diff --git a/src/AcDream.App/Rendering/Shaders/terrain_modern.vert b/src/AcDream.App/Rendering/Shaders/terrain_modern.vert
index 473cba5..9427a55 100644
--- a/src/AcDream.App/Rendering/Shaders/terrain_modern.vert
+++ b/src/AcDream.App/Rendering/Shaders/terrain_modern.vert
@@ -136,5 +136,12 @@ void main() {
     vRoad0    = unpackOverlayLayer(aPacked2.x, aPacked2.y, rotRd0,  baseUV);
     vRoad1    = unpackOverlayLayer(aPacked2.z, aPacked2.w, rotRd1,  baseUV);
 
-    gl_Position = uProjection * uView * vec4(aPos, 1.0);
+    // Retail zFightTerrainAdjust (acclient_2013_pseudo_c.txt:1120769 = 0.00999999978,
+    // applied per terrain vertex inside ACRender::landPolysDraw at line 702254,
+    // address 006b6402). Render terrain 1 cm below its physical Z so coplanar
+    // building floors win the depth test. Physics path is unaffected — it reads
+    // the un-nudged heightmap via TerrainSurface.SampleZ.
+    // Closes issue #100; supersedes the hiddenTerrainCells cell-collapse hack.
+    vec3 terrainPos = vec3(aPos.xy, aPos.z - 0.01);
+    gl_Position = uProjection * uView * vec4(terrainPos, 1.0);
 }