Architecture and lifecycle

Ownership chain

Use this default chain:

server-authoritative gameplay state
  -> replicated actor/component/property
  -> local player presentation model or Viewmodel
  -> local widget tree

widget interaction
  -> semantic local intent
  -> owning PlayerController/Pawn/component
  -> validated gameplay call or Server RPC

Widgets are local presentation objects. They must not own canonical inventory, health, match, or save state. UI may predict presentation, but authoritative correction comes from gameplay.

Local-player ownership

• Create player UI with an owning PlayerController/LocalPlayer.
• Prefer AddToPlayerScreen for player-specific full-screen UI; it targets the player's viewport section. Use AddToViewport only when the UI is intentionally viewport-global.
• In split screen, keep one root layout/presentation model per local player.
• Set the owning player on world-space Widget Components when per-player display matters.
• Never fetch player zero as a substitute for correct ownership.

Widget lifecycle

• OnInitialized/NativeOnInitialized: one-time instance initialization.
• Construct/NativeConstruct: Slate construction; it may run multiple times when the widget leaves and re-enters the hierarchy.
• Destruct/NativeDestruct: release hierarchy-time subscriptions/resources, while allowing that the UObject can still exist.
• NativeOnActivated/NativeOnDeactivated: Common Activatable Widget screen-active lifetime.

Bind and unbind symmetrically. Guard against duplicate delegate registration if construction or activation can repeat. Keep activation-time subscriptions scoped to activation.

State placement

State	Owner
Health, inventory, score, match phase	Replicated gameplay model
Display-formatted health, selected tab, sorted rows	Local presentation model/Viewmodel
Hover, focus, animation progress	Widget
Input mapping/profile	Local Player input subsystem/user settings
Screen stack and modal state	Local root UI/CommonUI layer manager

Failure checks

• UI works for client 1 but not client 2: inspect owning local player and player-zero lookups.
• callbacks duplicate after reopening: inspect Construct/activation bindings and unbind path.
• client UI changes but server state does not: route intent through an owned replicated actor.
• listen server appears correct: repeat on a remote client; host-local ownership can hide bugs.