diff --git a/src/Core/ZB.MOM.WW.OtOpcUa.Commons/Messages/Audit/AuditEvent.cs b/src/Core/ZB.MOM.WW.OtOpcUa.Commons/Messages/Audit/AuditEvent.cs
deleted file mode 100644
index ed12a26f..00000000
--- a/src/Core/ZB.MOM.WW.OtOpcUa.Commons/Messages/Audit/AuditEvent.cs
+++ /dev/null
@@ -1,17 +0,0 @@
-using ZB.MOM.WW.OtOpcUa.Commons.Types;
-
-namespace ZB.MOM.WW.OtOpcUa.Commons.Messages.Audit;
-
-/// <summary>
-/// Cluster-broadcast audit event consumed by the <c>AuditWriterActor</c> singleton, which
-/// batches and idempotently inserts into <c>ConfigAuditLog</c>.
-/// </summary>
-public sealed record AuditEvent(
-    Guid EventId,
-    string Category,
-    string Action,
-    string Actor,
-    DateTime OccurredAtUtc,
-    string? DetailsJson,
-    NodeId SourceNode,
-    CorrelationId CorrelationId);
diff --git a/src/Core/ZB.MOM.WW.OtOpcUa.Commons/ZB.MOM.WW.OtOpcUa.Commons.csproj b/src/Core/ZB.MOM.WW.OtOpcUa.Commons/ZB.MOM.WW.OtOpcUa.Commons.csproj
index e92789a1..f90281ea 100644
--- a/src/Core/ZB.MOM.WW.OtOpcUa.Commons/ZB.MOM.WW.OtOpcUa.Commons.csproj
+++ b/src/Core/ZB.MOM.WW.OtOpcUa.Commons/ZB.MOM.WW.OtOpcUa.Commons.csproj
@@ -7,6 +7,7 @@
 
     <ItemGroup>
         <PackageReference Include="Akka"/>
+        <PackageReference Include="ZB.MOM.WW.Audit"/>
     </ItemGroup>
 
 </Project>
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Audit/AuditOutcomeMapper.cs b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Audit/AuditOutcomeMapper.cs
new file mode 100644
index 00000000..c3e15072
--- /dev/null
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Audit/AuditOutcomeMapper.cs
@@ -0,0 +1,44 @@
+using ZB.MOM.WW.Audit;
+
+namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Audit;
+
+/// <summary>
+/// Maps OtOpcUa's audit <c>Action</c> vocabulary onto the canonical
+/// <see cref="AuditOutcome"/>. The vocabulary is the set of values documented on
+/// <c>ConfigAuditLog.EventType</c>: config verbs are <see cref="AuditOutcome.Success"/>,
+/// the two authorization-rejection events are <see cref="AuditOutcome.Denied"/>. OtOpcUa
+/// emits no <see cref="AuditOutcome.Failure"/> events today.
+/// </summary>
+/// <remarks>
+/// Pure function — no live emit sites construct an <see cref="AuditEvent"/> in production
+/// (the structured audit path is dormant; all live audit flows through the bespoke stored
+/// procedure path). This helper exists so that when the structured path is wired up, the
+/// required <c>Outcome</c> field is derived consistently from the action verb. Tested, not
+/// yet exercised in production.
+/// </remarks>
+public static class AuditOutcomeMapper
+{
+    /// <summary>
+    /// Derives the canonical <see cref="AuditOutcome"/> for an OtOpcUa audit action verb.
+    /// Unknown verbs default to <see cref="AuditOutcome.Success"/> (config writes are the
+    /// overwhelming majority and the only non-success cases are the two explicit
+    /// authorization rejections enumerated below).
+    /// </summary>
+    /// <param name="action">The audit action verb (e.g. <c>DraftCreated</c>, <c>OpcUaAccessDenied</c>).</param>
+    /// <returns>The mapped outcome.</returns>
+    public static AuditOutcome FromAction(string action) => action switch
+    {
+        "OpcUaAccessDenied" or "CrossClusterNamespaceAttempt" => AuditOutcome.Denied,
+        "DraftCreated"
+            or "DraftEdited"
+            or "Published"
+            or "RolledBack"
+            or "NodeApplied"
+            or "ClusterCreated"
+            or "NodeAdded"
+            or "CredentialAdded"
+            or "CredentialDisabled"
+            or "ExternalIdReleased" => AuditOutcome.Success,
+        _ => AuditOutcome.Success,
+    };
+}
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Audit/AuditWriterActor.cs b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Audit/AuditWriterActor.cs
index 96922799..00099bca 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Audit/AuditWriterActor.cs
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Audit/AuditWriterActor.cs
@@ -1,7 +1,7 @@
 using Akka.Actor;
 using Akka.Event;
 using Microsoft.EntityFrameworkCore;
-using ZB.MOM.WW.OtOpcUa.Commons.Messages.Audit;
+using ZB.MOM.WW.Audit;
 using ZB.MOM.WW.OtOpcUa.Configuration;
 using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
 
@@ -19,8 +19,13 @@ namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Audit;
 /// <c>UX_ConfigAuditLog_EventId</c> (cross-restart safety — a retry of an already-flushed
 /// batch hits the constraint and we drop the duplicate insert without losing the rest of
 /// the batch).
+///
+/// Implements the shared <see cref="IAuditWriter"/> seam: <see cref="WriteAsync"/> is a
+/// best-effort, never-throwing entry point that simply <c>Tell</c>s this actor and returns
+/// a completed task, so non-Akka callers can emit canonical audit events through the same
+/// batching/dedup pipeline as in-cluster <c>Tell</c> traffic.
 /// </summary>
-public sealed class AuditWriterActor : ReceiveActor, IWithTimers
+public sealed class AuditWriterActor : ReceiveActor, IWithTimers, IAuditWriter
 {
     public const int FlushBatchSize = 500;
     public static readonly TimeSpan FlushInterval = TimeSpan.FromSeconds(5);
@@ -52,6 +57,23 @@ public sealed class AuditWriterActor : ReceiveActor, IWithTimers
         Timers.StartPeriodicTimer("flush", Flush.Instance, FlushInterval);
     }
 
+    /// <summary>
+    /// <see cref="IAuditWriter"/> seam. Best-effort and never throws: routes the event onto this
+    /// actor's mailbox via <c>Tell</c> (thread-safe from any caller) so it flows through the same
+    /// batching + dedup pipeline as in-cluster traffic, then returns immediately. The actual
+    /// persistence happens asynchronously on the next flush; a write failure there is logged and
+    /// the batch dropped (per the best-effort audit contract).
+    /// </summary>
+    /// <param name="evt">The canonical audit event to persist.</param>
+    /// <param name="ct">Unused — enqueue is synchronous and non-blocking.</param>
+    /// <returns>A completed task.</returns>
+    public Task WriteAsync(AuditEvent evt, CancellationToken ct = default)
+    {
+        // Akka Tell is safe to call from any thread and never throws to the caller.
+        Self.Tell(evt);
+        return Task.CompletedTask;
+    }
+
     private void HandleEvent(AuditEvent evt)
     {
         // In-buffer dedup. Last write wins on duplicate EventId within the batch — events
@@ -74,13 +96,13 @@ public sealed class AuditWriterActor : ReceiveActor, IWithTimers
             {
                 db.ConfigAuditLogs.Add(new ConfigAuditLog
                 {
-                    Timestamp = evt.OccurredAtUtc,
+                    Timestamp = evt.OccurredAtUtc.UtcDateTime,
                     Principal = evt.Actor,
                     EventType = $"{evt.Category}:{evt.Action}",
-                    NodeId = evt.SourceNode.Value,
+                    NodeId = evt.SourceNode,
                     DetailsJson = evt.DetailsJson,
                     EventId = evt.EventId,
-                    CorrelationId = evt.CorrelationId.Value,
+                    CorrelationId = evt.CorrelationId,
                 });
             }
             db.SaveChanges();
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/ZB.MOM.WW.OtOpcUa.ControlPlane.csproj b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/ZB.MOM.WW.OtOpcUa.ControlPlane.csproj
index 57565199..6993960c 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/ZB.MOM.WW.OtOpcUa.ControlPlane.csproj
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/ZB.MOM.WW.OtOpcUa.ControlPlane.csproj
@@ -15,6 +15,7 @@
         <PackageReference Include="Akka.Cluster.Hosting"/>
         <PackageReference Include="Akka.Cluster.Tools"/>
         <PackageReference Include="Microsoft.EntityFrameworkCore"/>
+        <PackageReference Include="ZB.MOM.WW.Audit"/>
     </ItemGroup>
 
     <ItemGroup>
diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/AuditWriterActorTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/AuditWriterActorTests.cs
index 60a5002c..685e2cba 100644
--- a/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/AuditWriterActorTests.cs
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/AuditWriterActorTests.cs
@@ -1,8 +1,7 @@
 using Akka.Actor;
 using Shouldly;
 using Xunit;
-using ZB.MOM.WW.OtOpcUa.Commons.Messages.Audit;
-using ZB.MOM.WW.OtOpcUa.Commons.Types;
+using ZB.MOM.WW.Audit;
 using ZB.MOM.WW.OtOpcUa.ControlPlane.Audit;
 using ZB.MOM.WW.OtOpcUa.ControlPlane.Tests.Harness;
 
@@ -11,15 +10,18 @@ namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests;
 public sealed class AuditWriterActorTests : ControlPlaneActorTestBase
 {
     private static AuditEvent NewEvent(Guid eventId, string action = "Edit", string actor = "joe") =>
-        new(
-            eventId,
-            "Config",
-            action,
-            actor,
-            DateTime.UtcNow,
-            DetailsJson: "{\"field\":\"value\"}",
-            SourceNode: NodeId.Parse("node-a"),
-            CorrelationId: CorrelationId.NewId());
+        new()
+        {
+            EventId = eventId,
+            Category = "Config",
+            Action = action,
+            Actor = actor,
+            OccurredAtUtc = DateTimeOffset.UtcNow,
+            Outcome = AuditOutcomeMapper.FromAction(action),
+            DetailsJson = "{\"field\":\"value\"}",
+            SourceNode = "node-a",
+            CorrelationId = Guid.NewGuid(),
+        };
 
     /// <summary>Verifies that buffered events flush when count threshold is reached.</summary>
     [Fact]
@@ -102,4 +104,91 @@ public sealed class AuditWriterActorTests : ControlPlaneActorTestBase
         row.EventType.ShouldBe("Config:Edit");
         row.NodeId.ShouldBe("node-a");
     }
+
+    /// <summary>Verifies that a null SourceNode/CorrelationId on the canonical event persists as null
+    /// (the canonical fields are now nullable; the actor must not assume they are set).</summary>
+    [Fact]
+    public void Null_sourceNode_and_correlationId_persist_as_null()
+    {
+        var dbFactory = NewInMemoryDbFactory();
+        var actor = Sys.ActorOf(AuditWriterActor.Props(dbFactory));
+
+        actor.Tell(new AuditEvent
+        {
+            EventId = Guid.NewGuid(),
+            Category = "Config",
+            Action = "Published",
+            Actor = "joe",
+            OccurredAtUtc = DateTimeOffset.UtcNow,
+            Outcome = AuditOutcome.Success,
+            SourceNode = null,
+            CorrelationId = null,
+        });
+
+        Watch(actor);
+        actor.Tell(PoisonPill.Instance);
+        ExpectTerminated(actor);
+
+        using var db = dbFactory.CreateDbContext();
+        var row = db.ConfigAuditLogs.Single();
+        row.NodeId.ShouldBeNull();
+        row.CorrelationId.ShouldBeNull();
+    }
+
+    /// <summary>Verifies the IAuditWriter.WriteAsync seam is best-effort: it completes
+    /// synchronously, never throws, and routes the event onto the actor's own mailbox
+    /// (<c>Self.Tell</c>) — i.e. the same buffer + dedup + flush pipeline asserted by the Tell
+    /// tests above. Reaches the concrete instance via a TestActorRef.</summary>
+    [Fact]
+    public async Task WriteAsync_is_best_effort_and_routes_onto_the_actor_mailbox()
+    {
+        var dbFactory = NewInMemoryDbFactory();
+        var testRef = ActorOfAsTestActorRef<AuditWriterActor>(AuditWriterActor.Props(dbFactory));
+        IAuditWriter writer = testRef.UnderlyingActor;
+
+        var task = writer.WriteAsync(NewEvent(Guid.NewGuid(), action: "Published"));
+        task.IsCompletedSuccessfully.ShouldBeTrue("WriteAsync must be best-effort and complete synchronously");
+        await Should.NotThrowAsync(async () => await task);
+    }
+
+    /// <summary>Verifies that an AuditEvent delivered to the actor's mailbox — which is exactly
+    /// what the WriteAsync seam does via Self.Tell — is buffered and persisted with the canonical
+    /// fields intact.</summary>
+    [Fact]
+    public void Mailbox_delivery_persists_the_canonical_fields()
+    {
+        var dbFactory = NewInMemoryDbFactory();
+        var actor = Sys.ActorOf(AuditWriterActor.Props(dbFactory));
+
+        var eventId = Guid.NewGuid();
+        actor.Tell(NewEvent(eventId, action: "Published"));
+
+        Watch(actor);
+        actor.Tell(PoisonPill.Instance);
+        ExpectTerminated(actor);
+
+        using var db = dbFactory.CreateDbContext();
+        var row = db.ConfigAuditLogs.Single();
+        row.EventId.ShouldBe(eventId);
+        row.EventType.ShouldBe("Config:Published");
+        row.NodeId.ShouldBe("node-a");
+    }
+
+    /// <summary>Verifies the Outcome derivation table: config verbs → Success, the two
+    /// authorization-rejection events → Denied.</summary>
+    [Theory]
+    [InlineData("DraftCreated", AuditOutcome.Success)]
+    [InlineData("DraftEdited", AuditOutcome.Success)]
+    [InlineData("Published", AuditOutcome.Success)]
+    [InlineData("RolledBack", AuditOutcome.Success)]
+    [InlineData("NodeApplied", AuditOutcome.Success)]
+    [InlineData("ClusterCreated", AuditOutcome.Success)]
+    [InlineData("NodeAdded", AuditOutcome.Success)]
+    [InlineData("CredentialAdded", AuditOutcome.Success)]
+    [InlineData("CredentialDisabled", AuditOutcome.Success)]
+    [InlineData("ExternalIdReleased", AuditOutcome.Success)]
+    [InlineData("OpcUaAccessDenied", AuditOutcome.Denied)]
+    [InlineData("CrossClusterNamespaceAttempt", AuditOutcome.Denied)]
+    public void Outcome_is_derived_from_the_action_vocabulary(string action, AuditOutcome expected) =>
+        AuditOutcomeMapper.FromAction(action).ShouldBe(expected);
 }