diff --git a/SVSim.BattleEngine.Tests/HeadlessFixture.cs b/SVSim.BattleEngine.Tests/HeadlessFixture.cs
index 92db08f..9952e61 100644
--- a/SVSim.BattleEngine.Tests/HeadlessFixture.cs
+++ b/SVSim.BattleEngine.Tests/HeadlessFixture.cs
@@ -202,6 +202,19 @@ namespace SVSim.BattleEngine.Tests
             var dm = GameMgr.GetIns().GetDataMgr();
             SetField(dm, "_playerCharaId", HeadlessMasterData.PlayerCharaId);
             SetField(dm, "_enemyCharaId", HeadlessMasterData.EnemyCharaId);
+            // NetworkBattleManagerBase.CreateBackgroundId() (M13) reads
+            // GameMgr.GetIns().GetNetworkUserInfoData().GetFieldId() when the RecoveryManager yields no
+            // bg id (NullRecoveryManager.BackGroundId == -1). In production RealTimeNetworkAgent seeds
+            // this NetworkUserInfoData at match start; the bare construction path leaves GameMgr's
+            // _netUser null (no lazy init, unlike the other GodObject getters). Seed a no-op instance
+            // whose _selfInfo carries just "fieldId" (GetFieldId reads _selfInfo["fieldId"]); field id 1
+            // == ForestField, a valid background. Nothing here drives game state — it only satisfies the
+            // network mgr's background lookup so a single-battle-only SingleBattleMgr never needs.
+            var netUser = new NetworkUserInfoData();
+            netUser.SetSelfInfo(
+                new System.Collections.Generic.Dictionary<string, object> { ["fieldId"] = 1 },
+                isWatchReplayRecovery: false);
+            GameMgr.GetIns().SetNetworkUserInfoData(netUser);
             _done = true;
         }
 
diff --git a/SVSim.BattleEngine.Tests/NetworkMgrConstructionProbeTests.cs b/SVSim.BattleEngine.Tests/NetworkMgrConstructionProbeTests.cs
new file mode 100644
index 0000000..18a5f2a
--- /dev/null
+++ b/SVSim.BattleEngine.Tests/NetworkMgrConstructionProbeTests.cs
@@ -0,0 +1,25 @@
+using NUnit.Framework;
+using SVSim.BattleEngine.Rng;
+using Wizard.BattleMgr;
+
+namespace SVSim.BattleEngine.Tests
+{
+    // M13 step 1 (the M2 ConstructionProbe pattern): can a NetworkBattleManagerBase-derived mgr be
+    // built headless at all? NetworkBattleManagerSetup constructs NetworkTouchControl(this,
+    // _battleCamera, _backGround) + RegisterActionManager + OperateReceive — the largest new shim
+    // surface since M5's prefab path. Isolate "ctor runs" before any play is driven.
+    [TestFixture]
+    public class NetworkMgrConstructionProbeTests
+    {
+        [Test]
+        public void HeadlessNetworkBattleMgr_constructs_headless()
+        {
+            HeadlessEngineEnv.EnsureInitialized();
+            Assert.DoesNotThrow(() =>
+            {
+                var mgr = new HeadlessNetworkBattleMgr(new HeadlessContentsCreator());
+                Assert.That(mgr, Is.Not.Null);
+            });
+        }
+    }
+}
diff --git a/SVSim.BattleEngine/Rng/HeadlessNetworkBattleMgr.cs b/SVSim.BattleEngine/Rng/HeadlessNetworkBattleMgr.cs
new file mode 100644
index 0000000..e5f5956
--- /dev/null
+++ b/SVSim.BattleEngine/Rng/HeadlessNetworkBattleMgr.cs
@@ -0,0 +1,37 @@
+using Wizard;
+using Wizard.BattleMgr;
+
+namespace SVSim.BattleEngine.Rng
+{
+    // The headless authoritative NETWORK battle mgr — the emitting twin of HeadlessBattleMgr. Emission
+    // lives on NetworkBattleManagerBase (NetworkBattleSender's ctor demands one), so the M13 emit read
+    // needs this subclass; HeadlessBattleMgr : SingleBattleMgr cannot reach the sender. RNG overrides are
+    // identical to HeadlessBattleMgr (the same BattleManagerBase virtuals + RandomSourceBridge), so the
+    // M14 rand-list emit reuses this mgr unchanged. M13's deterministic card never exercises a roll.
+    public sealed class HeadlessNetworkBattleMgr : NetworkBattleManagerBase
+    {
+        private readonly IRandomSource _rng;
+
+        public HeadlessNetworkBattleMgr(IBattleMgrContentsCreator contentsCreator, IRandomSource rng = null)
+            : base(contentsCreator)
+        {
+            _rng = rng ?? new SeededRandomSource(contentsCreator.RandomSeed);
+        }
+
+        public override int StableRandom(int val)
+        {
+            double unit = _rng.NextUnit();
+            randomResult = unit;
+            return RandomSourceBridge.Range(val, unit);
+        }
+
+        public override double StableRandomDouble()
+        {
+            double unit = _rng.NextUnit();
+            randomResult = unit;
+            return unit;
+        }
+
+        public override int StableRandomOnlySelf(int val) => _rng.NextSelf(val);
+    }
+}