diff --git a/docs/superpowers/plans/2026-05-08-phase-n4-rendering-foundation.md b/docs/superpowers/plans/2026-05-08-phase-n4-rendering-foundation.md
index 7c55aba..6458ac5 100644
--- a/docs/superpowers/plans/2026-05-08-phase-n4-rendering-foundation.md
+++ b/docs/superpowers/plans/2026-05-08-phase-n4-rendering-foundation.md
@@ -800,7 +800,24 @@ EOF
 
 ---
 
-### Task 6: `WbDatReaderAdapter` — bridge our `DatCollection` to WB's `IDatReaderWriter`
+### Task 6: ~~WbDatReaderAdapter~~ — OBSOLETED 2026-05-08
+
+**Adjustment 1 (2026-05-08):** discovered during pre-Task-6 grep that
+WB ships `WorldBuilder.Shared.Services.DefaultDatReaderWriter`, a
+concrete `IDatReaderWriter` implementation that takes a dat-directory
+path and constructs all four databases (Portal / HighRes / Language +
+CellRegions) internally. We can instantiate it directly with the same
+`%USERPROFILE%\Documents\Asheron's Call` path acdream's `DatCollection`
+uses; both will open the same dat files with separate handles. Memory
+cost: ~50-100 MB of duplicate index caches, acceptable for foundation
+work. Task 9 incorporates the construction step directly.
+
+If memory pressure surfaces during week 2 stress testing, revisit by
+writing a real bridge that shares index caches with our `DatCollection`.
+
+**No work for this task — skip and proceed to Task 7.**
+
+### Task 6 (original — kept for history)
 
 **Files:**
 - Create: `src/AcDream.App/Rendering/Wb/WbDatReaderAdapter.cs`
diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index b00345d..543a1f4 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -28,6 +28,9 @@ public sealed class GameWindow : IDisposable
     private InstancedMeshRenderer? _staticMesh;
     private Shader? _meshShader;
     private TextureCache? _textureCache;
+    /// <summary>Phase N.4: WB-backed rendering pipeline adapter. Non-null only
+    /// when <c>ACDREAM_USE_WB_FOUNDATION=1</c> is set; null otherwise.</summary>
+    private AcDream.App.Rendering.Wb.WbMeshAdapter? _wbMeshAdapter;
     private SamplerCache? _samplerCache;
     private DebugLineRenderer? _debugLines;
     // K-fix4 (2026-04-26): default OFF. The orange BSP / green cylinder
@@ -1421,6 +1424,19 @@ public sealed class GameWindow : IDisposable
         // WorldBuilder reference at
         // references/WorldBuilder/Chorizite.OpenGLSDLBackend/OpenGLGraphicsDevice.cs:115-132.
         _samplerCache = new SamplerCache(_gl);
+
+        // Phase N.4 — WB rendering pipeline foundation. Constructed only when
+        // ACDREAM_USE_WB_FOUNDATION=1 is set; otherwise the legacy renderer
+        // path stays in charge. The full ObjectMeshManager bring-up is
+        // deferred to Task 9 — for now this is a stub adapter that exposes
+        // the public API so call sites can wire without behavioral effect.
+        if (AcDream.App.Rendering.Wb.WbFoundationFlag.IsEnabled)
+        {
+            var wbLogger = Microsoft.Extensions.Logging.Abstractions.NullLogger<AcDream.App.Rendering.Wb.WbMeshAdapter>.Instance;
+            _wbMeshAdapter = new AcDream.App.Rendering.Wb.WbMeshAdapter(_gl, _dats, wbLogger);
+            Console.WriteLine("[N.4] WbFoundation flag is ENABLED — routing static content through ObjectMeshManager.");
+        }
+
         _staticMesh = new InstancedMeshRenderer(_gl, _meshShader, _textureCache);
 
         // Phase G.1 sky renderer — its own shader (sky.vert / sky.frag)
@@ -8625,6 +8641,8 @@ public sealed class GameWindow : IDisposable
         _skyRenderer?.Dispose();      // depends on sampler cache; dispose first
         _samplerCache?.Dispose();
         _textureCache?.Dispose();
+        _wbMeshAdapter?.Dispose();    // Phase N.4 WB foundation — null when flag off
+
         _meshShader?.Dispose();
         _terrain?.Dispose();
         _shader?.Dispose();