#87 root cause: the level-crossing zone-record send was missing -- observers never saw damage

The binary's effect watcher (FUN_0042aa2c) raises
ForceUpdate(DamageZoneUpdateModelFlag) when a zone's damageLevel CROSSES a
band-descriptor threshold (FUN_0042a5f4, master-gated on entity+0x28 & 0xc)
-- that send is how every other pod's replicant learns zone levels
mid-fight. The port's band hub kept only the graphic-state branch, so an
observer's copy sat at 0.0 until destruction: no enemy hull darkening, no
doll movement, ever (the night-10 "no armour discoloration" report).

Restored the level branch with the already-reconstructed DescriptorCrossed
(@0042a5f4) + the master gate on both branches (mesh swap still runs on
every instance). 2-node verified: A-side armour watcher pushed 114 level
changes; every replicant peak matched the master's finals to 4 decimals
(dtorso 0.9321 == 0.9321).

Render path cleared separately (gotcha #23 discharged): BT_ARMOR_FORCE 0/1
A/B captures prove the tint renders (hull -> charcoal at 1.0). Solo
perception is the authentic economy: 2-25 pt lasers vs 68-185 pt pools.

Bench: zonewalk.sh node A now carries BT_ARMOR_LOG + BT_SHOT_EVERY (the
standing zone-replication receipt) + digest_walk.py; armorpx.sh is the
force-pair pixel rig.

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

context/combat-damage.md

@@ -1009,6 +1009,48 @@ returned NULL) -- the cascade "ran" and touched nothing, which is why blown-off
 arms left firing gun pods across every chassis (Conn Man's three-chassis audit).
 See reconstruction-gotchas #25.
 
+## Zone-LEVEL replication -- the observer's picture (#87 root cause, 2026-08-03) [T1 decomp / T2 verified]
+
+How an OBSERVER (replicant holder) learns a mech's zone damageLevels, end to end:
+
+1. Damage messages do NOT echo locally: `Entity::Dispatch` on a REPLICANT
+   forwards to the master's node and returns (ENTITY.cpp:244) -- there is no
+   broadcast-bus application. The MASTER alone consumes `TakeDamage`.
+2. The master ships levels via zone UPDATE RECORDS
+   (`DamageZone::Write/ReadUpdateRecord`, `DamageZoneUpdateModelBit`), gated by
+   `ForceUpdate(DamageZoneUpdateModelFlag)`.
+3. **Who raises the flag (the binary's effect watcher `FUN_0042aa2c @0042aa2c`,
+   the BT analog of the engine's `EntityEffectWatcher` -- which itself never
+   runs for mechs: mech zones carry BAND DESCRIPTORS, the engine `ExplosionTable`
+   stays NULL and `EntityEffectWatcher` is constructed nowhere in the image):**
+   * level branch (zone changedFlags & 4): if the rise CROSSES a band-descriptor
+     threshold (`FUN_0042a5f4` = `Mech__DamageZone::DescriptorCrossed`) AND the
+     entity is a MASTER (`(entity+0x28 & 0xc) == 0`) -> `*(entity+0x18) |= 2`
+     (= ForceUpdate(DamageZoneUpdateModelFlag)).
+   * gstate branch (changedFlags & 8): ForceUpdate unconditionally (masters).
+   So observers track a fight at **band-crossing granularity** -- not per hit.
+4. Consumption on the observer is passive: `ReadUpdateRecord` writes the level,
+   the armour watcher (`TickArmourDamage`) re-reads zones every frame and pushes
+   the draw-op tint; the doll gauges read `damageLevel*100` continuously.
+
+**The port had dropped the level branch** -- mechdmg.cpp's band hub ForceUpdated
+only on `graphicState != Exists`, so every observer's copy sat at 0.0 until a
+zone DESTRUCTED: no enemy hull darkening, no observer-side doll movement, ever
+(the "no armour discoloration" night-10 report). Restored 2026-08-03
+(mechdmg.cpp band loop: `DescriptorCrossed(prev, level)` + master gate on both
+branches). Verified 2-node: A-side watcher pushed 114 level changes; every
+replicant peak matched the master's final level to 4 decimals (dtorso 0.9321
+both sides).
+
+Render-path note (gotcha #23 discharged): the tint itself was pixel-proven with
+`BT_ARMOR_FORCE` A/B captures -- all-zones 1.0 renders the hull charcoal (0.1x
+floor), so "no discoloration" was never the renderer. Solo/master-side
+perception is the authentic ECONOMY: 2-25 pt laser events vs 68-185 pt zone
+pools = single-digit % levels = a 2-10% darkening + a doll tick of a few color
+indices. The cockpit doll maps all 28 zones (L4GAUGE.CFG:4788-4814 cmArmor
+lines -- feet + lower legs included); a "leg shots never show" report is those
+zones' levels peaking ~0.08-0.13, not a wiring gap.
+
 ## The hit-location CYLINDER -- raw-bytes audit + chassis->table map (2026-08-02) [T1]
 
 Full independent verification of the type-29 DamageLookupTable streams, parsed

context/decomp-reference.md

@@ -183,6 +183,7 @@ rows until sanity fails (`python + struct`, see the session commits `cc2b109`/`2
 - `class Damage { damageType(enum Collision/Ballistic/Explosive/Laser/Energy), damageAmount, damageForce, surfaceNormal, impactPoint, burstCount }`. [T1]
 - Weapon effect id: **"explode" = 13** (`Explosion::Make`). [T2]
 - `DestroyEntityMessage(id,size)` removes an entity — but a killed mech STAYS (a WRECK); death = a STATE transition (`SetGraphicState(DestroyedGraphicState)`), NOT removal. Issuing removal-on-death is the P5 teardown bug (do not). [T2]
+- **BT effect watcher (zone replication + band effects)** [T1, 2026-08-03]: ctor `FUN_0042a984 @0042a984` (hooks entity+0xbc, allocs oldLevel[damageZoneCount@+0x11c]); Execute `FUN_0042aa2c @0042aa2c` — per zone: flag&4 → `FUN_0042a664` DescriptorForLevel + `FUN_0042a5f4` DescriptorCrossed(old,new) → **crossed && master (`(entity+0x28 & 0xc)==0`) → `*(ushort*)(entity+0x18) |= 2`** (= `ForceUpdate(DamageZoneUpdateModelFlag)`, the zone-record send); flag&8 → `FUN_0042a6c4` DescriptorForGraphicState + the same master-gated ForceUpdate; descriptor → effect via `FUN_0043663c/FUN_004364e4` (renderer mgr @`DAT_004efc94+0x38`); changedFlags reset when (master && !pending-update) or replicant. Zone band table @ zone+0xd4; level @+0x158; gstate @+0x78. Engine `EntityEffectWatcher`/`ExplosionTable` are DEAD for mechs (table NULL, watcher never constructed — band descriptors replace them). Port: mechdmg.cpp band hub. See [[combat-damage]] §Zone-LEVEL replication.
 
 ---
 

context/multiplayer.md

@@ -70,6 +70,13 @@ emulator** (⚠ `NotationFile::ReadText` expects NUL-SEPARATED lines). [T2]
   console LAUNCH). SIX bugs fixed to get here (dead-reckoner install, replicant-motion DeadReckon,
   master emission threshold, emission gated on RunningMission, the console-must-LAUNCH fact, replicant
   validity). [T2]
+- **Zone-level replication (#87, 2026-08-03):** an observer's copy of a mech learns zone damageLevels
+  ONLY from zone update records, and the master sends those on BAND-THRESHOLD CROSSINGS (binary effect
+  watcher `FUN_0042aa2c`: `DescriptorCrossed` + master gate → `ForceUpdate(DamageZoneUpdateModelFlag)`)
+  plus every graphic-state change — never per hit. Damage messages do NOT echo locally (replicant
+  `Dispatch` forwards to the master and returns). The port had only the gstate branch (observers saw
+  0.0 until destruction); the level branch was restored + 2-node verified (replicant peaks == master
+  finals to 4 decimals). Full mechanism: [[combat-damage]] §Zone-LEVEL replication. [T1/T2]
 - **Wire-format bug class found+fixed:** MakeMessages replicate RAW over TCP, so string payload must be
   INLINE (`char[N]` at the binary offsets), not a `const char*` pointer (garbage cross-pod). Check
   EVERY MakeMessage for pointer payloads. [T2]

context/test-harness.md

@@ -106,6 +106,13 @@ SERVOS the torso twist + aim elevation until the centered reticle's pick ray
 and advances. `[walk] ZONE/FIRE/HOLD` lines on A pair with `[dmghit]` on B.
 Launch: `bash scratchpad/night10/zonewalk.sh` (relay included; NO kill timer —
 the session stays up for observation; teardown = taskkill btl4).
+Node A also carries `BT_ARMOR_LOG=1` + `BT_SHOT_EVERY=300 BT_SHOT_PREFIX=zwA`
+(added for #87): the armour watcher's `[armor] ... level P -> Q` lines on A are
+the OBSERVER-side receipt that B's zone levels replicated (the walk is the
+standing zone-replication bench — A-side peaks must match B's `[dmghit]`
+finals), and the numbered captures are the pixel record of the enemy hull
+darkening. Digest: `python scratchpad/night10/digest_walk.py` (per-zone hits,
+amt/hit, level first→last on B; replicant peaks seen by A; zone-repl lines).
 Companion scalpels: `BT_ASPECT_TEST=1` (the zero-premise frame probe — 4
 world-cardinal self-impacts + one at each weapon's physical MUZZLE, the
 left/right anchors that caught the #124 reflection-vs-rotation error);