docs(plan): A7 Fix D implementation plan — 5 tasks (#140)

Task-by-task TDD plan: (1) extract GlobalLightPacker (Core, pure) + test + refactor WbDrawDispatcher; (2) lock the bake contract via LightBake conformance test on the captured golden torches; (3) D-1 clamp the point-light sum on its own in mesh_modern.vert; (4) D-2 EnvCellRenderer binds its own per-cell light set (SSBO 4+5) via SelectForObject over cell bounds; (5) correct register AP-35 + reconcile Fix B. Concrete code + exact insertion points; visual verification is the acceptance gate. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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+# A7 Fix D — torch over-brightness on indoor walls — Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Make outdoor objects and indoor cell walls near torches render warm-but-bounded like retail, instead of blowing out warm-white.
+
+**Architecture:** Two orthogonal fixes. **D-1**: in `mesh_modern.vert`, accumulate point/spot lights into their own sum and clamp it to `[0,1]` BEFORE adding ambient+sun (mirrors retail `SetStaticLightingVertexColors`). **D-2**: `EnvCellRenderer` binds its OWN per-cell point-light set (SSBO 4+5) instead of reading the light set `WbDrawDispatcher` last left bound. A shared `GlobalLightPacker` (Core, pure) packs the global-light SSBO so the two renderers can't drift. `LightBake.cs` is the C# conformance oracle.
+
+**Tech Stack:** C# .NET 10, Silk.NET OpenGL (bindless + MDI SSBOs), GLSL 460. Tests: xUnit in `tests/AcDream.Core.Tests`.
+
+**Spec:** [`docs/superpowers/specs/2026-06-18-a7-fixd-torch-overbright-design.md`](../specs/2026-06-18-a7-fixd-torch-overbright-design.md)
+
+**Ground-truth golden (live cdb, Holtburg):** wall torches are `LightKind.Point`, `Intensity=100`, `Range = falloff×1.3` (falloff 3–5 → Range 3.9–6.5 m), warm colours `(1.0, 0.588, 0.314)` orange and `(0.980, 0.843, 0.612)` cream. The per-channel cap pins each torch to its colour ⇒ warm, never white.
+
+**Pre-flight (every task):** worktree is `C:\Users\erikn\source\repos\acdream\.claude\worktrees\thirsty-goldberg-51bb9b` (cwd). Build: `dotnet build src/AcDream.App/AcDream.App.csproj -c Debug`. Core tests: `dotnet test tests/AcDream.Core.Tests/AcDream.Core.Tests.csproj`. The retail client locks the DLLs — it must be closed before a build.
+
+---
+
+## Task 1: Extract `GlobalLightPacker` (shared, pure) + refactor `WbDrawDispatcher`
+
+Pull the global-light SSBO float packing out of `WbDrawDispatcher.UploadGlobalLights` into a pure Core helper so `EnvCellRenderer` (Task 4) reuses the exact same layout. No behaviour change.
+
+**Files:**
+- Create: `src/AcDream.Core/Lighting/GlobalLightPacker.cs`
+- Create: `tests/AcDream.Core.Tests/Lighting/GlobalLightPackerTests.cs`
+- Modify: `src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs:1813-1848` (`UploadGlobalLights`)
+
+- [ ] **Step 1: Write the failing test**
+
+Create `tests/AcDream.Core.Tests/Lighting/GlobalLightPackerTests.cs`:
+
+```csharp
+using System.Numerics;
+using AcDream.Core.Lighting;
+using Xunit;
+
+namespace AcDream.Core.Tests.Lighting;
+
+public class GlobalLightPackerTests
+{
+    [Fact]
+    public void Pack_WritesSixteenFloatsPerLight_InTheExpectedLayout()
+    {
+        var light = new LightSource
+        {
+            Kind          = LightKind.Point,
+            WorldPosition = new Vector3(10f, 20f, 30f),
+            WorldForward  = new Vector3(0f, 0f, 1f),
+            ColorLinear   = new Vector3(1.0f, 0.588f, 0.314f),
+            Intensity     = 100f,
+            Range         = 5.2f,
+            ConeAngle     = 0f,
+        };
+        float[] buffer = System.Array.Empty<float>();
+
+        int count = GlobalLightPacker.Pack(new[] { light }, ref buffer);
+
+        Assert.Equal(1, count);
+        Assert.True(buffer.Length >= 16);
+        // posAndKind
+        Assert.Equal(10f, buffer[0]); Assert.Equal(20f, buffer[1]); Assert.Equal(30f, buffer[2]);
+        Assert.Equal((float)(int)LightKind.Point, buffer[3]);
+        // dirAndRange
+        Assert.Equal(0f, buffer[4]); Assert.Equal(0f, buffer[5]); Assert.Equal(1f, buffer[6]);
+        Assert.Equal(5.2f, buffer[7]);
+        // colorAndIntensity
+        Assert.Equal(1.0f, buffer[8]); Assert.Equal(0.588f, buffer[9]); Assert.Equal(0.314f, buffer[10]);
+        Assert.Equal(100f, buffer[11]);
+        // coneAngleEtc
+        Assert.Equal(0f, buffer[12]);
+    }
+
+    [Fact]
+    public void Pack_NullOrEmpty_ReturnsZero_AndBufferHasAtLeastOneSlot()
+    {
+        float[] buffer = System.Array.Empty<float>();
+        int count = GlobalLightPacker.Pack(null, ref buffer);
+        Assert.Equal(0, count);
+        Assert.True(buffer.Length >= GlobalLightPacker.FloatsPerLight);
+    }
+}
+```
+
+- [ ] **Step 2: Run the test to verify it fails**
+
+Run: `dotnet test tests/AcDream.Core.Tests/AcDream.Core.Tests.csproj --filter GlobalLightPackerTests`
+Expected: FAIL — `GlobalLightPacker` does not exist (compile error).
+
+- [ ] **Step 3: Implement `GlobalLightPacker`**
+
+Create `src/AcDream.Core/Lighting/GlobalLightPacker.cs`:
+
+```csharp
+using System;
+using System.Collections.Generic;
+
+namespace AcDream.Core.Lighting;
+
+/// <summary>
+/// Packs a point-light snapshot into the flat float layout the bindless mesh
+/// shader reads at SSBO binding=4 (<c>mesh_modern.vert</c> <c>GlobalLight gLights[]</c>):
+/// 16 floats (4 vec4) per light — posAndKind, dirAndRange, colorAndIntensity,
+/// coneAngleEtc. Pure (no GL), so both <c>WbDrawDispatcher</c> and
+/// <c>EnvCellRenderer</c> share ONE layout and cannot drift.
+/// </summary>
+public static class GlobalLightPacker
+{
+    public const int FloatsPerLight = 16;
+
+    /// <summary>
+    /// Fill <paramref name="buffer"/> (grown + zero-cleared as needed) with the
+    /// packed snapshot; returns the light count <c>n</c>. The buffer always has at
+    /// least <see cref="FloatsPerLight"/> floats (so a zero-light frame still
+    /// uploads a non-empty SSBO). Callers upload <c>max(n,1) * FloatsPerLight</c> floats.
+    /// </summary>
+    public static int Pack(IReadOnlyList<LightSource>? snapshot, ref float[] buffer)
+    {
+        int n = snapshot?.Count ?? 0;
+        int floatsNeeded = Math.Max(n, 1) * FloatsPerLight;
+        if (buffer.Length < floatsNeeded)
+            buffer = new float[floatsNeeded + FloatsPerLight * 16];
+        Array.Clear(buffer, 0, floatsNeeded);
+
+        for (int i = 0; i < n; i++)
+        {
+            var L = snapshot![i];
+            int o = i * FloatsPerLight;
+            buffer[o + 0] = L.WorldPosition.X;
+            buffer[o + 1] = L.WorldPosition.Y;
+            buffer[o + 2] = L.WorldPosition.Z;
+            buffer[o + 3] = (int)L.Kind;
+            buffer[o + 4] = L.WorldForward.X;
+            buffer[o + 5] = L.WorldForward.Y;
+            buffer[o + 6] = L.WorldForward.Z;
+            buffer[o + 7] = L.Range;
+            buffer[o + 8]  = L.ColorLinear.X;
+            buffer[o + 9]  = L.ColorLinear.Y;
+            buffer[o + 10] = L.ColorLinear.Z;
+            buffer[o + 11] = L.Intensity;
+            buffer[o + 12] = L.ConeAngle;
+        }
+        return n;
+    }
+}
+```
+
+- [ ] **Step 4: Run the test to verify it passes**
+
+Run: `dotnet test tests/AcDream.Core.Tests/AcDream.Core.Tests.csproj --filter GlobalLightPackerTests`
+Expected: PASS (2 tests).
+
+- [ ] **Step 5: Refactor `WbDrawDispatcher.UploadGlobalLights` to use the packer**
+
+In `src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs`, replace the body of `UploadGlobalLights` (1813-1848) with:
+
+```csharp
+    private unsafe void UploadGlobalLights()
+    {
+        int n = AcDream.Core.Lighting.GlobalLightPacker.Pack(_pointSnapshot, ref _globalLightData);
+        int count = n > 0 ? n : 1;          // never zero-size
+        fixed (float* gp = _globalLightData)
+            UploadSsbo(_globalLightsSsbo, 4, gp,
+                count * AcDream.Core.Lighting.GlobalLightPacker.FloatsPerLight * sizeof(float));
+    }
+```
+
+Leave the `_globalLightData` field declaration (line 145) as-is; the packer grows it.
+
+- [ ] **Step 6: Build and run the full Core test suite**
+
+Run: `dotnet build src/AcDream.App/AcDream.App.csproj -c Debug`
+Then: `dotnet test tests/AcDream.Core.Tests/AcDream.Core.Tests.csproj`
+Expected: build green; all tests pass (no regression — the packing is byte-identical).
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add src/AcDream.Core/Lighting/GlobalLightPacker.cs tests/AcDream.Core.Tests/Lighting/GlobalLightPackerTests.cs src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs
+git commit -m "refactor(lighting): extract GlobalLightPacker (shared binding=4 layout) — A7 Fix D prep
+
+Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>"
+```
+
+---
+
+## Task 2: Lock the bake contract — `LightBake` conformance test on golden torches
+
+`LightBake.cs` already implements the correct retail math (per-light cap + sum + `[0,1]` clamp, skip directional). This test pins the contract the D-1 shader change must mirror, using the captured golden torch values. It PASSES against the existing `LightBake` (this is a characterization/lock test — there is no failing-first step because the C# oracle is already correct; the bug lives in GLSL, which is verified by review in Task 3 + the user's visual check).
+
+**Files:**
+- Create: `tests/AcDream.Core.Tests/Lighting/LightBakeConformanceTests.cs`
+
+- [ ] **Step 1: Write the conformance test**
+
+Create `tests/AcDream.Core.Tests/Lighting/LightBakeConformanceTests.cs`:
+
+```csharp
+using System.Collections.Generic;
+using System.Numerics;
+using AcDream.Core.Lighting;
+using Xunit;
+
+namespace AcDream.Core.Tests.Lighting;
+
+/// <summary>
+/// Golden conformance for the retail bake (calc_point_light + the [0,1] clamp),
+/// driven by the live-cdb-captured Holtburg wall torches. Pins the contract that
+/// mesh_modern.vert's pointContribution + the new pointAcc clamp (A7 Fix D, D-1)
+/// must mirror line-for-line. See docs/research/2026-06-18-lighting-a7-fixABC-shipped-fixD-handoff.md.
+/// </summary>
+public class LightBakeConformanceTests
+{
+    private static LightSource OrangeTorch(Vector3 pos) => new()
+    {
+        Kind = LightKind.Point,
+        WorldPosition = pos,
+        ColorLinear = new Vector3(1.0f, 0.588f, 0.314f), // captured orange
+        Intensity = 100f,
+        Range = 4f * 1.3f,                               // falloff 4 × static_light_factor
+        IsLit = true,
+    };
+
+    [Theory]
+    [InlineData(1f)]
+    [InlineData(2f)]
+    [InlineData(3f)]
+    [InlineData(4f)]
+    [InlineData(5f)]
+    public void SingleOrangeTorch_IsWarmAndBounded_NeverWhite(float dist)
+    {
+        // Wall vertex at the origin, normal facing the torch (+X). Torch out along +X.
+        var vtx = Vector3.Zero;
+        var normal = Vector3.UnitX;
+        var torch = OrangeTorch(new Vector3(dist, 0f, 0f));
+
+        var c = LightBake.ComputeVertexColor(vtx, normal, new[] { torch });
+
+        // Every channel bounded to [0,1] — intensity=100 must NOT blow to white.
+        Assert.InRange(c.X, 0f, 1f);
+        Assert.InRange(c.Y, 0f, 1f);
+        Assert.InRange(c.Z, 0f, 1f);
+        // Warm hue preserved while lit (R ≥ G ≥ B), matching the torch colour ordering.
+        if (c.X > 0f)
+        {
+            Assert.True(c.X >= c.Y, $"R({c.X}) >= G({c.Y}) at d={dist}");
+            Assert.True(c.Y >= c.Z, $"G({c.Y}) >= B({c.Z}) at d={dist}");
+        }
+    }
+
+    [Fact]
+    public void BeyondRange_ContributesNothing()
+    {
+        var torch = OrangeTorch(new Vector3(100f, 0f, 0f)); // far past Range
+        var c = LightBake.ComputeVertexColor(Vector3.Zero, Vector3.UnitX, new[] { torch });
+        Assert.Equal(Vector3.Zero, c);
+    }
+
+    [Fact]
+    public void ManyOverlappingIntenseTorches_StillClampToOne()
+    {
+        // Eight near-white intensity-100 torches all 1.5 m from the vertex: the
+        // [0,1] saturate must hold (no overflow past 1.0 per channel).
+        var lights = new List<LightSource>();
+        for (int i = 0; i < 8; i++)
+            lights.Add(new LightSource
+            {
+                Kind = LightKind.Point,
+                WorldPosition = new Vector3(1.5f, 0.1f * i, 0f),
+                ColorLinear = new Vector3(0.98f, 0.95f, 0.9f),
+                Intensity = 100f,
+                Range = 5.2f,
+                IsLit = true,
+            });
+
+        var c = LightBake.ComputeVertexColor(Vector3.Zero, Vector3.UnitX, lights);
+        Assert.InRange(c.X, 0f, 1f);
+        Assert.InRange(c.Y, 0f, 1f);
+        Assert.InRange(c.Z, 0f, 1f);
+    }
+}
+```
+
+- [ ] **Step 2: Run the test — verify it PASSES on existing LightBake**
+
+Run: `dotnet test tests/AcDream.Core.Tests/AcDream.Core.Tests.csproj --filter LightBakeConformanceTests`
+Expected: PASS (7 cases). If any case FAILS, stop — `LightBake` (the oracle) diverges from the expected bake contract and that must be understood before changing the shader. (This is the lock; it should be green.)
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add tests/AcDream.Core.Tests/Lighting/LightBakeConformanceTests.cs
+git commit -m "test(lighting): lock the bake contract on golden torches (A7 Fix D oracle)
+
+Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>"
+```
+
+---
+
+## Task 3: D-1 — clamp the torch sum on its own in `mesh_modern.vert`
+
+Give point/spot lights their own accumulator and saturate it to `[0,1]` before it joins ambient+sun. Mirrors `LightBake.ComputeVertexColor` (Task 2) and retail `SetStaticLightingVertexColors`. The per-light cap and `pointContribution` are untouched. GLSL is not unit-testable in-process — correctness is the line-for-line match to `LightBake` (cite it) plus the user's visual check.
+
+**Files:**
+- Modify: `src/AcDream.App/Rendering/Shaders/mesh_modern.vert:183-209` (`accumulateLights`)
+
+- [ ] **Step 1: Apply the clamp split**
+
+Replace the body of `accumulateLights` (183-209) with the following. The ambient base and sun loop are byte-identical; only the point loop changes (own accumulator + `min(pointAcc, 1.0)`):
+
+```glsl
+vec3 accumulateLights(vec3 N, vec3 worldPos, int instanceIndex) {
+    vec3 lit = uCellAmbient.xyz;
+
+    // SUN / directional — material-lit term (added with ambient, NOT into the
+    // torch sum), unchanged from before.
+    int activeLights = int(uCellAmbient.w);
+    for (int i = 0; i < 8; ++i) {
+        if (i >= activeLights) break;
+        if (int(uLights[i].posAndKind.w) != 0) continue;   // directional only
+        vec3 Ldir = -uLights[i].dirAndRange.xyz;
+        float ndl = max(0.0, dot(N, Ldir));
+        lit += uLights[i].colorAndIntensity.xyz * uLights[i].colorAndIntensity.w * ndl;
+    }
+
+    // POINT / SPOT torches: their OWN accumulator (A7 Fix D, D-1). Retail's
+    // SetStaticLightingVertexColors sums the static point lights from BLACK and
+    // clamps the SUM to [0,1] before anything else (it is a baked emissive term),
+    // so a few warm intensity-100 torches can't push the whole pixel to white the
+    // way folding them into ambient+sun did. Matches LightBake.ComputeVertexColor
+    // (tests/AcDream.Core.Tests/Lighting/LightBakeConformanceTests). Per-light cap
+    // inside pointContribution is unchanged.
+    vec3 pointAcc = vec3(0.0);
+    int base = instanceIndex * 8;
+    for (int k = 0; k < 8; ++k) {
+        int gi = instanceLightIdx[base + k];
+        if (gi < 0) continue;
+        pointAcc += pointContribution(N, worldPos, gLights[gi]);
+    }
+    lit += min(pointAcc, vec3(1.0));   // clamp the torch sum on its own (retail baked emissive)
+
+    return lit;                        // frag still does the final min(lit, 1.0)
+}
+```
+
+(`mesh_modern.frag:92`'s `lit = min(lit, vec3(1.0))` and the lightning bump at `:89` are unchanged — they remain the final pixel clamp.)
+
+- [ ] **Step 2: Build**
+
+Run: `dotnet build src/AcDream.App/AcDream.App.csproj -c Debug`
+Expected: green. (Shaders are loaded at runtime from disk; the build only confirms nothing else broke.)
+
+- [ ] **Step 3: Review the math against the oracle**
+
+Confirm by reading both side-by-side that the shader's point path now matches `LightBake`:
+- `mesh_modern.vert` `pointContribution` ↔ `LightBake.PointContribution` (range gate, wrap, norm, per-channel `min(scale·col, col)`) — already equal.
+- new `min(pointAcc, vec3(1.0))` ↔ `LightBake.ComputeVertexColor`'s final `Clamp(·,0,1)` over the point sum.
+No code change expected here — this is the verification step the commit message cites.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/AcDream.App/Rendering/Shaders/mesh_modern.vert
+git commit -m "fix(render): A7 Fix D D-1 — clamp the point-light sum on its own (#140)
+
+accumulateLights folded ambient+sun+torches into one accumulator clamped only
+in the frag, so a few warm intensity-100 torches blew walls/objects to white.
+Mirror retail SetStaticLightingVertexColors: sum point/spot into pointAcc, clamp
+to [0,1] (the baked emissive), THEN add ambient+sun, frag final-clamps. Matches
+LightBake.ComputeVertexColor (LightBakeConformanceTests). Per-light cap unchanged.
+
+Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>"
+```
+
+---
+
+## Task 4: D-2 — `EnvCellRenderer` binds its OWN per-cell light set (SSBO 4+5)
+
+Stop the cell shell from reading the leaked `WbDrawDispatcher` light set. EnvCellRenderer uploads its own binding-4 global lights (from the frame's `PointSnapshot`, via `GlobalLightPacker`) and a binding-5 per-instance light-set buffer, computing each cell's set with `LightManager.SelectForObject` over the cell's world bounds — mirroring the existing `_cellIdToSlot` per-instance pattern.
+
+**Files:**
+- Modify: `src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs` (fields ~70-110; `AllocateMdiBuffers` 207-236; new setter near 262; `RenderModernMDIInternal` 1007-~1234)
+- Modify: `src/AcDream.App/Rendering/GameWindow.cs:~7777` (wire the snapshot)
+
+- [ ] **Step 1: Add fields + the per-frame snapshot setter**
+
+In `EnvCellRenderer.cs`, near the other scratch-buffer fields (after `_clipSlotBuffer`/`_clipSlotData`, ~line 110), add:
+
+```csharp
+    // A7 Fix D (D-2): this renderer owns its lighting (self-contained GL state,
+    // like uViewProjection) instead of reading the SSBO 4/5 WbDrawDispatcher last
+    // left bound. binding=4 = global point-light snapshot (same data/indices as the
+    // dispatcher, via GlobalLightPacker); binding=5 = 8 int indices per instance.
+    private uint _globalLightsSsbo;                       // binding=4
+    private float[] _globalLightData = new float[AcDream.Core.Lighting.GlobalLightPacker.FloatsPerLight * 16];
+    private uint _instLightSetSsbo;                       // binding=5
+    private int[] _lightSetData = new int[1024 * AcDream.Core.Lighting.LightManager.MaxLightsPerObject];
+    private System.Collections.Generic.IReadOnlyList<AcDream.Core.Lighting.LightSource>? _pointSnapshot;
+    private readonly System.Collections.Generic.Dictionary<uint, int[]> _cellLightSetCache = new();
+```
+
+Near `SetClipRouting` (~262) add the per-frame setter:
+
+```csharp
+    /// <summary>
+    /// A7 Fix D (D-2): hand the renderer this frame's point-light snapshot
+    /// (LightManager.PointSnapshot). Call once per frame BEFORE Render, alongside
+    /// the WbDrawDispatcher snapshot wire-in. Indices in the per-cell light sets
+    /// reference this snapshot, which is also uploaded to binding=4 here, so the
+    /// pass is self-contained. Null/empty ⇒ shells receive no point lights.
+    /// </summary>
+    public void SetPointSnapshot(
+        System.Collections.Generic.IReadOnlyList<AcDream.Core.Lighting.LightSource>? snapshot)
+        => _pointSnapshot = snapshot;
+```
+
+- [ ] **Step 2: Generate the two SSBOs in `AllocateMdiBuffers`**
+
+In `AllocateMdiBuffers` (207-236), before the final `_gl.BindBuffer(... 0)` calls (line 234), add:
+
+```csharp
+        // A7 Fix D (D-2): binding=4 global lights + binding=5 per-instance light set.
+        _gl.GenBuffers(1, out _globalLightsSsbo);
+        _gl.BindBuffer(GLEnum.ShaderStorageBuffer, _globalLightsSsbo);
+        _gl.BufferData(GLEnum.ShaderStorageBuffer,
+            (nuint)(_globalLightData.Length * sizeof(float)), null, GLEnum.DynamicDraw);
+
+        _gl.GenBuffers(1, out _instLightSetSsbo);
+        _gl.BindBuffer(GLEnum.ShaderStorageBuffer, _instLightSetSsbo);
+        _gl.BufferData(GLEnum.ShaderStorageBuffer,
+            (nuint)(_modernInstanceCapacity * AcDream.Core.Lighting.LightManager.MaxLightsPerObject * sizeof(int)),
+            null, GLEnum.DynamicDraw);
+```
+
+- [ ] **Step 3: Add the per-cell light-set helper**
+
+Add this private method to `EnvCellRenderer` (e.g. just below `RenderModernMDIInternal`). It returns the cached 8-int set for a cell, computing it once per frame from the cell's world bounds + the snapshot via the static `SelectForObject`:
+
+```csharp
+    // A7 Fix D (D-2): the up-to-8 point lights reaching a cell, by the cell's world
+    // bounding sphere (camera-independent, like WbDrawDispatcher.ComputeEntityLightSet).
+    // Cached per frame; unused slots are -1 (shader adds no point light there).
+    private int[] GetCellLightSet(uint cellId)
+    {
+        if (_cellLightSetCache.TryGetValue(cellId, out var cached)) return cached;
+
+        var set = new int[AcDream.Core.Lighting.LightManager.MaxLightsPerObject];
+        System.Array.Fill(set, -1);
+
+        var snap = _pointSnapshot;
+        if (snap is { Count: > 0 } &&
+            _landblocks.TryGetValue(cellId & 0xFFFF0000u, out var lb) &&
+            lb.EnvCellBounds.TryGetValue(cellId, out var b))
+        {
+            Vector3 center = (b.Min + b.Max) * 0.5f;
+            float radius = (b.Max - b.Min).Length() * 0.5f;
+            AcDream.Core.Lighting.LightManager.SelectForObject(snap, center, radius, set);
+        }
+        _cellLightSetCache[cellId] = set;
+        return set;
+    }
+```
+
+(`WbBoundingBox` has public `Vector3 Min` / `Vector3 Max` — confirmed at `WbFrustum.cs:15-16`.)
+
+- [ ] **Step 4: Upload binding 4, fill + upload binding 5, and bind both in `RenderModernMDIInternal`**
+
+(a) At the TOP of `RenderModernMDIInternal` (after the `if (drawCalls.Count == 0 ...) return;` guard, ~1014), clear the per-frame cache:
+
+```csharp
+        _cellLightSetCache.Clear();
+```
+
+(b) Where `_clipSlotData` is filled per instance (1195-1206), add a parallel fill of `_lightSetData` right after it:
+
+```csharp
+        // A7 Fix D (D-2): per-instance 8-int light set, parallel to the transforms,
+        // keyed on the cell each shell instance belongs to (mirrors _clipSlotData).
+        int lightStride = AcDream.Core.Lighting.LightManager.MaxLightsPerObject;
+        if (_lightSetData.Length < uniqueInstanceCount * lightStride)
+            _lightSetData = new int[System.Math.Max(_lightSetData.Length * 2, uniqueInstanceCount * lightStride)];
+        for (int i = 0; i < uniqueInstanceCount; i++)
+        {
+            int[] cellSet = GetCellLightSet(allInstances[i].CellId);
+            System.Array.Copy(cellSet, 0, _lightSetData, i * lightStride, lightStride);
+        }
+```
+
+(c) Where the four buffers are uploaded (the `_clipSlotData` upload ends ~1209-1214), add the binding-4 + binding-5 uploads:
+
+```csharp
+        // A7 Fix D (D-2): upload binding=4 (global lights) + binding=5 (per-instance set).
+        int lightCount = AcDream.Core.Lighting.GlobalLightPacker.Pack(_pointSnapshot, ref _globalLightData);
+        int glUploadCount = lightCount > 0 ? lightCount : 1;
+        _gl.BindBuffer(GLEnum.ShaderStorageBuffer, _globalLightsSsbo);
+        _gl.BufferData(GLEnum.ShaderStorageBuffer,
+            (nuint)(glUploadCount * AcDream.Core.Lighting.GlobalLightPacker.FloatsPerLight * sizeof(float)),
+            null, GLEnum.DynamicDraw);
+        fixed (float* gp = _globalLightData)
+            _gl.BufferSubData(GLEnum.ShaderStorageBuffer, 0,
+                (nuint)(glUploadCount * AcDream.Core.Lighting.GlobalLightPacker.FloatsPerLight * sizeof(float)), gp);
+
+        _gl.BindBuffer(GLEnum.ShaderStorageBuffer, _instLightSetSsbo);
+        _gl.BufferData(GLEnum.ShaderStorageBuffer,
+            (nuint)(uniqueInstanceCount * lightStride * sizeof(int)), null, GLEnum.DynamicDraw);
+        fixed (int* lp = _lightSetData)
+            _gl.BufferSubData(GLEnum.ShaderStorageBuffer, 0,
+                (nuint)(uniqueInstanceCount * lightStride * sizeof(int)), lp);
+```
+
+(d) In the bind block (1225-1230, after `BindClipRegionBinding2();`), add:
+
+```csharp
+        _gl.BindBufferBase(GLEnum.ShaderStorageBuffer, 4, _globalLightsSsbo);
+        _gl.BindBufferBase(GLEnum.ShaderStorageBuffer, 5, _instLightSetSsbo);
+```
+
+- [ ] **Step 5: Wire the snapshot from GameWindow**
+
+In `GameWindow.cs`, immediately after the existing `_wbDrawDispatcher?.SetSceneLights(Lighting.PointSnapshot);` (line ~7777), add:
+
+```csharp
+            _envCellRenderer?.SetPointSnapshot(Lighting.PointSnapshot);   // A7 Fix D (D-2)
+```
+
+- [ ] **Step 6: Dispose the new buffers**
+
+In `EnvCellRenderer.Dispose` (search for the existing `_gl.DeleteBuffer(...)` cleanup), add:
+
+```csharp
+        if (_globalLightsSsbo != 0) _gl.DeleteBuffer(_globalLightsSsbo);
+        if (_instLightSetSsbo != 0) _gl.DeleteBuffer(_instLightSetSsbo);
+```
+
+- [ ] **Step 7: Build**
+
+Run: `dotnet build src/AcDream.App/AcDream.App.csproj -c Debug`
+Expected: green. Fix any `WbBoundingBox` field-name or namespace mismatches surfaced by the compiler.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs src/AcDream.App/Rendering/GameWindow.cs
+git commit -m "fix(render): A7 Fix D D-2 — EnvCell shell binds its own per-cell light set (#140)
+
+The cell shell read whatever light set (SSBO 4/5) WbDrawDispatcher last left
+bound, lighting walls with a leaked set. EnvCellRenderer now uploads its own
+binding=4 global lights (frame PointSnapshot via GlobalLightPacker) + a binding=5
+per-instance set, computed per cell by LightManager.SelectForObject over the
+cell's world bounds (mirrors _cellIdToSlot + WbDrawDispatcher.ComputeEntityLightSet).
+
+Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>"
+```
+
+---
+
+## Task 5: Divergence register — correct AP-35, reconcile the Fix B row
+
+**Files:**
+- Modify: `docs/architecture/retail-divergence-register.md` (AP-35 row, line ~134; the Fix B per-object-light-selection row)
+
+- [ ] **Step 1: Correct AP-35**
+
+Find the `AP-35` row. It currently describes the point-light path as per-pixel
+`mesh_modern.frag:52` with the half-Lambert wrap "neither ported". Rewrite the row to
+reflect reality after Fix A + Fix D D-1:
+- Path is per-vertex Gouraud in `mesh_modern.vert` (`pointContribution` ~:153, wrap ~:163), not per-pixel `frag`.
+- The half-Lambert wrap + the `norm` (`distsq·d`) attenuation ARE ported (vert + `LightBake.cs`).
+- The point-light sum is now clamped to `[0,1]` on its own (D-1), matching `SetStaticLightingVertexColors`.
+- Update the `file:line` to `src/AcDream.App/Rendering/Shaders/mesh_modern.vert` and cite `LightBake.cs` as the conformance oracle.
+
+- [ ] **Step 2: Reconcile the Fix B per-object-light-selection row**
+
+Find the row describing Fix B (per-object 8-light selection by sphere overlap vs
+retail's per-vertex sum over the full static list — `minimize_object_lighting`
+0x0054d480). Confirm its wording now covers EnvCell **shells** too (D-2 selects per
+cell-sphere via the same `SelectForObject`). If it only mentions GfxObjs, extend the
+"file:line" / description to include `EnvCellRenderer.GetCellLightSet`. Do NOT add a
+new contradicting row.
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add docs/architecture/retail-divergence-register.md
+git commit -m "docs(register): correct AP-35 (per-vertex+wrap ported, point sum clamped) — A7 Fix D
+
+Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>"
+```
+
+---
+
+## Final verification (after all tasks)
+
+- [ ] `dotnet build src/AcDream.App/AcDream.App.csproj -c Debug` green.
+- [ ] `dotnet test tests/AcDream.Core.Tests/AcDream.Core.Tests.csproj` green (GlobalLightPacker + LightBakeConformance + no regressions).
+- [ ] **Visual (user, acceptance gate):** launch the client against live ACE, go to Holtburg. Confirm (a) outdoor objects near torches no longer blow out warm-white, and (b) the meeting-hall walls render warm-but-dim like retail. This is the sign-off the spec requires.
+- [ ] Update `docs/ISSUES.md` / roadmap if #140 is tracked there (move to Recently closed with the commit SHAs once the user signs off visually).
+
+## Notes for the implementer
+
+- **No D3D-FF port.** Do not touch `config_hardware_light`-style `color×intensity / 1/d / Range×1.5` math — it is the wrong oracle for the baked walls (handoff warning).
+- **No CPU bake.** `LightBake.cs` stays the test oracle only; the runtime path is the in-shader clamp (chosen approach).
+- **Self-contained GL state.** EnvCellRenderer must bind binding 4 + 5 ITSELF every draw (per `feedback_render_self_contained_gl_state`); do not assume WbDrawDispatcher left them bound — that leak is the bug.
+- **Don't touch the purple portal** — confirmed correct.