Docs: exploding-barrels Build Spec + session log Part J + roadmap tick

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

Docs/Vault/03_Design/Exploding_Barrels_Build_Spec.md

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+---
+title: Exploding_Barrels_Build_Spec
+type: note
+permalink: gamevault/03-design/exploding-barrels-build-spec
+---
+
+# Exploding Barrels — Build Spec (Phase 1.5 hazard v1, design-review-hardened)
+
+Review: `wf_2cb10454-fdf` (3 lenses, 23 agents, 13 findings CONFIRMED / 3 refuted; the first run lost 8
+verifiers to a session limit and was resumed from cache — the [[workflow-agent-quota-failures-look-clean]]
+protocol held). This spec is the fold; it supersedes the pre-review draft.
+
+## The core mechanism: the FUSE (one fix for both HIGHs)
+
+On pop the barrel does NOT die. The server zeroes the barrel's REPLICATED `BlightClutter.Remaining` and adds
+a server-only `BarrelFuse { uint ExplodeTick }` (`TickUtil.NonZero(now + Tuning.BarrelFuseTicks≈36)`). The
+client therefore sees `Remaining==0` on a still-alive barrel across multiple snapshots → an unambiguous
+"about to blow" cue, and the boom-vs-puff choice at despawn keys on the CACHED `Remaining<=0` — a room-
+teardown despawn carries `Remaining>0` → **no false booms** (HIGH #1: despawn-inference is cause-blind;
+players stand in torn-down rooms through RouteSelect — RunDirectorSystem.cs:247-251, WorldFeedbackSystem
+prune :96-119). Detonation is the AUTHORING moment → `DamageEvent.SourceTick = TickUtil.NonZero(detonation
+tick)` honors the authored-tick contract dash i-frames negate against (HIGH #2; DamageEvent.cs:20-24).
+The fuse also: dissolves the melee self-hit complaint (pop → step out), creates the bait loop (lure enemies
+onto a lit barrel), and — because the fuse lives ON the RoomTag'd barrel — room teardown/Staging sweep
+clean fused barrels for free (the orphaned-ExplosionEvent lifecycle findings dissolve).
+
+## Server
+
+- **Seeding** (RoomFieldSystem clutter loop): `bc.Variant = crng.NextFloat() < 0.25f ? (byte)3 : (byte)(i % 3)`
+  (seeded rng, deterministic; variants 0-2 stay cosmetic).
+- **Pop sites** (BOTH: ResourceHarvestSystem projectile sweep; MeleeComboSystem isServer-gated harvest block):
+  gate on `isClutter && Variant==3` INSIDE the destroyed-bitset guard (nodes share the packed arrays with
+  Variant slot 0 — confirmed LOW). On rem<=0 for an explosive: mark destroyed[i] (unhittable this tick),
+  `SetComponent(BlightClutter{Remaining=0,...})` + `ecb.AddComponent(BarrelFuse{ExplodeTick})` — NO destroy.
+  Both target snapshots SKIP entries with `Remaining <= 0` (a fused barrel is not hittable → no double-pop).
+- **`HazardExplosionSystem`** (new, ProjectM.Server, plain `SimulationSystemGroup`, NO ordering attributes,
+  NO lifecycle gating — a fused barrel must always drain (confirmed LOW: never RequireForUpdate-gate it);
+  `TryGetSingleton<NetworkTime>` invalid → skip tick, fuse persists): query `(BarrelFuse, LocalTransform)`;
+  when `ExplodeTick` elapses (NetworkTick.IsNewerThan semantics): radius scan (XZ, `Tuning.BarrelExplodeRadius
+  ≈3.25`) — players via the BossAISystem:62-70 gather VERBATIM (`Health>0 && RegionTag==Expedition`; confirmed:
+  dead players persist at death pos for DelayTicks) + enemies (`EnemyTag && Health>0`, excludes Dying corpses)
+  → `AppendToBuffer(DamageEvent{ Amount=Tuning.BarrelExplodeDamage≈26, SourceNetworkId=-1, SourceTick=
+  TickUtil.NonZero(now) })` → `ecb.DestroyEntity(barrel)` (single destroy site).
+  **SourceNetworkId = -1** (environment convention — confirmed: a player id would score+consume Charger
+  whiff-punish windows via HealthApplyDamageSystem:102, the sole reader).
+- **No chain reactions** v1 (clutter has Remaining, not Health). Damage numbers as `Tuning` consts v1;
+  promote to TuningConfig knobs when the knob-table extension is worth it (confirmed-LOW tension, deferred
+  deliberately — noted here per [[ask-before-deferring-during-implementation]]: the overlay knob table is a
+  separate mechanical slice).
+
+## Client (all new work — confirmed: NO existing per-variant path; Variant is read by zero client systems)
+
+- **WorldFeedbackSystem**: add `Variant` to the Cache struct; at prune, `IsClutter && Variant==3 &&
+  Remaining<=0` → BIG boom (burst + `DynamicLightSystem.RequestFlash` large orange + low boom SFX); else the
+  existing small puff. Teardown despawns (Remaining>0) keep the puff.
+- **DynamicLightSystem**: Variant==3 barrels get a red glow light (node-glow pattern); when the cached
+  `Remaining<=0` (fuse lit) the glow strobes hard — the flee cue. (Body tint via URPMaterialPropertyBaseColor
+  on LEG children = polish, deferred.)
+
+## Tests
+
+- ResourceHarvestSystemTests: explosive pop → BarrelFuse added, Remaining==0, entity ALIVE; fused barrel
+  not re-hittable.
+- New HazardExplosionSystemTests: elapsed fuse → DamageEvent(Amount, SourceNetworkId=-1) on in-radius living
+  enemy AND living player, dead player skipped, out-of-radius skipped, barrel destroyed once; un-elapsed
+  fuse → nothing.
+
+## Wire/bake classification
+
+ZERO new [GhostField]s / ghost prefabs / RPCs; `BarrelFuse` is server-only; Variant==3 rides the existing
+replicated byte. No new ordering edges. Re-bake: none (code + seeded-value only).