diff --git a/src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Commands/ShelveCommand.cs b/src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Commands/ShelveCommand.cs
index 3b962643..0c03386d 100644
--- a/src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Commands/ShelveCommand.cs
+++ b/src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI/Commands/ShelveCommand.cs
@@ -31,9 +31,10 @@ public class ShelveCommand : CommandBase
     public string Kind { get; init; } = default!;
 
     /// <summary>
-    /// Gets the shelving duration in seconds for Timed shelving (ignored for OneShot and Unshelve).
+    /// Gets the shelving duration in seconds for Timed shelving (must be &gt; 0; ignored for OneShot and Unshelve).
+    /// The value is passed in seconds by the operator and converted to milliseconds for the OPC UA TimedShelve call.
     /// </summary>
-    [CommandOption("duration", 'd', Description = "Shelving duration in seconds (required for --kind Timed)")]
+    [CommandOption("duration", 'd', Description = "Shelving duration in seconds (must be > 0; in seconds, converted to milliseconds for the OPC UA call; required for --kind Timed)")]
     public double DurationSeconds { get; init; }
 
     /// <summary>
@@ -61,9 +62,9 @@ public class ShelveCommand : CommandBase
             var statusCode = await service.ShelveAlarmAsync(NodeId, shelveKind, DurationSeconds, ct);
 
             if (StatusCode.IsGood(statusCode))
-                await console.Output.WriteLineAsync($"Shelve ({shelveKind}) successful: {NodeId}");
+                await console.Output.WriteLineAsync($"{shelveKind} successful: {NodeId}");
             else
-                await console.Output.WriteLineAsync($"Shelve ({shelveKind}) failed: {statusCode}");
+                await console.Output.WriteLineAsync($"{shelveKind} failed: {statusCode}");
         }
         finally
         {
diff --git a/src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/IOpcUaClientService.cs b/src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/IOpcUaClientService.cs
index 8d9d5916..2eafcbd4 100644
--- a/src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/IOpcUaClientService.cs
+++ b/src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/IOpcUaClientService.cs
@@ -123,7 +123,9 @@ public interface IOpcUaClientService : IDisposable
     /// <param name="conditionNodeId">The condition node associated with the alarm being shelved.</param>
     /// <param name="kind">The shelve operation: <c>OneShot</c>, <c>Timed</c>, or <c>Unshelve</c>.</param>
     /// <param name="shelvingTimeSeconds">
-    /// For <c>Timed</c> shelving: the shelving duration in seconds. Ignored for <c>OneShot</c> and <c>Unshelve</c>.
+    /// For <c>Timed</c> shelving: the shelving duration in seconds (must be &gt; 0).
+    /// This value is converted to milliseconds when passed to the OPC UA <c>TimedShelve</c> method
+    /// (<c>Duration</c> is milliseconds per OPC UA Part 9). Ignored for <c>OneShot</c> and <c>Unshelve</c>.
     /// </param>
     /// <param name="ct">The cancellation token that aborts the shelve request.</param>
     /// <returns>
diff --git a/src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/OpcUaClientService.cs b/src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/OpcUaClientService.cs
index 45d88aec..28d9870c 100644
--- a/src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/OpcUaClientService.cs
+++ b/src/Client/ZB.MOM.WW.OtOpcUa.Client.Shared/OpcUaClientService.cs
@@ -417,7 +417,9 @@ public sealed class OpcUaClientService : IOpcUaClientService
 
         // The shelve methods live on the ShelvingState child of the condition node.
         // conditionNodeId is the alarm/condition node; append .ShelvingState to get the state machine node.
-        var shelvingStateNodeId = NodeId.Parse(conditionNodeId + ".ShelvingState");
+        var shelvingStateNodeId = conditionNodeId.EndsWith(".ShelvingState")
+            ? NodeId.Parse(conditionNodeId)
+            : NodeId.Parse(conditionNodeId + ".ShelvingState");
 
         NodeId methodId;
         object[] inputArgs;
@@ -433,7 +435,8 @@ public sealed class OpcUaClientService : IOpcUaClientService
                     throw new ArgumentOutOfRangeException(nameof(shelvingTimeSeconds),
                         "Timed shelving requires a positive shelvingTimeSeconds value.");
                 methodId = MethodIds.AlarmConditionType_ShelvingState_TimedShelve;
-                inputArgs = [shelvingTimeSeconds];
+                // OPC UA Part 9 TimedShelve ShelvingTime input is a Duration (Double) in milliseconds.
+                inputArgs = [shelvingTimeSeconds * 1000.0];
                 break;
             case ShelveKind.Unshelve:
                 methodId = MethodIds.AlarmConditionType_ShelvingState_Unshelve;
diff --git a/tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeSessionAdapter.cs b/tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeSessionAdapter.cs
index d5ea10e6..5abf1068 100644
--- a/tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeSessionAdapter.cs
+++ b/tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeSessionAdapter.cs
@@ -202,11 +202,18 @@ internal sealed class FakeSessionAdapter : ISessionAdapter
     /// </summary>
     public Exception? CallMethodException { get; set; }
 
+    /// <summary>
+    /// Records the input arguments passed to each <see cref="CallMethodAsync"/> invocation.
+    /// Index 0 is the first call, index 1 the second, etc.
+    /// </summary>
+    public List<object[]> CallMethodInputArgs { get; } = [];
+
     /// <inheritdoc />
     public Task<IList<object>?> CallMethodAsync(NodeId objectId, NodeId methodId, object[] inputArguments,
         CancellationToken ct = default)
     {
         CallMethodCount++;
+        CallMethodInputArgs.Add(inputArguments);
         if (CallMethodException != null)
             throw CallMethodException;
         return Task.FromResult<IList<object>?>(null);
diff --git a/tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/OpcUaClientServiceTests.cs b/tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/OpcUaClientServiceTests.cs
index 0213728b..5f4d3d07 100644
--- a/tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/OpcUaClientServiceTests.cs
+++ b/tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/OpcUaClientServiceTests.cs
@@ -1057,6 +1057,123 @@ public class OpcUaClientServiceTests : IDisposable
         session.CallMethodCount.ShouldBe(1);
     }
 
+    // --- ConfirmAlarm tests ---
+
+    /// <summary>
+    /// Verifies that a successful confirm call returns <see cref="StatusCodes.Good"/>
+    /// and reaches the session adapter's CallMethodAsync exactly once.
+    /// </summary>
+    [Fact]
+    public async Task ConfirmAlarmAsync_OnSuccess_ReturnsGood()
+    {
+        var session = new FakeSessionAdapter();
+        _sessionFactory.EnqueueSession(session);
+        await _service.ConnectAsync(ValidSettings());
+
+        var result = await _service.ConfirmAlarmAsync("ns=2;s=Cond", new byte[] { 1, 2 }, "confirmed");
+
+        result.ShouldBe(StatusCodes.Good);
+        session.CallMethodCount.ShouldBe(1);
+    }
+
+    /// <summary>
+    /// Verifies that a <see cref="ServiceResultException"/> from the session is captured and returned
+    /// as a bad <see cref="StatusCode"/> rather than propagating to the caller.
+    /// </summary>
+    [Fact]
+    public async Task ConfirmAlarmAsync_OnServiceResultException_ReturnsBadStatusCode()
+    {
+        var session = new FakeSessionAdapter
+        {
+            CallMethodException = new ServiceResultException(
+                StatusCodes.BadConditionAlreadyEnabled, "already confirmed")
+        };
+        _sessionFactory.EnqueueSession(session);
+        await _service.ConnectAsync(ValidSettings());
+
+        var result = await _service.ConfirmAlarmAsync("ns=2;s=Cond", new byte[] { 1, 2 }, "confirmed");
+
+        StatusCode.IsBad(result).ShouldBeTrue();
+        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyEnabled);
+    }
+
+    // --- ShelveAlarm tests ---
+
+    /// <summary>
+    /// Verifies that OneShot shelving calls the session adapter once with no input arguments.
+    /// </summary>
+    [Fact]
+    public async Task ShelveAlarmAsync_OneShot_CallsMethodWithNoArgs()
+    {
+        var session = new FakeSessionAdapter();
+        _sessionFactory.EnqueueSession(session);
+        await _service.ConnectAsync(ValidSettings());
+
+        var result = await _service.ShelveAlarmAsync("ns=2;s=Cond", ShelveKind.OneShot);
+
+        result.ShouldBe(StatusCodes.Good);
+        session.CallMethodCount.ShouldBe(1);
+        session.CallMethodInputArgs[0].ShouldBeEmpty();
+    }
+
+    /// <summary>
+    /// Verifies that Timed shelving passes the duration converted to milliseconds (seconds × 1000)
+    /// as the first input argument — regression guard for the Important 1 units bug.
+    /// </summary>
+    [Fact]
+    public async Task ShelveAlarmAsync_Timed_PassesDurationInMilliseconds()
+    {
+        var session = new FakeSessionAdapter();
+        _sessionFactory.EnqueueSession(session);
+        await _service.ConnectAsync(ValidSettings());
+
+        const double durationSeconds = 30.0;
+        var result = await _service.ShelveAlarmAsync("ns=2;s=Cond", ShelveKind.Timed, durationSeconds);
+
+        result.ShouldBe(StatusCodes.Good);
+        session.CallMethodCount.ShouldBe(1);
+        session.CallMethodInputArgs[0].Length.ShouldBe(1);
+        session.CallMethodInputArgs[0][0].ShouldBe(durationSeconds * 1000.0);
+    }
+
+    /// <summary>
+    /// Verifies that Unshelve calls the session adapter once with no input arguments.
+    /// </summary>
+    [Fact]
+    public async Task ShelveAlarmAsync_Unshelve_CallsMethodWithNoArgs()
+    {
+        var session = new FakeSessionAdapter();
+        _sessionFactory.EnqueueSession(session);
+        await _service.ConnectAsync(ValidSettings());
+
+        var result = await _service.ShelveAlarmAsync("ns=2;s=Cond", ShelveKind.Unshelve);
+
+        result.ShouldBe(StatusCodes.Good);
+        session.CallMethodCount.ShouldBe(1);
+        session.CallMethodInputArgs[0].ShouldBeEmpty();
+    }
+
+    /// <summary>
+    /// Verifies that a <see cref="ServiceResultException"/> from the session is captured and returned
+    /// as a bad <see cref="StatusCode"/> rather than propagating to the caller.
+    /// </summary>
+    [Fact]
+    public async Task ShelveAlarmAsync_OnServiceResultException_ReturnsBadStatusCode()
+    {
+        var session = new FakeSessionAdapter
+        {
+            CallMethodException = new ServiceResultException(
+                StatusCodes.BadConditionAlreadyShelved, "already shelved")
+        };
+        _sessionFactory.EnqueueSession(session);
+        await _service.ConnectAsync(ValidSettings());
+
+        var result = await _service.ShelveAlarmAsync("ns=2;s=Cond", ShelveKind.OneShot);
+
+        StatusCode.IsBad(result).ShouldBeTrue();
+        result.Code.ShouldBe(StatusCodes.BadConditionAlreadyShelved);
+    }
+
     // --- Alarm fallback path (Client.Shared-011) ---
 
     /// <summary>