fiix adjacent walls pushed up

packages/core/src/hooks/spatial-grid/spatial-grid-manager.ts

@@ -183,11 +183,24 @@ export function wallOverlapsPolygon(
   end: [number, number],
   polygon: Array<[number, number]>,
 ): boolean {
-  const startInside = pointInPolygon(start[0], start[1], polygon)
+  const dx = end[0] - start[0]
-  const endInside = pointInPolygon(end[0], end[1], polygon)
+  const dz = end[1] - start[1]
+  const len = Math.sqrt(dx * dx + dz * dz)
 
-  // At least one endpoint strictly inside the polygon
+  // Nudge endpoint test points a tiny step inward along the wall direction before
-  if (startInside || endInside) return true
+  // testing containment. pointInPolygon (ray casting) produces false positives for
+  // points exactly on polygon vertices or edges — specifically the minimum-z corner
+  // of an axis-aligned polygon returns "inside" because the ray hits the opposite
+  // vertical edge exactly at its base. Nudging by 1e-6 m avoids this: a wall that
+  // merely starts at a slab corner and extends outward will have its nudged point
+  // clearly outside, while a wall that genuinely starts inside stays inside.
+  if (len > 1e-10) {
+    const step = Math.min(1e-6, len * 0.01)
+    const nx = (dx / len) * step
+    const nz = (dz / len) * step
+    if (pointInPolygon(start[0] + nx, start[1] + nz, polygon)) return true
+    if (pointInPolygon(end[0] - nx, end[1] - nz, polygon)) return true
+  }
 
   // Check if midpoint is inside (catches walls crossing through)
   const midX = (start[0] + end[0]) / 2