diff --git a/src/AcDream.App/Composition/InteractionRetainedUiComposition.cs b/src/AcDream.App/Composition/InteractionRetainedUiComposition.cs
index ec368803..90bbc822 100644
--- a/src/AcDream.App/Composition/InteractionRetainedUiComposition.cs
+++ b/src/AcDream.App/Composition/InteractionRetainedUiComposition.cs
@@ -842,6 +842,17 @@ internal sealed class RetailInteractionRetainedUiCompositionFactory
                     d.Actions.Selection,
                     text => d.Communication.AddText(text, RetailLogTextType.ClientLocal)),
                 Cursor: new RetailUiCursorBindings(cursorFeedback, cursorManager),
+                // #409 follow-on ("Item 2"): world-object hover tooltip.
+                // Reuses the SAME world-hover pick cursorFeedback's own
+                // worldTargetProvider already calls (UIElement_SmartBoxWrapper::
+                // FindObject's 3D-raycast fallback — RetailWorldPicker's exact
+                // port) and the SAME ClientObjectTable name resolver
+                // ResolveWorldObjectName already uses elsewhere in this file.
+                WorldTooltip: new WorldTooltipRuntimeBindings(
+                    HoverGuidAtCursor: () => late.Selection.PickAtCursor(includeSelf: true),
+                    ResolveName: guid => d.Inventory.Objects.Get(guid)?.GetAppropriateName(),
+                    Enabled: () => d.Character.Options.GetOptionBit(
+                        CharacterOptionId.ShowTooltips)),
                 Confirmations: new ConfirmationRuntimeBindings(
                     (type, context, accepted) =>
                         late.Session.CurrentSession?.SendConfirmationResponse(
diff --git a/src/AcDream.App/UI/Layout/RetailTooltipPresenter.cs b/src/AcDream.App/UI/Layout/RetailTooltipPresenter.cs
index dd43c8fb..0ceab77f 100644
--- a/src/AcDream.App/UI/Layout/RetailTooltipPresenter.cs
+++ b/src/AcDream.App/UI/Layout/RetailTooltipPresenter.cs
@@ -173,20 +173,36 @@ public sealed class RetailTooltipPresenter : IDisposable
         if (layoutDid == 0u)
             return;
 
+        if (TryBuildAndMountPopup(widget.AuthoredTooltipRootElementId, layoutDid, tooltipText!))
+            _owner = widget;
+    }
+
+    /// <summary>
+    /// Shared popup-build/mount body for BOTH tooltip triggers this class
+    /// owns: the UI-element hover-dwell path above (<see cref="OnTooltipShow"/>,
+    /// per-widget authored <c>P0x47</c>/<c>P0x48</c>) and the world-object
+    /// hover path below (<see cref="UpdateWorldHoverTooltip"/>, the fixed
+    /// popup-skin pair every game-code <c>SetTooltip</c> caller in this
+    /// family resolves to). Extracted unchanged from the pre-#411-follow-on
+    /// <c>OnTooltipShow</c> body — same F4/F5/F8 fixes, same failure
+    /// handling.
+    /// </summary>
+    private bool TryBuildAndMountPopup(uint rootElementId, uint layoutDid, string tooltipText)
+    {
         ImportedLayout? layout;
         try
         {
-            layout = _createLayout(layoutDid, widget.AuthoredTooltipRootElementId);
+            layout = _createLayout(layoutDid, rootElementId);
         }
         catch (Exception error)
         {
             Console.WriteLine(
                 $"[UI] #409 tooltip popup layout=0x{layoutDid:X8} "
-                + $"root=0x{widget.AuthoredTooltipRootElementId:X8} failed to build: {error.Message}");
-            return;
+                + $"root=0x{rootElementId:X8} failed to build: {error.Message}");
+            return false;
         }
         if (layout is null)
-            return;
+            return false;
 
         UiElement root = layout.Root;
         UiElement? textChild = root.AuthoredTooltipTextChildElementId != 0u
@@ -202,7 +218,7 @@ public sealed class RetailTooltipPresenter : IDisposable
         // show an empty, unsized 30x30 bevel artifact instead of retail's
         // silent no-op.
         if (textChild is not UiText text)
-            return;
+            return false;
 
         // F4: null the per-frame anchor recompute on BOTH the popup root and
         // its text child before resizing, the same shape the sibling
@@ -216,7 +232,7 @@ public sealed class RetailTooltipPresenter : IDisposable
         text.LayoutPolicy = null;
         text.Anchors = AnchorEdges.None;
 
-        ApplyTooltipText(root, text, tooltipText!);
+        ApplyTooltipText(root, text, tooltipText);
 
         SetClickThroughRecursive(root);
         PositionAtMouse(root);
@@ -224,7 +240,7 @@ public sealed class RetailTooltipPresenter : IDisposable
         _host.AddChild(root);
         _host.BringToFront(root);
         _popupRoot = root;
-        _owner = widget;
+        return true;
     }
 
     private void OnTooltipHide(UiElement widget)
@@ -240,6 +256,122 @@ public sealed class RetailTooltipPresenter : IDisposable
         _host.RemoveChild(_popupRoot);
         _popupRoot = null;
         _owner = null;
+        _worldTooltipShowing = false;
+    }
+
+    // ── World-object hover tooltip (docs/ISSUES.md #409 follow-on) ─────────
+    //
+    // Port of UIElement_SmartBoxWrapper::RecvNotice_SmartBoxObjectFound
+    // @0x004E5AD0's tooltip half (@0x004E5D13-@0x004E5E00). Unlike the
+    // dwell-timer UI-element path above, this trigger is EDGE-fired: retail
+    // calls SetTooltip + StartTooltipAtMouse IMMEDIATELY when SmartBox's
+    // found-object id CHANGES (@0x004E5D74/@0x004E5DFB) — no dwell wait —
+    // gated per-edge by PlayerModule::ShowTooltips (@0x004E5D21,
+    // CharacterOptionId.ShowTooltips in this port's CharacterOptionTable).
+    // The text is ACCWeenieObject::GetObjectName(id, NAME_APPROPRIATE, 0)
+    // (@0x004E5D3B) — the SAME call UIElement_UIItem::UpdateTooltip uses,
+    // but WITHOUT that item-cell's separate stack-count "%d %s" prefix
+    // (RecvNotice_SmartBoxObjectFound's own text-building block has no
+    // count logic at all — a real, decomp-confirmed asymmetry versus
+    // UiItemSlot's GetTooltipDisplayName).
+    //
+    // The found-object id itself comes from UIElement_SmartBoxWrapper::
+    // FindObject @0x004E5430, called every frame from Global_Loop
+    // @0x004E5620 using the CURRENT mouse position regardless of what has
+    // input focus. FindObject special-cases m_pElementLastOver casting to
+    // UIElement_UIItem (SmartBox::set_found_object(itemID) — item cells
+    // own their own answer, ported as UiItemSlot.GetTooltipText, Item 1);
+    // otherwise it runs the ordinary 3D raycast even under non-item UI
+    // chrome. This port narrows that second branch to "no UI element
+    // hovered at all" (see WorldHoverGuidProvider's own doc) rather than
+    // reproducing the raycast-under-windows edge case.
+    //
+    // UIElement_SmartBoxWrapper is registered class 0x10000030
+    // (Register @0x0047A47E) but an exhaustive live-DAT sweep
+    // (TooltipLiveDatTests.SmartBoxWrapper_HasNoAuthoredElementDesc_
+    // AnywhereInstalled) found ZERO elements of that type anywhere
+    // installed — unlike the UIItem catalog's 49 standalone template
+    // prototypes, the 3D-viewport wrapper is evidently constructed
+    // directly by gmGamePlayUI's own mode setup rather than from a
+    // walkable authored ElementDesc, so its own P0x47/P0x48 cannot be
+    // read from the DAT. This port therefore REUSES the item catalog's
+    // confirmed uniform popup-locator pair (WorldPopupRootElementId/
+    // WorldPopupLayoutDid below) — the SAME "generic runtime-text" skin
+    // every other game-code SetTooltip caller in this family draws from —
+    // as the best-evidenced inference for the unrecoverable constant.
+
+    /// <summary>Same popup skin every UIItem prototype resolves to
+    /// (<see cref="UiItemSlot"/>'s own <c>ItemTooltipRootElementId</c>) —
+    /// see this section's own doc note on why the exact value cannot be
+    /// read off an authored <c>UIElement_SmartBoxWrapper</c> ElementDesc.</summary>
+    private const uint WorldPopupRootElementId = 0x10000395u;
+    private const uint WorldPopupLayoutDid = 0x21000041u;
+
+    private uint _worldHoverGuid;
+    private bool _worldTooltipShowing;
+
+    /// <summary>
+    /// The world-hover pick (retail's <c>SmartBox::find_object</c> via
+    /// <c>UIElement_SmartBoxWrapper::FindObject @0x004E5430</c>'s fallback
+    /// branch) — a per-frame "what's under the cursor right now" query,
+    /// distinct from click-driven <c>SelectionState</c>. Queried only when
+    /// <see cref="UiRoot.Pick"/> finds no UI element under the cursor
+    /// (mirrors <c>FindObject</c>'s <c>m_pElementLastOver</c> check, narrowed
+    /// per this section's own doc note). Null/unset disables the whole
+    /// world-hover path (no world tooltip, matching a client build that
+    /// never wires it).
+    /// </summary>
+    public Func<uint?>? WorldHoverGuidProvider { get; set; }
+
+    /// <summary>
+    /// <c>ACCWeenieObject::GetObjectName(id, NAME_APPROPRIATE, 0)</c> —
+    /// resolve the found guid's display name. Returning null/empty shows no
+    /// tooltip for that guid (matching retail's own non-empty-string guard
+    /// at <c>@0x004E5D48</c>).
+    /// </summary>
+    public Func<uint, string?>? WorldHoverNameResolver { get; set; }
+
+    /// <summary>
+    /// <c>PlayerModule::ShowTooltips</c> (<c>CharacterOptionId.ShowTooltips</c>) —
+    /// read once per found-object edge, exactly where retail reads it
+    /// (<c>@0x004E5D21</c>). A mid-hover option toggle takes effect at the
+    /// NEXT found-object change, matching retail's own edge-only
+    /// re-evaluation rather than a live per-frame re-check.
+    /// </summary>
+    public Func<bool>? WorldTooltipsEnabled { get; set; }
+
+    private void UpdateWorldHoverTooltip()
+    {
+        if (WorldHoverGuidProvider is null)
+            return;
+
+        uint found = _host.Pick(_host.MouseX, _host.MouseY) is null
+            ? WorldHoverGuidProvider() ?? 0u
+            : 0u;
+
+        if (found == _worldHoverGuid)
+            return;   // no change -> RecvNotice_SmartBoxObjectFound never re-fires
+        _worldHoverGuid = found;
+
+        if (found == 0u)
+        {
+            if (_worldTooltipShowing)
+                RemovePopup();
+            return;
+        }
+
+        if (WorldTooltipsEnabled?.Invoke() != true)
+            return;
+
+        string? text = WorldHoverNameResolver?.Invoke(found);
+        if (string.IsNullOrEmpty(text))
+            return;
+
+        // A UI-element popup cannot be showing here: UiRoot's own hover
+        // (queried above) is null whenever this branch runs, so its dwell
+        // timer never arms and OnTooltipShow never fires concurrently.
+        if (TryBuildAndMountPopup(WorldPopupRootElementId, WorldPopupLayoutDid, text))
+            _worldTooltipShowing = true;
     }
 
     /// <summary>Force-hides whatever tooltip is currently showing, if any.
@@ -371,6 +503,8 @@ public sealed class RetailTooltipPresenter : IDisposable
     {
         if (_popupRoot is not null)
             _host.BringToFront(_popupRoot);
+
+        UpdateWorldHoverTooltip();
     }
 
     public void Dispose()
diff --git a/src/AcDream.App/UI/RetailUiRuntime.cs b/src/AcDream.App/UI/RetailUiRuntime.cs
index 15961ae3..64304dfd 100644
--- a/src/AcDream.App/UI/RetailUiRuntime.cs
+++ b/src/AcDream.App/UI/RetailUiRuntime.cs
@@ -333,6 +333,17 @@ public sealed record RetailUiCursorBindings(
     CursorFeedbackController Feedback,
     RetailCursorManager Manager);
 
+/// <summary>
+/// #409 follow-on (docs/ISSUES.md "Item 2"): world-object hover tooltip
+/// bindings for <see cref="RetailTooltipPresenter"/>'s world-hover half — see
+/// that class's own doc note on <c>UIElement_SmartBoxWrapper::
+/// RecvNotice_SmartBoxObjectFound @0x004E5AD0</c>.
+/// </summary>
+public sealed record WorldTooltipRuntimeBindings(
+    Func<uint?> HoverGuidAtCursor,
+    Func<uint, string?> ResolveName,
+    Func<bool> Enabled);
+
 public sealed record ConfirmationRuntimeBindings(
     Action<uint, uint, bool> SendResponse);
 
@@ -435,6 +446,7 @@ public sealed record RetailUiRuntimeBindings(
     ExternalContainerRuntimeBindings ExternalContainer,
     VendorRuntimeBindings Vendor,
     RetailUiCursorBindings Cursor,
+    WorldTooltipRuntimeBindings WorldTooltip,
     ConfirmationRuntimeBindings Confirmations,
     AppraisalRuntimeBindings Appraisal,
     OptionsRuntimeBindings Options,
@@ -3366,7 +3378,15 @@ public sealed class RetailUiRuntime : IDisposable
             }
         }
 
-        TooltipPresenter = new RetailTooltipPresenter(Host.Root, CreateTooltipLayout);
+        TooltipPresenter = new RetailTooltipPresenter(Host.Root, CreateTooltipLayout)
+        {
+            // #409 follow-on ("Item 2"): the world-object hover half —
+            // see RetailTooltipPresenter's own doc note on
+            // UIElement_SmartBoxWrapper::RecvNotice_SmartBoxObjectFound.
+            WorldHoverGuidProvider = () => _bindings.WorldTooltip.HoverGuidAtCursor(),
+            WorldHoverNameResolver = _bindings.WorldTooltip.ResolveName,
+            WorldTooltipsEnabled = () => _bindings.WorldTooltip.Enabled(),
+        };
 
         if (_bindings.Chat.Store is { } store)
         {
diff --git a/tests/AcDream.App.Tests/UI/Layout/RetailTooltipPresenterTests.cs b/tests/AcDream.App.Tests/UI/Layout/RetailTooltipPresenterTests.cs
index 18b69384..4095519f 100644
--- a/tests/AcDream.App.Tests/UI/Layout/RetailTooltipPresenterTests.cs
+++ b/tests/AcDream.App.Tests/UI/Layout/RetailTooltipPresenterTests.cs
@@ -589,4 +589,148 @@ public sealed class RetailTooltipPresenterTests
             if (FindById(child, datElementId) is { } found) return found;
         return null;
     }
+
+    // ── World-object hover tooltip (docs/ISSUES.md #409 follow-on) ─────────
+    // Port of UIElement_SmartBoxWrapper::RecvNotice_SmartBoxObjectFound
+    // @0x004E5AD0: edge-fired (no dwell wait), gated by PlayerModule::
+    // ShowTooltips, uses the fixed popup-skin pair every game-code
+    // SetTooltip caller in this family shares (see RetailTooltipPresenter's
+    // own doc note on why UIElement_SmartBoxWrapper's own P0x47/P0x48
+    // cannot be read from the installed DAT).
+
+    private const uint WorldFoundGuid = 0x80000123u;
+
+    [Fact]
+    public void WorldHover_ShowsImmediately_NoDwellWait()
+    {
+        var (root, presenter, requests) = CreateHarness();
+        presenter.WorldHoverGuidProvider = () => WorldFoundGuid;
+        presenter.WorldHoverNameResolver = guid => guid == WorldFoundGuid ? "A Drudge" : null;
+        presenter.WorldTooltipsEnabled = () => true;
+        int childrenBefore = root.Children.Count;
+
+        // A single Tick — no root.Tick dwell timer involved at all, unlike
+        // every UI-element case above.
+        presenter.Tick();
+
+        Assert.Equal(childrenBefore + 1, root.Children.Count);
+        Assert.Single(requests, r => r == (0x21000041u, 0x10000395u));
+    }
+
+    [Fact]
+    public void WorldHover_HidesWhenTheFoundGuidClears()
+    {
+        var (root, presenter, _) = CreateHarness();
+        uint? found = WorldFoundGuid;
+        presenter.WorldHoverGuidProvider = () => found;
+        presenter.WorldHoverNameResolver = _ => "A Drudge";
+        presenter.WorldTooltipsEnabled = () => true;
+        int childrenBefore = root.Children.Count;
+
+        presenter.Tick();
+        Assert.Equal(childrenBefore + 1, root.Children.Count);
+
+        found = null;
+        presenter.Tick();
+
+        Assert.Equal(childrenBefore, root.Children.Count);
+    }
+
+    [Fact]
+    public void WorldHover_ShowTooltipsOff_ShowsNothing()
+    {
+        // PlayerModule::ShowTooltips @0x004E5D21 gates the whole block —
+        // UpdateCursorState (the found-cursor swap) is NOT gated by it, but
+        // that is a separate mechanism this presenter does not own.
+        var (root, presenter, requests) = CreateHarness();
+        presenter.WorldHoverGuidProvider = () => WorldFoundGuid;
+        presenter.WorldHoverNameResolver = _ => "A Drudge";
+        presenter.WorldTooltipsEnabled = () => false;
+        int childrenBefore = root.Children.Count;
+
+        presenter.Tick();
+
+        Assert.Empty(requests);
+        Assert.Equal(childrenBefore, root.Children.Count);
+    }
+
+    [Fact]
+    public void WorldHover_NoNameResolved_ShowsNothing()
+    {
+        var (_, presenter, requests) = CreateHarness();
+        presenter.WorldHoverGuidProvider = () => WorldFoundGuid;
+        presenter.WorldHoverNameResolver = _ => null;
+        presenter.WorldTooltipsEnabled = () => true;
+
+        presenter.Tick();
+
+        Assert.Empty(requests);
+    }
+
+    [Fact]
+    public void WorldHover_SuppressedWhileHoveringAUiElement()
+    {
+        // FindObject @0x004E5430: m_pElementLastOver != null routes through
+        // the UI-item special case or falls through to the 3D raycast —
+        // either way the found-object pipeline here must not also fire for
+        // whatever the mouse is currently over. This port narrows that to
+        // "no UI element hovered at all" (see the class's own doc note).
+        var (root, presenter, requests) = CreateHarness();
+        var uiElement = new HoverTarget { Left = 100, Top = 100, Width = 40, Height = 20 };
+        root.AddChild(uiElement);
+        root.OnMouseMove(110, 110);
+
+        presenter.WorldHoverGuidProvider = () => WorldFoundGuid;
+        presenter.WorldHoverNameResolver = _ => "A Drudge";
+        presenter.WorldTooltipsEnabled = () => true;
+
+        presenter.Tick();
+
+        Assert.Empty(requests);
+    }
+
+    [Fact]
+    public void WorldHover_ReEvaluatesGateAndTextOnlyOnTheFoundGuidEdge()
+    {
+        // RecvNotice_SmartBoxObjectFound only re-runs when SmartBox::
+        // set_found_object's target actually changes — a per-frame poll of
+        // the SAME found id must not re-read ShowTooltips or re-resolve the
+        // name every tick.
+        var (_, presenter, requests) = CreateHarness();
+        int gateReads = 0, nameReads = 0;
+        presenter.WorldHoverGuidProvider = () => WorldFoundGuid;
+        presenter.WorldHoverNameResolver = _ => { nameReads++; return "A Drudge"; };
+        presenter.WorldTooltipsEnabled = () => { gateReads++; return true; };
+
+        presenter.Tick();
+        presenter.Tick();
+        presenter.Tick();
+
+        Assert.Equal(1, gateReads);
+        Assert.Equal(1, nameReads);
+        Assert.Single(requests);
+    }
+
+    [Fact]
+    public void WorldHover_TextIsPlainAppropriateName_NoStackCountPrefix()
+    {
+        // RecvNotice_SmartBoxObjectFound's own text-building block
+        // (@0x004E5D3B-@0x004E5D74) has no "%d %s" stack-count logic —
+        // unlike UIElement_UIItem::UpdateTooltip's item-cell tooltip. The
+        // resolver contract here is plain GetAppropriateName, not
+        // GetTooltipDisplayName; this pin just documents the caller's
+        // resolver is free to return whatever plain text it wants and the
+        // presenter applies it verbatim (no separate count formatting is
+        // ever added by this class).
+        var (root, presenter, _) = CreateHarness();
+        presenter.WorldHoverGuidProvider = () => WorldFoundGuid;
+        presenter.WorldHoverNameResolver = _ => "Iron Bars";
+        presenter.WorldTooltipsEnabled = () => true;
+
+        presenter.Tick();
+
+        UiElement popup = Assert.Single(root.Children);
+        UiElement? textChild = FindById(popup, TextChildId);
+        Assert.IsType<UiText>(textChild);
+    }
 }
diff --git a/tests/AcDream.App.Tests/UI/Layout/TooltipLiveDatTests.cs b/tests/AcDream.App.Tests/UI/Layout/TooltipLiveDatTests.cs
index 19c7a2fa..326b618b 100644
--- a/tests/AcDream.App.Tests/UI/Layout/TooltipLiveDatTests.cs
+++ b/tests/AcDream.App.Tests/UI/Layout/TooltipLiveDatTests.cs
@@ -217,6 +217,125 @@ public sealed class TooltipLiveDatTests
     private const uint OptionsToggleRowTemplateId = 0x10000218u;
     private const uint OptionsToggleCheckboxId = 0x10000219u;
 
+    /// <summary>Retail's <c>UIElement_UIItem</c> registered class id
+    /// (<c>UIElement_UIItem::Register @0x0047A488</c>:
+    /// <c>RegisterElementClass(0x10000032, ...)</c>). The catalog also holds a
+    /// handful of type-3 (plain UIRegion) housekeeping elements used only as
+    /// BaseElement bases for the real prototypes below — never selected by any
+    /// list's own cell-template attribute, so they are excluded from this
+    /// scan.</summary>
+    private const uint UiItemElementType = 0x10000032u;
+
+    /// <summary>
+    /// Item-tooltip investigation (docs/ISSUES.md #409 follow-on): pins the
+    /// finding that justifies <c>UiItemSlot</c> hardcoding a single popup-
+    /// locator pair rather than reading it per prototype. Every standalone
+    /// UIItem prototype (type <c>0x10000032</c>) in the shared cell-template
+    /// catalog (<see cref="ItemListCellTemplate.CatalogLayoutId"/>, LayoutDesc
+    /// <c>0x21000037</c>) resolves the SAME <c>P0x47/P0x48</c> pair through
+    /// catalog inheritance — <c>0x10000395</c> within <c>0x21000041</c>, one of
+    /// the four popup skins <see cref="TooltipCatalog_EveryPopupSkin_SharesTheSameTextChild"/>
+    /// already pins. None author literal <c>P0x49</c> text or the <c>P0x4B</c>
+    /// on-bit — matching retail's runtime-text game-code sites
+    /// (<c>UIElement_UIItem::UpdateTooltip @0x004E1CB0</c> sets both the text
+    /// and the on-bit itself; see <see cref="RetailTooltipPresenter.OnTooltipShow"/>'s
+    /// <c>fromRuntime</c> bypass).
+    /// </summary>
+    [InstalledDatFact]
+    public void UiItemCatalog_EveryPrototype_SharesTheSamePopupLocator()
+    {
+        using var dats = new DatCollection(DatDirectory, DatAccessType.Read);
+
+        ElementInfo? catalog = LayoutImporter.ImportInfos(dats, ItemListCellTemplate.CatalogLayoutId);
+        Assert.NotNull(catalog);
+        Assert.True(catalog!.Children.Count >= 40,
+            $"expected the shared UIItem catalog to hold dozens of prototypes, found {catalog.Children.Count}.");
+
+        var prototypes = catalog.Children.Where(c => c.Type == UiItemElementType).ToList();
+        Assert.True(prototypes.Count >= 30,
+            $"expected the shared UIItem catalog to hold dozens of type-0x10000032 prototypes, found {prototypes.Count}.");
+
+        foreach (ElementInfo prototype in prototypes)
+        {
+            Assert.True(prototype.TooltipRootElementId == UiItemTooltipRootElementId,
+                $"prototype 0x{prototype.Id:X8} authors P0x47=0x{prototype.TooltipRootElementId:X8}, expected 0x{UiItemTooltipRootElementId:X8}.");
+            Assert.True(prototype.TooltipLayoutDid == TooltipCatalogLayoutId,
+                $"prototype 0x{prototype.Id:X8} authors P0x48=0x{prototype.TooltipLayoutDid:X8}, expected 0x{TooltipCatalogLayoutId:X8}.");
+            Assert.False(prototype.TooltipText.HasValue,
+                $"prototype 0x{prototype.Id:X8} unexpectedly authors literal P0x49 tooltip text.");
+        }
+
+        // Concrete owning lists select DIFFERENT prototype ids (attribute
+        // 0x1000000E) for their own cell shape, but every one of those
+        // prototypes still resolves the same popup locator above — so
+        // UiItemSlot's hardcoded pair is correct regardless of which list
+        // spawned the cell.
+        ElementInfo? inventoryTree = LayoutImporter.ImportInfos(dats, 0x21000023u);
+        ElementInfo? contentsGrid = inventoryTree is null
+            ? null : AllDescendants(inventoryTree).FirstOrDefault(x => x.Id == 0x100001C6u);
+        Assert.NotNull(contentsGrid);
+        Assert.True(contentsGrid!.TryGetEffectiveProperty(0x1000000Eu, out UiPropertyValue protoProp));
+        Assert.NotEqual(0u, (uint)protoProp.UnsignedValue);
+
+        ElementInfo? toolbarTree = LayoutImporter.ImportInfos(dats, 0x21000016u);
+        ElementInfo? toolbarSlot = toolbarTree is null
+            ? null : AllDescendants(toolbarTree).FirstOrDefault(x => x.Id == 0x100001A7u);
+        Assert.NotNull(toolbarSlot);
+        Assert.True(toolbarSlot!.TryGetEffectiveProperty(0x1000000Eu, out UiPropertyValue toolbarProtoProp));
+        Assert.NotEqual(0u, (uint)toolbarProtoProp.UnsignedValue);
+        // Different lists really do select different prototypes.
+        Assert.NotEqual((uint)protoProp.UnsignedValue, (uint)toolbarProtoProp.UnsignedValue);
+    }
+
+    /// <summary>
+    /// World-object tooltip investigation (docs/ISSUES.md #409 follow-on).
+    /// <c>UIElement_SmartBoxWrapper</c> (retail's registered class
+    /// <c>0x10000030</c>, <c>UIElement_SmartBoxWrapper::Register @0x0047A47E</c>)
+    /// is the caller of the world-hover tooltip's own
+    /// <c>UIElement::SetTooltip</c>/<c>StartTooltipAtMouse</c> pair
+    /// (<c>RecvNotice_SmartBoxObjectFound @0x004E5AD0</c>, calls at
+    /// <c>@0x004E5D74</c>/<c>@0x004E5DFB</c>) — but this exhaustive sweep of
+    /// every installed <c>LayoutDesc</c> found ZERO elements of that type
+    /// anywhere. Unlike the UIItem catalog (49 standalone template
+    /// prototypes, all authoring the SAME popup locator), the 3D-viewport
+    /// wrapper is evidently constructed directly by game code
+    /// (<c>gmGamePlayUI</c>'s own mode setup) rather than from a walkable
+    /// authored <c>ElementDesc</c>, so its own <c>P0x47</c>/<c>P0x48</c>
+    /// cannot be read from the DAT the way every other tooltip trigger's
+    /// can. <see cref="RetailTooltipPresenter"/>'s world-hover popup therefore
+    /// REUSES the item-catalog's confirmed uniform pair
+    /// (<c>P0x47=0x10000395</c>/<c>P0x48=0x21000041</c>) — the SAME "generic
+    /// runtime-text" skin every other game-code <c>SetTooltip</c> caller in
+    /// this family (items, the Options checkboxes, the radar) draws from —
+    /// as the best-evidenced inference rather than leaving world-object
+    /// tooltips unimplemented over one unrecoverable hex constant.
+    /// </summary>
+    [InstalledDatFact]
+    public void SmartBoxWrapper_HasNoAuthoredElementDesc_AnywhereInstalled()
+    {
+        using var dats = new DatCollection(DatDirectory, DatAccessType.Read);
+
+        int found = 0;
+        foreach (uint layoutId in dats.GetAllIdsOfType<LayoutDesc>())
+        {
+            ElementInfo? tree;
+            try { tree = LayoutImporter.ImportInfos(dats, layoutId); }
+            catch { continue; }
+            if (tree is null) continue;
+
+            found += AllDescendants(tree).Count(e => e.Type == SmartBoxWrapperElementType);
+        }
+
+        Assert.Equal(0, found);
+    }
+
+    /// <summary>Retail's <c>UIElement_SmartBoxWrapper</c> registered class id.</summary>
+    private const uint SmartBoxWrapperElementType = 0x10000030u;
+
+    /// <summary>The item-cell popup-locator P0x47, hardcoded onto every
+    /// <see cref="UiItemSlot"/> — see that class's own doc comment.</summary>
+    private const uint UiItemTooltipRootElementId = 0x10000395u;
+
     private static IEnumerable<UiElement> AllWidgets(UiElement root)
     {
         yield return root;