diff --git a/game/reconstructed/mech4.cpp b/game/reconstructed/mech4.cpp
index 21e2d2e..4e28719 100644
--- a/game/reconstructed/mech4.cpp
+++ b/game/reconstructed/mech4.cpp
@@ -5541,6 +5541,49 @@ void
 			gBTGenSelKey = pulse ? s_gsID : 0;
 		}
 
+		// SELF-DAMAGE HARNESS (BT_SELF_DAMAGE=<amount per second>, off by default).
+		// The whole RESPAWN family -- torso twist after respawn (#70), ammo/weapon
+		// reset (#22), coolant/heat/generator restore (#55), the respawn latch
+		// (#57) -- was untestable on a bench because nothing can kill the LOCAL
+		// pilot in solo: BT_MP_FORCE_DMG only targets REPLICANTS, and a solo
+		// dummy never shoots back.  This dispatches an unaimed TakeDamage at our
+		// OWN mech once a second, through the SAME virtual Entity::Dispatch path
+		// a real beam hit uses -- so the cylinder hit-location lookup, the zone
+		// cascade, the vital-subsystem kill and the authentic death/respawn cycle
+		// all run for real.  Nothing is poked directly.
+		// e.g. BT_SELF_DAMAGE=40 kills a fresh mech in well under a minute.
+		// ONE DEATH ONLY: latch off as soon as we die, so everything observed
+		// AFTER the respawn is the respawn's own doing and not the harness still
+		// shooting us.  (Live damage knocks the power bus down, which is exactly
+		// the signal a respawn test is trying to read.)
+		static int s_sdSpent = 0;
+		if (IsMechDestroyed())
+			s_sdSpent = 1;
+		if ((Entity *)this == application->GetViewpointEntity()
+			&& getenv("BT_SELF_DAMAGE") && !s_sdSpent
+			&& !IsMechDestroyed() && damageZoneCount > 0)
+		{
+			static float s_sdAccum = 0.0f;
+			s_sdAccum += dt;
+			if (s_sdAccum >= 1.0f)
+			{
+				s_sdAccum = 0.0f;
+				Damage dmg;
+				dmg.damageType   = Damage::ExplosiveDamageType;
+				float want = (float)atof(getenv("BT_SELF_DAMAGE"));
+				dmg.damageAmount = (want > 0.0f) ? want : 20.0f;
+				dmg.burstCount   = 1;
+				dmg.impactPoint  = localOrigin.linearPosition;
+				Entity::TakeDamageMessage td(
+					Entity::TakeDamageMessageID,
+					sizeof(Entity::TakeDamageMessage),
+					GetEntityID(), -1 /*unaimed -> cylinder table resolves the zone*/, dmg);
+				DEBUG_STREAM << "[selfdmg] " << dmg.damageAmount
+					<< " to own mech (unaimed)" << std::endl << std::flush;
+				Dispatch(&td);
+			}
+		}
+
 		// task #13 scripted verify (BT_VALVE_TEST=1): one MoveValve press at
 		// frame ~600 -- Condenser1's valveState cycles 1 -> 5, so the flow
 		// redistribution gives it 5/10 of the total coolant flow ([valve] log