diff --git a/docs/research/2026-08-30-fw-walk-oracle/posed/street-portal-gate-dump.txt b/docs/research/2026-08-30-fw-walk-oracle/posed/street-portal-gate-dump.txt
new file mode 100644
index 00000000..4786eec3
--- /dev/null
+++ b/docs/research/2026-08-30-fw-walk-oracle/posed/street-portal-gate-dump.txt
@@ -0,0 +1,30 @@
+pose cell=a9b40029 origin=<132.77141, 23.892355, 96.33006>
+building a9b4001a: dist=54.7 eff=0.0 eyeLocal=<47.290646, 28.046478, 2.3300629> portals=3
+  level BSP portal refs: 3
+  ref idx=2 other=a9b4016e rawSide=0 exact=True planeD@eye=-43.04 eyeSide=1 clipN=0 gate(side==rawSide)=reject
+  ref idx=1 other=a9b4016d rawSide=0 exact=True planeD@eye=51.54 eyeSide=0 clipN=0 gate(side==rawSide)=PASS
+  ref idx=0 other=a9b4016c rawSide=0 exact=True planeD@eye=33.35 eyeSide=0 clipN=0 gate(side==rawSide)=PASS
+building a9b4001e: dist=120.2 eff=20.2 eyeLocal=<107.64956, 48.678543, 30.330063> portals=10
+  level BSP portal refs: 10
+  ref idx=6 other=a9b40107 rawSide=0 exact=True planeD@eye=115.15 eyeSide=0 clipN=4 gate(side==rawSide)=PASS
+  ref idx=9 other=a9b4010b rawSide=0 exact=True planeD@eye=59.68 eyeSide=0 clipN=4 gate(side==rawSide)=PASS
+  ref idx=4 other=a9b40102 rawSide=0 exact=True planeD@eye=112.65 eyeSide=0 clipN=6 gate(side==rawSide)=PASS
+  ref idx=3 other=a9b40103 rawSide=0 exact=True planeD@eye=-102.65 eyeSide=1 clipN=6 gate(side==rawSide)=reject
+  ref idx=7 other=a9b40109 rawSide=0 exact=True planeD@eye=59.68 eyeSide=0 clipN=4 gate(side==rawSide)=PASS
+  ref idx=8 other=a9b4010a rawSide=0 exact=True planeD@eye=59.68 eyeSide=0 clipN=4 gate(side==rawSide)=PASS
+  ref idx=5 other=a9b40106 rawSide=0 exact=True planeD@eye=116.65 eyeSide=0 clipN=4 gate(side==rawSide)=PASS
+  ref idx=0 other=a9b40100 rawSide=0 exact=True planeD@eye=-25.33 eyeSide=1 clipN=4 gate(side==rawSide)=reject
+  ref idx=1 other=a9b40100 rawSide=0 exact=True planeD@eye=-25.33 eyeSide=1 clipN=4 gate(side==rawSide)=reject
+  ref idx=2 other=a9b40100 rawSide=0 exact=True planeD@eye=-25.33 eyeSide=1 clipN=4 gate(side==rawSide)=reject
+building a9b40022: dist=28.3 eff=0.0 eyeLocal=<12.107626, 25.2714, 2.3300629> portals=3
+  level BSP portal refs: 3
+  ref idx=2 other=a9b4015e rawSide=0 exact=True planeD@eye=17.11 eyeSide=0 clipN=0 gate(side==rawSide)=PASS
+  ref idx=0 other=a9b40164 rawSide=0 exact=True planeD@eye=-14.27 eyeSide=1 clipN=0 gate(side==rawSide)=reject
+  ref idx=1 other=a9b40165 rawSide=0 exact=True planeD@eye=35.27 eyeSide=0 clipN=0 gate(side==rawSide)=PASS
+building a9b40026: dist=117.7 eff=17.7 eyeLocal=<-28.271423, 111.60765, 30.330063> portals=5
+  level BSP portal refs: 5
+  ref idx=1 other=a9b40120 rawSide=1 exact=True planeD@eye=-117.26 eyeSide=1 clipN=4 gate(side==rawSide)=PASS
+  ref idx=2 other=a9b40122 rawSide=0 exact=True planeD@eye=117.26 eyeSide=0 clipN=4 gate(side==rawSide)=PASS
+  ref idx=4 other=a9b40125 rawSide=0 exact=True planeD@eye=117.26 eyeSide=0 clipN=4 gate(side==rawSide)=PASS
+  ref idx=3 other=a9b40124 rawSide=0 exact=True planeD@eye=-22.07 eyeSide=1 clipN=4 gate(side==rawSide)=reject
+  ref idx=0 other=a9b4011f rawSide=0 exact=True planeD@eye=-22.07 eyeSide=1 clipN=4 gate(side==rawSide)=reject
diff --git a/tests/AcDream.App.Tests/Rendering/Walk/WalkPortalGateDumpTests.cs b/tests/AcDream.App.Tests/Rendering/Walk/WalkPortalGateDumpTests.cs
new file mode 100644
index 00000000..2049bfb0
--- /dev/null
+++ b/tests/AcDream.App.Tests/Rendering/Walk/WalkPortalGateDumpTests.cs
@@ -0,0 +1,88 @@
+using AcDream.App.Tests.Rendering;
+using AcDream.App.Rendering.Walk;
+using DatReaderWriter;
+using DatReaderWriter.Options;
+using System.Numerics;
+using System.Text;
+
+namespace AcDream.App.Tests.Rendering.Walk;
+
+/// <summary>
+/// FW1 look-in gate microscope: for the street fixture pose, dump every
+/// gate input for building a9b4001a (retail punches it) vs a9b4001e
+/// (retail does not): raw portal flags, the BSP-emitted polygon's plane,
+/// the eye's signed distance and side, and the active-view clip count.
+/// Writes the dump to the scratch directory; always passes.
+/// </summary>
+[Trait("Lane", "InstalledDat")]
+public sealed class WalkPortalGateDumpTests
+{
+    [Fact]
+    public void Dump_the_gate_inputs_for_a_punching_and_a_silent_building()
+    {
+        string? datDir = CornerFloodReplayTests.ResolveDatDir();
+        if (datDir is null)
+        {
+            Assert.Fail("Lane=InstalledDat requires an installed retail DAT directory.");
+        }
+        IReadOnlyList<WalkOracleFrame> frames =
+            WalkOracleTrace.Load("posed/holtburg-street-outdoor");
+        WalkOracleFrame frame = frames[1];
+        Assert.NotNull(frame.Pose);
+        using var dats = new DatCollection(datDir!, DatAccessType.Read);
+        WalkLandscapeDatBuilder.BuiltWorld world =
+            WalkLandscapeDatBuilder.Build(dats, frame.Pose!.CellId);
+        var ctx = new WalkTraceReplayContext(frame.Pose, world.Cells)
+        {
+            Buildings = world.Buildings,
+        };
+        // Install the outdoor default view as the active clip context.
+        var defaultView = new WalkPortalView();
+        WalkCopyView.AppendFullViewportQuad(
+            defaultView, ctx.Rays, ctx.WorldViewpoint,
+            ctx.ViewportWidth, ctx.ViewportHeight);
+        ctx.SetActiveView(defaultView, 0);
+
+        var dump = new StringBuilder();
+        Span<WalkScreenPoint> clipped = stackalloc WalkScreenPoint[64];
+        dump.AppendLine($"pose cell={frame.Pose.CellId:x8} origin={frame.Pose.Origin}");
+        foreach (uint id in new[] { 0xA9B4001Au, 0xA9B4001Eu, 0xA9B40022u, 0xA9B40026u })
+        {
+            WalkBuilding building = world.Buildings.Keys.Single(b => b.PositionCellId == id);
+            float dist = ctx.ViewerDistanceTo(building);
+            Vector3 eyeInBuilding = ctx.ViewpointInBuilding(building);
+            dump.AppendLine(
+                $"building {id:x8}: dist={dist:f1} eff={MathF.Max(0f, dist - 100f):f1} "
+                + $"eyeLocal={eyeInBuilding} portals={building.Portals.Length}");
+            WalkBspNode? bsp = building.SelectDrawingBsp(dist);
+            var refs = new List<WalkPortalRef>();
+            Collect(bsp, refs);
+            dump.AppendLine($"  level BSP portal refs: {refs.Count}");
+            foreach (WalkPortalRef portalRef in refs)
+            {
+                ref WalkBldPortal bp = ref building.Portals[portalRef.PortalIndex];
+                float d = Vector3.Dot(portalRef.Polygon.Plane.Normal, eyeInBuilding)
+                    + portalRef.Polygon.Plane.D;
+                int side = d > WalkVisibilityMath.Epsilon ? 0
+                    : d < -WalkVisibilityMath.Epsilon ? 1 : 2;
+                int n = ctx.ClipBuildingPolygon(building, portalRef.Polygon, side, clipped);
+                dump.AppendLine(
+                    $"  ref idx={portalRef.PortalIndex} other={bp.OtherCellId:x8} "
+                    + $"rawSide={bp.PortalSide} exact={bp.ExactMatch} "
+                    + $"planeD@eye={d:f2} eyeSide={side} clipN={n} "
+                    + $"gate(side==rawSide)={(side == bp.PortalSide ? "PASS" : "reject")}");
+            }
+        }
+        string path = Path.Combine(Path.GetTempPath(), "fw1-portal-gate-dump.txt");
+        File.WriteAllText(path, dump.ToString());
+        Assert.True(true);
+    }
+
+    private static void Collect(WalkBspNode? node, List<WalkPortalRef> into)
+    {
+        if (node is null) return;
+        if (node.InPortals is not null) into.AddRange(node.InPortals);
+        Collect(node.PosNode, into);
+        Collect(node.NegNode, into);
+    }
+}