diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayTagProvisioner.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayTagProvisioner.cs
index 986f82ab..b160f04f 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayTagProvisioner.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayTagProvisioner.cs
@@ -17,7 +17,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway;
 ///     as <see cref="HistorianProvisionResult.Failed"/> and returns. The method never throws and never
 ///     logs tag values, hostnames, or credentials.
 /// </remarks>
-public sealed class GatewayTagProvisioner : IHistorianProvisioning
+public sealed class GatewayTagProvisioner : IHistorianProvisioning, IAsyncDisposable
 {
     /// <summary>
     ///     Storage rate (ms) stamped on every provisioned analog tag. The gateway's <c>EnsureTags</c> path
@@ -104,4 +104,13 @@ public sealed class GatewayTagProvisioner : IHistorianProvisioning
             return new HistorianProvisionResult(requests.Count, Ensured: 0, Skipped: skipped, Failed: definitions.Count);
         }
     }
+
+    /// <summary>
+    ///     Disposes the underlying gateway client (and its gRPC channel). The DI container owns this
+    ///     provisioner as a singleton (<c>AddHistorianProvisioning</c>), so this fires once at host
+    ///     shutdown — closing the channel gracefully, matching the read (<see cref="GatewayHistorianDataSource"/>)
+    ///     and alarm-write (<see cref="GatewayAlarmHistorianWriter"/>) paths' dispose ownership.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    public ValueTask DisposeAsync() => _client.DisposeAsync();
 }
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/Mapping/AlarmEventMapper.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/Mapping/AlarmEventMapper.cs
index a0112dcd..bdda3fc5 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/Mapping/AlarmEventMapper.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/Mapping/AlarmEventMapper.cs
@@ -1,5 +1,6 @@
 using Google.Protobuf.WellKnownTypes;
 using ZB.MOM.WW.HistorianGateway.Contracts.Grpc;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 using ZB.MOM.WW.OtOpcUa.Core.AlarmHistorian;
 
 namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Mapping;
@@ -10,6 +11,25 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Mapping;
 /// </summary>
 internal static class AlarmEventMapper
 {
+    /// <summary>
+    /// Maps <see cref="AlarmSeverity"/> to the numeric OPC UA Part 9 priority (1-1000) carried in the
+    /// wire event's <c>Severity</c> property, per the <see cref="AlarmHistorianEvent.Severity"/>
+    /// contract ("Mapped to Historian's numeric priority on the sink side"). The read side
+    /// (<see cref="EventMapper.ToHistoricalEvent"/>) <c>int.TryParse</c>s this same property, so it
+    /// must stay a numeric string — the enum's <c>.ToString()</c> name (e.g. "High") is NOT
+    /// parseable and used to silently collapse every read-back severity to the minimum (1). The
+    /// values mirror the existing native-alarm convention
+    /// (<c>ZB.MOM.WW.OtOpcUa.Runtime.Drivers.NativeAlarmProjector.MapSeverity</c>).
+    /// </summary>
+    private static string ToNumericSeverity(AlarmSeverity severity) => severity switch
+    {
+        AlarmSeverity.Low => "200",
+        AlarmSeverity.Medium => "500",
+        AlarmSeverity.High => "700",
+        AlarmSeverity.Critical => "900",
+        _ => "500",
+    };
+
     /// <summary>Maps an alarm historian event to a gateway event.</summary>
     /// <param name="alarm">The driver-agnostic alarm event.</param>
     /// <returns>The gateway wire event ready for <c>SendEvent</c>.</returns>
@@ -36,7 +56,7 @@ internal static class AlarmEventMapper
             historianEvent.Properties["AlarmId"] = alarm.AlarmId;
         historianEvent.Properties["AlarmName"] = alarm.AlarmName;
         historianEvent.Properties["EventKind"] = alarm.EventKind;
-        historianEvent.Properties["Severity"] = alarm.Severity.ToString();
+        historianEvent.Properties["Severity"] = ToNumericSeverity(alarm.Severity);
         historianEvent.Properties["User"] = alarm.User;
         historianEvent.Properties["Message"] = alarm.Message;
         if (alarm.Comment is not null)
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayTagProvisionerTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayTagProvisionerTests.cs
index b03a9af9..798a0dca 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayTagProvisionerTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayTagProvisionerTests.cs
@@ -149,6 +149,27 @@ public sealed class GatewayTagProvisionerTests
         Assert.Equal(1, result.Failed); // non-blocking: no throw
     }
 
+    /// <summary>
+    /// Driver.Historian.Gateway-002: unlike its siblings (<c>GatewayHistorianDataSource</c>,
+    /// <c>GatewayAlarmHistorianWriter</c>), <see cref="GatewayTagProvisioner"/> had no dispose path at
+    /// all — the gRPC channel <c>GatewayHistorian.CreateProvisioner</c> opens was never closed. The
+    /// provisioner is registered as a process-lifetime DI singleton
+    /// (<c>AddHistorianProvisioning</c>), and the built-in container disposes any singleton instance
+    /// it creates that implements <see cref="IAsyncDisposable"/>/<see cref="IDisposable"/> — regardless
+    /// of the registered service-interface type — so implementing it here is sufficient for a clean
+    /// shutdown with no other wiring change.
+    /// </summary>
+    [Fact]
+    public async Task DisposeAsync_disposes_underlying_client()
+    {
+        var fake = new FakeHistorianGatewayClient();
+        var p = Provisioner(fake);
+
+        await ((IAsyncDisposable)p).DisposeAsync();
+
+        Assert.Equal(1, fake.DisposeCallCount);
+    }
+
     [Fact]
     public async Task Ensured_count_reflects_successful_results()
     {
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/Mapping/AlarmEventMapperTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/Mapping/AlarmEventMapperTests.cs
index f26784ec..e0b489b1 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/Mapping/AlarmEventMapperTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/Mapping/AlarmEventMapperTests.cs
@@ -23,12 +23,41 @@ public sealed class AlarmEventMapperTests
         Assert.Equal("A1", e.Properties["AlarmId"]);
         Assert.Equal("HiHi", e.Properties["AlarmName"]);
         Assert.Equal("Activated", e.Properties["EventKind"]);
-        Assert.Equal("High", e.Properties["Severity"]);
+        // Severity is the AlarmHistorianEvent.Severity XML doc contract: "Mapped to Historian's
+        // numeric priority on the sink side" — NOT the .NET enum name. EventMapper.ParseSeverity on
+        // the read side int.TryParse()s this same property, so a non-numeric string (the old bug:
+        // alarm.Severity.ToString() == "High") silently always read back as the minimum severity (1).
+        Assert.Equal("700", e.Properties["Severity"]);
         Assert.Equal("operator1", e.Properties["User"]);
         Assert.Equal("ack note", e.Properties["Comment"]);
         Assert.Equal("Temp high", e.Properties["Message"]);
     }
 
+    /// <summary>
+    /// Driver.Historian.Gateway-001 regression: the write side (<see cref="AlarmEventMapper"/>) and
+    /// the read side (<see cref="EventMapper"/>) must agree on the wire representation of severity —
+    /// a numeric OPC UA Part 9 priority string, matching the convention already used elsewhere in the
+    /// codebase for the same enum (<c>NativeAlarmProjector.MapSeverity</c>: Low=200/Medium=500/
+    /// High=700/Critical=900). Round-tripping through both mappers must reproduce the numeric severity,
+    /// not collapse to the minimum every time.
+    /// </summary>
+    [Theory]
+    [InlineData(AlarmSeverity.Low, (ushort)200)]
+    [InlineData(AlarmSeverity.Medium, (ushort)500)]
+    [InlineData(AlarmSeverity.High, (ushort)700)]
+    [InlineData(AlarmSeverity.Critical, (ushort)900)]
+    public void Severity_round_trips_through_EventMapper_as_numeric_priority(AlarmSeverity severity, ushort expected)
+    {
+        var a = new AlarmHistorianEvent("A1", "Area/Line/Pump1", "HiHi", "LimitAlarm",
+            severity, "Activated", "m", "operator1", null,
+            new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc));
+
+        var wire = AlarmEventMapper.ToHistorianEvent(a);
+        var readBack = EventMapper.ToHistoricalEvent(wire);
+
+        Assert.Equal(expected, readBack.Severity);
+    }
+
     [Fact]
     public void Null_comment_is_omitted_not_null()
     {