User report during the #170 gate: pack-melee monsters partly inside each
other with slightly stale facings vs retail on the same ACE. Investigation
(report-only) pinned two code-grounded causes, both already-tracked R5-V3
scope, fix APPROVED by the user:
1. TS-39 — sticky melee is a no-op: ACE arms melee chases with Sticky
(Monster_Navigation.cs:416); retail's arrival hands off to
PositionManager::StickTo -> StickyManager::adjust_offset (0x00555430,
per-tick 0.3m edge gap + facing tracking); acdream's StickTo/Unstick
seams are unbound so attackers freeze at stale arrival poses.
2. Arrival radii are zero: getOwnRadius () => 0f (the R5-V3 pin) and
RouteServerMoveTo never sets MovementStruct.Radius/Height — retail/ACE
arrive edge-to-edge with setup-derived radii (ACE PhysicsObj.MoveToObject
reads the TARGET's PartArray radius/height).
Ruled out: the between-snap collision sweep (remotes run full
ResolveWithTransition; CollisionExemption keeps creatures collidable).
Caveat recorded: ACE has no server-side monster avoidance — acceptance is
retail PARITY, not zero overlap.
ISSUES #171 filed; handoff docs/research/2026-07-04-171-sticky-melee-handoff.md
+ pickup docs/research/2026-07-04-171-pickup-prompt.md; memory index updated.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
d413ac2a29