diff --git a/SVSim.BattleNode/Reliability/OutboundSequencer.cs b/SVSim.BattleNode/Reliability/OutboundSequencer.cs
new file mode 100644
index 0000000..da7d7a3
--- /dev/null
+++ b/SVSim.BattleNode/Reliability/OutboundSequencer.cs
@@ -0,0 +1,27 @@
+using SVSim.BattleNode.Protocol;
+
+namespace SVSim.BattleNode.Reliability;
+
+/// <summary>
+/// Per-session outbound ledger. Assigns monotonic playSeq to ordered pushes and archives
+/// them for future Resume retransmit (v2). No-stock control pushes (BattleFinish/JudgeResult/Resume)
+/// are wrapped with no playSeq and skip the archive.
+/// </summary>
+public sealed class OutboundSequencer
+{
+    private long _next = 1;
+    private readonly Dictionary<long, MsgEnvelope> _archive = new();
+
+    public IReadOnlyDictionary<long, MsgEnvelope> Archive => _archive;
+
+    public MsgEnvelope AssignAndArchive(MsgEnvelope envelope)
+    {
+        var seq = _next++;
+        var stamped = envelope with { PlaySeq = seq };
+        _archive[seq] = stamped;
+        return stamped;
+    }
+
+    public MsgEnvelope WrapNoStock(MsgEnvelope envelope) =>
+        envelope with { PlaySeq = null };
+}
diff --git a/SVSim.UnitTests/BattleNode/Reliability/OutboundSequencerTests.cs b/SVSim.UnitTests/BattleNode/Reliability/OutboundSequencerTests.cs
new file mode 100644
index 0000000..21e0698
--- /dev/null
+++ b/SVSim.UnitTests/BattleNode/Reliability/OutboundSequencerTests.cs
@@ -0,0 +1,52 @@
+using NUnit.Framework;
+using SVSim.BattleNode.Protocol;
+using SVSim.BattleNode.Reliability;
+
+namespace SVSim.UnitTests.BattleNode.Reliability;
+
+[TestFixture]
+public class OutboundSequencerTests
+{
+    private static MsgEnvelope MakeEnvelope(NetworkBattleUri uri) =>
+        new(uri, ViewerId: 1, Uuid: "u", Bid: null, Try: 0, Cat: EmitCategory.Battle,
+            PubSeq: null, PlaySeq: null, Body: new Dictionary<string, object?>());
+
+    [Test]
+    public void AssignAndArchive_FirstCall_ReturnsEnvelopeWithPlaySeq1()
+    {
+        var seq = new OutboundSequencer();
+        var assigned = seq.AssignAndArchive(MakeEnvelope(NetworkBattleUri.BattleStart));
+
+        Assert.That(assigned.PlaySeq, Is.EqualTo(1));
+    }
+
+    [Test]
+    public void AssignAndArchive_SubsequentCalls_ReturnContiguousSequence()
+    {
+        var seq = new OutboundSequencer();
+        Assert.That(seq.AssignAndArchive(MakeEnvelope(NetworkBattleUri.Matched)).PlaySeq, Is.EqualTo(1));
+        Assert.That(seq.AssignAndArchive(MakeEnvelope(NetworkBattleUri.BattleStart)).PlaySeq, Is.EqualTo(2));
+        Assert.That(seq.AssignAndArchive(MakeEnvelope(NetworkBattleUri.Deal)).PlaySeq, Is.EqualTo(3));
+    }
+
+    [Test]
+    public void NoStockControlPush_DoesNotAssignPlaySeqOrArchive()
+    {
+        var seq = new OutboundSequencer();
+        var env = seq.WrapNoStock(MakeEnvelope(NetworkBattleUri.BattleFinish));
+
+        Assert.That(env.PlaySeq, Is.Null);
+        Assert.That(seq.Archive, Is.Empty);
+    }
+
+    [Test]
+    public void Archive_ContainsArchivedEnvelopesKeyedByPlaySeq()
+    {
+        var seq = new OutboundSequencer();
+        seq.AssignAndArchive(MakeEnvelope(NetworkBattleUri.Matched));
+        seq.AssignAndArchive(MakeEnvelope(NetworkBattleUri.BattleStart));
+
+        Assert.That(seq.Archive.Keys, Is.EquivalentTo(new[] { 1L, 2L }));
+        Assert.That(seq.Archive[1L].Uri, Is.EqualTo(NetworkBattleUri.Matched));
+    }
+}