diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index b323bed..4df8455 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -10727,7 +10727,16 @@ public sealed class GameWindow : IDisposable
 
         // Step 5: per-other-building 3-bit stencil pipeline.
         // WB VisibilityManager.cs:157-232
-        if (didInsideStencil && otherBuildings.Count > 0)
+        //
+        // FIX 2026-05-28 (post-first-visual-gate): Step 5 is GATED OFF BY DEFAULT.
+        // First visual gate showed perf collapse + texture flicker indoors because
+        // Step 5 iterates EVERY loaded other-building per frame (109 at Holtburg),
+        // each doing 5 GL draws (mark/end-query/punch/render-opaque/render-trans/reset)
+        // = ~545 extra draws/frame with no frustum culling. The driver hit TDR
+        // limits. Set ACDREAM_A8_STEP5=1 to re-enable for cross-building visibility
+        // testing once we add per-building frustum culling.
+        bool step5Enabled = string.Equals(Environment.GetEnvironmentVariable("ACDREAM_A8_STEP5"), "1", StringComparison.Ordinal);
+        if (step5Enabled && didInsideStencil && otherBuildings.Count > 0)
         {
             gl.Enable(EnableCap.StencilTest);
             gl.ColorMask(false, false, false, false);
@@ -10791,7 +10800,18 @@ public sealed class GameWindow : IDisposable
         {
             gl.Disable(EnableCap.StencilTest);
             gl.StencilMask(0xFFu);
-            gl.ColorMask(true, true, true, false);
+            // FIX 2026-05-28: WB exits with ColorMask(t,t,t,FALSE) — alpha-bit
+            // off. That breaks subsequent acdream rendering (particles +
+            // anything that relies on alpha-to-coverage writing alpha). Restore
+            // full ColorMask before returning to the outer render frame.
+            //
+            // Step 5's iteration loop (when ACDREAM_A8_STEP5=1) leaves
+            // DepthMask=false / CullFace=disabled / ColorMask=(f,f,f,f) on
+            // its last iteration. Restore to acdream-default before returning.
+            gl.ColorMask(true, true, true, true);
+            gl.DepthMask(true);
+            gl.DepthFunc(DepthFunction.Less);
+            gl.Enable(EnableCap.CullFace);
         }
     }