diff --git a/src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs b/src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs
index 0307c13..592b26a 100644
--- a/src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs
+++ b/src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs
@@ -959,6 +959,27 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         shader.Use();
         shader.SetInt("uFilterByCell", 0);
 
+        // Phase U.4 ROOT-CAUSE FIX (cell-shell "transparent walls / only bluish
+        // background, flickering when moving"): establish this pass's BLEND + DepthMask
+        // state OURSELVES rather than inheriting it. Render(Opaque) runs right after the
+        // terrain draw (which sets neither) and after particles / last frame's transparent
+        // pass — so whatever left GL_BLEND enabled made the OPAQUE shells composite their
+        // (often sub-1.0 alpha) wall textures against the bluish clear color (terrain is
+        // Skip'd indoors), toggling with per-frame ordering → flicker. Mirror the working
+        // WbDrawDispatcher passes (Disable(Blend)+DepthMask(true) opaque;
+        // Enable(Blend)+DepthMask(false) transparent). Restored to opaque defaults at the
+        // end of the draw loop so a Transparent pass can't leak into later draws.
+        if (renderPass == WbRenderPass.Transparent)
+        {
+            _gl.Enable(EnableCap.Blend);
+            _gl.DepthMask(false);
+        }
+        else
+        {
+            _gl.Disable(EnableCap.Blend);
+            _gl.DepthMask(true);
+        }
+
         // WB BaseObjectRenderManager.cs:718-740: group batches by CullMode + additive flag.
         var batchesByCullMode = new Dictionary<int, List<(ObjectRenderBatch batch, int instanceCount, int instanceOffset)>>();
         int totalDraws = 0;
@@ -1174,6 +1195,12 @@ public sealed unsafe class EnvCellRenderer : IDisposable
             currentDrawOffset += numDraws;
         }
 
+        // Phase U.4: leave a clean opaque-default render state (mirrors WbDrawDispatcher's
+        // post-transparent restore) so a Transparent pass's Blend-on / DepthMask-off does
+        // not leak into particles or the next frame's draws.
+        _gl.Disable(EnableCap.Blend);
+        _gl.DepthMask(true);
+
         // WB BaseObjectRenderManager.cs:845-847:
         shader.SetInt("uDrawIDOffset", 0);
         _gl.BindBuffer(GLEnum.DrawIndirectBuffer, 0);