refactor(render): delete superseded alpha sidecars

Remove the dead classic-group CachedBatch/InstanceGroup sort-center sidecar and its cache, append, reset, and diagnostic-digest plumbing. Remove the discarded camera parameter chain from grouped alpha deferral and dispatcher submission diagnostics while preserving walk/particle CYpt keys, FIFO submission ordinals, and opaque camera distance.

Add production-facing reflection/source pins for the deleted shapes and camera chain, retained per-cell and opaque owners, the exact three AlphaFlushCounts reasons, and deleted alpha-order symbols. Update directly affected cache/digest/group lifecycle tests and record the complete section 22 result.

Gates: Release 0W/0E; focused App 132/132 plus Core 29/29; new pins 4/4; real allocation pins 2/2 at 0 B; shaders 32/32; hermetic 16755/16755; InstalledDat exactly 385 pass, 10 documented fail, 1 skip; diff-check clean.

Mutations: InstanceGroup and CachedBatch sidecars fail their Assert.Null pins; Defer and digest camera parameters fail method-shape pins; false count prose fails the exact-reason pin; RetailAlphaOrdering resurrection fails the deletion pin. Each was restored independently before the final matrix.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/research/2026-09-01-overhaul/s4-depth-alpha-packet.md

@@ -1990,3 +1990,93 @@ call reachability, diagnostic-digest consequences, cache/reset/storage
 lifecycle, allocation, allowed scope, every mutation claim, and all gate
 counts. A failed lens gets one bounded fix contract; a third fix round stops
 and is written up. Dual PASS lands c3b and unlocks G3.
+
+### 22.7 S4-c3b implementation result (implementer, 2026-09-04)
+
+PASS for the bounded implementation return. The classic grouped dispatcher no
+longer carries `CachedBatch.LocalSortCenter` or
+`InstanceGroup.LocalSortCenters`; their constructor/cache-hit/append/reset/
+release and diagnostic-hash plumbing is gone. The discarded alpha camera
+parameter is also absent from `DeferTransparentGroups`,
+`BuildTransparentSubmissionDigest`, `CreateDispatcherSubmission`,
+`ObserveCurrentDispatcherSubmission`, and
+`ObserveClassifiedDispatcherSubmission`, with no camera tombstone remaining.
+The diagnostic transparent digest therefore hashes only rendered state plus the
+live submission ordinal, as intended.
+
+Production-facing reflection/source pins prove the deletion and retain the
+separate live owners: `WalkClassifiedBatch.LocalSortCenter`/
+`SortDistanceSq`, the transformed authored-center per-cell stable descending
+sort, and `PartitionInstanceGroups(cameraWorldPosition)` feeding opaque
+`InstanceGroup.SortDistance`. Existing cache-hit matrix composition,
+transparent submission-order digest, group lifecycle, walk/particle merge,
+queue/router, allocation, and shader/state tests remain green. The
+`AlphaFlushCounts_*` source-truth pin keeps exactly the content-empty replay,
+AP-238 `(cell,list)` coalescing, and AP-239/AP-240 list-membership reasons and
+explicitly preserves the fact that the former broad “per instance versus per
+subset” explanation was false. Static production truth rejects resurrection of
+`RetailAlphaOrdering`, `FlushFartherThan`, alpha-submit `viewerDistance`, or a
+discarded camera tombstone.
+
+Automated return:
+
+- The first `dotnet build AcDream.slnx -c Release --no-restore` invocation did
+  not reach compilation because the fresh worktree had no
+  `obj/project.assets.json` files (`NETSDK1004`, 57 projects). One
+  `dotnet restore AcDream.slnx` populated those assets; the Release rerun then
+  passed with 0 warnings / 0 errors. This was dependency preparation, not a
+  product retry.
+- focused App
+  `InstanceGroupClearTests|WalkStaticStreamPopulatorTests|ParticleRendererRouteTests|WalkFrameDriverTests|RetailAlphaQueueTests|RetailParticleGeometryClassifierTests`
+  — PASS, 132/132; focused Core
+  `WbDrawDispatcherBucketingTests|EntityClassificationCacheTests` — PASS,
+  29/29 (161/161 aggregate);
+- the four new deletion/truth pins — PASS, 4/4 after every mutation restore;
+- real warmed
+  `ProductionCellObjectParticleMerge_WarmedPathAllocatesZeroBytes|ProductionImmediateMesh_WarmedDrawImmediateParticleSubmissionRhiDoesNotAllocate`
+  — PASS, 2/2, both observing 0 managed bytes;
+- `VulkanShaderDescriptorContractTests|VulkanShaderManifestTests|RenderPackSpirvValidatorTests`
+  — PASS, 32/32; no shader, SPIR-V, manifest, RHI, or pipeline file changed;
+- official no-retry 14-assembly hermetic gate — PASS, 16,755 passed / 0
+  skipped / 0 failed; evidence
+  `artifacts/s4-c3b-hermetic-20260904`;
+- InstalledDat with explicit `C:\Turbine\Asheron's Call`, inclusive of the
+  retained KnownFailures — 385 passed / 10 expected failed / 1 skipped. The
+  failures were exactly TowerAscent, the two #383 layout sweeps,
+  `Oh_doorway_still_first_frame_diff` (#458), and the six
+  `AlphaFlushCounts_*`; the skip remained `Sweep_the_lookin_gate_decodes_against_the_street_fixture`.
+  No new failure appeared; evidence
+  `artifacts/s4-c3b-installed-inclusive-20260904`.
+
+Mutation ledger (each mutation was applied alone and restored by patch before
+the next; the restored pin set passed 4/4):
+
+1. Restoring `InstanceGroup.LocalSortCenters` first failed
+   `ClassicGroupedShapes_DeleteDeadSortCenterSidecarsButRetainWalkCyptKey` at
+   its second `Assert.Null`: expected null; actual
+   `List<Vector3> LocalSortCenters`.
+2. Restoring `CachedBatch.LocalSortCenter` first failed the same pin at its
+   first `Assert.Null`: expected null; actual `Vector3 LocalSortCenter`.
+3. Restoring the `DeferTransparentGroups(Vector3, Matrix4x4)` parameter and
+   tombstone first failed
+   `AlphaSubmissionShapes_DeleteDeadCameraChainButRetainOpaqueCameraDistance`:
+   `Assert.Equal` expected `[Matrix4x4]`, actual `[Vector3, Matrix4x4]`.
+4. Restoring `cameraWorldPosition` on
+   `BuildTransparentSubmissionDigest` first failed the same pin's next
+   `Assert.DoesNotContain`: the parameter collection contained
+   `Vector3 cameraWorldPosition` at position 1.
+5. Replacing the exact three-reason prose with a false broad fourth reason
+   first failed
+   `AlphaFlushCountKnownFailure_StatesOnlyTheThreeExactReasons` at
+   `Assert.Contains`: the required `former broad "per instance versus per
+   subset" explanation was false.` substring was absent.
+6. Restoring an executable `RetailAlphaOrdering` symbol first failed
+   `ClassicGroupedAlphaSourceTruth_DeletesDeadOrderingChainAndPreservesLiveOwners`
+   at `Assert.DoesNotContain`: substring `RetailAlphaOrdering` was found.
+
+The implementation changes only the three allowed production files, the two
+named App test files, the one directly affected Core rendering test file, and
+this result. AD-119 and AP-238 through AP-243, queue/router/list membership,
+capacities, barriers, particles, per-cell ordering, building/private/portal
+distances, shaders/RHI, package/content, and graphical behavior are unchanged.
+No graphical client was launched.

src/AcDream.App/Rendering/Wb/CachedBatch.cs

@@ -9,8 +9,6 @@ namespace AcDream.App.Rendering.Wb;
 /// subPart contributes its own <see cref="CachedBatch"/> entries, with
 /// <see cref="RestPose"/> already containing the
 /// <c>subPart.PartTransform * meshRef.PartTransform</c> product.
-/// <see cref="LocalSortCenter"/> preserves the authored GfxObj key used by
-/// retail's delayed-alpha viewer-distance ordering on cache hits.
 /// <see cref="Group"/> is a registration-checked fast handle into the
 /// dispatcher's bounded group table; a retired or synthetic entry falls back
 /// to key lookup and refreshes this array entry.
@@ -25,7 +23,6 @@ internal readonly record struct CachedBatch(
     GroupKey Key,
     GpuTextureSlot TextureSlot,
     Matrix4x4 RestPose,
-    Vector3 LocalSortCenter = default,
     WbDrawDispatcher.InstanceGroup? Group = null,
     long GroupRegistration = 0);
 

src/AcDream.App/Rendering/Wb/WbDrawDispatcher.WalkClassify.cs

@@ -143,13 +143,12 @@ public sealed partial class WbDrawDispatcher
     /// one needs to reach the alpha queue: <see cref="IsOpaque"/> (so the
     /// populator can route without re-deriving it from
     /// <see cref="GroupKey.Translucency"/>) and <see cref="LocalSortCenter"/>
-    /// (the authored GfxObj sort center — the same value
+    /// (the authored GfxObj sort center consumed by the live per-cell CYpt
-    /// <c>InstanceGroup.LocalSortCenters</c> carries per instance today; S4-c2
+    /// sort; the classic grouped path has no corresponding sidecar).
-    /// deleted its one alpha-ordering consumer, <c>RetailAlphaOrdering.ComputeViewerDistance</c>,
+    /// <c>WalkStaticStreamPopulator</c> transforms it through the part model
-    /// but S4-c3a restores its retail use: <c>WalkStaticStreamPopulator</c>
+    /// and retains the resulting squared CYpt key in
-    /// transforms it through the part model and retains the resulting
+    /// <see cref="SortDistanceSq"/> before the per-cell stable sort. The key
-    /// squared CYpt key in <see cref="SortDistanceSq"/> before the per-cell
+    /// feeds two FIFO alpha lists; neither queue sorts.
-    /// stable sort. The key feeds two FIFO alpha lists; neither queue sorts.
     /// </summary>
     internal readonly record struct WalkClassifiedBatch(
         GroupKey Key,

src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs

@@ -1818,8 +1818,7 @@ public sealed partial class WbDrawDispatcher : IDisposable
             ObserveClassifiedDispatcherSubmission(observeCurrentPath,
                 visibleInstanceCount: 0,
                 immediateInstanceCount: 0,
-                deferTransparent: false,
+                deferTransparent: false);
-                camPos);
             _cpuStopwatch.Stop();
             if (diag) MaybeFlushDiag();
             return;
@@ -1841,8 +1840,7 @@ public sealed partial class WbDrawDispatcher : IDisposable
             ObserveClassifiedDispatcherSubmission(observeCurrentPath,
                 visibleInstanceCount: 0,
                 immediateInstanceCount: 0,
-                deferTransparent,
+                deferTransparent);
-                camPos);
             _cpuStopwatch.Stop();
             if (diag) MaybeFlushDiag();
             return;
@@ -1850,7 +1848,7 @@ public sealed partial class WbDrawDispatcher : IDisposable
 
         _opaqueDraws.Sort(CompareOpaqueSubmissionOrder);
         if (deferTransparent)
-            DeferTransparentGroups(camPos, vp);
+            DeferTransparentGroups(vp);
         else
             _translucentDraws.Sort(CompareTransparentSubmissionOrder);
 
@@ -1969,8 +1967,7 @@ public sealed partial class WbDrawDispatcher : IDisposable
         ObserveClassifiedDispatcherSubmission(observeCurrentPath,
             totalInstances,
             immediateInstances,
-            deferTransparent,
+            deferTransparent);
-            camPos);
 
         // Campaign V slice V11: every per-frame upload is a frame ring slice
         // bound through the borrowed world pass, which retires the buffer-set
@@ -2153,8 +2150,7 @@ public sealed partial class WbDrawDispatcher : IDisposable
     private void ObserveCurrentDispatcherSubmission(
         int visibleInstanceCount,
         int immediateInstanceCount,
-        bool deferTransparent,
+        bool deferTransparent)
-        Vector3 cameraWorldPosition)
     {
         ICurrentRenderDispatcherObserver? observer =
             _currentRenderSceneObserver;
@@ -2168,7 +2164,6 @@ public sealed partial class WbDrawDispatcher : IDisposable
                 deferTransparent,
                 _opaqueDraws,
                 _translucentDraws,
-                cameraWorldPosition,
                 _alphaFingerprintScratch);
         observer.ObserveDispatcherSubmission(in submission);
     }
@@ -2177,16 +2172,14 @@ public sealed partial class WbDrawDispatcher : IDisposable
         bool observeCurrentPath,
         int visibleInstanceCount,
         int immediateInstanceCount,
-        bool deferTransparent,
+        bool deferTransparent)
-        Vector3 cameraWorldPosition)
     {
         if (observeCurrentPath)
         {
             ObserveCurrentDispatcherSubmission(
                 visibleInstanceCount,
                 immediateInstanceCount,
-                deferTransparent,
+                deferTransparent);
-                cameraWorldPosition);
         }
     }
 
@@ -2197,7 +2190,6 @@ public sealed partial class WbDrawDispatcher : IDisposable
             bool deferTransparent,
             IReadOnlyList<InstanceGroup> opaque,
             IReadOnlyList<InstanceGroup> transparent,
-            Vector3 cameraWorldPosition,
             List<AlphaFingerprint> alphaScratch)
     {
         // The no-VAO production early-out deliberately skips group
@@ -2226,7 +2218,6 @@ public sealed partial class WbDrawDispatcher : IDisposable
         RenderSceneHash128 transparentDigest =
             BuildTransparentSubmissionDigest(
                 acceptedTransparent,
-                cameraWorldPosition,
                 alphaScratch);
         RenderSceneHash128 transparentSetDigest =
             BuildOpaqueSubmissionDigest(acceptedTransparent);
@@ -2285,11 +2276,8 @@ public sealed partial class WbDrawDispatcher : IDisposable
 
     private static RenderSceneHash128 BuildTransparentSubmissionDigest(
         IReadOnlyList<InstanceGroup> groups,
-        Vector3 cameraWorldPosition,
         List<AlphaFingerprint> scratch)
     {
-        _ = cameraWorldPosition; // S4-c2: the digest reflects retail's FIFO
-                                 // submission order, not a distance sort.
         scratch.Clear();
         for (int groupIndex = 0;
              groupIndex < groups.Count;
@@ -2395,7 +2383,6 @@ public sealed partial class WbDrawDispatcher : IDisposable
         int index)
     {
         hash.Add(group.Matrices[index]);
-        hash.Add(group.LocalSortCenters[index]);
         hash.Add(group.Slots[index]);
         InstanceLightSet lights = group.LightSets[index];
         for (int lightIndex = 0;
@@ -2410,11 +2397,8 @@ public sealed partial class WbDrawDispatcher : IDisposable
         hash.Add(group.SelectionLighting[index]);
     }
 
-    private void DeferTransparentGroups(Vector3 cameraWorldPosition, Matrix4x4 viewProjection)
+    private void DeferTransparentGroups(Matrix4x4 viewProjection)
     {
-        _ = cameraWorldPosition; // S4-c2: retail's queues are FIFO, not distance-sorted; kept as a
-                                 // parameter so callers need not change (WalkClassify's sibling
-                                 // call site still needs it for nothing else either).
         RetailAlphaQueue queue = _alphaQueue!;
         if (_deferredAlpha.Count == 0)
             _deferredAlphaViewProjection = viewProjection;
@@ -2858,7 +2842,7 @@ public sealed partial class WbDrawDispatcher : IDisposable
     internal static void ApplyCacheHit(
         EntityCacheEntry entry,
         Matrix4x4 entityWorld,
-        Action<GroupKey, Matrix4x4, Vector3> appendInstance)
+        Action<GroupKey, Matrix4x4> appendInstance)
     {
         foreach (var cached in entry.Batches)
         {
@@ -2869,8 +2853,7 @@ public sealed partial class WbDrawDispatcher : IDisposable
             // out of sync with it.
             appendInstance(
                 cached.Key,
-                cached.RestPose * entityWorld,
+                cached.RestPose * entityWorld);
-                cached.LocalSortCenter);
         }
     }
 
@@ -2899,7 +2882,7 @@ public sealed partial class WbDrawDispatcher : IDisposable
                     GroupRegistration = group.Registration,
                 };
             }
-            AppendInstanceToGroup(group!, model, cached.LocalSortCenter);
+            AppendInstanceToGroup(group!, model);
         }
     }
 
@@ -3012,11 +2995,10 @@ public sealed partial class WbDrawDispatcher : IDisposable
     /// </summary>
     private void AppendInstanceToGroup(
         GroupKey key,
-        Matrix4x4 model,
+        Matrix4x4 model)
-        Vector3 localSortCenter)
     {
         InstanceGroup grp = GetOrCreateInstanceGroup(key);
-        AppendInstanceToGroup(grp, model, localSortCenter);
+        AppendInstanceToGroup(grp, model);
     }
 
     private InstanceGroup GetOrCreateInstanceGroup(GroupKey key)
@@ -3047,12 +3029,10 @@ public sealed partial class WbDrawDispatcher : IDisposable
 
     private void AppendInstanceToGroup(
         InstanceGroup grp,
-        Matrix4x4 model,
+        Matrix4x4 model)
-        Vector3 localSortCenter)
     {
         grp.LastUsedFrame = _groupFrame;
         grp.Matrices.Add(model);
-        grp.LocalSortCenters.Add(localSortCenter);
         grp.SubmissionOrders.Add(_nextInstanceSubmissionOrder++);
         grp.Slots.Add(_currentEntitySlot); // Phase U.4 — parallel to Matrices
         AppendCurrentLightSet(grp);        // Fix B — 8 ints per instance, parallel to Matrices
@@ -3231,7 +3211,6 @@ public sealed partial class WbDrawDispatcher : IDisposable
 
             InstanceGroup grp = GetOrCreateInstanceGroup(key);
             grp.Matrices.Add(model);
-            grp.LocalSortCenters.Add(renderData.SortCenter);
             grp.SubmissionOrders.Add(_nextInstanceSubmissionOrder++);
             grp.Slots.Add(_currentEntitySlot); // Phase U.4 — parallel to Matrices
             AppendCurrentLightSet(grp);        // Fix B — 8 ints per instance, parallel to Matrices
@@ -3241,7 +3220,6 @@ public sealed partial class WbDrawDispatcher : IDisposable
                 key,
                 texSlot,
                 restPose,
-                renderData.SortCenter,
                 grp,
                 grp.Registration));
         }
@@ -3712,11 +3690,6 @@ public sealed partial class WbDrawDispatcher : IDisposable
         public float SortDistance;  // squared distance from camera to first instance, for opaque sort
         public readonly List<Matrix4x4> Matrices = new();
 
-        // Retail CPhysicsPart::CYpt uses the transformed GfxObj sort center,
-        // not the entity origin. Parallel to Matrices so delayed-alpha
-        // submissions retain the exact per-part key after material grouping.
-        public readonly List<Vector3> LocalSortCenters = new();
-
         // Retail CShadowPart::insertion_sort (0x006B5130) is stable for equal
         // CYpt. Material groups erase authored entity/part/batch traversal
         // unless that order is retained explicitly. SubmissionOrders[i] is
@@ -3771,7 +3744,6 @@ public sealed partial class WbDrawDispatcher : IDisposable
         public void ClearPerInstanceData()
         {
             Matrices.Clear();
-            LocalSortCenters.Clear();
             SubmissionOrders.Clear();
             Slots.Clear();
             LightSets.Clear();
@@ -3785,7 +3757,6 @@ public sealed partial class WbDrawDispatcher : IDisposable
         {
             ClearPerInstanceData();
             Matrices.TrimExcess();
-            LocalSortCenters.TrimExcess();
             SubmissionOrders.TrimExcess();
             Slots.TrimExcess();
             LightSets.TrimExcess();

tests/AcDream.App.Tests/Rendering/Walk/WalkStaticStreamPopulatorTests.cs

@@ -345,6 +345,54 @@ public sealed class WalkStaticStreamPopulatorTests
         Assert.Contains("0x005A06B7..0x005A0720", register, StringComparison.Ordinal);
     }
 
+    [Fact]
+    public void ClassicGroupedAlphaSourceTruth_DeletesDeadOrderingChainAndPreservesLiveOwners()
+    {
+        string root = FindRepoRoot();
+        string dispatcher = File.ReadAllText(Path.Combine(
+            root, "src", "AcDream.App", "Rendering", "Wb", "WbDrawDispatcher.cs"));
+        string cachedBatch = File.ReadAllText(Path.Combine(
+            root, "src", "AcDream.App", "Rendering", "Wb", "CachedBatch.cs"));
+        string walkClassifier = File.ReadAllText(Path.Combine(
+            root, "src", "AcDream.App", "Rendering", "Wb", "WbDrawDispatcher.WalkClassify.cs"));
+        string alphaProduction = dispatcher + cachedBatch + walkClassifier;
+
+        Assert.Contains(
+            "Vector3.DistanceSquared(cameraWorldPosition, groupPosition)",
+            dispatcher,
+            StringComparison.Ordinal);
+        Assert.Contains("group.SortDistance =", dispatcher, StringComparison.Ordinal);
+        Assert.Contains("Vector3 LocalSortCenter", walkClassifier, StringComparison.Ordinal);
+        Assert.Contains("float SortDistanceSq", walkClassifier, StringComparison.Ordinal);
+        Assert.DoesNotContain("RetailAlphaOrdering", alphaProduction, StringComparison.Ordinal);
+        Assert.DoesNotContain("FlushFartherThan(", alphaProduction, StringComparison.Ordinal);
+        Assert.DoesNotContain("viewerDistance", alphaProduction, StringComparison.Ordinal);
+        Assert.DoesNotContain("_ = cameraWorldPosition", dispatcher, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void AlphaFlushCountKnownFailure_StatesOnlyTheThreeExactReasons()
+    {
+        string root = FindRepoRoot();
+        string alphaTranscript = File.ReadAllText(Path.Combine(
+            root,
+            "tests",
+            "AcDream.App.Tests",
+            "Rendering",
+            "Walk",
+            "WalkTraceConformanceTests.AlphaDepthTranscript.cs"));
+
+        Assert.Contains("THREE independent reasons", alphaTranscript, StringComparison.Ordinal);
+        Assert.Contains("GfxObj/particle mesh content at all", alphaTranscript, StringComparison.Ordinal);
+        Assert.Contains("AP-238 coalesces transparent", alphaTranscript, StringComparison.Ordinal);
+        Assert.Contains("one token per <c>(cell,list)</c>", alphaTranscript, StringComparison.Ordinal);
+        Assert.Contains("AP-239/AP-240 change", alphaTranscript, StringComparison.Ordinal);
+        Assert.Contains(
+            "former broad \"per instance versus per subset\" explanation was false.",
+            alphaTranscript,
+            StringComparison.Ordinal);
+    }
+
     private static string FindRepoRoot()
     {
         string? directory = AppContext.BaseDirectory;
@@ -907,7 +955,7 @@ public sealed class WalkStaticStreamPopulatorTests
             "DeferTransparentGroups",
             BindingFlags.Instance | BindingFlags.NonPublic)!;
 
-        defer.Invoke(fx.Dispatcher, [Vector3.Zero, Matrix4x4.Identity]);
+        defer.Invoke(fx.Dispatcher, [Matrix4x4.Identity]);
 
         Assert.Equal(0, fx.AlphaQueue!.PendingCount);
         Assert.Contains(
@@ -947,7 +995,6 @@ public sealed class WalkStaticStreamPopulatorTests
             Translucency = TranslucencyKind.AlphaBlend,
         };
         group.Matrices.Add(Matrix4x4.Identity);
-        group.LocalSortCenters.Add(Vector3.Zero);
         group.SubmissionOrders.Add(0);
         group.Slots.Add(0);
         group.LightSets.Add(WbDrawDispatcher.InstanceLightSet.Disabled);

tests/AcDream.App.Tests/Rendering/Wb/InstanceGroupClearTests.cs

@@ -1,4 +1,5 @@
 using System.Numerics;
+using System.Reflection;
 using AcDream.App.Rendering.Scene;
 using AcDream.App.Rendering.Wb;
 using AcDream.Core.Meshing;
@@ -104,7 +105,6 @@ public class InstanceGroupClearTests
             deferTransparent: true,
             opaque: [],
             transparent: [first, second],
-            cameraWorldPosition: Vector3.Zero,
             alphaScratch: scratch);
         var reversedMaterialGroups =
             WbDrawDispatcher.CreateDispatcherSubmission(
@@ -113,7 +113,6 @@ public class InstanceGroupClearTests
                 deferTransparent: true,
                 opaque: [],
                 transparent: [second, first],
-                cameraWorldPosition: Vector3.Zero,
                 alphaScratch: scratch);
 
         Assert.Equal(
@@ -128,7 +127,6 @@ public class InstanceGroupClearTests
             deferTransparent: true,
             opaque: [],
             transparent: [first, second],
-            cameraWorldPosition: Vector3.Zero,
             alphaScratch: scratch);
 
         Assert.NotEqual(
@@ -154,7 +152,6 @@ public class InstanceGroupClearTests
                 deferTransparent: false,
                 opaque: [],
                 transparent: [],
-                cameraWorldPosition: Vector3.Zero,
                 alphaScratch: scratch);
         CurrentRenderDispatcherSubmission actual =
             WbDrawDispatcher.CreateDispatcherSubmission(
@@ -163,7 +160,6 @@ public class InstanceGroupClearTests
                 deferTransparent: false,
                 opaque: [stale],
                 transparent: [stale],
-                cameraWorldPosition: Vector3.Zero,
                 alphaScratch: scratch);
 
         Assert.Equal(expected, actual);
@@ -188,7 +184,6 @@ public class InstanceGroupClearTests
                 deferTransparent: true,
                 opaque: [],
                 transparent: [ordinary],
-                cameraWorldPosition: Vector3.Zero,
                 alphaScratch: scratch);
         CurrentRenderDispatcherSubmission buildingSubmission =
             WbDrawDispatcher.CreateDispatcherSubmission(
@@ -197,7 +192,6 @@ public class InstanceGroupClearTests
                 deferTransparent: true,
                 opaque: [],
                 transparent: [building],
-                cameraWorldPosition: Vector3.Zero,
                 alphaScratch: scratch);
 
         Assert.NotEqual(
@@ -208,6 +202,63 @@ public class InstanceGroupClearTests
             buildingSubmission.TransparentSetDigest);
     }
 
+    [Fact]
+    public void ClassicGroupedShapes_DeleteDeadSortCenterSidecarsButRetainWalkCyptKey()
+    {
+        Assert.Null(typeof(CachedBatch).GetProperty("LocalSortCenter"));
+        Assert.Null(typeof(WbDrawDispatcher.InstanceGroup).GetField("LocalSortCenters"));
+
+        Type walkBatch = typeof(WbDrawDispatcher).GetNestedType(
+            "WalkClassifiedBatch",
+            BindingFlags.NonPublic)
+            ?? throw new InvalidOperationException("WalkClassifiedBatch was not found.");
+        Assert.Equal(typeof(Vector3), walkBatch.GetProperty("LocalSortCenter")?.PropertyType);
+        Assert.Equal(typeof(float), walkBatch.GetProperty("SortDistanceSq")?.PropertyType);
+    }
+
+    [Fact]
+    public void AlphaSubmissionShapes_DeleteDeadCameraChainButRetainOpaqueCameraDistance()
+    {
+        Type dispatcher = typeof(WbDrawDispatcher);
+        MethodInfo defer = dispatcher.GetMethod(
+            "DeferTransparentGroups",
+            BindingFlags.Instance | BindingFlags.NonPublic)
+            ?? throw new InvalidOperationException("DeferTransparentGroups was not found.");
+        MethodInfo transparentDigest = dispatcher.GetMethod(
+            "BuildTransparentSubmissionDigest",
+            BindingFlags.Static | BindingFlags.NonPublic)
+            ?? throw new InvalidOperationException("BuildTransparentSubmissionDigest was not found.");
+        MethodInfo createSubmission = dispatcher.GetMethod(
+            "CreateDispatcherSubmission",
+            BindingFlags.Static | BindingFlags.NonPublic)
+            ?? throw new InvalidOperationException("CreateDispatcherSubmission was not found.");
+        MethodInfo observeCurrent = dispatcher.GetMethod(
+            "ObserveCurrentDispatcherSubmission",
+            BindingFlags.Instance | BindingFlags.NonPublic)
+            ?? throw new InvalidOperationException("ObserveCurrentDispatcherSubmission was not found.");
+        MethodInfo observeClassified = dispatcher.GetMethod(
+            "ObserveClassifiedDispatcherSubmission",
+            BindingFlags.Instance | BindingFlags.NonPublic)
+            ?? throw new InvalidOperationException("ObserveClassifiedDispatcherSubmission was not found.");
+
+        Assert.Equal([typeof(Matrix4x4)], defer.GetParameters().Select(static p => p.ParameterType));
+        Assert.DoesNotContain(transparentDigest.GetParameters(), static p => p.ParameterType == typeof(Vector3));
+        Assert.DoesNotContain(createSubmission.GetParameters(), static p => p.ParameterType == typeof(Vector3));
+        Assert.DoesNotContain(observeCurrent.GetParameters(), static p => p.ParameterType == typeof(Vector3));
+        Assert.DoesNotContain(observeClassified.GetParameters(), static p => p.ParameterType == typeof(Vector3));
+
+        MethodInfo partition = dispatcher.GetMethod(
+            "PartitionInstanceGroups",
+            BindingFlags.Static | BindingFlags.NonPublic)
+            ?? throw new InvalidOperationException("PartitionInstanceGroups was not found.");
+        Assert.Contains(
+            partition.GetParameters(),
+            static p => p.Name == "cameraWorldPosition" && p.ParameterType == typeof(Vector3));
+        Assert.Equal(
+            typeof(float),
+            typeof(WbDrawDispatcher.InstanceGroup).GetField("SortDistance")?.FieldType);
+    }
+
     [Fact]
     public void CachedGroupHandle_RequiresLiveMatchingRegistration()
     {
@@ -392,7 +443,6 @@ public class InstanceGroupClearTests
             Translucency = TranslucencyKind.AlphaBlend,
         };
         group.Matrices.Add(Matrix4x4.CreateTranslation(10f, 0f, 0f));
-        group.LocalSortCenters.Add(Vector3.Zero);
         group.SubmissionOrders.Add(submissionOrder);
         group.Slots.Add(0u);
         group.LightSets.Add(WbDrawDispatcher.InstanceLightSet.Disabled);
@@ -404,9 +454,9 @@ public class InstanceGroupClearTests
     }
 
     // #193 (regression from #188, 2026-07-09): WbDrawDispatcher's InstanceGroup holds
-    // nine per-instance parallel lists — Matrices, LocalSortCenters,
+    // eight per-instance parallel lists — Matrices, SubmissionOrders, Slots,
-    // SubmissionOrders, Slots, LightSets, IndoorFlags, Opacities, and
+    // LightSets, IndoorFlags, Opacities, DetailCategories, and
-    // DetailCategories, SelectionLighting — appended in lockstep
+    // SelectionLighting — appended in lockstep
     // (one entry per drawn instance) every frame. The
     // per-frame reset must clear ALL of them. #188 added Opacities but left it out of
     // the inline clear loop, so it grew one float per instance per frame forever; as
@@ -418,7 +468,6 @@ public class InstanceGroupClearTests
     {
         var grp = new WbDrawDispatcher.InstanceGroup();
         grp.Matrices.Add(Matrix4x4.Identity);
-        grp.LocalSortCenters.Add(Vector3.Zero);
         grp.SubmissionOrders.Add(0);
         grp.Slots.Add(1u);
         grp.LightSets.Add(WbDrawDispatcher.InstanceLightSet.Disabled);
@@ -430,7 +479,6 @@ public class InstanceGroupClearTests
         grp.ClearPerInstanceData();
 
         Assert.Empty(grp.Matrices);
-        Assert.Empty(grp.LocalSortCenters);
         Assert.Empty(grp.SubmissionOrders);
         Assert.Empty(grp.Slots);
         Assert.Empty(grp.LightSets);

tests/AcDream.Core.Tests/Rendering/Wb/WbDrawDispatcherBucketingTests.cs

@@ -417,8 +417,7 @@ public sealed class WbDrawDispatcherBucketingTests
         uint firstIndex,
         int indexCount,
         uint texSlot,
-        Matrix4x4? restPose = null,
+        Matrix4x4? restPose = null)
-        Vector3? localSortCenter = null)
     {
         var key = new GroupKey(
             FirstIndex: firstIndex,
@@ -431,8 +430,7 @@ public sealed class WbDrawDispatcherBucketingTests
         return new CachedBatch(
             key,
             new AcDream.App.Rendering.Gpu.GpuTextureSlot(texSlot),
-            restPose ?? Matrix4x4.Identity,
+            restPose ?? Matrix4x4.Identity);
-            localSortCenter ?? Vector3.Zero);
     }
 
     [Fact]
@@ -488,8 +486,7 @@ public sealed class WbDrawDispatcherBucketingTests
         // Production code: this is the !isAnimated && _cache.TryGet branch
         // at the top of the per-entity loop body in Draw.
         var groups = new Dictionary<GroupKey, List<Matrix4x4>>();
-        var sortCenters = new List<Vector3>();
+        void AppendInstance(GroupKey k, Matrix4x4 m)
-        void AppendInstance(GroupKey k, Matrix4x4 m, Vector3 localSortCenter)
         {
             if (!groups.TryGetValue(k, out var list))
             {
@@ -497,7 +494,6 @@ public sealed class WbDrawDispatcherBucketingTests
                 groups[k] = list;
             }
             list.Add(m);
-            sortCenters.Add(localSortCenter);
         }
 
         Assert.True(cache.TryGet(EntityId, LandblockId, out var entryHit));
@@ -519,35 +515,6 @@ public sealed class WbDrawDispatcherBucketingTests
         // appended matrix must equal entityWorld.
         foreach (var (_, list) in groups)
             Assert.Equal(entityWorld, list[0]);
-        Assert.All(sortCenters, center => Assert.Equal(Vector3.Zero, center));
-    }
-
-    [Fact]
-    public void ApplyCacheHit_PreservesAuthoredSortCenter()
-    {
-        Vector3 authoredCenter = new(1.25f, -2.5f, 7.75f);
-        var entry = new EntityCacheEntry
-        {
-            EntityId = 100,
-            LandblockHint = 0xA9B40000u,
-            Batches =
-            [
-                MakeCachedBatch(
-                    ibo: 1,
-                    firstIndex: 0,
-                    indexCount: 6,
-                    texSlot: 0xAA,
-                    localSortCenter: authoredCenter),
-            ],
-        };
-        Vector3 observedCenter = default;
-
-        WbDrawDispatcher.ApplyCacheHit(
-            entry,
-            Matrix4x4.Identity,
-            (_, _, center) => observedCenter = center);
-
-        Assert.Equal(authoredCenter, observedCenter);
     }
 
     [Fact]
@@ -788,7 +755,7 @@ public sealed class WbDrawDispatcherBucketingTests
         const uint EntityId = 100;
         const int MeshRefCount = 3;
 
-        void AppendInstance(GroupKey k, Matrix4x4 m, Vector3 localSortCenter)
+        void AppendInstance(GroupKey k, Matrix4x4 m)
         {
             if (!groups.TryGetValue(k, out var list))
             {