_preserve_CLR_type_status_and_timestamp_rules(Variant upstream, object? expected)
+    {
+        var (driver, session) = Connected();
+        using var _ = driver;
+        session.Setup(s => s.ReadAsync(It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
+            It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>())).ReturnsAsync(new ReadResponse
+            { Results = [new DataValue(upstream, StatusCodes.UncertainLastUsableValue, DateTimeUtc.MinValue, DateTimeUtc.MinValue)] });
+        var before = DateTime.UtcNow;
+        var read = (await driver.ReadAsync([Reference], TestContext.Current.CancellationToken)).Single();
+        AssertPayload(read, expected, before);
+        DataValueSnapshot? notified = null;
+        driver.OnDataChange += (_, e) => notified = e.Snapshot;
+        var handle = driver.AddSubscriptionForTest([Reference]);
+        driver.DeliverNotificationForTest(handle, Reference,
+            new DataValue(upstream, StatusCodes.UncertainLastUsableValue, DateTimeUtc.MinValue, DateTimeUtc.MinValue));
+        AssertPayload(notified.ShouldNotBeNull(), expected, before);
+    }
+
+    private static void AssertPayload(DataValueSnapshot snapshot, object? expected, DateTime before)
+    {
+        snapshot.Value.ShouldBe(expected);
+        snapshot.Value?.GetType().ShouldBe(expected?.GetType());
+        snapshot.StatusCode.ShouldBe(StatusCodes.UncertainLastUsableValue.Code);
+        snapshot.SourceTimestampUtc.ShouldBeNull();
+        snapshot.ServerTimestampUtc.ShouldBeGreaterThanOrEqualTo(before);
+        snapshot.ServerTimestampUtc.Kind.ShouldBe(DateTimeKind.Utc);
+    }
+
+    [Theory]
+    [InlineData(0)]
+    [InlineData(1)]
+    [InlineData(2)]
+    public async Task Read_and_notification_detach_upstream_buffers(int shape)
+    {
+        var (driver, session) = Connected();
+        using var _ = driver;
+        byte[] bytes = [1, 2];
+        short[] numbers = [3, 4];
+        // ReadOnlyMemory constructors deliberately alias the backing SDK buffer. Copying the
+        // test input before the adapter sees it would make the ownership assertion vacuous.
+        var value = shape switch
+        {
+            0 => Variant.From(new ByteString(bytes.AsMemory())),
+            1 => Variant.From(new ArrayOf<short>(numbers.AsMemory())),
+            _ => Variant.From((ArrayOf<ByteString>)[new ByteString(bytes.AsMemory())]),
+        };
+        object expected = shape switch { 0 => new byte[] { 1, 2 }, 1 => new short[] { 3, 4 }, _ => new byte[][] { [1, 2] } };
+        session.Setup(s => s.ReadAsync(It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
+            It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>())).ReturnsAsync(new ReadResponse { Results = [new DataValue(value)] });
+        var read = (await driver.ReadAsync([Reference], TestContext.Current.CancellationToken)).Single();
+        DataValueSnapshot? notified = null;
+        driver.OnDataChange += (_, e) => notified = e.Snapshot;
+        driver.DeliverNotificationForTest(driver.AddSubscriptionForTest([Reference]), Reference, new DataValue(value));
+        bytes[0] = 99;
+        numbers[0] = 99;
+        read.Value.ShouldBe(expected);
+        notified.ShouldNotBeNull().Value.ShouldBe(expected);
+    }
+
+    [Fact]
+    public async Task Matrix_read_and_notification_are_refused_per_item_without_materialization()
+    {
+        var (driver, session) = Connected();
+        using var _ = driver;
+        var sourceTime = new DateTime(2026, 11, 10, 1, 2, 3, DateTimeKind.Utc);
+        var serverTime = sourceTime.AddSeconds(1);
+        var matrix = Variant.From(new int[,] { { 1, 2 }, { 3, 4 } }.ToMatrixOf());
+        session.Setup(s => s.ReadAsync(It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
+            It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>())).ReturnsAsync(new ReadResponse
+            { Results = [new DataValue(matrix, StatusCodes.Good, sourceTime, serverTime),
+                new DataValue(Variant.From(42), StatusCodes.Good, sourceTime, serverTime)] });
+        var results = await driver.ReadAsync([Reference, Reference], TestContext.Current.CancellationToken);
+        results[0].Value.ShouldBeNull();
+        results[0].StatusCode.ShouldBe(StatusCodes.BadTypeMismatch.Code);
+        results[0].SourceTimestampUtc.ShouldBe(sourceTime);
+        results[0].ServerTimestampUtc.ShouldBe(serverTime);
+        results[1].Value.ShouldBe(42);
+        results[1].StatusCode.ShouldBe(StatusCodes.Good.Code);
+        DataValueSnapshot? notified = null;
+        driver.OnDataChange += (_, e) => notified = e.Snapshot;
+        driver.DeliverNotificationForTest(driver.AddSubscriptionForTest([Reference]), Reference,
+            new DataValue(matrix, StatusCodes.UncertainLastUsableValue, sourceTime, serverTime));
+        notified.ShouldNotBeNull().Value.ShouldBeNull();
+        notified.StatusCode.ShouldBe(StatusCodes.BadTypeMismatch.Code);
+        notified.SourceTimestampUtc.ShouldBe(sourceTime);
+        notified.ServerTimestampUtc.ShouldBe(serverTime);
+    }
+
+    [Fact]
+    public async Task Write_passes_scalar_shaped_arrays_once_and_rejects_unsupported_values_before_IO()
+    {
+        var (driver, session) = Connected();
+        using var _ = driver;
+        short[] caller = [7, 8];
+        ArrayOf<WriteValue> sent = default;
+        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()))
+            .Callback<RequestHeader, ArrayOf<WriteValue>, CancellationToken>((_, writes, _) => { sent = writes; caller[0] = 99; })
+            .ReturnsAsync(new WriteResponse { Results = [StatusCodes.Good] });
+        var result = await driver.WriteAsync([new(Reference, caller), new(Reference, new object()), new(Reference, new int[1, 1])], TestContext.Current.CancellationToken);
+        result.Select(r => r.StatusCode).ShouldBe([StatusCodes.Good.Code, StatusCodes.BadTypeMismatch.Code, StatusCodes.BadTypeMismatch.Code]);
+        sent.Count.ShouldBe(1);
+        sent[0].Value.WrappedValue.TypeInfo.ValueRank.ShouldBe(ValueRanks.OneDimension);
+        UpstreamValueMapping.ToClr(sent[0].Value.WrappedValue).ShouldBe(new short[] { 7, 8 });
+        session.Verify(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()), Times.Once);
+    }
+}

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientSessionLossTests.cs

@@ -41,7 +41,7 @@ public sealed class OpcUaClientSessionLossTests
     {
         var mock = new Mock<ISession>(MockBehavior.Loose);
         mock.SetupGet(s => s.MessageContext)
-            .Returns(new ServiceMessageContext(SdkTelemetry.Context));
+            .Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         return mock;
     }
@@ -60,17 +60,17 @@ public sealed class OpcUaClientSessionLossTests
     }
 
     private static DataValue Good(object value, DateTime ts) =>
-        new(new Variant(value), StatusCodes.Good, ts, ts);
+        new(VariantHelper.CastFrom(value), StatusCodes.Good, ts, ts);
 
     private static void SetupRead(Mock<ISession> session, params object[] values) =>
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
-            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, CancellationToken _) =>
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ArrayOf<ReadValueId> nodes, CancellationToken _) =>
                 new ReadResponse
                 {
                     ResponseHeader = new ResponseHeader(),
-                    Results = [.. nodes.Select((_, i) => new DataValue(new Variant(values[i]), StatusCodes.Good, DateTime.UtcNow, DateTime.UtcNow))],
+                    Results = [.. nodes.ToList().Select((_, i) => new DataValue(VariantHelper.CastFrom(values[i]), StatusCodes.Good, DateTime.UtcNow, DateTime.UtcNow))],
                     DiagnosticInfos = [],
                 });
 
@@ -500,11 +500,11 @@ public sealed class OpcUaClientSessionLossTests
     private static void SetupReadAt(Mock<ISession> session, object value, DateTime sourceTime) =>
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(new ReadResponse
             {
                 ResponseHeader = new ResponseHeader(),
-                Results = [new DataValue(new Variant(value), StatusCodes.Good, sourceTime, sourceTime)],
+                Results = [new DataValue(VariantHelper.CastFrom(value), StatusCodes.Good, sourceTime, sourceTime)],
                 DiagnosticInfos = [],
             });
 
@@ -702,7 +702,7 @@ public sealed class OpcUaClientSessionLossTests
         var readAt = t0.AddSeconds(10);
         session.Setup(s => s.ReadAsync(
                 It.IsAny<RequestHeader>(), It.IsAny<double>(), It.IsAny<TimestampsToReturn>(),
-                It.IsAny<ReadValueIdCollection>(), It.IsAny<CancellationToken>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(new ReadResponse
             {
                 ResponseHeader = new ResponseHeader(),

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientStaleNoSubscriptionTests.cs

@@ -42,7 +42,7 @@ public sealed class OpcUaClientStaleNoSubscriptionTests
     {
         var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions { RawTags = Tags }, "opcua-763");
         var session = new Mock<ISession>(MockBehavior.Loose);
-        session.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(SdkTelemetry.Context));
+        session.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         session.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         var clock = new ManualClock(new DateTimeOffset(2026, 11, 9, 12, 0, 0, TimeSpan.Zero));
         drv.Clock = clock;
@@ -209,7 +209,7 @@ public sealed class OpcUaClientSlowDeleteTests
         RawTagEntry[] tags = [new(SpeedRef, JsonSerializer.Serialize(new { nodeId = "ns=0;s=Speed" }), WriteIdempotent: true)];
         var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions { RawTags = tags }, "opcua-764");
         var session = new Mock<ISession>(MockBehavior.Loose);
-        session.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(SdkTelemetry.Context));
+        session.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         session.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         var clock = new ManualClock(new DateTimeOffset(2026, 11, 10, 12, 0, 0, TimeSpan.Zero));
         drv.Clock = clock;

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientStaleSessionRaceTests.cs

@@ -46,20 +46,20 @@ public sealed class OpcUaClientStaleSessionRaceTests
         // MessageContext. This getter is read in the driver's synchronous prologue (before the
         // gate), so signalling here proves the pre-gate capture path has run.
         mock.SetupGet(s => s.MessageContext)
-            .Returns(new ServiceMessageContext(ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.SdkTelemetry.Context))
+            .Returns(ServiceMessageContext.Create(ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.SdkTelemetry.Context))
             .Callback(() => prologueReached?.TrySetResult());
         mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         // Acknowledge issues its wire call via CallAsync; stub it so AcknowledgeAsync can run to
         // completion against whichever session it ends up binding to.
         mock.Setup(s => s.CallAsync(
                 It.IsAny<RequestHeader>(),
-                It.IsAny<CallMethodRequestCollection>(),
+                It.IsAny<ArrayOf<CallMethodRequest>>(),
                 It.IsAny<CancellationToken>()))
             .ReturnsAsync(new CallResponse
             {
                 ResponseHeader = new ResponseHeader(),
-                Results = new CallMethodResultCollection(),
-                DiagnosticInfos = new DiagnosticInfoCollection(),
+                Results = new List<CallMethodResult>(),
+                DiagnosticInfos = new List<DiagnosticInfo>(),
             });
         return mock;
     }
@@ -67,10 +67,10 @@ public sealed class OpcUaClientStaleSessionRaceTests
     private static void VerifyAckWireHitNewSessionNotOld(Mock<ISession> newSession, Mock<ISession> oldSession)
     {
         newSession.Verify(s => s.CallAsync(
-            It.IsAny<RequestHeader>(), It.IsAny<CallMethodRequestCollection>(), It.IsAny<CancellationToken>()),
+            It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()),
             Times.Once);
         oldSession.Verify(s => s.CallAsync(
-            It.IsAny<RequestHeader>(), It.IsAny<CallMethodRequestCollection>(), It.IsAny<CancellationToken>()),
+            It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<CallMethodRequest>>(), It.IsAny<CancellationToken>()),
             Times.Never);
     }
 

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientSubscribeCleanupTests.cs

@@ -30,7 +30,7 @@ public sealed class OpcUaClientSubscribeCleanupTests
     {
         var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions { RawTags = Tags }, "opcua-o1");
         var session = new Mock<ISession>(MockBehavior.Loose);
-        session.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(SdkTelemetry.Context));
+        session.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         session.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         drv.SetSessionForTest(session.Object);
         drv.SetNamespaceMapForTest(NamespaceMap.FromTable(new NamespaceTable(), Tags));

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientWriteHealthTests.cs

@@ -28,7 +28,7 @@ public sealed class OpcUaClientWriteHealthTests
     {
         var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions { RawTags = Tags }, "opcua-write-health");
         var session = new Mock<ISession>(MockBehavior.Loose);
-        session.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext(SdkTelemetry.Context));
+        session.SetupGet(s => s.MessageContext).Returns(ServiceMessageContext.Create(SdkTelemetry.Context));
         session.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
         drv.SetSessionForTest(session.Object);
         drv.SetNamespaceMapForTest(NamespaceMap.FromTable(new NamespaceTable(), Tags));
@@ -44,7 +44,7 @@ public sealed class OpcUaClientWriteHealthTests
     {
         var (drv, session) = NewConnectedDriver(new DriverHealth(DriverState.Degraded, Stale, "read failed"));
         using var _ = drv;
-        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<WriteValueCollection>(), It.IsAny<CancellationToken>()))
+        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(new WriteResponse
             {
                 ResponseHeader = new ResponseHeader(),
@@ -54,7 +54,7 @@ public sealed class OpcUaClientWriteHealthTests
 
         var results = await drv.WriteAsync(Write(), TestContext.Current.CancellationToken);
 
-        results.Single().StatusCode.ShouldBe(StatusCodes.BadNotWritable, "the upstream refusal still passes through verbatim");
+        results.Single().StatusCode.ShouldBe(StatusCodes.BadNotWritable.Code, "the upstream refusal still passes through verbatim");
         var h = drv.GetHealth();
         h.State.ShouldBe(DriverState.Healthy);
         h.LastSuccessfulRead.ShouldNotBeNull().ShouldBeGreaterThan(Stale);
@@ -67,7 +67,7 @@ public sealed class OpcUaClientWriteHealthTests
     {
         var (drv, session) = NewConnectedDriver(new DriverHealth(DriverState.Healthy, Stale, null));
         using var _ = drv;
-        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<WriteValueCollection>(), It.IsAny<CancellationToken>()))
+        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()))
             .ThrowsAsync(new ServiceResultException(StatusCodes.BadConnectionClosed));
 
         var results = await drv.WriteAsync(Write(), TestContext.Current.CancellationToken);
@@ -89,8 +89,8 @@ public sealed class OpcUaClientWriteHealthTests
         var (drv, session) = NewConnectedDriver(healthy);
         using var _ = drv;
         using var cts = new CancellationTokenSource();
-        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<WriteValueCollection>(), It.IsAny<CancellationToken>()))
-            .Returns(async (RequestHeader _, WriteValueCollection _, CancellationToken ct) =>
+        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()))
+            .Returns(async (RequestHeader _, ArrayOf<WriteValue> _, CancellationToken ct) =>
             {
                 cts.Cancel();
                 await Task.Delay(Timeout.Infinite, ct);
@@ -128,7 +128,7 @@ public sealed class OpcUaClientWriteHealthTests
     {
         var (drv, session) = NewConnectedDriver(new DriverHealth(DriverState.Healthy, Stale, null));
         using var _ = drv;
-        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<WriteValueCollection>(), It.IsAny<CancellationToken>()))
+        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()))
             .ThrowsAsync(new OperationCanceledException("SDK request timeout"));
 
         var results = await drv.WriteAsync(Write(), TestContext.Current.CancellationToken);
@@ -149,7 +149,7 @@ public sealed class OpcUaClientWriteHealthTests
         using var _ = drv;
         drv.RaiseKeepAliveForTest(StatusCodes.BadNoCommunication);
         drv.GetHealth().State.ShouldBe(DriverState.Degraded, "positive control: the outage is published");
-        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<WriteValueCollection>(), It.IsAny<CancellationToken>()))
+        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(new WriteResponse { ResponseHeader = new ResponseHeader(), Results = [StatusCodes.Good], DiagnosticInfos = [] });
 
         await drv.WriteAsync(Write(), TestContext.Current.CancellationToken);