diff --git a/archreview/plans/R2-08-ldap-historyread-async-plan.md.tasks.json b/archreview/plans/R2-08-ldap-historyread-async-plan.md.tasks.json
index 9f18d8f3..530ed9e9 100644
--- a/archreview/plans/R2-08-ldap-historyread-async-plan.md.tasks.json
+++ b/archreview/plans/R2-08-ldap-historyread-async-plan.md.tasks.json
@@ -7,7 +7,7 @@
     { "id": "R2-08-T4", "subject": "LdapOpcUaUserAuthenticator: WaitAsync wall-clock bound + SemaphoreSlim concurrency cap with release-on-core-completion (turns T1 green)", "status": "completed", "blockedBy": ["R2-08-T1", "R2-08-T2"] },
     { "id": "R2-08-T5", "subject": "Directory-outage circuit: fail-fast deny after N consecutive system-side failures, half-open after cooldown", "status": "completed", "blockedBy": ["R2-08-T3", "R2-08-T4"] },
     { "id": "R2-08-T6", "subject": "Outage-sim integration test (real library, unroutable host, via internal HandleImpersonation) + SDK m_eventLock contract doc + docs/security.md", "status": "completed", "blockedBy": ["R2-08-T4"] },
-    { "id": "R2-08-T7", "subject": "S3 sequential-serving repro test (RED): MaxObservedConcurrency >= 2 on an 8-node Raw batch — fails on current code", "status": "pending", "blockedBy": [] },
+    { "id": "R2-08-T7", "subject": "S3 sequential-serving repro test (RED): MaxObservedConcurrency >= 2 on an 8-node Raw batch — fails on current code", "status": "completed", "blockedBy": [] },
     { "id": "R2-08-T8", "subject": "ServerHistorianOptions: HistoryReadBatchParallelism/MaxConcurrentHistoryReadBatches/HistoryReadDeadline + Validate warnings + node-manager properties + hosted-service wiring", "status": "pending", "blockedBy": [] },
     { "id": "R2-08-T9", "subject": "Async-ify ServeNode + Processed/AtTime arms (ct threading, OCE=>BadTimeout, behavior-neutral)", "status": "pending", "blockedBy": ["R2-08-T7", "R2-08-T8"] },
     { "id": "R2-08-T10", "subject": "Async-ify ServeRawPaged (page read + tie-cluster over-fetch) + extract ServeEventsAsync", "status": "pending", "blockedBy": ["R2-08-T9"] },
diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/NodeManagerHistoryReadConcurrencyTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/NodeManagerHistoryReadConcurrencyTests.cs
new file mode 100644
index 00000000..37599d8a
--- /dev/null
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/NodeManagerHistoryReadConcurrencyTests.cs
@@ -0,0 +1,200 @@
+using System.Diagnostics;
+using Microsoft.Extensions.Logging.Abstractions;
+using Opc.Ua;
+using Opc.Ua.Server;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using HistorianRead = ZB.MOM.WW.OtOpcUa.Core.Abstractions.HistoryReadResult;
+using SdkHistoryReadResult = Opc.Ua.HistoryReadResult;
+
+namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests;
+
+/// <summary>
+///     Arch-review 03/S3 — the node-manager's HistoryRead arms must serve a multi-node batch with BOUNDED
+///     per-node parallelism, a per-request deadline, and a process-wide concurrent-batch limiter, rather
+///     than block-bridging the gateway per node sequentially on an SDK request thread. Boots the same real
+///     <see cref="OtOpcUaSdkServer"/> harness as <see cref="NodeManagerHistoryReadTests"/> and drives the
+///     public <c>HistoryRead</c> with a delaying fake <see cref="IHistorianDataSource"/> that records the
+///     maximum observed concurrent reads (deterministic — no raw-timing dependence for the primary
+///     assertions).
+/// </summary>
+public sealed class NodeManagerHistoryReadConcurrencyTests : IDisposable
+{
+    private static CancellationToken Ct => TestContext.Current.CancellationToken;
+
+    private readonly string _pkiRoot = Path.Combine(
+        Path.GetTempPath(),
+        $"otopcua-historyread-conc-{Guid.NewGuid():N}");
+
+    /// <summary>
+    ///     RED repro (03/S3): a single Raw HistoryRead naming 8 historized nodes against a 150 ms-per-read
+    ///     backend must serve at least two nodes concurrently. On the current sequential <c>foreach</c> the
+    ///     max observed concurrency is pinned at 1, so this fails.
+    /// </summary>
+    [Fact]
+    public async Task Raw_batch_is_served_with_bounded_parallelism()
+    {
+        var (host, server) = await BootAsync();
+        var nm = server.NodeManager!;
+        var fake = new ConcurrencyTrackingHistorianDataSource(TimeSpan.FromMilliseconds(150));
+        nm.HistorianDataSource = fake;
+
+        var nodeIds = MaterializeHistorizedNodes(nm, count: 8);
+
+        var details = new ReadRawModifiedDetails
+        {
+            StartTime = DateTime.UtcNow.AddHours(-1),
+            EndTime = DateTime.UtcNow,
+            NumValuesPerNode = 10,
+            IsReadModified = false,
+        };
+
+        var sw = Stopwatch.StartNew();
+        await Task.Run(() => InvokeHistoryRead(server, nm, details, nodeIds), Ct)
+            .WaitAsync(TimeSpan.FromSeconds(15), Ct);
+        sw.Stop();
+
+        // Primary (deterministic): the batch was served with >1 node in flight at once.
+        fake.MaxObservedConcurrency.ShouldBeGreaterThanOrEqualTo(2);
+
+        await host.DisposeAsync();
+    }
+
+    /// <summary>Materialises <paramref name="count"/> historized Float variables and returns their NodeIds.</summary>
+    private static NodeId[] MaterializeHistorizedNodes(OtOpcUaNodeManager nm, int count)
+    {
+        var ids = new NodeId[count];
+        for (var i = 0; i < count; i++)
+        {
+            var key = $"eq/tag{i}";
+            nm.EnsureVariable(key, parentFolderNodeId: null, displayName: $"Tag{i}", dataType: "Float",
+                writable: false, historianTagname: $"WW.Tag{i}");
+            ids[i] = nm.TryGetVariable(key)!.NodeId;
+        }
+
+        return ids;
+    }
+
+    /// <summary>Issues one HistoryRead batch for all supplied node ids in order.</summary>
+    private static (IList<SdkHistoryReadResult> Results, IList<ServiceResult> Errors) InvokeHistoryRead(
+        OtOpcUaSdkServer server, OtOpcUaNodeManager nm, HistoryReadDetails details, params NodeId[] nodeIds)
+    {
+        var context = new OperationContext(
+            new RequestHeader(), secureChannelContext: null, RequestType.HistoryRead, identity: null);
+
+        var nodesToRead = nodeIds.Select(id => new HistoryReadValueId { NodeId = id }).ToList();
+        var results = Enumerable.Repeat<SdkHistoryReadResult>(null!, nodeIds.Length).ToList();
+        var errors = Enumerable.Repeat<ServiceResult>(null!, nodeIds.Length).ToList();
+
+        nm.HistoryRead(
+            context,
+            details,
+            TimestampsToReturn.Both,
+            releaseContinuationPoints: false,
+            nodesToRead,
+            results,
+            errors);
+
+        return (results, errors);
+    }
+
+    /// <summary>
+    ///     A delaying fake historian source that tracks the maximum number of reads in flight at once
+    ///     (via interlocked live-counter) so a test can prove per-node parallelism deterministically.
+    /// </summary>
+    private sealed class ConcurrencyTrackingHistorianDataSource(TimeSpan delay) : IHistorianDataSource
+    {
+        private int _current;
+        private int _max;
+
+        /// <summary>The highest number of concurrently in-flight reads observed.</summary>
+        public int MaxObservedConcurrency => Volatile.Read(ref _max);
+
+        private async Task<HistorianRead> TrackAsync(CancellationToken ct)
+        {
+            var now = Interlocked.Increment(ref _current);
+            UpdateMax(now);
+            try
+            {
+                await Task.Delay(delay, ct).ConfigureAwait(false);
+            }
+            finally
+            {
+                Interlocked.Decrement(ref _current);
+            }
+
+            return new HistorianRead(
+                new[] { new DataValueSnapshot(1.0f, StatusCodes.Good, DateTime.UtcNow, DateTime.UtcNow) }, null);
+        }
+
+        private void UpdateMax(int observed)
+        {
+            int cur;
+            while ((cur = Volatile.Read(ref _max)) < observed &&
+                   Interlocked.CompareExchange(ref _max, observed, cur) != cur)
+            {
+            }
+        }
+
+        public Task<HistorianRead> ReadRawAsync(
+            string fullReference, DateTime startUtc, DateTime endUtc, uint maxValuesPerNode,
+            CancellationToken cancellationToken) => TrackAsync(cancellationToken);
+
+        public Task<HistorianRead> ReadProcessedAsync(
+            string fullReference, DateTime startUtc, DateTime endUtc, TimeSpan interval,
+            HistoryAggregateType aggregate, CancellationToken cancellationToken) => TrackAsync(cancellationToken);
+
+        public Task<HistorianRead> ReadAtTimeAsync(
+            string fullReference, IReadOnlyList<DateTime> timestampsUtc, CancellationToken cancellationToken) =>
+            TrackAsync(cancellationToken);
+
+        public Task<HistoricalEventsResult> ReadEventsAsync(
+            string? sourceName, DateTime startUtc, DateTime endUtc, int maxEvents,
+            CancellationToken cancellationToken) =>
+            Task.FromResult(new HistoricalEventsResult(Array.Empty<HistoricalEvent>(), null));
+
+        public HistorianHealthSnapshot GetHealthSnapshot() => NullHistorianDataSource.Instance.GetHealthSnapshot();
+
+        public void Dispose()
+        {
+        }
+    }
+
+    private async Task<(OpcUaApplicationHost Host, OtOpcUaSdkServer Server)> BootAsync()
+    {
+        var host = new OpcUaApplicationHost(
+            new OpcUaApplicationHostOptions
+            {
+                ApplicationName = "OtOpcUa.HistoryReadConcTest",
+                ApplicationUri = $"urn:OtOpcUa.HistoryReadConcTest:{Guid.NewGuid():N}",
+                OpcUaPort = AllocateFreePort(),
+                PublicHostname = "localhost",
+                PkiStoreRoot = _pkiRoot,
+            },
+            NullLogger<OpcUaApplicationHost>.Instance);
+
+        var server = new OtOpcUaSdkServer();
+        await host.StartAsync(server, Ct);
+        return (host, server);
+    }
+
+    private static int AllocateFreePort()
+    {
+        using var listener = new System.Net.Sockets.TcpListener(System.Net.IPAddress.Loopback, 0);
+        listener.Start();
+        var port = ((System.Net.IPEndPoint)listener.LocalEndpoint).Port;
+        listener.Stop();
+        return port;
+    }
+
+    /// <summary>Cleans up the PKI root directory.</summary>
+    public void Dispose()
+    {
+        if (Directory.Exists(_pkiRoot))
+        {
+            try { Directory.Delete(_pkiRoot, recursive: true); }
+            catch { /* best-effort cleanup */ }
+        }
+    }
+}