diff --git a/SVSim.BattleNode/Sessions/IBattleSessionStore.cs b/SVSim.BattleNode/Sessions/IBattleSessionStore.cs
new file mode 100644
index 0000000..541ead7
--- /dev/null
+++ b/SVSim.BattleNode/Sessions/IBattleSessionStore.cs
@@ -0,0 +1,13 @@
+namespace SVSim.BattleNode.Sessions;
+
+public interface IBattleSessionStore
+{
+    /// <summary>Register a battle minted by the matching bridge, awaiting a WS connect.</summary>
+    void RegisterPending(PendingBattle battle);
+
+    /// <summary>Look up the pending battle. Returns null if not present.</summary>
+    PendingBattle? TryGetPending(string battleId);
+
+    /// <summary>Mark a battle as no longer pending (e.g. on successful connect or explicit close).</summary>
+    bool RemovePending(string battleId);
+}
diff --git a/SVSim.BattleNode/Sessions/InMemoryBattleSessionStore.cs b/SVSim.BattleNode/Sessions/InMemoryBattleSessionStore.cs
new file mode 100644
index 0000000..2f14512
--- /dev/null
+++ b/SVSim.BattleNode/Sessions/InMemoryBattleSessionStore.cs
@@ -0,0 +1,17 @@
+using System.Collections.Concurrent;
+
+namespace SVSim.BattleNode.Sessions;
+
+public sealed class InMemoryBattleSessionStore : IBattleSessionStore
+{
+    private readonly ConcurrentDictionary<string, PendingBattle> _pending = new();
+
+    public void RegisterPending(PendingBattle battle) =>
+        _pending[battle.BattleId] = battle;
+
+    public PendingBattle? TryGetPending(string battleId) =>
+        _pending.TryGetValue(battleId, out var b) ? b : null;
+
+    public bool RemovePending(string battleId) =>
+        _pending.TryRemove(battleId, out _);
+}
diff --git a/SVSim.BattleNode/Sessions/PendingBattle.cs b/SVSim.BattleNode/Sessions/PendingBattle.cs
new file mode 100644
index 0000000..28dbb88
--- /dev/null
+++ b/SVSim.BattleNode/Sessions/PendingBattle.cs
@@ -0,0 +1,7 @@
+namespace SVSim.BattleNode.Sessions;
+
+/// <summary>
+/// Sparse pre-connect record: enough to validate the incoming WS connect and resolve
+/// the viewer. Full BattleSession is created on connect.
+/// </summary>
+public sealed record PendingBattle(string BattleId, long ViewerId);
diff --git a/SVSim.UnitTests/BattleNode/Sessions/InMemoryBattleSessionStoreTests.cs b/SVSim.UnitTests/BattleNode/Sessions/InMemoryBattleSessionStoreTests.cs
new file mode 100644
index 0000000..7582ea0
--- /dev/null
+++ b/SVSim.UnitTests/BattleNode/Sessions/InMemoryBattleSessionStoreTests.cs
@@ -0,0 +1,43 @@
+using NUnit.Framework;
+using SVSim.BattleNode.Sessions;
+
+namespace SVSim.UnitTests.BattleNode.Sessions;
+
+[TestFixture]
+public class InMemoryBattleSessionStoreTests
+{
+    private InMemoryBattleSessionStore _store = null!;
+
+    [SetUp] public void Setup() => _store = new InMemoryBattleSessionStore();
+
+    [Test]
+    public void RegisterThenGet_ReturnsRegisteredBattle()
+    {
+        var battle = new PendingBattle("bid-1", 906243102);
+        _store.RegisterPending(battle);
+
+        Assert.That(_store.TryGetPending("bid-1"), Is.EqualTo(battle));
+    }
+
+    [Test]
+    public void Get_UnknownBattleId_ReturnsNull()
+    {
+        Assert.That(_store.TryGetPending("nope"), Is.Null);
+    }
+
+    [Test]
+    public void Remove_ReturnsTrueWhenPresent_FalseWhenAbsent()
+    {
+        _store.RegisterPending(new PendingBattle("bid", 1));
+        Assert.That(_store.RemovePending("bid"), Is.True);
+        Assert.That(_store.RemovePending("bid"), Is.False);
+    }
+
+    [Test]
+    public void Register_DuplicateBattleId_OverwritesPrior()
+    {
+        _store.RegisterPending(new PendingBattle("bid", 1));
+        _store.RegisterPending(new PendingBattle("bid", 2));
+        Assert.That(_store.TryGetPending("bid")!.ViewerId, Is.EqualTo(2));
+    }
+}