--- a/addons/core/Scripts/Game/ERR/40_Chat/ERR_NativeSmoke.c
+++ b/addons/core/Scripts/Game/ERR/40_Chat/ERR_NativeSmoke.c
@@ -1,5 +1,21 @@
 // Explicit, local Workbench diagnostic only. Never compiled into game/server builds.
 #ifdef WORKBENCH
+modded class ERR_HQ
+{
+ bool ERR_IsolateMountedBMP()
+ {
+  string bmp;
+  if (!ERR_NativeMountedAmmoProbe.Enabled() || !System.GetCLIParam("errMountedBMP", bmp) || bmp != "1"
+   || !m_Mode || m_Mode != ERR_GameMode.Get() || m_Mode.StartMode() != 0 || m_Mode.Phase() != ERR_Phase.PRISON
+   || !m_Hunters || m_Hunters.Deployed() != 0 || !m_Towns) return false;
+  // Neither service ticks in PRISON. Town creation is synchronous; there are
+  // no queued town soldiers to cancel or existing populations to refund here.
+  m_Hunters.Stop();
+  m_Towns.Stop();
+  return true;
+ }
+}
+
 modded class ERR_GameMode
 {
 	// Read-only normal-route stock witness; no courier, movement or arming action.
@@ -838,6 +854,20 @@
 			}
 			if (m_ERRTestMountedAmmo)
 			{
+				string mountedBMP;
+				if (System.GetCLIParam("errMountedBMP", mountedBMP) && mountedBMP == "1")
+				{
+					string bmpMines, bmpSwap, bmpCourier;
+					bool mixedBMP = (System.GetCLIParam("errMineStock", bmpMines) && bmpMines == "1")
+					 || (System.GetCLIParam("errMountedSwapEligibility", bmpSwap) && bmpSwap == "1")
+					 || (System.GetCLIParam("errMountedCourier", bmpCourier) && bmpCourier == "1");
+					if (!ERR_Check(!mixedBMP && StartMode() == 0 && Phase() == ERR_Phase.PRISON,
+					 "BMP accounting isolation requires prison start and no mine/swap/courier variants")) return;
+					ERR_HQ bmpHQ = ERR_HQ.Get();
+					if (!ERR_Check(bmpHQ && bmpHQ.ERR_IsolateMountedBMP(),
+					 "BMP accounting isolation precedes opening hunter and town admissions")) return;
+					Print("ERR BMP FIXTURE: opening hunters and new town admissions stopped before prison escape; original site troops, automatic convoy target, body cap, stock and proof deadline unchanged");
+				}
 				// Protect only this diagnostic observer while normal enemy forces continue.
 				DamageManagerComponent mountedObserverDamage = DamageManagerComponent.Cast(m_ERRSmokePlayer.FindComponent(DamageManagerComponent));
 				if (!ERR_Check(mountedObserverDamage != null, "mounted observer has native damage component")) return;