diff --git a/src/AcDream.App/UI/PluginSidePanel.cs b/src/AcDream.App/UI/PluginSidePanel.cs
index b43f8b48e..2e91bc2c8 100644
--- a/src/AcDream.App/UI/PluginSidePanel.cs
+++ b/src/AcDream.App/UI/PluginSidePanel.cs
@@ -224,11 +224,29 @@ public sealed class PluginSidePanel : UiPanel, IDisposable, IRetainedWindowState
         BorderThickness = 1f;
         Visible = false;
 
+        // Anchors = None on both: the shelf is the SOLE layout owner of these
+        // children (LayoutChrome, called from Reflow, repositions them every
+        // time the shelf's own Width/Height changes — collapse/expand,
+        // entries added/removed, row-wrap). UiElement.ApplyAnchor is called
+        // for every child on every draw; for any child whose Anchors is not
+        // AnchorEdges.None it captures the Left/Top/Width/Height margins
+        // ONCE on the FIRST draw and re-applies that frozen snapshot on
+        // every subsequent draw, silently overwriting whatever LayoutChrome
+        // had just written. Left at the default Left|Top, the grip/toggle
+        // therefore stayed pinned at their EXPANDED geometry after a
+        // collapse (owner report 2026-09-06: the toggle ended up outside
+        // the collapsed shelf and the ancestor clip removed it — "I dont
+        // see the < after I minimize the window"). Anchoring is simply the
+        // wrong mechanism for a child whose layout owner already re-derives
+        // its full geometry every reflow; ResetAnchorCapture() would only
+        // patch this one call site; the actual fix is to never engage the
+        // capture-and-freeze machinery for these children at all.
         _grip = new ShelfGripPanel
         {
             WindowMoveHandle = true,
             BackgroundColor = Vector4.Zero,
             BorderColor = Vector4.Zero,
+            Anchors = AnchorEdges.None,
         };
         _toggle = new UiSimpleButton
         {
@@ -238,6 +256,7 @@ public sealed class PluginSidePanel : UiPanel, IDisposable, IRetainedWindowState
             DatFont = _font,
             Outline = true,
             TextSource = () => _collapsed ? "<" : ">",
+            Anchors = AnchorEdges.None,
         };
         _toggle.Click += ToggleCollapsed;
         AddChild(_grip);
@@ -285,6 +304,13 @@ public sealed class PluginSidePanel : UiPanel, IDisposable, IRetainedWindowState
         {
             Width = ButtonExtent,
             Height = ButtonExtent,
+            // Anchors = None for the same reason as _grip/_toggle above:
+            // Reflow() is the sole owner of each entry button's Left/Top
+            // (row-wrap column/row placement), rewritten on every add/
+            // remove/collapse. Left at the default anchor, ApplyAnchor would
+            // freeze a button at whatever column/row it first drew in and
+            // never let a later removal's row-wrap actually move it.
+            Anchors = AnchorEdges.None,
         };
         button.Click += () =>
         {
diff --git a/tests/AcDream.App.Tests/UI/PluginSidePanelToggleGlyphClipTests.cs b/tests/AcDream.App.Tests/UI/PluginSidePanelToggleGlyphClipTests.cs
index fee36108a..34b74ed0b 100644
--- a/tests/AcDream.App.Tests/UI/PluginSidePanelToggleGlyphClipTests.cs
+++ b/tests/AcDream.App.Tests/UI/PluginSidePanelToggleGlyphClipTests.cs
@@ -266,4 +266,236 @@ public sealed class PluginSidePanelToggleGlyphClipTests
         Assert.True(shelf.Height > 20f, $"collapsed shelf height ({shelf.Height}) is not button-sized");
         Assert.NotEqual(expandedHeight, shelf.Height);
     }
+
+    /// <summary>
+    /// Owner-reported defect (2026-09-06 live probe): after collapsing the
+    /// shelf, the grip and toggle stayed pinned at the EXPANDED geometry —
+    /// the toggle ended up outside the 24px collapsed shelf and the ancestor
+    /// clip removed it, so the owner saw the tab with no <c>&lt;</c>.
+    ///
+    /// <para>
+    /// Root cause: <see cref="UiElement.ApplyAnchor"/> is called for every
+    /// child on every draw. For any child whose <see cref="UiElement.Anchors"/>
+    /// is not <see cref="AnchorEdges.None"/>, it captures the Left/Top/Width/
+    /// Height margins ONCE on the FIRST draw and re-applies that snapshot on
+    /// every subsequent draw — overwriting whatever
+    /// <see cref="PluginSidePanel.LayoutChrome"/>/<c>Reflow</c> set in between.
+    /// <see cref="UiRoot.Tick"/> never draws, so a test that only ticks (as
+    /// every prior collapse test in this tree does) never exercises this path
+    /// at all — this test drives two REAL <see cref="UiRoot.Draw"/> passes,
+    /// with a real toggle click in between, to reproduce it.
+    /// </para>
+    ///
+    /// <para>
+    /// Uses a bitmap-fallback font (<c>font: null</c>) deliberately, per the
+    /// investigation's direction, so this reproduction runs in every CI lane
+    /// without an installed retail DAT — unlike the <c>Lane=InstalledDat</c>
+    /// tests above, which require one.
+    /// </para>
+    /// </summary>
+    [Fact]
+    public void Collapse_AfterADraw_RepositionsGripAndToggle_NotFrozenAtExpandedGeometry()
+    {
+        var root = new UiRoot { Width = 800f, Height = 600f };
+        using var shelf = new PluginSidePanel(root.WindowManager, _ => (0u, 0, 0), font: null);
+        root.AddChild(shelf);
+
+        for (int i = 0; i < 2; i++)
+        {
+            var frame = new UiPanel { Width = 200f, Height = 100f };
+            root.AddChild(frame);
+            RetailWindowHandle handle = root.WindowManager.Register(
+                $"plugin:acdream.test:{i}", frame);
+            shelf.Add(
+                new PluginUiOwner($"acdream.test.{i}", $"Test Plugin {i}"),
+                new PluginPanelDescriptor("main", $"Test Plugin {i}"),
+                handle);
+        }
+
+        root.Tick(0.016d, 16L);
+
+        var device = new RecordingGpuDevice();
+        var renderer = new TextRenderer(device, new NullGpuFrameSource(), "unused");
+        var ctx = new UiRenderContext(renderer, new Vector2(800f, 600f));
+
+        // ── First draw: this is what CAPTURES the anchor snapshot (at the
+        // expanded geometry) — nothing is wrong yet, since the snapshot
+        // matches the current (correct) layout. ──────────────────────────
+        renderer.Begin(new Vector2(800f, 600f));
+        root.Draw(ctx);
+
+        UiSimpleButton toggle = Assert.Single(
+            shelf.Children,
+            c => c is UiSimpleButton && c is not PluginSidePanel.PluginShelfButton) as UiSimpleButton
+            ?? throw new InvalidOperationException("toggle button not found");
+        UiElement grip = Assert.Single(
+            shelf.Children,
+            c => c is UiPanel && c is not UiSimpleButton);
+
+        float expandedShelfHeight = shelf.Height;
+        float expandedBandHeight = shelf.ExpandedGripBandHeight;
+        float toggleWidth = toggle.Width;
+
+        Assert.Equal(0f, grip.Left);
+        Assert.Equal(0f, grip.Top);
+        Assert.Equal(shelf.Width - toggleWidth, grip.Width, 3);
+        Assert.Equal(expandedBandHeight, grip.Height, 3);
+        Assert.Equal(shelf.Width - toggleWidth, toggle.Left, 3);
+        Assert.Equal(0f, toggle.Top);
+        Assert.Equal(expandedBandHeight, toggle.Height, 3);
+
+        // ── Collapse via a REAL press/release through UiRoot (the production
+        // input path), not the state controller directly. ────────────────
+        int toggleX = (int)shelf.Left + (int)shelf.Width - 8;
+        int toggleY = (int)shelf.Top + 4;
+        root.OnMouseDown(UiMouseButton.Left, toggleX, toggleY);
+        root.OnMouseUp(UiMouseButton.Left, toggleX, toggleY);
+        Assert.True(shelf.CaptureWindowState().Collapsed);
+
+        // ── Second draw: must reflect the COLLAPSED geometry. Pre-fix, the
+        // anchor snapshot captured above wins instead: grip/toggle stay at
+        // their EXPANDED Left/Width/Height regardless of what LayoutChrome
+        // just wrote via Reflow. ───────────────────────────────────────────
+        renderer.Begin(new Vector2(800f, 600f));
+        root.Draw(ctx);
+
+        Assert.Equal(0f, grip.Left);
+        Assert.Equal(0f, grip.Top);
+        Assert.Equal(shelf.Width - toggleWidth, grip.Width, 3);
+        Assert.Equal(shelf.Height, grip.Height, 3);
+        Assert.Equal(shelf.Width - toggleWidth, toggle.Left, 3);
+        Assert.Equal(0f, toggle.Top);
+        Assert.Equal(shelf.Height, toggle.Height, 3);
+        Assert.True(
+            toggle.Left + toggle.Width <= shelf.Width + 0.01f,
+            $"toggle (Left={toggle.Left}, Width={toggle.Width}) lies outside " +
+            $"the collapsed shelf (Width={shelf.Width}) — the ancestor clip " +
+            "would remove it, matching the owner's \"no <\" report.");
+
+        // ── Expand again: the geometry must be restored too, via another
+        // real click. ──────────────────────────────────────────────────────
+        int toggleX2 = (int)shelf.Left + (int)shelf.Width - 8;
+        int toggleY2 = (int)shelf.Top + 4;
+        root.OnMouseDown(UiMouseButton.Left, toggleX2, toggleY2);
+        root.OnMouseUp(UiMouseButton.Left, toggleX2, toggleY2);
+        Assert.False(shelf.CaptureWindowState().Collapsed);
+
+        renderer.Begin(new Vector2(800f, 600f));
+        root.Draw(ctx);
+
+        Assert.Equal(expandedShelfHeight, shelf.Height, 3);
+        Assert.Equal(0f, grip.Left);
+        Assert.Equal(0f, grip.Top);
+        Assert.Equal(shelf.Width - toggleWidth, grip.Width, 3);
+        Assert.Equal(expandedBandHeight, grip.Height, 3);
+        Assert.Equal(shelf.Width - toggleWidth, toggle.Left, 3);
+        Assert.Equal(0f, toggle.Top);
+        Assert.Equal(expandedBandHeight, toggle.Height, 3);
+    }
+
+    /// <summary>
+    /// Same double-draw pin as
+    /// <see cref="Collapse_AfterADraw_RepositionsGripAndToggle_NotFrozenAtExpandedGeometry"/>,
+    /// but for the <see cref="PluginSidePanel.PluginShelfButton"/> ENTRIES
+    /// rather than the grip/toggle: a multi-column row-wrapped layout, draw,
+    /// remove one entry (a real window unregister — the same path a plugin
+    /// unload takes), draw again. Every remaining button's Left/Top must
+    /// match what a FRESH single-pass layout of the same final entry set
+    /// would produce — not a stale position captured from the 12-entry
+    /// layout on the first draw.
+    ///
+    /// <para>
+    /// Compares against an independent "reference" shelf built directly with
+    /// the final (post-removal) entry set and drawn exactly once, so the
+    /// expected geometry is derived from the real layout math rather than
+    /// re-hard-coded private constants (<c>OuterPadding</c>/<c>ButtonExtent</c>/
+    /// <c>ButtonGap</c> are private to <see cref="PluginSidePanel"/>).
+    /// </para>
+    /// </summary>
+    [Fact]
+    public void MultiColumnReflow_AfterADraw_EveryRemainingButtonMatchesAFreshSinglePassLayout()
+    {
+        const int entryCount = 12;
+
+        var root = new UiRoot { Width = 800f, Height = 260f };
+        using var shelf = new PluginSidePanel(root.WindowManager, _ => (0u, 0, 0), font: null);
+        root.AddChild(shelf);
+
+        var handles = new RetailWindowHandle[entryCount];
+        for (int i = 0; i < entryCount; i++)
+        {
+            var frame = new UiPanel { Width = 200f, Height = 100f };
+            root.AddChild(frame);
+            handles[i] = root.WindowManager.Register($"plugin:acdream.test:{i}", frame);
+            shelf.Add(
+                new PluginUiOwner($"acdream.test.{i}", $"Test Plugin {i}"),
+                new PluginPanelDescriptor("main", $"Test Plugin {i}"),
+                handles[i]);
+        }
+
+        root.Tick(0.016d, 16L);
+
+        var device = new RecordingGpuDevice();
+        var renderer = new TextRenderer(device, new NullGpuFrameSource(), "unused");
+        var ctx = new UiRenderContext(renderer, new Vector2(800f, 600f));
+
+        // ── First draw: captures anchors at the full 12-entry layout. ─────
+        renderer.Begin(new Vector2(800f, 600f));
+        root.Draw(ctx);
+
+        // ── Remove the FIRST entry — every remaining button shifts down one
+        // slot, so this exercises the widest possible reflow. ─────────────
+        root.WindowManager.Unregister(handles[0].Name);
+        Assert.Equal(entryCount - 1, shelf.EntryCount);
+
+        // ── Second draw: must reflect the fresh 11-entry reflow. Pre-fix,
+        // each surviving button stays pinned at its ORIGINAL 12-entry
+        // position/size instead. ───────────────────────────────────────────
+        renderer.Begin(new Vector2(800f, 600f));
+        root.Draw(ctx);
+
+        List<PluginSidePanel.PluginShelfButton> afterRemoval =
+            shelf.Children.OfType<PluginSidePanel.PluginShelfButton>().ToList();
+        Assert.Equal(entryCount - 1, afterRemoval.Count);
+
+        // ── Reference: an independent shelf built directly with the SAME
+        // final 11-entry set (never having been through a 12-entry layout),
+        // ticked and drawn exactly once. ───────────────────────────────────
+        var referenceRoot = new UiRoot { Width = 800f, Height = 260f };
+        using var referenceShelf = new PluginSidePanel(
+            referenceRoot.WindowManager, _ => (0u, 0, 0), font: null);
+        referenceRoot.AddChild(referenceShelf);
+        for (int i = 1; i < entryCount; i++)
+        {
+            var frame = new UiPanel { Width = 200f, Height = 100f };
+            referenceRoot.AddChild(frame);
+            RetailWindowHandle handle = referenceRoot.WindowManager.Register(
+                $"plugin:acdream.reference:{i}", frame);
+            referenceShelf.Add(
+                new PluginUiOwner($"acdream.reference.{i}", $"Test Plugin {i}"),
+                new PluginPanelDescriptor("main", $"Test Plugin {i}"),
+                handle);
+        }
+        referenceRoot.Tick(0.016d, 16L);
+        var referenceDevice = new RecordingGpuDevice();
+        var referenceRenderer = new TextRenderer(referenceDevice, new NullGpuFrameSource(), "unused");
+        var referenceCtx = new UiRenderContext(referenceRenderer, new Vector2(800f, 600f));
+        referenceRenderer.Begin(new Vector2(800f, 600f));
+        referenceRoot.Draw(referenceCtx);
+
+        List<PluginSidePanel.PluginShelfButton> reference =
+            referenceShelf.Children.OfType<PluginSidePanel.PluginShelfButton>().ToList();
+        Assert.Equal(reference.Count, afterRemoval.Count);
+
+        for (int i = 0; i < afterRemoval.Count; i++)
+        {
+            Assert.Equal(reference[i].Left, afterRemoval[i].Left, 3);
+            Assert.Equal(reference[i].Top, afterRemoval[i].Top, 3);
+            Assert.Equal(reference[i].Width, afterRemoval[i].Width, 3);
+            Assert.Equal(reference[i].Height, afterRemoval[i].Height, 3);
+        }
+
+        Assert.Equal(shelf.Width, referenceShelf.Width, 3);
+        Assert.Equal(shelf.Height, referenceShelf.Height, 3);
+    }
 }