diff --git a/game/reconstructed/heatfamily_reslice.cpp b/game/reconstructed/heatfamily_reslice.cpp
index c67f899..5fa2f1f 100644
--- a/game/reconstructed/heatfamily_reslice.cpp
+++ b/game/reconstructed/heatfamily_reslice.cpp
@@ -979,9 +979,24 @@ void BTRecomputeCondenserValves(Entity *owner)
 
 	// DIAG (BT_VALVE=<n>): force every condenser's valve detent so the coolant/jam
 	// mechanic can be tested at a known coolant level (0=closed/uncooled .. 50=max).
+	// DIAG (BT_VALVE_BOOST=<condenserNumber>): the authentic "coolant priority" test --
+	// give ONE condenser the max detent (50) and starve the rest to the min (1), i.e.
+	// route the coolant SHARE to that condenser (share ~0.9 vs the ~1/N baseline).
 	{
 		const char *fv = getenv("BT_VALVE");
-		if (fv && fv[0])
+		const char *fb = getenv("BT_VALVE_BOOST");
+		if (fb && fb[0])
+		{
+			int boostNum = atoi(fb);
+			for (int i = 0; i < count; ++i)
+			{
+				Subsystem *s = owner->GetSubsystem(i);
+				if (s != 0 && s->IsDerivedFrom(condClass))
+					((Condenser *)s)->valveState =
+						(((Condenser *)s)->condenserNumber == boostNum) ? 50 : 1;
+			}
+		}
+		else if (fv && fv[0])
 		{
 			int v = atoi(fv);
 			for (int i = 0; i < count; ++i)