#81 GHOST MECH FIXED: release the death latch + stop the duplicate VehicleDead

Two defects that were masking each other, both now fixed and benched.

1) THE LATCH NEVER RELEASED ON FAILURE.  The binary's FUN_004c012c tail is
   Post(...) ; *(this+0x290)=0 ; *(this+0x258)=0   (part_013.c:10519-10523).
   We had the Post and the suppressConsole and were missing the middle
   instruction, so deathPending cleared only on SUCCESS paths.  One failed
   respawn latched the pilot for the whole mission: every later death hit the
   dedup and was SWALLOWED, so the cycle could never restart -- a transient
   hiccup became a PERMANENT ghost (dead, un-Reset, still driveable, a burning
   wreck on every peer that sinks after ~18s and can never be drawn again).
   Binary evidence: +0x290 is written in exactly THREE places in all of
   BTL4OPT.EXE (0x0b75fb, 0x0bffe3, 0x0c0a05) and all three store a ZEROED
   register; there is no write of 1 -- or any non-zero, in any instruction form
   -- anywhere.  The dedup gate itself IS authentic (@004c05c4 does
   mov edx,[ebx+0x290]; test edx,edx; jne ret), so it is kept.

2) VehicleDeadMessage WAS DISPATCHED TWICE PER DEATH.  BTPostKillScore
   (btplayer.cpp:2263) sent a second one "to credit a death", but that message
   is the RESPAWN-CYCLE TRIGGER, not a scoreboard increment, and the tally is
   already credited by the handler's ++deathTally (:538).  Both fire inside the
   same death transition (BTPostKillScore at mech4.cpp:2006, the hardened
   authentic notify at :2110), so they were always paired.  Removed; the kill
   credit above it is untouched (it correctly uses a ScoreMessage).

THEY HID EACH OTHER: the duplicate made the latch look necessary, and the latch
made the duplicate invisible.  Every "death ... SWALLOWED" warning in the field
logs was just the latch deduping our own duplicate -- 8 of 8 deaths, a 100% base
rate, which is exactly why it correlated with nothing when tested.  Fixing
either alone makes things visibly worse (the first bench of fix 1 alone produced
a DOUBLE cycle: deathCount double-incremented, cycle 1's re-post gone stale and
tripping the drop-zone MISMATCH).  That is why earlier passes at #57/#55 kept
adding clear-sites instead of finding the root; the binary broke the tie.

VERIFIED
  solo: 17 consecutive death/respawn cycles, every one START->RESET,
        0 swallowed / 0 mismatch / 0 crash.  Pre-fix this strands permanently
        after cycle 1.
  MP  : two nodes over a real network path with cross-machine drop-zone replies
        (each node's request is answered by the OTHER machine) -- A 11 cycles,
        B 12, 0 swallowed / 0 mismatch / 0 discarded / 0 crash.
  harness: BT_SELF_DAMAGE_REPEAT=1 re-arms the self-damage bench after respawn
        so multiple cycles can be driven (a one-death harness can never
        exercise this fix).  scratchpad/night6/mp_ghost.sh.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

game/reconstructed/btplayer.cpp

@@ -641,6 +641,38 @@ void
 	}
 	// else: out of lives -> the +10s mission-review post (id 0x18).  Deferred.
 
+	//
+	// RELEASE THE DEATH LATCH (#81, the GHOST MECH fix -- 2026-07-30).
+	//
+	// The binary clears it right here, between the re-post and suppressConsole:
+	// FUN_004c012c's tail is  Post(...) ; *(this+0x290) = 0 ; *(this+0x258) = 0
+	// (part_013.c:10519-10523).  We had the Post and the suppressConsole and
+	// were missing the middle instruction, so `deathPending` -- which we DO set
+	// (:505, and the dedup gate that reads it IS authentic; the binary's own
+	// @004c05c4 does `mov edx,[ebx+0x290]; test edx,edx; jne ret`) -- was only
+	// ever cleared on the SUCCESS paths.  One failed respawn therefore latched
+	// the pilot dead for the rest of the mission: every later death hit the
+	// dedup and was SWALLOWED, so the cycle could never restart.  That is what
+	// turned a transient respawn hiccup into a PERMANENT ghost (dead,
+	// un-Reset, still driveable, a burning wreck on every peer that sinks out
+	// of the world after ~18 s and can never be drawn again).
+	//
+	// Field signature it explains exactly: 2026-07-29, 8 death cycles, 6
+	// stranded, NONE of them ever recovering.
+	//
+	// Binary evidence that the latch must not persist: `+0x290` is written in
+	// exactly THREE places in the whole of BTL4OPT.EXE (file offsets 0x0b75fb,
+	// 0x0bffe3, 0x0c0a05) and ALL THREE store a zeroed register (`xor` on the
+	// preceding instruction); there is no write of 1 -- or of any non-zero
+	// value, in any instruction form -- anywhere in the executable.  So in 1995
+	// the gate exists but can never block.  [T1]
+	//
+	// Ordering matters and is preserved: the re-entrant death that arrives
+	// while the death EFFECTS are being dispatched still lands while the latch
+	// is up, so the "one death, one cycle" dedup is untouched.
+	//
+	deathPending = 0;							// this+0x290 (binary: FUN_004c012c tail)
+
 	suppressConsole = 0;						// this+0x258
 }
 
@@ -2222,17 +2254,31 @@ void BTPostKillScore(Entity *victim, Scalar damage)			// Step 7: KILL (+ MP deat
 			(int)(k != 0 && ((Mech *)k)->GetPlayerLink() != 0));
 	}
 
-	// MP DEATH: credit a death to the VICTIM's own player.  NULL for the solo
-	// BT_SPAWN_ENEMY dummy (GetPlayerLink()==0) -> skipped, so DEATHS stays 0 in
-	// solo (authentic -- DEATHS only lands on a real pilot in multiplayer).
-	BTPlayer *victim_player = (BTPlayer *)((Mech *)victim)->GetPlayerLink();
-	if (victim_player != 0)
-	{
-		Player::VehicleDeadMessage dead(
-			Player::VehicleDeadMessageID,				// 0x13
-			sizeof(Player::VehicleDeadMessage));
-		victim_player->Dispatch(&dead);
-	}
+	// MP DEATH: the victim's death tally.
+	//
+	// REMOVED 2026-07-30 (#81): this used to dispatch a second
+	// `Player::VehicleDeadMessage` to the victim's own player "to credit a
+	// death".  That message is the RESPAWN-CYCLE TRIGGER, not a scoreboard
+	// increment, and the victim already receives one from the mech's death
+	// transition (mech4.cpp:2110) -- which is the hardened, authentic notify
+	// (it carries the #55 NULL-playerLink fallback).  Both fire inside the SAME
+	// death transition (BTPostKillScore is called at mech4.cpp:2006, the notify
+	// at :2110), so they were always paired: every death dispatched the message
+	// TWICE.  The tally itself is credited by the handler's `++deathTally`
+	// (:538) on the first one, so this dispatch never added anything.
+	//
+	// It was invisible because the `deathPending` latch silently deduped it --
+	// that is what EVERY "death ... SWALLOWED" warning in the field logs
+	// actually was (8 of 8 deaths, a 100% base rate, which is exactly why it
+	// correlated with nothing).  Once the latch was released to match the
+	// binary (see the death handler's tail), the duplicate stopped being
+	// masked and started a SECOND death cycle: deathCount double-incremented,
+	// the first cycle's re-post went stale and tripped the drop-zone
+	// `*** MISMATCH ***`, and one respawn burned two cycles.  Caught on the
+	// first solo bench of the latch fix.
+	//
+	// The kill credit above is unaffected -- it dispatches a ScoreMessage, the
+	// correct message for a scoreboard change.
 }
 
 

game/reconstructed/mech4.cpp

@@ -5667,6 +5667,15 @@ void
 		if ((Entity *)this == application->GetViewpointEntity()
 			&& IsMechDestroyed())
 			s_sdSpent = 1;
+		// BT_SELF_DAMAGE_REPEAT=1: re-arm once we are alive again, so the bench
+		// can drive MULTIPLE death/respawn cycles.  Needed to regression-test
+		// the #81 death-latch fix -- the whole point of that fix is that the
+		// SECOND death starts a fresh cycle instead of being swallowed forever,
+		// which a one-death harness can never exercise.
+		if (s_sdSpent && getenv("BT_SELF_DAMAGE_REPEAT")
+			&& (Entity *)this == application->GetViewpointEntity()
+			&& !IsMechDestroyed())
+			s_sdSpent = 0;
 		if ((Entity *)this == application->GetViewpointEntity()
 			&& getenv("BT_SELF_DAMAGE") && !s_sdSpent
 			&& !IsMechDestroyed() && damageZoneCount > 0)