diff --git a/SVSim.BattleNode/Sessions/Participants/RealParticipant.cs b/SVSim.BattleNode/Sessions/Participants/RealParticipant.cs
index d2ec4d9..3a0caed 100644
--- a/SVSim.BattleNode/Sessions/Participants/RealParticipant.cs
+++ b/SVSim.BattleNode/Sessions/Participants/RealParticipant.cs
@@ -28,6 +28,13 @@ public sealed class RealParticipant : IBattleParticipant
     public InboundTracker Inbound { get; } = new();
     public OutboundSequencer Outbound { get; } = new();
 
+    /// <summary>Per-side handshake progression. Session reads this when gating
+    /// handshake-phase synthesis (Matched / BattleStart / Deal / Swap response /
+    /// Ready). Session transitions via the setter after dispatch. Defaults to
+    /// AwaitingInitNetwork; only RealParticipant tracks this — bots have no phase
+    /// because they never send the gating URIs.</summary>
+    internal BattleSessionPhase Phase { get; set; } = BattleSessionPhase.AwaitingInitNetwork;
+
     public event Func<MsgEnvelope, CancellationToken, Task>? FrameEmitted;
 
     public RealParticipant(WebSocket ws, long viewerId, MatchContext context,
diff --git a/SVSim.UnitTests/BattleNode/Sessions/Participants/RealParticipantTests.cs b/SVSim.UnitTests/BattleNode/Sessions/Participants/RealParticipantTests.cs
index 2613657..79d4049 100644
--- a/SVSim.UnitTests/BattleNode/Sessions/Participants/RealParticipantTests.cs
+++ b/SVSim.UnitTests/BattleNode/Sessions/Participants/RealParticipantTests.cs
@@ -90,6 +90,43 @@ public class RealParticipantTests
         Assert.That(result, Is.EqualTo(int.MinValue));
     }
 
+    [Test]
+    public void Phase_defaults_to_AwaitingInitNetwork()
+    {
+        var ws = new TestWebSocket();
+        var p = new RealParticipant(ws, viewerId: 1, FixtureCtx(),
+            NullLogger<RealParticipant>.Instance);
+
+        Assert.That(p.Phase, Is.EqualTo(SVSim.BattleNode.Sessions.BattleSessionPhase.AwaitingInitNetwork));
+    }
+
+    [Test]
+    public void Phase_setter_is_visible_to_same_assembly()
+    {
+        var ws = new TestWebSocket();
+        var p = new RealParticipant(ws, viewerId: 1, FixtureCtx(),
+            NullLogger<RealParticipant>.Instance);
+
+        // Setter is `internal`; SVSim.UnitTests has InternalsVisibleTo on SVSim.BattleNode.
+        p.Phase = SVSim.BattleNode.Sessions.BattleSessionPhase.AfterReady;
+
+        Assert.That(p.Phase, Is.EqualTo(SVSim.BattleNode.Sessions.BattleSessionPhase.AfterReady));
+    }
+
+    [Test]
+    public void Phase_is_per_instance_not_shared()
+    {
+        var wsA = new TestWebSocket();
+        var wsB = new TestWebSocket();
+        var a = new RealParticipant(wsA, viewerId: 1, FixtureCtx(), NullLogger<RealParticipant>.Instance);
+        var b = new RealParticipant(wsB, viewerId: 2, FixtureCtx(), NullLogger<RealParticipant>.Instance);
+
+        a.Phase = SVSim.BattleNode.Sessions.BattleSessionPhase.AfterReady;
+
+        Assert.That(b.Phase, Is.EqualTo(SVSim.BattleNode.Sessions.BattleSessionPhase.AwaitingInitNetwork),
+            "B's Phase must not change when A's Phase is set.");
+    }
+
     private static MatchContext FixtureCtx() => new(
         SelfDeckCardIds: Enumerable.Range(1, 30).Select(_ => 100_011_010L).ToList(),
         ClassId: "1", CharaId: "1", CardMasterName: "card_master_node_10015",