diff --git a/src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs b/src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs
index abf3a6a..cf713c0 100644
--- a/src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs
+++ b/src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs
@@ -48,7 +48,12 @@ public sealed unsafe class EnvCellRenderer : IDisposable
     private EnvCellVisibilitySnapshot _activeSnapshot = new();
 
     // Shader (set by caller via Initialize).
-    private GLSLShader? _shader;
+    // Uses acdream's legacy Shader type (not WB's GLSLShader) to match the
+    // existing wire-in pattern in GameWindow.cs where _meshShader is loaded
+    // for mesh_modern.{vert,frag} and shared across multiple consumers.
+    // API mapping: Bind() -> Use(), SetUniform(s, int) -> SetInt(s, int),
+    //              SetUniform(s, Vector4) -> SetVec4(s, Vector4).
+    private AcDream.App.Rendering.Shader? _shader;
     private bool _initialized;
 
     // List pool — copied from WB ObjectRenderManagerBase.
@@ -94,7 +99,7 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         _frustum = frustum;
     }
 
-    public void Initialize(GLSLShader shader)
+    public void Initialize(AcDream.App.Rendering.Shader shader)
     {
         _shader = shader;
         AllocateMdiBuffers();
@@ -577,7 +582,10 @@ public sealed unsafe class EnvCellRenderer : IDisposable
     //   - Drop the _useModernRendering branch (our codebase asserts modern at startup per Phase N.5).
     //   - Drop SelectedInstance/HoveredInstance highlight block (lines 486-510) — no editor state.
     //   - Replace RenderModernMDI(base) with private RenderModernMDIInternal.
-    //   - shader.Bind() / SetUniform API: use our GLSLShader.Bind() + SetUniform(string,int).
+    //   - shader.Bind() / SetUniform API: mapped to acdream's legacy Shader
+    //     class (Use() + SetInt/SetVec4/SetMatrix4) to match the existing
+    //     wire-in pattern in GameWindow.cs where _meshShader is loaded once
+    //     for mesh_modern.{vert,frag} and shared with WbDrawDispatcher.
     // ---------------------------------------------------------------------------
 
     public void Render(WbRenderPass renderPass)
@@ -602,12 +610,12 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         {
             var snapshot = _activeSnapshot;
             // WB EnvCellRenderManager.cs:403-404:
-            _shader.Bind();
+            _shader.Use();
             _poolIndex = snapshot.BatchedByCell.Count; // reset point (mirrors WB line 405)
 
             // WB EnvCellRenderManager.cs:406-409: uniform state setup.
-            _shader.SetUniform("uRenderPass", (int)renderPass);
-            _shader.SetUniform("uFilterByCell", 0);
+            _shader.SetInt("uRenderPass", (int)renderPass);
+            _shader.SetInt("uFilterByCell", 0);
 
             var allInstances = new List<InstanceData>();
             var drawCalls    = new List<(ObjectRenderData renderData, int count, int offset)>();
@@ -687,8 +695,8 @@ public sealed unsafe class EnvCellRenderer : IDisposable
             // WB EnvCellRenderManager.cs:486-510: selection/hover highlights — DROPPED (no editor state).
 
             // WB EnvCellRenderManager.cs:506-509: cleanup.
-            _shader.SetUniform("uHighlightColor", new System.Numerics.Vector4(0, 0, 0, 0));
-            _shader.SetUniform("uRenderPass", (int)renderPass);
+            _shader.SetVec4("uHighlightColor", new System.Numerics.Vector4(0, 0, 0, 0));
+            _shader.SetInt("uRenderPass", (int)renderPass);
             _gl.BindVertexArray(0);
             _currentVao = 0;
 
@@ -710,7 +718,7 @@ public sealed unsafe class EnvCellRenderer : IDisposable
     // ---------------------------------------------------------------------------
 
     private void RenderModernMDIInternal(
-        GLSLShader shader,
+        AcDream.App.Rendering.Shader shader,
         List<(ObjectRenderData renderData, int count, int offset)> drawCalls,
         List<InstanceData> allInstances,
         WbRenderPass renderPass)
@@ -722,8 +730,8 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         if (passIdx < 0 || passIdx > 2) return;
 
         // WB BaseObjectRenderManager.cs:715-716:
-        shader.Bind();
-        shader.SetUniform("uFilterByCell", 0);
+        shader.Use();
+        shader.SetInt("uFilterByCell", 0);
 
         // WB BaseObjectRenderManager.cs:718-740: group batches by CullMode + additive flag.
         var batchesByCullMode = new Dictionary<int, List<(ObjectRenderBatch batch, int instanceCount, int instanceOffset)>>();
@@ -873,15 +881,15 @@ public sealed unsafe class EnvCellRenderer : IDisposable
             if (isAdditive)
             {
                 _gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.One);
-                shader.SetUniform("uRenderPass", (int)renderPass | 0x100);
+                shader.SetInt("uRenderPass", (int)renderPass | 0x100);
             }
             else
             {
                 _gl.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.OneMinusSrcAlpha);
-                shader.SetUniform("uRenderPass", (int)renderPass);
+                shader.SetInt("uRenderPass", (int)renderPass);
             }
 
-            shader.SetUniform("uDrawIDOffset", currentDrawOffset);
+            shader.SetInt("uDrawIDOffset", currentDrawOffset);
             int numDraws = group.Value.Count;
             _gl.MultiDrawElementsIndirect(
                 PrimitiveType.Triangles,
@@ -894,7 +902,7 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         }
 
         // WB BaseObjectRenderManager.cs:845-847:
-        shader.SetUniform("uDrawIDOffset", 0);
+        shader.SetInt("uDrawIDOffset", 0);
         _gl.BindBuffer(GLEnum.DrawIndirectBuffer, 0);
     }