test: verify SDK 2 driver boundaries and lifecycle contracts

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>
+    /// <param name="ownedApplication">The SDK application whose certificate manager this session owns.</param>
-    internal OpcUaClientBrowseSession(ISession session, NamespaceMap nsMap, NodeId rootNodeId, IDisposable? ownedCredential = null)
+    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 name = (At(1)?.WrappedValue.AsBoxedObject() as LocalizedText?)?.Text ?? resolved.ToString() ?? nodeId;
-        var dataType = At(2)?.Value is NodeId dt
+        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 valueRank = At(3)?.WrappedValue.AsBoxedObject() is int vr ? vr : ValueRanks.Scalar;
-        var access = At(4)?.Value is byte ab ? ab : (byte)0;
+        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
+        var displayName = rf.DisplayName.Text
-                          ?? rf.BrowseName?.Name
+                          ?? 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(); }
+        if (_ownedApplication is not null)
-        catch { /* best-effort */ }
+        {
+            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
+            // The SDK application owns its certificate manager until the browse session takes it.
-            // over; any failure before that releases it here instead of leaving it to the GC.
+            if (ownedApplication is not null) await ownedApplication.DisposeAsync().ConfigureAwait(false);
-            ownedCertificate?.Dispose();
             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;
+        try
+        {
+            await config.ValidateAsync(ApplicationType.Client, ct).ConfigureAwait(false);
             await app.CheckApplicationInstanceCertificatesAsync(silent: true, lifeTimeInMonths: null, ct)
                 .ConfigureAwait(false);
-        return config;
+            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) =>
+        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)
     {
+        ct.ThrowIfCancellationRequested();
         var resolved = await OpcUaUserIdentityFactory.ResolveSecretRefsAsync(opts, secretResolver, ct).ConfigureAwait(false);
-        if (resolved.AuthType != OpcUaAuthType.Certificate)
+        return OpcUaUserIdentityFactory.Build(resolved);
-        {
-            return (OpcUaUserIdentityFactory.Build(resolved), null);
-        }
-
-        var certificate = OpcUaUserIdentityFactory.LoadCertificate(resolved);
-        return (new UserIdentity(certificate), certificate);
     }
 
     /// <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.Numeric => $"i={nodeId.IdentifierAsString}",
-        IdType.String => $"s={nodeId.Identifier}",
+        IdType.String => $"s={nodeId.IdentifierAsString}",
-        IdType.Guid => $"g={nodeId.Identifier}",
+        IdType.Guid => $"g={nodeId.IdentifierAsString}",
-        IdType.Opaque => $"b={Convert.ToBase64String((byte[])nodeId.Identifier)}",
+        IdType.Opaque => $"b={nodeId.IdentifierAsString}",
-        _ => $"s={nodeId.Identifier}",
+        _ => 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;
+    private Func<Opc.Ua.Security.Certificates.Certificate, ServiceResult, bool>? _certValidationHandler;
-    /// <summary>The <see cref="CertificateValidator"/> that owns <see cref="_certValidationHandler"/>.</summary>
+    /// <summary>The <see cref="ICertificateManager"/> that owns <see cref="_certValidationHandler"/>.</summary>
-    private CertificateValidator? _certValidatorRef;
+    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 Func<Opc.Ua.Security.Certificates.Certificate, ServiceResult, bool>? Handler { get; set; }
-        public CertificateValidator? Validator { 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);
+                        _driverInstanceId, certificate.Subject, error.StatusCode.Code);
-                    e.Accept = false;
+                    return false;
-                    return;
                 }
-                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;
+            if (server.DiscoveryUrls.IsNull) continue;
-            foreach (var serverDiscoveryUrl in server.DiscoveryUrls)
+            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(
+                    results[r] = ToSnapshot(dv, now);
-                        Value: dv.Value,
-                        StatusCode: dv.StatusCode.Code,
-                        SourceTimestampUtc: dv.SourceTimestamp == DateTime.MinValue ? null : dv.SourceTimestamp,
-                        ServerTimestampUtc: dv.ServerTimestamp == DateTime.MinValue ? now : dv.ServerTimestamp);
                 }
                 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 browseName = rf.BrowseName.Name ?? childId.ToString();
-            var displayName = rf.DisplayName?.Text ?? browseName;
+            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(
+        var snapshot = ToSnapshot(dv, DateTime.UtcNow);
-            Value: dv.Value,
-            StatusCode: dv.StatusCode.Code,
-            SourceTimestampUtc: dv.SourceTimestamp == DateTime.MinValue ? null : dv.SourceTimestamp,
-            ServerTimestampUtc: dv.ServerTimestamp == DateTime.MinValue ? DateTime.UtcNow : dv.ServerTimestamp);
         // 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
+            && UpstreamValueMapping.ToClr(fields[AlarmFieldActiveState]) is bool active
-            && fields[AlarmFieldAckedState].Value is bool acked)
+            && 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 sourceField = UpstreamValueMapping.ToClr(fields[AlarmFieldSourceNode]);
-        var conditionField = fields[AlarmFieldConditionId].Value;
+        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;
+            upstreamCondition = conditionField is NodeId cn && !cn.IsNull ? keyOf(cn) : string.Empty;
-            var sourceKey = sourceField is NodeId sn && !NodeId.IsNull(sn) ? keyOf(sn) : 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 eventType = UpstreamValueMapping.ToClr(fields[AlarmFieldEventType])?.ToString() ?? "BaseEventType";
-        var message = (fields[AlarmFieldMessage].Value as LocalizedText)?.Text ?? string.Empty;
+        var message = (UpstreamValueMapping.ToClr(fields[AlarmFieldMessage]) as LocalizedText?)?.Text ?? string.Empty;
-        var severity = fields[AlarmFieldSeverity].Value is ushort sev ? sev : (ushort)0;
+        var severity = UpstreamValueMapping.ToClr(fields[AlarmFieldSeverity]) is ushort sev ? sev : (ushort)0;
-        var time = fields[AlarmFieldTime].Value is DateTime t ? t : DateTime.UtcNow;
+        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,
+        DataChangeNotification dc => dc.MonitoredItems.Count,
-        EventNotificationList ev => ev.Events?.Count ?? 0,
+        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
+    ///     single-threaded context (OPC UA stack thread). Local session and certificate-manager
-    ///     the SDK's own finalizer on GC (no sync-over-async).
+    ///     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/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>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
-            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, 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,
+                        ContinuationPoint = FakeContinuationPoint.ToByteString(),
-                        References = new ReferenceDescriptionCollection { firstRef },
+                        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>(),
+                    ContinuationPoint = ByteString.Empty,
-                    References = new ReferenceDescriptionCollection(),
+                    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 });
+        f[0] = Variant.From(new ByteString((eventId ?? new byte[] { 1 }).AsMemory()));
-        if (eventType is not null) f[1] = new Variant(eventType);
+        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>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
-            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, 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.BadSessionIdInvalid.Code,
-        StatusCodes.BadSessionClosed,
+        StatusCodes.BadSessionClosed.Code,
-        StatusCodes.BadSessionNotActivated,
+        StatusCodes.BadSessionNotActivated.Code,
-        StatusCodes.BadServerHalted,
+        StatusCodes.BadServerHalted.Code,
     ];
 
     public static TheoryData<uint> AmbiguousStatuses =>
     [
-        StatusCodes.BadNoCommunication,
+        StatusCodes.BadNoCommunication.Code,
-        StatusCodes.BadNotConnected,
+        StatusCodes.BadNotConnected.Code,
-        StatusCodes.BadRequestTimeout,
+        StatusCodes.BadRequestTimeout.Code,
-        StatusCodes.BadTimeout,
+        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,
+            ContinuationPoint = FakeContinuationPoint.ToByteString(),
-            References = new ReferenceDescriptionCollection { firstRef },
+            References = new List<ReferenceDescription> { firstRef },
         };
         var browseResp = new BrowseResponse
         {
             ResponseHeader = new ResponseHeader(),
-            Results = new BrowseResultCollection { browseResult },
+            Results = new List<BrowseResult> { browseResult },
-            DiagnosticInfos = new DiagnosticInfoCollection(),
+            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>(),
+            ContinuationPoint = ByteString.Empty,
-            References = new ReferenceDescriptionCollection(),
+            References = new List<ReferenceDescription>(),
         };
         var releaseResp = new BrowseNextResponse
         {
             ResponseHeader = new ResponseHeader(),
-            Results = new BrowseResultCollection { emptyReleaseResult },
+            Results = new List<BrowseResult> { emptyReleaseResult },
-            DiagnosticInfos = new DiagnosticInfoCollection(),
+            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,
+            ContinuationPoint = FakeContinuationPoint.ToByteString(),
-            References = new ReferenceDescriptionCollection { firstRef },
+            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 },
+                Results = new List<BrowseResult> { browseResult },
-                DiagnosticInfos = new DiagnosticInfoCollection(),
+                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>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
-            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, 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>()))
+        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()))
-            .Returns(async (RequestHeader _, WriteValueCollection nodes, 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>()))
+                It.IsAny<ArrayOf<BrowseDescription>>(), It.IsAny<CancellationToken>()))
-            .Returns(async (RequestHeader _, ViewDescription _, uint _, BrowseDescriptionCollection _, 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>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
-            .Returns(async (RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, 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>()))
+                It.IsAny<ArrayOf<ReadValueId>>(), It.IsAny<CancellationToken>()))
-            .ReturnsAsync((RequestHeader _, double _, TimestampsToReturn _, ReadValueIdCollection nodes, 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(),
+                Results = new List<CallMethodResult>(),
-                DiagnosticInfos = new DiagnosticInfoCollection(),
+                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>()))
+        session.Setup(s => s.WriteAsync(It.IsAny<RequestHeader>(), It.IsAny<ArrayOf<WriteValue>>(), It.IsAny<CancellationToken>()))
-            .Returns(async (RequestHeader _, WriteValueCollection _, CancellationToken ct) =>
+            .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);