diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index f7b503b..f68e8c3 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -11070,13 +11070,37 @@ public sealed class GameWindow : IDisposable
             gl.Disable(EnableCap.Blend);
             _envCellRenderer!.Render(AcDream.App.Rendering.Wb.WbRenderPass.Opaque, currentEnvCellIds);
 
-            // Transparency pass.
+            // Phase A8.F (#2): translucent cell geometry clipped to each cell's portal-chain
+            // region (stencil BIT 2). Opaque cells already clip correctly via depth (left
+            // untouched above — Q4 fidelity-vs-perf decision). Bit 1 (OutsideView mask) is
+            // preserved: every bit-2 op below uses StencilMask 0x02 and never clears the
+            // whole stencil. The camera cell's region is full-screen, so it (and any cell
+            // without a non-empty region) renders unclipped.
             gl.Enable(EnableCap.Blend);
             gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.OneMinusSrcAlpha);
             gl.DepthMask(false);
-            _envCellRenderer!.Render(AcDream.App.Rendering.Wb.WbRenderPass.Transparent, currentEnvCellIds);
+            foreach (var cellId in currentEnvCellIds)
+            {
+                var oneCell = new System.Collections.Generic.HashSet<uint> { cellId };
+                if (cellId != cameraCell.CellId
+                    && portalFrame.CellViews.TryGetValue(cellId, out var cv) && !cv.IsEmpty)
+                {
+                    _indoorStencilPipeline!.MarkRegionBit2(cv.Polygons);
+                    _indoorStencilPipeline.EnableBit2CellPass();
+                    _meshShader!.Use();
+                    _envCellRenderer!.Render(AcDream.App.Rendering.Wb.WbRenderPass.Transparent, oneCell);
+                    gl.Disable(EnableCap.StencilTest);
+                    _indoorStencilPipeline.ResetRegionBit2(cv.Polygons); // clear bit 2 for next cell; bit 1 intact
+                }
+                else
+                {
+                    _meshShader!.Use();
+                    _envCellRenderer!.Render(AcDream.App.Rendering.Wb.WbRenderPass.Transparent, oneCell);
+                }
+            }
             gl.DepthMask(true);
             gl.Disable(EnableCap.Blend);
+            gl.Disable(EnableCap.StencilTest); // ensure clean for Step 4 (which re-enables for bit-1 terrain gate)
         }
 
         // FIX 2026-05-28 (post-third-visual-gate): render IndoorPass entities.
diff --git a/src/AcDream.App/Rendering/IndoorCellStencilPipeline.cs b/src/AcDream.App/Rendering/IndoorCellStencilPipeline.cs
index a35b8c7..a887c87 100644
--- a/src/AcDream.App/Rendering/IndoorCellStencilPipeline.cs
+++ b/src/AcDream.App/Rendering/IndoorCellStencilPipeline.cs
@@ -347,6 +347,77 @@ public sealed unsafe class IndoorCellStencilPipeline : IDisposable
         _gl.Disable(EnableCap.StencilTest);
     }
 
+    /// <summary>
+    /// Phase A8.F (#2): mark stencil BIT 2 (only) wherever the NDC region covers, preserving bit 1.
+    /// Color/depth writes off. Enables the stencil test and leaves it enabled. Used to clip a single
+    /// cell's translucent geometry to its portal-chain screen region without disturbing the bit-1
+    /// OutsideView mask. Pair with EnableBit2CellPass (render) then ResetRegionBit2 (clear).
+    /// </summary>
+    public void MarkRegionBit2(System.Collections.Generic.IReadOnlyList<ViewPolygon> region)
+        => DrawRegionBit2(region, setBit: true);
+
+    /// <summary>Phase A8.F (#2): clear stencil BIT 2 (only) wherever the NDC region covers, preserving
+    /// bit 1. Call after rendering a cell so the next cell starts with bit 2 == 0 in this region.</summary>
+    public void ResetRegionBit2(System.Collections.Generic.IReadOnlyList<ViewPolygon> region)
+        => DrawRegionBit2(region, setBit: false);
+
+    /// <summary>Phase A8.F (#2): set render state to draw geometry only where bit 2 is set (read-only
+    /// stencil). Call between MarkRegionBit2 and the cell's draw.</summary>
+    public void EnableBit2CellPass()
+    {
+        _gl.Enable(EnableCap.StencilTest);
+        _gl.StencilFunc(StencilFunction.Equal, 0x02, 0x02u); // bit 2 set
+        _gl.StencilMask(0x00u);                              // read-only — do not touch bit 1 or bit 2
+        _gl.StencilOp(StencilOp.Keep, StencilOp.Keep, StencilOp.Keep);
+    }
+
+    // Triangulate the NDC region (fan, z=0) and draw it writing only bit 2 (set or clear).
+    // StencilMask 0x02 guarantees bit 1 is never modified. Color/depth writes off.
+    private void DrawRegionBit2(System.Collections.Generic.IReadOnlyList<ViewPolygon> region, bool setBit)
+    {
+        int triVerts = 0;
+        foreach (var p in region) if (!p.IsEmpty) triVerts += (p.Vertices.Length - 2) * 3;
+        if (triVerts == 0) return;
+
+        var verts = new Vector3[triVerts];
+        int idx = 0;
+        foreach (var p in region)
+        {
+            if (p.IsEmpty) continue;
+            var v0 = new Vector3(p.Vertices[0], 0f);
+            for (int i = 1; i < p.Vertices.Length - 1; i++)
+            {
+                verts[idx++] = v0;
+                verts[idx++] = new Vector3(p.Vertices[i], 0f);
+                verts[idx++] = new Vector3(p.Vertices[i + 1], 0f);
+            }
+        }
+
+        if (triVerts > _vboCapacityVerts) AllocateVbo(Math.Max(triVerts * 2, 1024));
+        _gl.BindBuffer(BufferTargetARB.ArrayBuffer, _vbo);
+        fixed (Vector3* p = verts)
+            _gl.BufferSubData(BufferTargetARB.ArrayBuffer, 0, (nuint)(triVerts * sizeof(Vector3)), p);
+        _gl.BindBuffer(BufferTargetARB.ArrayBuffer, 0);
+
+        var identity = Matrix4x4.Identity;
+        _gl.Enable(EnableCap.StencilTest);
+        _gl.ColorMask(false, false, false, false);
+        _gl.DepthMask(false);
+        _gl.DepthFunc(DepthFunction.Always);
+        _gl.Disable(EnableCap.CullFace);
+        _gl.StencilMask(0x02u);                                 // ONLY bit 2 — bit 1 preserved
+        _gl.StencilFunc(StencilFunction.Always, setBit ? 0x02 : 0x00, 0xFFu);
+        _gl.StencilOp(StencilOp.Keep, StencilOp.Keep, StencilOp.Replace);
+        _shader.Use();
+        _gl.UniformMatrix4(_uViewProjectionLoc, 1, false, (float*)&identity);
+        _gl.Uniform1(_uWriteFarDepthLoc, 0);
+        _gl.BindVertexArray(_vao);
+        _gl.DrawArrays(PrimitiveType.Triangles, 0, (uint)triVerts);
+        _gl.BindVertexArray(0);
+        _gl.Enable(EnableCap.CullFace);
+        _gl.ColorMask(true, true, true, true);
+    }
+
     /// <summary>
     /// Step 4 of WB's RenderInsideOut: enable stencil read-only with
     /// ref=1, so subsequent terrain + outdoor entity draws are gated