feat(ui): centralize retail selection state

docs/architecture/acdream-architecture.md

@@ -102,7 +102,11 @@ retained gameplay tree, LayoutDesc importer, window runtime, and panel
 controllers. Neither presentation stack owns independent game-state truth.
 Plugins register retained gameplay markup through the BCL-only
 `AcDream.Plugin.Abstractions.IUiRegistry`; they do not import App or ImGui
-assemblies.
+assemblies. Core `SelectionState` is the sole selected-object owner for world,
+radar, inventory, paperdoll, toolbar, use/examine consumers, and plugins;
+`IPluginHost.Selection` exposes that same state and retail-style old/new callback.
+Temporary pointer modes are separate App orchestration in `InteractionState` and
+must never become a competing selection owner.
 
 Every retained gameplay window has a typed `RetailWindowHandle` and at most one
 `IRetainedPanelController` lifecycle owner. Multi-controller windows use
@@ -164,6 +168,7 @@ src/
     IPluginHost.cs            -> done
     IGameState.cs             -> done
     IEvents.cs                -> done
+    ISelectionService.cs      -> done
   
   AcDream.App/               Layer 1 + Layer 4 wiring
     Rendering/

docs/architecture/code-structure.md

@@ -214,8 +214,9 @@ What `GameWindow` loses:
   `LiveSessionController`.
 - `_entitiesByServerGuid` + per-entity dictionaries + ServerGuid↔Id
   translation → moved into `LiveEntityRuntime`.
-- `WorldPicker` + `_selectedGuid` + `SendUse` / `SendPickUp` → moved
+- `WorldPicker` + selection-driven `SendUse` / `SendPickUp` orchestration → moved
-  into `SelectionInteractionController`.
+  into `SelectionInteractionController`; Core `SelectionState` remains the
+  already-shipped session owner and is injected into that controller.
 - Per-frame draw orchestration → moved into `RenderFrameOrchestrator`.
 
 The eventual `GameEntity` aggregation (target state described in
@@ -289,7 +290,7 @@ All four M1 demo targets must still work.
 
 ### Step 4 — `SelectionInteractionController`
 
-**Scope:** Extract `WorldPicker`, `_selectedGuid`, `SendUse`,
+**Scope:** Extract `WorldPicker`, the Core `SelectionState` consumers, `SendUse`,
 `SendPickUp`, and the `InputAction.Select*` / `UseSelected` /
 `SelectionPickUp` switch cases into one controller. Depends on Step 3
 (uses `LiveEntityRuntime`).

docs/architecture/retail-divergence-register.md

@@ -104,7 +104,7 @@ accepted-divergence entries (#96, #49, #50).
 
 ---
 
-## 3. Documented approximation (AP) — 99 active rows
+## 3. Documented approximation (AP) — 98 active rows
 
 Wave-0 UI ledger repair (2026-07-10) retired stale AP-38, resolved the AP-84
 collision, restored overwritten paperdoll rows as AP-92/AP-93, and registered
@@ -162,8 +162,7 @@ AP-94..AP-110 for the confirmed retail-UI completion gaps.
 | AP-53 | Contents grid slot count defaults to 102 (main pack) or 24 (side bag) when the open container's `ItemsCapacity` is absent/0. Container-switching is now wired (D.2b): clicking a side bag sends `Use 0x0036` and the grid repopulates from `ViewContents 0x0196`. This row covers only the capacity *default* when the server omits `ItemsCapacity`. | `src/AcDream.App/UI/Layout/InventoryController.cs` (`Populate`) | `ItemsCapacity` is not reliably on every ClientObject yet; 102/24 are the retail standard capacities. Retire when `ItemsCapacity` is confirmed delivered for all containers. | A non-102/24 pack shows the wrong empty-slot count — cosmetic only. | retail main-pack capacity 102; side-pack 24; ACE `ItemsCapacity`; `ViewContents 0x0196` |
 | AP-54 | Inventory window vertical resize is a toolkit approximation: bottom-edge drag, expand-only (Min = dat default 372 px, Max = 560 px constant), contents grid/sub-window/scrollbar/backdrop stretched via overridden `Left\|Top\|Bottom` anchors. | `src/AcDream.App/Rendering/GameWindow.cs` (inventory frame setup) | retail's gmInventoryUI resize lives in keystone.dll (no decomp); the anchor-stretch + 372..560 range matches the observed retail behavior for the dev loop. | The expand range / which elements reflow could differ from retail (e.g. retail may allow shrink-below-default); shrink is intentionally disabled for now. | retail gmInventoryUI resize (keystone.dll, no decomp); `UiNineSlicePanel` resize |
 | AP-55 | The toolbar's item slots keep the hardcoded `UiItemSlot.EmptySprite = 0x060074CF` rather than resolving their cell template via attribute `0x1000000e`. Correct in outcome (the toolbar's `0x1000000e` resolves to a generic prototype whose empty media is `0x060074CF`) but not dat-resolved. | `src/AcDream.App/UI/UiItemSlot.cs` (`EmptySprite` default); `src/AcDream.App/UI/Layout/ToolbarController.cs` | The inventory lists now port the retail resolver (`ItemListCellTemplate`); the toolbar was left on its hardcoded default to avoid regressing frozen, working art. Retire when the toolbar is routed through `ItemListCellTemplate`. | If a future toolbar layout's `0x1000000e` points at a non-generic prototype, the toolbar would show stale art. | `UIElement_ItemList::InternalCreateItem` 0x004e3570; catalog `0x21000037` |
-| AP-57 | The open-container triangle (`0x06005D9C`) + selected-item square (`0x06004D21`) are drawn as **procedural `UiItemSlot` overlays** keyed by controller state (`_openContainer`/`_selectedItem`), reproducing the retail keying (`item.itemID == openContainerId / selectedItemId` per `UpdateOpenContainerIndicator 0x004e3070` / `ItemList_SetSelectedItem 0x004e2fe0`) but not via the dat prototype's `m_elem_Icon_OpenContainer`/`m_elem_Icon_Selected` state elements + `SetOpenContainerState`/`SetSelectedState` calls. | `src/AcDream.App/UI/UiItemSlot.cs`; `src/AcDream.App/UI/Layout/InventoryController.cs` | The procedural overlay produces the correct visual result; the 36×36 container prototype (`0x1000033F`) lacks the square child, so the procedural overlay is the only way to show the square on a selected bag — the dat-state path retail uses would require the prototype to be richer than it is. | A cell that should show an indicator via a dat-state path retail uses but we don't would be missed; outcome currently matches retail for the open/selected indicator cases. | `UIElement_ItemList::UpdateOpenContainerIndicator` 0x004e3070; `ItemList_SetSelectedItem` 0x004e2fe0; `SetOpenContainerState` 0x004e1200; `SetSelectedState` 0x004e1240 |
+| AP-57 | The open-container triangle (`0x06005D9C`) + selected-item square (`0x06004D21`) are drawn as **procedural `UiItemSlot` overlays** keyed by `_openContainer` plus Core `SelectionState.SelectedObjectId`, reproducing the retail keying (`item.itemID == openContainerId / selectedID` per `UpdateOpenContainerIndicator 0x004e3070` / `SetSelectedObject 0x0058c2e0`) but not via the dat prototype's `m_elem_Icon_OpenContainer`/`m_elem_Icon_Selected` state elements + `SetOpenContainerState`/`SetSelectedState` calls. | `src/AcDream.App/UI/UiItemSlot.cs`; `src/AcDream.App/UI/Layout/InventoryController.cs` | The procedural overlay produces the correct visual result; the 36×36 container prototype (`0x1000033F`) lacks the square child, so the procedural overlay is the only way to show the square on a selected bag — the dat-state path retail uses would require the prototype to be richer than it is. | A cell that should show an indicator via a dat-state path retail uses but we don't would be missed; outcome currently matches retail for the open/selected indicator cases. | `UIElement_ItemList::UpdateOpenContainerIndicator` 0x004e3070; `ACCWeenieObject::SetSelectedObject` 0x0058c2e0; `SetOpenContainerState` 0x004e1200; `SetSelectedState` 0x004e1240 |
-| AP-58 | Inventory item **selection is panel-local + visual-only** — clicking a grid item moves the green square but does not wire to the selected-object bar (`SelectedObjectController`) or to global 3D-world selection. | `src/AcDream.App/UI/Layout/InventoryController.cs` (`SelectItem`) | The selected-object bar + 3D-world selection wiring is deferred to the selection follow-up; the panel-local square is the correct first step. | Selecting an inventory item doesn't populate the selected-object strip as retail does — functional gap deferred. | `gmInventoryUI`/`gmBackpackUI` item-select → `ClientUISystem::SetSelectedObject`; `SelectedObjectController` |
 | AP-59 | The per-cell container **capacity bar** (retail `UIElement_UIItem::UpdateCapacityDisplay 0x004e16e0`, element `0x10000347`) is drawn as a **procedural `UiItemSlot` overlay** (track `0x06004D22` full + fill `0x06004D23` clipped bottom-up to `GetContents(guid).Count / ItemsCapacity`), not via a real dat `UIElement_Meter` child. **Right-anchored flush** (the dat rect X=26 in a 36px cell sat ~5px off the edge — flush per the visual gate) and **bottom-up fill assumed** (the dat `m_eDirection` 0x6f isn't read, cf. AP-50). A CLOSED side bag reads empty until opened (its contents aren't indexed until `ViewContents`) — faithful to retail's known-children count, divergent if retail pre-loads. | `src/AcDream.App/UI/UiItemSlot.cs` (`CapacityFill` draw); `src/AcDream.App/UI/Layout/InventoryController.cs` (`SetCapacityBar`) | UiItemSlot is a behavioral leaf that paints overlays procedurally (cf. AP-57); the meter sprites + fill formula are the faithful port. Right-anchor + bottom-up were visual-gate calls. Further visual polish is deferred — ISSUES #146. | Fill direction / exact bar rect could differ from retail's `m_eDirection` + dat X; closed-bag bars read empty if retail pre-loads container counts. | `UIElement_UIItem::UpdateCapacityDisplay` 0x004e16e0; element `0x10000347` (back `0x06004D22` / front `0x06004D23`); `GetNumContainedItems` |
 | AP-60 | Inventory drag **`OnDragLift` is a no-op** + the source cell is **not dimmed**: retail dims the lifted item's source cell (`RecvNotice_ItemListBeginDrag`); acdream leaves the item in place during the drag + the floating ghost. | `src/AcDream.App/UI/Layout/InventoryController.cs` | Cosmetic only — the dragged item is still unambiguously identifiable; dimming the source requires tracking the source cell reference across drag events, deferred to a polish pass. | A drag in progress doesn't visually mark its origin — cosmetic only, no functional effect. | `RecvNotice_ItemListBeginDrag` acclient_2013_pseudo_c.txt |
 | AP-61 | Drop on a **CLOSED side bag is advisory-accept**: the client can't know a closed bag's item count (contents aren't indexed until opened), so `OnDragOver` shows green + relies on the server's `InventoryServerSaveFailed` reject + the rollback; retail knows the count when loaded. | `src/AcDream.App/UI/Layout/InventoryController.cs` (`IsContainerFull`) | A drop into a closed-but-full bag shows green then snaps back (a flicker) instead of pre-showing red. Faithful only when the bag has been opened (then `GetContents` is populated). The server's `0x00A0` + optimistic rollback is the authoritative safety net. | A drop into a closed-but-full bag shows green → brief flicker → snap-back instead of retail's pre-emptive red circle. | `UIElement_ItemList::InqDropIconInfo 0x004e26f0` |

docs/plans/2026-04-11-roadmap.md

@@ -481,7 +481,7 @@ behavior. Estimated 17–26 days focused work, 3–5 weeks calendar.
 - **D.5 — Core panels.** Attributes (`chunk_00470000.c:FUN_0047ba70`), Skills (same), Paperdoll (`chunk_004A0000.c:FUN_004A5200`), Inventory, Spellbook (`chunk_004C0000.c`), Fellowship, Allegiance. Each uses the port sketches in slice 05. **(Targets `AcDream.UI.Abstractions` — ships with D.2a using ImGui-rendered widgets; reskinned by D.2b.)** The *chat* panel originally listed under D.5 shipped early in Phase I (I.4 input + I.7 combat translator superseded the chat-panel design here); this entry now covers Attributes / Skills / Paperdoll / Inventory / Spellbook / Fellowship / Allegiance only.
 - **✓ SHIPPED — D.5.1 — Toolbar (action bar).** Shipped 2026-06-16/17 (`30b28c2`→`0e7a083`, branch claude/hopeful-maxwell-214a12). First data-driven *game* panel: `gmToolbarUI` (`LayoutDesc 0x21000016`) — 18 shortcut slots from the persisted `PlayerDescription` SHORTCUT block, real **composited** item icons (opaque type-default underlay via the `EnumIDMap 0x10000004` resolve), **occupancy-gated slot numbers 1–9** (occupied = dark-box peace/war `0x10000042/43`; empty = background `0x1000005e` from cell composite `0x10000341`), **click-to-use** (`ItemHolder::UseObject` → `0x0036`), **peace/war stance** indicator live-wired to `CombatState`, **movable**, and a **chrome frame** (UiNineSlicePanel drawn over content via the new `UiElement.OnDrawAfterChildren` hook). New shared widgets `UiItemSlot` (`UIElement_UIItem` 0x10000032, procedural leaf) + `UiItemList` (`UIElement_ItemList` 0x10000031, factory branch) + `IconComposer` (CPU layered composite). `CreateObject.TryParse` extended to the full ACE-order weenie-header tail to capture `IconId`/`IconOverlay`/`IconUnderlay` → `ItemRepository.EnrichItem` → re-render. Spec/plan `docs/superpowers/{specs,plans}/2026-06-16-d2b-toolbar-phase1*.md`; research drop `docs/research/2026-06-16-*deep-dive.md` + synthesis. Divergence IA-16/IA-17 added. **User-confirmed** (numbers, icons, frame). Per-task spec+code-review throughout.
 - **✓ SHIPPED — D.5.2 — Stateful item-icon system.** Shipped 2026-06-17/18 (`419c3ac`..`fb288ad`, branch claude/hopeful-maxwell-214a12; **visually verified on a live Coldeve server**). Faithful retail icon composite (`IconData::RenderIcons` @0x0058d180): (1) `UiEffects` bitfield captured from the `CreateObject` weenie header (was discarded) → `ItemInstance.Effects`; (2) `IconComposer.GetIcon` rewritten as a 2-stage composite — Stage 1 = drag icon (base + custom overlay) + the effect treatment, Stage 2 = type-default underlay + custom underlay + drag. The effect treatment ports the **surface overload** of `SurfaceWindow::ReplaceColor` (`0x004415b0`): the textured effect tile (`EnumIDMap 0x10000005` by `LowestSetBit(effects)+1`, fallback `0x21` solid-black) is copied **per-pixel** into the icon's pure-white pixels — magical items take the tile's GRADIENT hue, mundane items go black; (3) `PublicUpdatePropertyInt (0x02CE)` parser + `WorldSession.ObjectIntPropertyUpdated` event + `GameWindow` subscription → `ItemRepository.UpdateIntProperty` → icon re-composites live. **Appraise (`0x00C9`) carries NO icon data** (ACE proof: `Icon`/`IconOverlay`/`IconUnderlay`/`UiEffects` all lack `[AssessmentProperty]`) — dropped as a no-op. **Two visual-verification fixes landed after the subagent build:** the `effects==0` recolor MUST run (mundane white edges → black, `40c97a5`) and the tint is a per-pixel GRADIENT not a flat color (the surface overload, `fb288ad`) — both confirmed via clean Ghidra + named decomp. Divergence: IA-16 retired; IA-18 (per-pixel surface-copy anti-regression) + AP-45 (0x02CE sequence) added; **AP-43/AP-44 retired by the visual fixes**. Spec/plan/research: `docs/superpowers/{specs,plans}/2026-06-17-d2b-stateful-icon*.md`, `docs/research/2026-06-17-stateful-icon-RESOLVED.md`.
-- **D.5 remaining — sub-phase ledger.** D.5.1 (toolbar + the `UiItemSlot`/`UiItemList`/`IconComposer` spine) ✅, D.5.2 (stateful icons) ✅, D.5.4 (client object/item data model) ✅, D.2b-B window manager (`abbd97b`) ✅, D.2b-B B-Grid (inventory sub-window mount + `UiItemList` grid) ✅, D.2b-B B-Controller (inventory population + burden meter + captions, `03fbf44`; **visually confirmed 2026-06-21** — two render bugs fixed at the gate `417b137`: backdrop wash-out [a #145 continuation — mounted sub-window slots must keep their own frame ZLevel, not inherit the base root's 1000] + captions [drive the host UiText directly]) ✅, D.2b-B B-Wire (`EncumbranceVal`/PropertyInt 5 wire delivery, AP-48/49 retired) ✅, inventory window finish Stage 1 (scroll/frame/vertical-resize/102-slot grid) ✅, empty-slot art ✅, container-switching + open/selected indicators + main-pack icon + per-bag capacity bar ✅, B-Drag (inventory drag-drop / item moving) ✅, **Sub-phase C (paperdoll): Slice 1 equip slots ✅ + Slice 2 3-D doll `UiViewport` (Type 0xD via the `IUiViewportRenderer` RTT seam) + Slots toggle ✅ (visually confirmed 2026-06-25, `8fa66c2` — pose/camera/heading all retail-verbatim)** ✅, **UI Studio** (`AcDream.App ui-studio`) ✅, **importer dat-fidelity (Fix A/B/C)** ✅, and **Character window** (`LayoutDesc 0x2100002E`, `CharacterStatController`) ✅ are shipped. Build order from here: **(d) finish the bar — D.5.3 remaining (selected-object meter/mana, stack entry/slider) + spell shortcuts + the selection→selected-object-bar wiring (AP-58); ISSUES #146/#147/#148.** Each ☐ below gets its own brainstorm → spec → plan.
+- **D.5 remaining — sub-phase ledger.** D.5.1 (toolbar + the `UiItemSlot`/`UiItemList`/`IconComposer` spine) ✅, D.5.2 (stateful icons) ✅, D.5.4 (client object/item data model) ✅, D.2b-B window manager (`abbd97b`) ✅, D.2b-B B-Grid (inventory sub-window mount + `UiItemList` grid) ✅, D.2b-B B-Controller (inventory population + burden meter + captions, `03fbf44`; **visually confirmed 2026-06-21** — two render bugs fixed at the gate `417b137`: backdrop wash-out [a #145 continuation — mounted sub-window slots must keep their own frame ZLevel, not inherit the base root's 1000] + captions [drive the host UiText directly]) ✅, D.2b-B B-Wire (`EncumbranceVal`/PropertyInt 5 wire delivery, AP-48/49 retired) ✅, inventory window finish Stage 1 (scroll/frame/vertical-resize/102-slot grid) ✅, empty-slot art ✅, container-switching + open/selected indicators + main-pack icon + per-bag capacity bar ✅, B-Drag (inventory drag-drop / item moving) ✅, **Sub-phase C (paperdoll): Slice 1 equip slots ✅ + Slice 2 3-D doll `UiViewport` (Type 0xD via the `IUiViewportRenderer` RTT seam) + Slots toggle ✅ (visually confirmed 2026-06-25, `8fa66c2` — pose/camera/heading all retail-verbatim)** ✅, **UI Studio** (`AcDream.App ui-studio`) ✅, **importer dat-fidelity (Fix A/B/C)** ✅, **Character window** (`LayoutDesc 0x2100002E`, `CharacterStatController`) ✅, and **Wave 3.1 unified selection** (Core `SelectionState`; AP-58 retired) ✅ are shipped. Build order from here: **finish Wave 3 item policy/router/cursors, then D.5.3 selected-object mana + stack entry/slider and the separate favorite-spell bars; ISSUES #146/#147/#197.** Each ☐ below gets its own focused oracle/spec/plan/gate.
 - **✓ SHIPPED — UI Studio** (2026-06-26, branch `claude/hopeful-maxwell-214a12`, ~33693c6→HEAD). Standalone `AcDream.App ui-studio <datdir> [--layout 0xNNNN | --dump <slug>] [--screenshot <png>]` Silk tool that previews any panel through the **production renderer** (`RenderBootstrap.cs` + GameWindow untouched). Sources: 26-window retail dump (`docs/research/2026-06-25-retail-ui-layout-dump.json`) via `--dump`, or live dat import + fixtures via `--layout`. Interactive canvas (click-routing to `UiHost`, Interact/Inspect ImGui toggle), headless `--screenshot`. Architecture: `src/AcDream.App/Studio/` (`StudioWindow`, `PanelFbo`, `FixtureProvider`, `LayoutSource`) + `src/AcDream.App/Rendering/RenderBootstrap.cs`. ISSUES #156 (inventory all-black in studio) and #157 (GameWindow font resolver) filed.
 - **✓ SHIPPED — Importer dat-fidelity** (Fix A/B/C, 2026-06-26, same branch). **Boundary established: look = importer (font/justification/color from dat); state/behavior = runtime controller logic.** Fix A: justification property `0x14`/`0x15` → `UiText` Centered/RightAligned/VerticalJustify. Fix B: FontColor property `0x1B` → `UiText.DefaultColor`; character colors proved RUNTIME (no importer fix). Fix C: FontDid → per-element dat font via a resolver in `DatWidgetFactory` — **STUDIO path only**; GameWindow passes `null` (Issue #157). Fix 4 (UIState-group activation): INVESTIGATED — no importer fix exists; the dat has no Visible encoding; runtime `gm*UI` is correct.
 - **✓ SHIPPED — Character window** (`LayoutDesc 0x2100002E`, `CharacterStatController`, 2026-06-26, same branch). **Visually user-confirmed 2026-06-26 — Attributes tab reads as retail.** Three tabs, header (name/heritage/PK), large-gold level number (dat font, `largeDatFont` 18px), "Total Experience (XP):" + "XP for next level:" captions, 9-row attribute list (icons + right-aligned values + Health/Stamina/Mana vitals), click-to-select (top/bottom selection bars + footer State-B "{Attr}: {value}" / "Experience To Raise: Infinity!" + affordability-gated raise triangles), centered footer. User noted "still needs some polish for later" — deferred to Issue #158.

docs/research/2026-07-10-retail-toolbar-interaction-pseudocode.md

@@ -979,8 +979,9 @@ implementation patch.
    is not a faithful `UseObject` port: it omits ready/vendor/trade/confirmations,
    the complete `DetermineUseResult` classification, container post-actions,
    `AttemptPlaceIn3D`, and retail busy semantics.
-6. Selection remains owned by `GameWindow._selectedGuid`; the previously documented
+6. **Resolved 2026-07-11:** selection is owned by Core `SelectionState` and shared
-   `Core.SelectionState` file is absent in this worktree.
+   by world/radar/inventory/paperdoll/toolbar/plugins; the former
+   `GameWindow._selectedGuid` and inventory-local selected item are gone.
 7. Current cursor catalog exposes only `0x27..0x29`. The reachable global catalog
    also includes `0x01..0x06` and `0x0A..0x0F`.
 8. Current cursor resolution uses a modern static priority chain. Retail instead

docs/superpowers/plans/2026-07-10-retail-ui-fidelity-completion.md

@@ -316,15 +316,24 @@ chrome and content together; full suite and user visual gate.
 
 ### 3.1 Centralize selection
 
-- [ ] Add Core `SelectionState` with selected guid, previous guid, reason/source,
+- [x] Add Core `SelectionState` with selected guid, previous guid, reason/source,
   and one change event.
-- [ ] Route world pick, radar click, inventory selection, paperdoll selection,
+- [x] Route world pick, radar click, inventory selection, paperdoll selection,
   toolbar selected strip, target indicator, examine/use, and plugins through it.
-- [ ] Delete panel-local competing selection state except transient hover/row focus.
+- [x] Delete panel-local competing selection state except transient hover/row focus.
-- [ ] Add one App interaction-state owner for `None`, `Use`, `Examine`, and
+- [x] Add one App interaction-state owner for `None`, `Use`, `Examine`, and
   `UseItemOnTarget(sourceGuid)`; Core selection remains session truth while target
   mode remains UI orchestration state.
 
+**Implementation (2026-07-11):** Core `SelectionState` ports
+`ACCWeenieObject::SetSelectedObject @ 0x0058C2E0`, including deduplication,
+previous/previous-valid tracking, object-removal clear, and plugin callbacks.
+World pick, radar, combat targeting, inventory, paperdoll slots, the selected
+toolbar strip, target indicator, use/pickup, PreviousSelection, and the new
+`IPluginHost.Selection` contract share that owner. `InteractionState` separately
+owns `None`/`Use`/`Examine`/`UseItemOnTarget`; `ItemInteractionController` now
+projects its pending source from that state. AP-58 retired.
+
 ### 3.2 Port item-use/drop legality into Core
 
 - [ ] Translate `ItemHolder::UseObject`, `DetermineUseResult`, and

memory/project_ui_architecture.md

@@ -120,3 +120,19 @@ window mounts, toolbar digit and inventory-cell asset lookup, plugin mounts,
 cursor feedback, persistence, automation, and retained tick/draw/restore/dispose
 paths live behind the runtime. The live Debug gate passed across two graceful
 restart cycles. Do not add panel mount bodies back to `GameWindow`.
+
+## 2026-07-11 selection and interaction ownership
+
+`AcDream.Core.Selection.SelectionState` is the only selected-object truth. It
+ports retail `ACCWeenieObject::SetSelectedObject`: deduplicate the current guid,
+remember previous and previous-valid guids, commit before firing one typed
+transition, and clear with the removed object retained as previous. World pick,
+radar, combat targeting, inventory, paperdoll slots, toolbar selected-object
+presentation, target indicator, use/pickup, PreviousSelection, and plugins all
+read or write this same owner. Plugins use `IPluginHost.Selection`; plugin event
+failures are isolated from the client and other plugins.
+
+`AcDream.App.UI.InteractionState` separately owns temporary pointer orchestration:
+`None`, `Use`, `Examine`, or `UseItemOnTarget(sourceGuid)`. Item target mode is a
+projection of this state, not a second selected-object field. Keep selection in
+Core and interaction modes in App when completing Wave 3.

src/AcDream.App/Plugins/AppPluginHost.cs

@@ -4,16 +4,23 @@ namespace AcDream.App.Plugins;
 
 public sealed class AppPluginHost : IPluginHost
 {
-    public AppPluginHost(IPluginLogger log, IGameState state, IEvents events, IUiRegistry ui)
+    public AppPluginHost(
+        IPluginLogger log,
+        IGameState state,
+        IEvents events,
+        ISelectionService selection,
+        IUiRegistry ui)
     {
         Log = log;
         State = state;
         Events = events;
+        Selection = selection;
         Ui = ui;
     }
 
     public IPluginLogger Log { get; }
     public IGameState State { get; }
     public IEvents Events { get; }
+    public ISelectionService Selection { get; }
     public IUiRegistry Ui { get; }
 }

src/AcDream.App/Program.cs

@@ -31,8 +31,10 @@ var runtimeOptions = RuntimeOptions.FromEnvironment(datDir);
 
 var worldGameState = new AcDream.Core.Plugins.WorldGameState();
 var worldEvents = new AcDream.Core.Plugins.WorldEvents();
+var selection = new AcDream.Core.Selection.SelectionState();
 var uiRegistry = new AcDream.App.Plugins.BufferedUiRegistry();
-var host = new AppPluginHost(new SerilogAdapter(Log.Logger), worldGameState, worldEvents, uiRegistry);
+var host = new AppPluginHost(
+    new SerilogAdapter(Log.Logger), worldGameState, worldEvents, selection, uiRegistry);
 
 var pluginsDir = Path.Combine(AppContext.BaseDirectory, "plugins");
 Log.Information("scanning plugins in {PluginsDir}", pluginsDir);
@@ -65,7 +67,8 @@ try
         catch (Exception ex) { Log.Error(ex, "plugin enable failed: {Id}", plugin.Manifest.Id); }
     }
 
-    using var window = new GameWindow(runtimeOptions, worldGameState, worldEvents, uiRegistry);
+    using var window = new GameWindow(
+        runtimeOptions, worldGameState, worldEvents, selection, uiRegistry);
     window.Run();
 }
 finally

src/AcDream.App/Rendering/GameWindow.cs

@@ -16,6 +16,7 @@ public sealed class GameWindow : IDisposable
     private readonly string _datDir;
     private readonly WorldGameState _worldGameState;
     private readonly WorldEvents _worldEvents;
+    private readonly AcDream.Core.Selection.SelectionState _selection;
     private IWindow? _window;
     private GL? _gl;
     private IInputContext? _input;
@@ -1032,24 +1033,6 @@ public sealed class GameWindow : IDisposable
     /// fields when a 0xF625 ObjDescEvent arrives carrying only updated visuals.
     /// </summary>
     private readonly Dictionary<uint, AcDream.Core.Net.WorldSession.EntitySpawn> _lastSpawnByGuid = new();
-    // Current selection: written by Q-cycle (combat) and LMB click (interact); cleared on entity despawn.
-    private uint? _selectedGuid;
-    /// <summary>Fires when the selected world object changes (retail gmToolbarUI selection-change event,
-    /// acclient_2013_pseudo_c.txt:198635). Private: only the internal SelectedObjectController subscribes.</summary>
-    private event Action<uint?>? SelectionChanged;
-    /// <summary>Currently-selected world object guid. The setter fires <see cref="SelectionChanged"/> only on
-    /// an actual change (dedup), so all writes go through here; reads may use the field directly.</summary>
-    private uint? SelectedGuid
-    {
-        get => _selectedGuid;
-        set
-        {
-            if (_selectedGuid == value) return;
-            _selectedGuid = value;
-            SelectionChanged?.Invoke(value);
-        }
-    }
-
     // B.6/B.7 (2026-05-16): pending close-range action that will be fired
     // once the local auto-walk overlay reports arrival (body has finished
     // rotating to face the target). Only set for close-range Use/PickUp;
@@ -1085,13 +1068,18 @@ public sealed class GameWindow : IDisposable
     private int _liveAnimRejectSingleFrame;
     private int _liveAnimRejectPartFrames;
 
-    public GameWindow(AcDream.App.RuntimeOptions options, WorldGameState worldGameState, WorldEvents worldEvents,
+    public GameWindow(
+        AcDream.App.RuntimeOptions options,
+        WorldGameState worldGameState,
+        WorldEvents worldEvents,
+        AcDream.Core.Selection.SelectionState selection,
         AcDream.App.Plugins.BufferedUiRegistry? uiRegistry = null)
     {
         _options = options ?? throw new System.ArgumentNullException(nameof(options));
         _datDir = options.DatDir;
         _worldGameState = worldGameState;
         _worldEvents = worldEvents;
+        _selection = selection ?? throw new System.ArgumentNullException(nameof(selection));
         _uiRegistry = uiRegistry;
         SpellBook = new AcDream.Core.Spells.Spellbook(SpellTable);
         LocalPlayer = new AcDream.Core.Player.LocalPlayerState(SpellBook);
@@ -1525,13 +1513,13 @@ public sealed class GameWindow : IDisposable
                 // B.7 Vivid Target Indicator — corner-triangle highlight
                 // around the currently-selected entity. Delegates pull
                 // live state from this GameWindow instance every frame:
-                //   - selected guid → _selectedGuid (set by PickAndStoreSelection)
+                //   - selected guid → shared SelectionState
                 //   - entity resolver → position from _entitiesByServerGuid +
                 //     itemType from ClientObjectTable (Objects) + last spawn
                 //   - camera → _cameraController.Active or (zero) when not
                 //     yet ready, in which case the panel bails on viewport==0.
                 _targetIndicator = new AcDream.App.UI.TargetIndicatorPanel(
-                    selectedGuidProvider: () => _selectedGuid,
+                    selectedGuidProvider: () => _selection.SelectedObjectId,
                     entityResolver: guid =>
                     {
                         if (!_entitiesByServerGuid.TryGetValue(guid, out var entity))
@@ -2078,7 +2066,7 @@ public sealed class GameWindow : IDisposable
                 playerGuid: () => _playerServerGuid,
                 playerYawRadians: () => _playerController?.Yaw ?? 0f,
                 playerCellId: () => _playerController?.CellId ?? 0u,
-                selectedGuid: () => _selectedGuid,
+                selectedGuid: () => _selection.SelectedObjectId,
                 coordinatesOnRadar: () => _persistedGameplay.CoordinatesOnRadar,
                 uiLocked: () => _persistedGameplay.LockUI);
             var retailChatVm = new AcDream.UI.Abstractions.Panels.Chat.ChatVM(Chat, displayLimit: 200);
@@ -2103,7 +2091,7 @@ public sealed class GameWindow : IDisposable
                             AcDream.UI.Abstractions.NullCommandBus.Instance),
                     Radar: new AcDream.App.UI.RadarRuntimeBindings(
                         radarSnapshotProvider.BuildSnapshot,
-                        guid => SelectedGuid = guid,
+                        _selection,
                         SetRetailUiLocked),
                     Toolbar: new AcDream.App.UI.ToolbarRuntimeBindings(
                         Objects,
@@ -2114,8 +2102,7 @@ public sealed class GameWindow : IDisposable
                         _itemInteractionController,
                         (index, guid) => _liveSession?.SendAddShortcut(index, guid),
                         index => _liveSession?.SendRemoveShortcut(index),
-                        handler => SelectionChanged += handler,
+                        _selection,
-                        handler => SelectionChanged -= handler,
                         handler => Combat.HealthChanged += handler,
                         handler => Combat.HealthChanged -= handler,
                         IsHealthBarTarget,
@@ -2137,7 +2124,8 @@ public sealed class GameWindow : IDisposable
                         (item, container, placement) =>
                             _liveSession?.SendPutItemInContainer(item, container, placement),
                         (item, mask) => _liveSession?.SendGetAndWieldItem(item, mask),
-                        _itemInteractionController),
+                        _itemInteractionController,
+                        _selection),
                     Cursor: new AcDream.App.UI.RetailUiCursorBindings(
                         cursorFeedbackController,
                         retailCursorManager),
@@ -4478,8 +4466,12 @@ public sealed class GameWindow : IDisposable
         _remoteLastMove.Remove(serverGuid);
         _entitiesByServerGuid.Remove(serverGuid);
         _lastSpawnByGuid.Remove(serverGuid);
-        if (_selectedGuid == serverGuid)
+        if (_selection.SelectedObjectId == serverGuid)
-            SelectedGuid = null;
+        {
+            _selection.Clear(
+                AcDream.Core.Selection.SelectionChangeSource.System,
+                AcDream.Core.Selection.SelectionChangeReason.SelectedObjectRemoved);
+        }
 
         // A7 indoor lighting: release this entity's owned lights on EVERY
         // removal, including the respawn-dedup path (former logDelete=false).
@@ -11874,6 +11866,10 @@ public sealed class GameWindow : IDisposable
                 SelectClosestCombatTarget(showToast: true);
                 break;
 
+            case AcDream.UI.Abstractions.Input.InputAction.SelectionPreviousSelection:
+                _selection.SelectPrevious();
+                break;
+
             case AcDream.UI.Abstractions.Input.InputAction.CombatToggleCombat:
                 ToggleLiveCombatMode();
                 break;
@@ -11903,7 +11899,7 @@ public sealed class GameWindow : IDisposable
                 break;
 
             case AcDream.UI.Abstractions.Input.InputAction.SelectionPickUp:
-                if (_selectedGuid is uint pickupTarget)
+                if (_selection.SelectedObjectId is uint pickupTarget)
                     SendPickUp(pickupTarget);
                 else
                     _debugVm?.AddToast("Nothing selected");
@@ -11979,7 +11975,7 @@ public sealed class GameWindow : IDisposable
 
     private uint? GetSelectedOrClosestCombatTarget()
     {
-        if (_selectedGuid is { } selected && IsLiveCreatureTarget(selected))
+        if (_selection.SelectedObjectId is { } selected && IsLiveCreatureTarget(selected))
             return selected;
 
         return SelectClosestCombatTarget(showToast: false);
@@ -12066,7 +12062,7 @@ public sealed class GameWindow : IDisposable
                 return;
             }
 
-            SelectedGuid = guid;
+            _selection.Select(guid, AcDream.Core.Selection.SelectionChangeSource.World);
             string label = DescribeLiveEntity(guid);
             Console.WriteLine($"[B.4b] pick guid=0x{guid:X8} name={label}");
             // B.7 (2026-05-15): one-shot per-pick diagnostic so we can
@@ -12107,7 +12103,7 @@ public sealed class GameWindow : IDisposable
 
     private void UseCurrentSelection()
     {
-        if (_selectedGuid is not uint sel)
+        if (_selection.SelectedObjectId is not uint sel)
         {
             _debugVm?.AddToast("Nothing selected");
             return;
@@ -12503,7 +12499,10 @@ public sealed class GameWindow : IDisposable
             bestGuid = guid;
         }
 
-        SelectedGuid = bestGuid;
+        if (bestGuid is { } selection)
+            _selection.Select(selection, AcDream.Core.Selection.SelectionChangeSource.Keyboard);
+        else
+            _selection.Clear(AcDream.Core.Selection.SelectionChangeSource.Keyboard);
         if (bestGuid is { } selected)
         {
             string label = DescribeLiveEntity(selected);
@@ -13592,6 +13591,8 @@ public sealed class GameWindow : IDisposable
         _retailUiRuntime?.Dispose();
         _retailUiRuntime = null;
         _uiHost = null;
+        _itemInteractionController?.Dispose();
+        _itemInteractionController = null;
 
         // Phase A.1: join the streamer worker thread before tearing down GL
         // state. The worker may still be processing a load job that references

src/AcDream.App/Studio/FixtureProvider.cs

@@ -113,6 +113,7 @@ public static class FixtureProvider
                 uint mainPackEmpty  = ItemListCellTemplate.ResolveEmptySprite(dats, 0x21000022u, 0x100001C9u);
 
                 var iconIds = MakeIconIds(stack);
+                var selection = new AcDream.Core.Selection.SelectionState();
 
                 InventoryController.Bind(
                     layout,
@@ -120,6 +121,7 @@ public static class FixtureProvider
                     playerGuid:             () => SampleData.PlayerGuid,
                     iconIds:                iconIds,
                     strength:               () => 100,
+                    selection:              selection,
                     datFont:                stack.VitalsDatFont,
                     contentsEmptySprite:    contentsEmpty,
                     sideBagEmptySprite:     sideBagEmpty,
@@ -133,6 +135,7 @@ public static class FixtureProvider
                     objects,
                     playerGuid:       () => SampleData.PlayerGuid,
                     iconIds:          iconIds,
+                    selection:        selection,
                     sendWield:        null,       // no live session in the studio
                     emptySlotSprite:  contentsEmpty,
                     datFont:          stack.VitalsDatFont);

src/AcDream.App/UI/InteractionState.cs

@@ -0,0 +1,54 @@
+namespace AcDream.App.UI;
+
+public enum InteractionModeKind
+{
+    None,
+    Use,
+    Examine,
+    UseItemOnTarget,
+}
+
+public readonly record struct InteractionMode(
+    InteractionModeKind Kind,
+    uint SourceObjectId = 0)
+{
+    public static InteractionMode None => new(InteractionModeKind.None);
+}
+
+public readonly record struct InteractionModeTransition(
+    InteractionMode Previous,
+    InteractionMode Current);
+
+/// <summary>
+/// Single App-layer owner for retail's pointer interaction mode. Core selection
+/// remains session truth; this state represents temporary UI orchestration.
+/// </summary>
+public sealed class InteractionState
+{
+    public InteractionMode Current { get; private set; } = InteractionMode.None;
+
+    public event Action<InteractionModeTransition>? Changed;
+
+    public bool EnterUse() => Set(new InteractionMode(InteractionModeKind.Use));
+
+    public bool EnterExamine() => Set(new InteractionMode(InteractionModeKind.Examine));
+
+    public bool EnterUseItemOnTarget(uint sourceObjectId)
+    {
+        if (sourceObjectId == 0)
+            throw new ArgumentOutOfRangeException(nameof(sourceObjectId));
+        return Set(new InteractionMode(InteractionModeKind.UseItemOnTarget, sourceObjectId));
+    }
+
+    public bool Clear() => Set(InteractionMode.None);
+
+    private bool Set(InteractionMode mode)
+    {
+        if (Current == mode)
+            return false;
+        InteractionMode previous = Current;
+        Current = mode;
+        Changed?.Invoke(new InteractionModeTransition(previous, mode));
+        return true;
+    }
+}

src/AcDream.App/UI/ItemInteractionController.cs

@@ -8,7 +8,7 @@ namespace AcDream.App.UI;
 /// target acquisition, and drag-out drops here instead of duplicating
 /// ItemHolder::UseObject fragments in each panel.
 /// </summary>
-public sealed class ItemInteractionController
+public sealed class ItemInteractionController : IDisposable
 {
     private static readonly EquipMask[] AutoEquipOrder =
     {
@@ -55,8 +55,10 @@ public sealed class ItemInteractionController
     private readonly Action<uint, uint>? _sendWield;
     private readonly Action<uint>? _sendDrop;
     private readonly Action<string>? _toast;
+    private readonly InteractionState _interactionState;
 
     private long _lastUseMs = long.MinValue / 2;
+    private bool _disposed;
 
     public ItemInteractionController(
         ClientObjectTable objects,
@@ -66,7 +68,8 @@ public sealed class ItemInteractionController
         Action<uint, uint>? sendWield,
         Action<uint>? sendDrop,
         Func<long>? nowMs = null,
-        Action<string>? toast = null)
+        Action<string>? toast = null,
+        InteractionState? interactionState = null)
     {
         _objects = objects ?? throw new ArgumentNullException(nameof(objects));
         _playerGuid = playerGuid ?? throw new ArgumentNullException(nameof(playerGuid));
@@ -76,15 +79,23 @@ public sealed class ItemInteractionController
         _sendDrop = sendDrop;
         _nowMs = nowMs ?? (() => Environment.TickCount64);
         _toast = toast;
+        _interactionState = interactionState ?? new InteractionState();
+        _interactionState.Changed += OnInteractionModeChanged;
     }
 
     public event Action? StateChanged;
 
     public uint PlayerGuid => _playerGuid();
 
-    public uint PendingSourceItem { get; private set; }
+    public InteractionState InteractionState => _interactionState;
 
-    public bool IsTargetModeActive => PendingSourceItem != 0;
+    public uint PendingSourceItem
+        => _interactionState.Current is { Kind: InteractionModeKind.UseItemOnTarget } mode
+            ? mode.SourceObjectId
+            : 0u;
+
+    public bool IsTargetModeActive
+        => _interactionState.Current.Kind == InteractionModeKind.UseItemOnTarget;
 
     public bool IsPendingSource(uint itemGuid)
         => itemGuid != 0 && itemGuid == PendingSourceItem;
@@ -188,8 +199,7 @@ public sealed class ItemInteractionController
 
     private void EnterTargetMode(uint sourceGuid)
     {
-        PendingSourceItem = sourceGuid;
+        _interactionState.EnterUseItemOnTarget(sourceGuid);
-        StateChanged?.Invoke();
         var name = _objects.Get(sourceGuid)?.Name;
         if (!string.IsNullOrWhiteSpace(name))
             _toast?.Invoke($"Choose a target for the {name}");
@@ -197,8 +207,17 @@ public sealed class ItemInteractionController
 
     private void ClearTargetMode()
     {
-        PendingSourceItem = 0;
+        _interactionState.Clear();
-        StateChanged?.Invoke();
+    }
+
+    private void OnInteractionModeChanged(InteractionModeTransition _)
+        => StateChanged?.Invoke();
+
+    public void Dispose()
+    {
+        if (_disposed) return;
+        _disposed = true;
+        _interactionState.Changed -= OnInteractionModeChanged;
     }
 
     private bool ConsumeUseThrottle()

src/AcDream.App/UI/Layout/InventoryController.cs

@@ -2,6 +2,7 @@ using System;
 using System.Numerics;
 using AcDream.App.UI;
 using AcDream.Core.Items;
+using AcDream.Core.Selection;
 
 namespace AcDream.App.UI.Layout;
 
@@ -53,7 +54,7 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
     private static readonly Vector4 CaptionColor = new(1f, 1f, 1f, 1f);
 
     private uint _openContainer;   // 0 = the main pack (the player); else the open side bag's guid
-    private uint _selectedItem;    // 0 = none; the panel-wide selected item (green square)
+    private readonly SelectionState _selection;
     private readonly Action<uint>? _sendUse;
     private readonly Action<uint>? _sendNoLongerViewing;
     private readonly Action<uint, uint, int>? _sendPutItemInContainer;   // (item, container, placement)
@@ -70,6 +71,7 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
         Func<uint> playerGuid,
         Func<ItemType, uint, uint, uint, uint, uint> iconIds,
         Func<int?> strength,
+        SelectionState selection,
         Func<string>? ownerName,
         UiDatFont? datFont,
         uint contentsEmptySprite,
@@ -90,6 +92,7 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
         _sendNoLongerViewing = sendNoLongerViewing;
         _sendPutItemInContainer = sendPutItemInContainer;
         _itemInteraction = itemInteraction;
+        _selection = selection ?? throw new ArgumentNullException(nameof(selection));
 
         WindowChromeController.BindCloseButton(layout, onClose);
 
@@ -152,8 +155,9 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
         // Rebuild on any change to the player's possessions.
         _objects.ObjectAdded   += OnObjectChanged;
         _objects.ObjectMoved   += OnObjectMoved;
-        _objects.ObjectRemoved += OnObjectChanged;
+        _objects.ObjectRemoved += OnObjectRemoved;
         _objects.ObjectUpdated += OnObjectChanged;
+        _selection.Changed += OnSelectionChanged;
         if (_itemInteraction is not null)
             _itemInteraction.StateChanged += OnInteractionStateChanged;
 
@@ -184,6 +188,7 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
         Func<uint> playerGuid,
         Func<ItemType, uint, uint, uint, uint, uint> iconIds,
         Func<int?> strength,
+        SelectionState selection,
         UiDatFont? datFont,
         Func<string>? ownerName = null,
         uint contentsEmptySprite = 0u,
@@ -194,14 +199,27 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
         Action<uint, uint, int>? sendPutItemInContainer = null,
         ItemInteractionController? itemInteraction = null,
         Action? onClose = null)
-        => new InventoryController(layout, objects, playerGuid, iconIds, strength, ownerName, datFont,
+        => new InventoryController(layout, objects, playerGuid, iconIds, strength, selection,
+                                   ownerName, datFont,
                                    contentsEmptySprite, sideBagEmptySprite, mainPackEmptySprite,
-                                   sendUse, sendNoLongerViewing, sendPutItemInContainer, itemInteraction, onClose);
+                                   sendUse, sendNoLongerViewing, sendPutItemInContainer, itemInteraction,
+                                   onClose);
 
     private void OnObjectChanged(ClientObject o)        { if (Concerns(o)) Populate(); }
+    private void OnObjectRemoved(ClientObject o)
+    {
+        if (_selection.SelectedObjectId == o.ObjectId)
+        {
+            _selection.Clear(
+                SelectionChangeSource.System,
+                SelectionChangeReason.SelectedObjectRemoved);
+        }
+        if (Concerns(o)) Populate();
+    }
     private void OnObjectMoved(ClientObject o, uint from, uint to)
         { if (Concerns(o) || from == _playerGuid() || to == _playerGuid()) Populate(); }
     private void OnInteractionStateChanged() => ApplyIndicators();
+    private void OnSelectionChanged(SelectionTransition _) => ApplyIndicators();
 
     /// <summary>True if the object is in (or wielded by) the player — i.e. a rebuild is warranted.</summary>
     private bool Concerns(ClientObject o)
@@ -402,8 +420,7 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
     private void SelectItem(uint guid)
     {
         if (guid == 0) return;
-        _selectedItem = guid;
+        _selection.Select(guid, SelectionChangeSource.Inventory);
-        ApplyIndicators();
     }
 
     /// <summary>Open a container (side bag or main pack): it becomes both the selected item and the
@@ -413,7 +430,7 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
     private void OpenContainer(uint guid)
     {
         if (guid == 0) return;
-        _selectedItem = guid;                       // the container cell is also the selected item
+        _selection.Select(guid, SelectionChangeSource.Inventory);
         uint open = EffectiveOpen();
         if (guid == open) { ApplyIndicators(); return; }   // already open — just move the square
 
@@ -444,7 +461,9 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
             var cell = list.GetItem(i);
             if (cell is null) continue;
             bool pendingTargetSource = _itemInteraction?.IsPendingSource(cell.ItemId) == true;
-            cell.Selected        = cell.ItemId != 0 && cell.ItemId == _selectedItem && !pendingTargetSource;
+            cell.Selected        = cell.ItemId != 0
+                && cell.ItemId == _selection.SelectedObjectId
+                && !pendingTargetSource;
             cell.IsOpenContainer = cell.ItemId != 0 && cell.ItemId == open;
         }
     }
@@ -533,8 +552,9 @@ public sealed class InventoryController : IItemListDragHandler, IRetainedPanelCo
         _disposed = true;
         _objects.ObjectAdded   -= OnObjectChanged;
         _objects.ObjectMoved   -= OnObjectMoved;
-        _objects.ObjectRemoved -= OnObjectChanged;
+        _objects.ObjectRemoved -= OnObjectRemoved;
         _objects.ObjectUpdated -= OnObjectChanged;
+        _selection.Changed -= OnSelectionChanged;
         if (_itemInteraction is not null)
             _itemInteraction.StateChanged -= OnInteractionStateChanged;
     }

src/AcDream.App/UI/Layout/PaperdollController.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using AcDream.App.UI;
 using AcDream.Core.Items;
+using AcDream.Core.Selection;
 
 namespace AcDream.App.UI.Layout;
 
@@ -76,6 +77,7 @@ public sealed class PaperdollController : IItemListDragHandler, IRetainedPanelCo
     private readonly Func<ItemType, uint, uint, uint, uint, uint> _iconIds;
     private readonly Action<uint, uint>? _sendWield;     // (itemGuid, equipMask) → GetAndWieldItem 0x001A
     private readonly ItemInteractionController? _itemInteraction;
+    private readonly SelectionState _selection;
     private readonly List<(EquipMask Mask, UiItemList List)> _slots = new();
 
     // ── Slots-toggle state ────────────────────────────────────────────────────────────────────────
@@ -86,11 +88,13 @@ public sealed class PaperdollController : IItemListDragHandler, IRetainedPanelCo
 
     private PaperdollController(
         ImportedLayout layout, ClientObjectTable objects, Func<uint> playerGuid,
-        Func<ItemType, uint, uint, uint, uint, uint> iconIds, Action<uint, uint>? sendWield,
+        Func<ItemType, uint, uint, uint, uint, uint> iconIds, SelectionState selection,
+        Action<uint, uint>? sendWield,
         uint emptySlotSprite, UiDatFont? datFont, ItemInteractionController? itemInteraction)
     {
         _objects = objects; _playerGuid = playerGuid; _iconIds = iconIds; _sendWield = sendWield;
         _itemInteraction = itemInteraction;
+        _selection = selection ?? throw new ArgumentNullException(nameof(selection));
 
         for (int i = 0; i < SlotMap.Length; i++)
         {
@@ -100,7 +104,16 @@ public sealed class PaperdollController : IItemListDragHandler, IRetainedPanelCo
             list.Cell.SourceKind  = ItemDragSource.Equipment;
             list.Cell.SlotIndex   = i;              // SlotMap position = this equipped item's drag-payload SourceSlot when dragged out to unwield
             list.Cell.EmptySprite = emptySlotSprite; // visible empty-slot frame so every position is seen + usable. The live
-            list.Cell.Clicked = () => { _itemInteraction?.AcquireSelfTarget(); };
+            list.Cell.Clicked = () =>
+            {
+                if (_itemInteraction?.IsTargetModeActive == true)
+                {
+                    _itemInteraction.AcquireSelfTarget();
+                    return;
+                }
+                if (list.Cell.ItemId != 0)
+                    _selection.Select(list.Cell.ItemId, SelectionChangeSource.Paperdoll);
+            };
             list.Cell.DoubleClicked = () =>
             {
                 if (list.Cell.ItemId != 0)
@@ -119,6 +132,7 @@ public sealed class PaperdollController : IItemListDragHandler, IRetainedPanelCo
         _objects.ObjectMoved   += OnObjectMoved;
         _objects.ObjectRemoved += OnObjectChanged;
         _objects.ObjectUpdated += OnObjectChanged;
+        _selection.Changed += OnSelectionChanged;
 
         // ── Slots-toggle wiring ───────────────────────────────────────────────────────────────────
         foreach (var id in ArmorSlotElementIds)
@@ -154,14 +168,18 @@ public sealed class PaperdollController : IItemListDragHandler, IRetainedPanelCo
 
     public static PaperdollController Bind(
         ImportedLayout layout, ClientObjectTable objects, Func<uint> playerGuid,
-        Func<ItemType, uint, uint, uint, uint, uint> iconIds, Action<uint, uint>? sendWield = null,
+        Func<ItemType, uint, uint, uint, uint, uint> iconIds, SelectionState selection,
+        Action<uint, uint>? sendWield = null,
         uint emptySlotSprite = 0u, UiDatFont? datFont = null,
         ItemInteractionController? itemInteraction = null)
-        => new PaperdollController(layout, objects, playerGuid, iconIds, sendWield, emptySlotSprite, datFont, itemInteraction);
+        => new PaperdollController(
+            layout, objects, playerGuid, iconIds, selection, sendWield, emptySlotSprite,
+            datFont, itemInteraction);
 
     private void OnObjectChanged(ClientObject o) { if (Concerns(o)) Populate(); }
     private void OnObjectMoved(ClientObject o, uint from, uint to)
     { if (Concerns(o) || from == _playerGuid() || to == _playerGuid()) Populate(); }
+    private void OnSelectionChanged(SelectionTransition _) => ApplySelectionIndicators();
 
     /// <summary>The object belongs to the player (wielded gear or pack contents) — so a change to it may
     /// add/remove/repaint a doll slot. Player-scoped: an NPC's or vendor's wielded item (which also carries
@@ -196,6 +214,16 @@ public sealed class PaperdollController : IItemListDragHandler, IRetainedPanelCo
             uint tex = _iconIds(worn.Type, worn.IconId, worn.IconUnderlayId, worn.IconOverlayId, worn.Effects);
             list.Cell.SetItem(worn.ObjectId, tex);
         }
+        ApplySelectionIndicators();
+    }
+
+    private void ApplySelectionIndicators()
+    {
+        foreach (var (_, list) in _slots)
+        {
+            list.Cell.Selected = list.Cell.ItemId != 0
+                && list.Cell.ItemId == _selection.SelectedObjectId;
+        }
     }
 
     private EquipMask MaskFor(UiItemList list)
@@ -251,5 +279,6 @@ public sealed class PaperdollController : IItemListDragHandler, IRetainedPanelCo
         _objects.ObjectMoved   -= OnObjectMoved;
         _objects.ObjectRemoved -= OnObjectChanged;
         _objects.ObjectUpdated -= OnObjectChanged;
+        _selection.Changed -= OnSelectionChanged;
     }
 }

src/AcDream.App/UI/Layout/SelectedObjectController.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Numerics;
 using AcDream.App.UI;
+using AcDream.Core.Selection;
 
 namespace AcDream.App.UI.Layout;
 
@@ -82,7 +83,7 @@ public sealed class SelectedObjectController : IRetainedPanelController
     private readonly Func<uint, bool>    _hasHealth;
     private readonly Func<uint, uint>    _stackSize;
     private readonly Action<uint>        _sendQueryHealth;
-    private readonly Action<Action<uint?>>       _unsubscribeSelectionChanged;
+    private readonly SelectionState _selection;
     private readonly Action<Action<uint, float>> _unsubscribeHealthChanged;
 
     // ── Live state (read by closures on the per-frame draw path) ────────────
@@ -96,8 +97,7 @@ public sealed class SelectedObjectController : IRetainedPanelController
 
     private SelectedObjectController(
         ImportedLayout layout,
-        Action<Action<uint?>>        subscribeSelectionChanged,
+        SelectionState selection,
-        Action<Action<uint?>>        unsubscribeSelectionChanged,
         Action<Action<uint, float>>  subscribeHealthChanged,
         Action<Action<uint, float>>  unsubscribeHealthChanged,
         Func<uint, bool>    isHealthTarget,
@@ -114,7 +114,7 @@ public sealed class SelectedObjectController : IRetainedPanelController
         _hasHealth       = hasHealth;
         _stackSize       = stackSize;
         _sendQueryHealth = sendQueryHealth;
-        _unsubscribeSelectionChanged = unsubscribeSelectionChanged;
+        _selection = selection ?? throw new ArgumentNullException(nameof(selection));
         _unsubscribeHealthChanged = unsubscribeHealthChanged;
 
         // Find elements — silently skip absent ones (partial/test layouts).
@@ -171,8 +171,10 @@ public sealed class SelectedObjectController : IRetainedPanelController
         }
 
         // Register the handlers LAST so the initial state is fully set up first.
-        subscribeSelectionChanged(OnSelectionChanged);
+        _selection.Changed += OnSelectionTransition;
         subscribeHealthChanged(OnHealthChanged);
+        if (_selection.SelectedObjectId is { } initial)
+            ApplySelection(initial);
     }
 
     /// <summary>
@@ -180,8 +182,7 @@ public sealed class SelectedObjectController : IRetainedPanelController
     /// Port of retail <c>gmToolbarUI::HandleSelectionChanged</c> + <c>RecvNotice_UpdateObjectHealth</c>.
     /// </summary>
     /// <param name="layout">Imported toolbar layout (LayoutDesc 0x21000016).</param>
-    /// <param name="subscribeSelectionChanged">Called once with <see cref="OnSelectionChanged"/>
+    /// <param name="selection">The single Core selected-object owner.</param>
-    /// (typical host: <c>h =&gt; SelectionChanged += h</c>).</param>
     /// <param name="subscribeHealthChanged">Called once with <see cref="OnHealthChanged"/>
     /// (typical host: <c>h =&gt; Combat.HealthChanged += h</c>) — drives meter visibility.</param>
     /// <param name="isHealthTarget">Returns true for guids that may show a health meter
@@ -195,8 +196,7 @@ public sealed class SelectedObjectController : IRetainedPanelController
     /// <param name="datFont">Dat font for the name label; null = debug bitmap font fallback.</param>
     public static SelectedObjectController Bind(
         ImportedLayout layout,
-        Action<Action<uint?>>        subscribeSelectionChanged,
+        SelectionState selection,
-        Action<Action<uint?>>        unsubscribeSelectionChanged,
         Action<Action<uint, float>>  subscribeHealthChanged,
         Action<Action<uint, float>>  unsubscribeHealthChanged,
         Func<uint, bool>    isHealthTarget,
@@ -207,7 +207,7 @@ public sealed class SelectedObjectController : IRetainedPanelController
         Action<uint>        sendQueryHealth,
         UiDatFont?          datFont)
         => new SelectedObjectController(
-            layout, subscribeSelectionChanged, unsubscribeSelectionChanged,
+            layout, selection,
             subscribeHealthChanged, unsubscribeHealthChanged,
             isHealthTarget, name, healthPercent, hasHealth, stackSize, sendQueryHealth, datFont);
 
@@ -215,7 +215,7 @@ public sealed class SelectedObjectController : IRetainedPanelController
     /// Port of <c>gmToolbarUI::HandleSelectionChanged</c> (<c>:198635</c>):
     /// clear-then-populate the selected-object strip on any selection change.
     /// </summary>
-    public void OnSelectionChanged(uint? guid)
+    private void ApplySelection(uint? guid)
     {
         // ── 1. Clear first (retail: SetText("") + m_pSelObjectField->SetState(0)
         //       + SetVisible(0) on the meters). ──────────────────────────────────────
@@ -279,11 +279,14 @@ public sealed class SelectedObjectController : IRetainedPanelController
         _overlay?.TrySetRetailState(state);
     }
 
+    private void OnSelectionTransition(SelectionTransition transition)
+        => ApplySelection(transition.SelectedObjectId);
+
     public void Dispose()
     {
         if (_disposed) return;
         _disposed = true;
-        _unsubscribeSelectionChanged(OnSelectionChanged);
+        _selection.Changed -= OnSelectionTransition;
         _unsubscribeHealthChanged(OnHealthChanged);
     }
 }

src/AcDream.App/UI/RetailUiRuntime.cs

@@ -6,6 +6,7 @@ using AcDream.App.UI.Testing;
 using AcDream.Core.Combat;
 using AcDream.Core.Items;
 using AcDream.Core.Net.Messages;
+using AcDream.Core.Selection;
 using AcDream.UI.Abstractions;
 using AcDream.UI.Abstractions.Panels.Chat;
 using AcDream.UI.Abstractions.Panels.Settings;
@@ -31,7 +32,7 @@ public sealed record ChatRuntimeBindings(ChatVM ViewModel, Func<ICommandBus> Com
 
 public sealed record RadarRuntimeBindings(
     Func<UiRadarSnapshot> Snapshot,
-    Action<uint> SelectObject,
+    SelectionState Selection,
     Action<bool> SetUiLocked);
 
 public sealed record ToolbarRuntimeBindings(
@@ -43,8 +44,7 @@ public sealed record ToolbarRuntimeBindings(
     ItemInteractionController ItemInteraction,
     Action<uint, uint>? SendAddShortcut,
     Action<uint>? SendRemoveShortcut,
-    Action<Action<uint?>> SubscribeSelectionChanged,
+    SelectionState Selection,
-    Action<Action<uint?>> UnsubscribeSelectionChanged,
     Action<Action<uint, float>> SubscribeHealthChanged,
     Action<Action<uint, float>> UnsubscribeHealthChanged,
     Func<uint, bool> IsHealthTarget,
@@ -65,7 +65,8 @@ public sealed record InventoryRuntimeBindings(
     Action<uint>? SendNoLongerViewing,
     Action<uint, uint, int>? SendPutItemInContainer,
     Action<uint, uint>? SendWield,
-    ItemInteractionController ItemInteraction);
+    ItemInteractionController ItemInteraction,
+    SelectionState Selection);
 
 public sealed record RetailUiPersistenceBindings(
     SettingsStore Store,
@@ -256,7 +257,7 @@ public sealed class RetailUiRuntime : IDisposable
         RadarController controller = RadarController.Bind(
             layout,
             _bindings.Radar.Snapshot,
-            _bindings.Radar.SelectObject,
+            guid => _bindings.Radar.Selection.Select(guid, SelectionChangeSource.Radar),
             setUiLocked: _bindings.Radar.SetUiLocked,
             datFont: _bindings.Assets.DefaultFont);
         RetailWindowFrame.Mount(Host.Root, radarRoot, _bindings.Assets.ResolveSprite,
@@ -354,8 +355,7 @@ public sealed class RetailUiRuntime : IDisposable
             peace, war, empty, b.ItemInteraction, b.SendAddShortcut, b.SendRemoveShortcut);
         SelectedObjectController = Layout.SelectedObjectController.Bind(
             layout,
-            b.SubscribeSelectionChanged,
+            b.Selection,
-            b.UnsubscribeSelectionChanged,
             b.SubscribeHealthChanged,
             b.UnsubscribeHealthChanged,
             b.IsHealthTarget,
@@ -570,13 +570,13 @@ public sealed class RetailUiRuntime : IDisposable
 
         InventoryRuntimeBindings b = _bindings.Inventory;
         InventoryController inventory = InventoryController.Bind(
-            layout, b.Objects, b.PlayerGuid, b.ResolveIcon, b.Strength,
+            layout, b.Objects, b.PlayerGuid, b.ResolveIcon, b.Strength, b.Selection,
             _bindings.Assets.DefaultFont, _bindings.Character.Provider.CharacterName,
             contents, sideBag, mainPack, b.SendUse, b.SendNoLongerViewing,
             b.SendPutItemInContainer, b.ItemInteraction,
             () => CloseWindow(WindowNames.Inventory));
         PaperdollController paperdoll = PaperdollController.Bind(
-            layout, b.Objects, b.PlayerGuid, b.ResolveIcon, b.SendWield,
+            layout, b.Objects, b.PlayerGuid, b.ResolveIcon, b.Selection, b.SendWield,
             contents, _bindings.Assets.DefaultFont, b.ItemInteraction);
         Host.WindowManager.AttachController(
             WindowNames.Inventory,

src/AcDream.App/UI/TargetIndicatorPanel.cs

@@ -24,7 +24,7 @@ namespace AcDream.App.UI;
 /// on internal state types:
 /// </para>
 /// <list type="bullet">
-///   <item><c>selectedGuidProvider</c> — host's current <c>_selectedGuid</c>.</item>
+///   <item><c>selectedGuidProvider</c> — Core <c>SelectionState</c>'s current guid.</item>
 ///   <item><c>entityResolver</c> — returns
 ///     <see cref="TargetInfo"/> for a given guid, or <c>null</c> if
 ///     the entity is no longer in the world (despawned).</item>

src/AcDream.Core/Selection/SelectionState.cs

@@ -0,0 +1,106 @@
+using AcDream.Plugin.Abstractions;
+
+namespace AcDream.Core.Selection;
+
+public enum SelectionChangeSource
+{
+    System,
+    World,
+    Radar,
+    Inventory,
+    Paperdoll,
+    Toolbar,
+    Keyboard,
+    Plugin,
+}
+
+public enum SelectionChangeReason
+{
+    Selected,
+    Cleared,
+    SelectedObjectRemoved,
+    PreviousSelection,
+}
+
+public readonly record struct SelectionTransition(
+    uint? PreviousObjectId,
+    uint? SelectedObjectId,
+    SelectionChangeSource Source,
+    SelectionChangeReason Reason);
+
+/// <summary>
+/// Single owner for the client's selected object. This ports the state behavior
+/// of retail <c>ACCWeenieObject::SetSelectedObject @ 0x0058C2E0</c>: changes are
+/// deduplicated, the old selection becomes the previous selection, and plugin/UI
+/// listeners receive one transition after state is committed.
+/// </summary>
+public sealed class SelectionState : ISelectionService
+{
+    private event Action<SelectionChangedEvent>? PluginChanged;
+
+    public uint? SelectedObjectId { get; private set; }
+    public uint? PreviousObjectId { get; private set; }
+    public uint? PreviousValidObjectId { get; private set; }
+
+    public event Action<SelectionTransition>? Changed;
+
+    event Action<SelectionChangedEvent> ISelectionService.Changed
+    {
+        add => PluginChanged += value;
+        remove => PluginChanged -= value;
+    }
+
+    public bool Select(
+        uint objectId,
+        SelectionChangeSource source,
+        SelectionChangeReason reason = SelectionChangeReason.Selected)
+        => objectId == 0
+            ? Clear(source)
+            : Set(objectId, source, reason);
+
+    public bool Clear(
+        SelectionChangeSource source,
+        SelectionChangeReason reason = SelectionChangeReason.Cleared)
+        => Set(null, source, reason);
+
+    public bool SelectPrevious(SelectionChangeSource source = SelectionChangeSource.Keyboard)
+        => PreviousObjectId is uint previous
+            && Set(previous, source, SelectionChangeReason.PreviousSelection);
+
+    bool ISelectionService.Select(uint objectId)
+        => Select(objectId, SelectionChangeSource.Plugin);
+
+    bool ISelectionService.Clear()
+        => Clear(SelectionChangeSource.Plugin);
+
+    private bool Set(
+        uint? selectedObjectId,
+        SelectionChangeSource source,
+        SelectionChangeReason reason)
+    {
+        if (SelectedObjectId == selectedObjectId)
+            return false;
+
+        uint? old = SelectedObjectId;
+        SelectedObjectId = selectedObjectId;
+        PreviousObjectId = old;
+        if (old is not null)
+            PreviousValidObjectId = old;
+
+        var transition = new SelectionTransition(old, selectedObjectId, source, reason);
+        Changed?.Invoke(transition);
+        DispatchPluginChanged(new SelectionChangedEvent(old, selectedObjectId));
+        return true;
+    }
+
+    private void DispatchPluginChanged(SelectionChangedEvent change)
+    {
+        Action<SelectionChangedEvent>? listeners = PluginChanged;
+        if (listeners is null) return;
+        foreach (Action<SelectionChangedEvent> listener in listeners.GetInvocationList())
+        {
+            try { listener(change); }
+            catch { /* plugin exceptions never escape into client state changes */ }
+        }
+    }
+}

src/AcDream.Plugin.Abstractions/IPluginHost.cs

@@ -10,5 +10,6 @@ public interface IPluginHost
     IPluginLogger Log { get; }
     IGameState State { get; }
     IEvents Events { get; }
+    ISelectionService Selection { get; }
     IUiRegistry Ui { get; }
 }

src/AcDream.Plugin.Abstractions/ISelectionService.cs

@@ -0,0 +1,19 @@
+namespace AcDream.Plugin.Abstractions;
+
+/// <summary>A plugin-safe selection transition matching retail's selected-target callback.</summary>
+public readonly record struct SelectionChangedEvent(
+    uint? PreviousObjectId,
+    uint? SelectedObjectId);
+
+/// <summary>
+/// Shared selected-object service. Plugins read and change the same selection
+/// used by the world, radar, inventory, paperdoll, and toolbar.
+/// </summary>
+public interface ISelectionService
+{
+    uint? SelectedObjectId { get; }
+    uint? PreviousObjectId { get; }
+    event Action<SelectionChangedEvent> Changed;
+    bool Select(uint objectId);
+    bool Clear();
+}

tests/AcDream.App.Tests/UI/InteractionStateTests.cs

@@ -0,0 +1,32 @@
+using AcDream.App.UI;
+
+namespace AcDream.App.Tests.UI;
+
+public sealed class InteractionStateTests
+{
+    [Fact]
+    public void Modes_HaveOneOwnerAndOneDeduplicatedTransitionStream()
+    {
+        var state = new InteractionState();
+        var changes = new List<InteractionModeTransition>();
+        state.Changed += changes.Add;
+
+        Assert.True(state.EnterUse());
+        Assert.False(state.EnterUse());
+        Assert.True(state.EnterExamine());
+        Assert.True(state.EnterUseItemOnTarget(0x100u));
+        Assert.True(state.Clear());
+
+        Assert.Equal(4, changes.Count);
+        Assert.Equal(InteractionModeKind.None, state.Current.Kind);
+        Assert.Equal(0x100u, changes[2].Current.SourceObjectId);
+    }
+
+    [Fact]
+    public void UseItemOnTarget_RejectsMissingSource()
+    {
+        var state = new InteractionState();
+        Assert.Throws<ArgumentOutOfRangeException>(() => state.EnterUseItemOnTarget(0));
+        Assert.Equal(InteractionMode.None, state.Current);
+    }
+}

tests/AcDream.App.Tests/UI/ItemInteractionControllerTests.cs

@@ -77,6 +77,10 @@ public sealed class ItemInteractionControllerTests
 
         Assert.True(h.Controller.IsTargetModeActive);
         Assert.True(h.Controller.IsPendingSource(0x50000A01u));
+        Assert.Equal(InteractionModeKind.UseItemOnTarget,
+            h.Controller.InteractionState.Current.Kind);
+        Assert.Equal(0x50000A01u,
+            h.Controller.InteractionState.Current.SourceObjectId);
         Assert.Empty(h.UseWithTarget);
     }
 

tests/AcDream.App.Tests/UI/Layout/InventoryControllerTests.cs

@@ -2,6 +2,7 @@ using System.Collections.Generic;
 using AcDream.App.UI;
 using AcDream.App.UI.Layout;
 using AcDream.Core.Items;
+using AcDream.Core.Selection;
 using Xunit;
 
 namespace AcDream.App.Tests.UI.Layout;
@@ -56,7 +57,8 @@ public class InventoryControllerTests
         int? strength = 100, List<uint>? uses = null, List<uint>? closes = null,
         List<(uint item, uint container, int placement)>? puts = null,
         string? ownerName = null,
-        Action? onClose = null)
+        Action? onClose = null,
+        SelectionState? selection = null)
         => InventoryController.Bind(layout, objects, () => Player,
             iconIds: (_, _, _, _, _) => 0u,
             strength: () => strength, datFont: null,
@@ -64,7 +66,8 @@ public class InventoryControllerTests
             sendUse: uses is null ? null : g => uses.Add(g),
             sendNoLongerViewing: closes is null ? null : g => closes.Add(g),
             sendPutItemInContainer: puts is null ? null : (i, c, p) => puts.Add((i, c, p)),
-            onClose: onClose);
+            onClose: onClose,
+            selection: selection ?? new SelectionState());
 
     private static UiButton MakeButton(uint id)
     {
@@ -316,7 +319,8 @@ public class InventoryControllerTests
     {
         var (layout, grid, containers, top, _, _, _, _) = BuildLayout();
         InventoryController.Bind(layout, new ClientObjectTable(), () => Player,
-            iconIds: (_, _, _, _, _) => 0u, strength: () => 100, datFont: null,
+            iconIds: (_, _, _, _, _) => 0u, strength: () => 100,
+            selection: new SelectionState(), datFont: null,
             contentsEmptySprite: 0x06004D20u, sideBagEmptySprite: 0x06005D9Cu, mainPackEmptySprite: 0x06005D9Cu);
 
         Assert.Equal(0x06004D20u, grid.GetItem(0)!.EmptySprite);        // a padded empty contents cell
@@ -414,6 +418,27 @@ public class InventoryControllerTests
         Assert.Empty(closes);
     }
 
+    [Fact]
+    public void ClickGridItem_updatesSharedSelection_andExternalSelectionMovesSquare()
+    {
+        var (layout, grid, _, _, _, _, _, _) = BuildLayout();
+        var objects = new ClientObjectTable();
+        SeedContained(objects, 0xAu, Player, slot: 0);
+        SeedContained(objects, 0xBu, Player, slot: 1);
+        var selection = new SelectionState();
+        Bind(layout, objects, selection: selection);
+
+        grid.GetItem(0)!.Clicked!();
+
+        Assert.Equal(0xAu, selection.SelectedObjectId);
+        Assert.True(grid.GetItem(0)!.Selected);
+
+        selection.Select(0xBu, SelectionChangeSource.World);
+
+        Assert.False(grid.GetItem(0)!.Selected);
+        Assert.True(grid.GetItem(1)!.Selected);
+    }
+
     [Fact]
     public void TargetMode_suppressesSelectedSquare_onPendingSource()
     {
@@ -439,6 +464,7 @@ public class InventoryControllerTests
         InventoryController.Bind(layout, objects, () => Player,
             iconIds: (_, _, _, _, _) => 0u,
             strength: () => 100,
+            selection: new SelectionState(),
             datFont: null,
             itemInteraction: interaction);
         grid.GetItem(0)!.Clicked!();
@@ -469,7 +495,7 @@ public class InventoryControllerTests
         (ItemType type, uint icon)? mainPackCall = null;
         InventoryController.Bind(layout, objects, () => Player,
             iconIds: (t, icon, _, _, _) => { if (icon == 0x0600127Eu) mainPackCall = (t, icon); return 0u; },
-            strength: () => 100, datFont: null);
+            strength: () => 100, selection: new SelectionState(), datFont: null);
 
         // Retail draws a constant backpack over the Container type-underlay (IconData::RenderIcons
         // IsThePlayer branch). The backpack RenderSurface 0x0600127E is visually confirmed (2026-06-22).

tests/AcDream.App.Tests/UI/Layout/InventoryFrameImportProbe.cs

@@ -110,6 +110,7 @@ public class InventoryFrameImportProbe
             playerGuid: static () => 0u,
             iconIds: static (_, _, _, _, _) => 0u,
             strength: static () => 100,
+            selection: new AcDream.Core.Selection.SelectionState(),
             datFont: null,
             onClose: () => closes++);
 

tests/AcDream.App.Tests/UI/Layout/PaperdollControllerTests.cs

@@ -2,6 +2,7 @@ using System.Collections.Generic;
 using AcDream.App.UI;
 using AcDream.App.UI.Layout;
 using AcDream.Core.Items;
+using AcDream.Core.Selection;
 using Xunit;
 
 namespace AcDream.App.Tests.UI.Layout;
@@ -34,11 +35,13 @@ public class PaperdollControllerTests
     }
 
     private static PaperdollController Bind(ImportedLayout layout, ClientObjectTable objects,
-        List<(uint item, uint mask)>? wields = null, uint emptySlot = 0u)
+        List<(uint item, uint mask)>? wields = null, uint emptySlot = 0u,
+        SelectionState? selection = null)
         => PaperdollController.Bind(layout, objects, () => Player,
             iconIds: (_, _, _, _, _) => 0x1234u,
             sendWield: wields is null ? null : (i, m) => wields.Add((i, m)),
-            emptySlotSprite: emptySlot);
+            emptySlotSprite: emptySlot,
+            selection: selection ?? new SelectionState());
 
     private static void SeedEquipped(ClientObjectTable t, uint guid, EquipMask loc)
     {
@@ -63,6 +66,21 @@ public class PaperdollControllerTests
         Assert.Equal(0u, lists[ShieldSlot].Cell.ItemId);     // shield slot empty
     }
 
+    [Fact]
+    public void ClickEquippedItem_updatesSharedSelection()
+    {
+        var (layout, lists) = BuildLayout();
+        var objects = new ClientObjectTable();
+        SeedEquipped(objects, 0xA01u, EquipMask.HeadWear);
+        var selection = new SelectionState();
+        Bind(layout, objects, selection: selection);
+
+        lists[HeadSlot].Cell.Clicked!();
+
+        Assert.Equal(0xA01u, selection.SelectedObjectId);
+        Assert.True(lists[HeadSlot].Cell.Selected);
+    }
+
     [Fact]
     public void Populate_matches_a_weapon_into_the_composite_slot()
     {

tests/AcDream.App.Tests/UI/Layout/SelectedObjectControllerTests.cs

@@ -4,6 +4,7 @@ using System.Linq;
 using System.Numerics;
 using AcDream.App.UI;
 using AcDream.App.UI.Layout;
+using AcDream.Core.Selection;
 using Xunit;
 
 namespace AcDream.App.Tests.UI.Layout;
@@ -65,7 +66,7 @@ public class SelectedObjectControllerTests
 
     private sealed class Harness
     {
-        public Action<uint?>? SelectionHandler;
+        public readonly SelectionState Selection = new();
         public Action<uint, float>? HealthHandler;
         public readonly List<uint> QueryHealthCalls = new();
 
@@ -75,17 +76,19 @@ public class SelectedObjectControllerTests
         public readonly Dictionary<uint, bool>   HasHealthMap    = new();
         public readonly Dictionary<uint, uint>   StackMap        = new();
 
-        public void FireSelection(uint? g) => SelectionHandler?.Invoke(g);
+        public void FireSelection(uint? g)
+        {
+            if (g is { } guid)
+                Selection.Select(guid, SelectionChangeSource.System);
+            else
+                Selection.Clear(SelectionChangeSource.System);
+        }
         public void FireHealth(uint g, float pct) => HealthHandler?.Invoke(g, pct);
 
         public SelectedObjectController Bind(ImportedLayout layout, UiDatFont? datFont = null)
             => SelectedObjectController.Bind(
                 layout,
-                subscribeSelectionChanged: h => SelectionHandler = h,
+                selection: Selection,
-                unsubscribeSelectionChanged: h =>
-                {
-                    if (SelectionHandler == h) SelectionHandler = null;
-                },
                 subscribeHealthChanged:    h => HealthHandler = h,
                 unsubscribeHealthChanged: h =>
                 {
@@ -362,7 +365,6 @@ public class SelectedObjectControllerTests
         h.NameMap[0x12345678u] = "Something";
         var c = h.Bind(layout);
 
-        Assert.NotNull(h.SelectionHandler);
         Assert.Null(Record.Exception(() => h.FireSelection(0x12345678u)));
         Assert.Null(Record.Exception(() => h.FireHealth(0x12345678u, 0.5f)));
         Assert.Null(Record.Exception(() => c.Tick(0.5)));
@@ -425,7 +427,6 @@ public class SelectedObjectControllerTests
         h.FireSelection(0xAA09u);
         h.FireHealth(0xAA09u, 0.5f);
 
-        Assert.Null(h.SelectionHandler);
         Assert.Null(h.HealthHandler);
         Assert.False(healthMeterEl.Visible);
         Assert.Empty(h.QueryHealthCalls);

tests/AcDream.App.Tests/UI/RetailUiInteractionFlowTests.cs

@@ -32,6 +32,7 @@ public sealed class RetailUiInteractionFlowTests
         public readonly List<uint> Uses = new();
         public readonly List<(uint Source, uint Target)> UseWithTarget = new();
         public readonly List<(uint Item, uint Mask)> Wields = new();
+        public readonly AcDream.Core.Selection.SelectionState Selection = new();
         public readonly List<uint> Drops = new();
         public long Now = 10_000;
 
@@ -149,6 +150,7 @@ public sealed class RetailUiInteractionFlowTests
                 playerGuid: () => Player,
                 iconIds: static (_, _, _, _, _) => 0x1234u,
                 strength: () => 100,
+                selection: Selection,
                 datFont: null,
                 itemInteraction: interaction);
 
@@ -167,6 +169,7 @@ public sealed class RetailUiInteractionFlowTests
                 Objects,
                 playerGuid: () => Player,
                 iconIds: static (_, _, _, _, _) => 0x1234u,
+                selection: Selection,
                 sendWield: (item, mask) => Wields.Add((item, mask)),
                 emptySlotSprite: 0x06004D20u);
 

tests/AcDream.Core.Tests/Plugins/PluginLoaderTests.cs

@@ -1,4 +1,5 @@
 using AcDream.Core.Plugins;
+using AcDream.Core.Selection;
 using AcDream.Plugin.Abstractions;
 
 namespace AcDream.Core.Tests.Plugins;
@@ -30,6 +31,7 @@ public class PluginLoaderTests
         public IPluginLogger Log { get; } = new StubLogger();
         public IGameState State { get; } = new StubState();
         public IEvents Events { get; } = new StubEvents();
+        public ISelectionService Selection { get; } = new SelectionState();
         public IUiRegistry Ui { get; } = new StubUiRegistry();
     }
 

tests/AcDream.Core.Tests/Selection/SelectionStateTests.cs

@@ -0,0 +1,100 @@
+using AcDream.Core.Selection;
+using AcDream.Plugin.Abstractions;
+
+namespace AcDream.Core.Tests.Selection;
+
+public sealed class SelectionStateTests
+{
+    [Fact]
+    public void Select_CommitsOneTransitionAndTracksPreviousLikeRetail()
+    {
+        var state = new SelectionState();
+        var transitions = new List<SelectionTransition>();
+        state.Changed += transitions.Add;
+
+        Assert.True(state.Select(0x50000001u, SelectionChangeSource.World));
+        Assert.True(state.Select(0x50000002u, SelectionChangeSource.Radar));
+
+        Assert.Equal(0x50000002u, state.SelectedObjectId);
+        Assert.Equal(0x50000001u, state.PreviousObjectId);
+        Assert.Equal(0x50000001u, state.PreviousValidObjectId);
+        Assert.Equal(2, transitions.Count);
+        Assert.Equal(SelectionChangeSource.Radar, transitions[1].Source);
+        Assert.Equal(SelectionChangeReason.Selected, transitions[1].Reason);
+    }
+
+    [Fact]
+    public void Select_SameObject_IsDeduplicated()
+    {
+        var state = new SelectionState();
+        int changed = 0;
+        state.Changed += _ => changed++;
+
+        Assert.True(state.Select(0x50000001u, SelectionChangeSource.World));
+        Assert.False(state.Select(0x50000001u, SelectionChangeSource.Inventory));
+
+        Assert.Equal(1, changed);
+        Assert.Null(state.PreviousObjectId);
+    }
+
+    [Fact]
+    public void SelectPrevious_SwapsCurrentAndPrevious()
+    {
+        var state = new SelectionState();
+        state.Select(0x50000001u, SelectionChangeSource.World);
+        state.Select(0x50000002u, SelectionChangeSource.World);
+
+        Assert.True(state.SelectPrevious());
+
+        Assert.Equal(0x50000001u, state.SelectedObjectId);
+        Assert.Equal(0x50000002u, state.PreviousObjectId);
+    }
+
+    [Fact]
+    public void ClearRemoved_PreservesRemovedObjectAsPreviousValid()
+    {
+        var state = new SelectionState();
+        SelectionTransition transition = default;
+        state.Changed += value => transition = value;
+        state.Select(0x50000001u, SelectionChangeSource.World);
+
+        Assert.True(state.Clear(
+            SelectionChangeSource.System,
+            SelectionChangeReason.SelectedObjectRemoved));
+
+        Assert.Null(state.SelectedObjectId);
+        Assert.Equal(0x50000001u, state.PreviousObjectId);
+        Assert.Equal(0x50000001u, state.PreviousValidObjectId);
+        Assert.Equal(SelectionChangeReason.SelectedObjectRemoved, transition.Reason);
+    }
+
+    [Fact]
+    public void PluginService_UsesSameStateAndEventStream()
+    {
+        var state = new SelectionState();
+        ISelectionService plugin = state;
+        SelectionChangedEvent change = default;
+        plugin.Changed += value => change = value;
+
+        Assert.True(plugin.Select(0x50000001u));
+
+        Assert.Equal(0x50000001u, state.SelectedObjectId);
+        Assert.Equal(0x50000001u, plugin.SelectedObjectId);
+        Assert.Null(change.PreviousObjectId);
+        Assert.Equal(0x50000001u, change.SelectedObjectId);
+    }
+
+    [Fact]
+    public void PluginListenerFailure_DoesNotEscapeOrBlockOtherPlugins()
+    {
+        var state = new SelectionState();
+        ISelectionService plugin = state;
+        int delivered = 0;
+        plugin.Changed += _ => throw new InvalidOperationException("plugin failure");
+        plugin.Changed += _ => delivered++;
+
+        Assert.Null(Record.Exception(() => plugin.Select(0x50000001u)));
+        Assert.Equal(1, delivered);
+        Assert.Equal(0x50000001u, state.SelectedObjectId);
+    }
+}