diff --git a/SVSim.BattleEngine/COPIED.manifest.tsv b/SVSim.BattleEngine/COPIED.manifest.tsv
index 66623dc..a48e2f9 100644
--- a/SVSim.BattleEngine/COPIED.manifest.tsv
+++ b/SVSim.BattleEngine/COPIED.manifest.tsv
@@ -62,7 +62,7 @@ BattleFinishToOpponentDisConnectChecker.cs	BattleFinishToOpponentDisConnectCheck
 BattleKeywordInfoListMgr.cs	BattleKeywordInfoListMgr.cs	a014170d0b3f5499635bcc2e29755dc2f3125d5a5a28b1741a4abc74b4abcf86	0
 BattleLifeTimeSharedObject.cs	BattleLifeTimeSharedObject.cs	ab8bc3703d268752a1de56ab5d3e9ebd276980c20076eb0ca300838b3db13d5f	0
 BattleLogTextBuilderAttachSkill.cs	BattleLogTextBuilderAttachSkill.cs	11c585ae931fa3dc734bb231d6da61df3b51b803516ca2c5d88a0c78bc7c0104	0
-BattleManagerBase.cs	BattleManagerBase.cs	b4181eac7af0ed578835ea75b7003e1b3466331006a35cd84b40139825680eb7	0
+BattleManagerBase.cs	BattleManagerBase.cs	849737bd494e33221b9f8672f67a685ca2372d23fae11ad2e1cfb5406caa5750	1
 BattleMenuMgr.cs	BattleMenuMgr.cs	7418699063e01641d0df1ed16773a9ac9418f418cc047fc18c5892eb7971d361	0
 BattlePlayer.cs	BattlePlayer.cs	001409844b46ddaf0a5edbce4e015749ece61053adf725a978987d7063a02632	0
 BattlePlayerBase.cs	BattlePlayerBase.cs	9d3a665158706460a52900008dcfcdf575dbe08cb6d3cc05e63e718b2885b51b	0
diff --git a/SVSim.BattleEngine/Engine/BattleManagerBase.cs b/SVSim.BattleEngine/Engine/BattleManagerBase.cs
index d6fa1d1..1b9bd0d 100644
--- a/SVSim.BattleEngine/Engine/BattleManagerBase.cs
+++ b/SVSim.BattleEngine/Engine/BattleManagerBase.cs
@@ -1583,7 +1583,7 @@ public class BattleManagerBase
 		return (int)Math.Floor((double)val * randomResult);
 	}
 
-	public double StableRandomDouble()
+	public virtual double StableRandomDouble()
 	{
 		if (IsForecast)
 		{
@@ -1594,7 +1594,7 @@ public class BattleManagerBase
 		return randomResult;
 	}
 
-	public int StableRandomOnlySelf(int val)
+	public virtual int StableRandomOnlySelf(int val)
 	{
 		if (IsForecast)
 		{
diff --git a/SVSim.BattleEngine/Patches/BattleManagerBase.rng-virtual.patch b/SVSim.BattleEngine/Patches/BattleManagerBase.rng-virtual.patch
new file mode 100644
index 0000000..f5bdb8f
--- /dev/null
+++ b/SVSim.BattleEngine/Patches/BattleManagerBase.rng-virtual.patch
@@ -0,0 +1,13 @@
+RNG seam (DP5): make StableRandomDouble() and StableRandomOnlySelf(int) `virtual` so the authored
+HeadlessBattleMgr can override all three RNG methods to delegate to an injected IRandomSource
+(StableRandom(int) is already virtual). This decouples the authoritative RNG roll from IsForecast's
+VFX-suppression+RNG-zeroing (design 2026-06-06-rng-seam, finding F2). ZERO logic change — only the
+`virtual` keyword is added; the method bodies are byte-for-byte the decomp.
+
+--- Engine/BattleManagerBase.cs  (~line 1586)
+-	public double StableRandomDouble()
++	public virtual double StableRandomDouble()
+
+--- Engine/BattleManagerBase.cs  (~line 1597)
+-	public int StableRandomOnlySelf(int val)
++	public virtual int StableRandomOnlySelf(int val)