fix: skip courtyard overlap check for different layers

lib/check-courtyard-overlap/checkCourtyardOverlap.ts

@@ -118,6 +118,10 @@ export function checkCourtyardOverlap(
       let overlapping = false
       outer: for (const a of byComponent.get(idA)!) {
         for (const b of byComponent.get(idB)!) {
+          // Skip overlap check if courtyards are on different layers
+          if ("layer" in a && "layer" in b && a.layer !== b.layer) {
+            continue
+          }
           const polyA = getCourtyardPolygon(a)
           const polyB = getCourtyardPolygon(b)
           if (polygonsOverlap(polyA, polyB)) {

tests/lib/check-pcb-component-overlap/courtyard-different-layers-no-overlap.test.tsx

@@ -0,0 +1,126 @@
+import { expect, test } from "bun:test"
+import { checkCourtyardOverlap } from "lib/check-courtyard-overlap/checkCourtyardOverlap"
+
+/**
+ * Two components at the same position but on different layers (top vs bottom)
+ * should NOT produce a courtyard overlap error.
+ *
+ * Regression test for: https://github.com/tscircuit/core/issues/2084
+ */
+
+test("courtyards on different layers should not produce overlap error", () => {
+  const circuitJson: any[] = [
+    {
+      type: "pcb_component",
+      pcb_component_id: "comp1",
+      source_component_id: "src1",
+      center: { x: 0, y: 0 },
+      layer: "top",
+      rotation: 0,
+      width: 4,
+      height: 2,
+    },
+    {
+      type: "source_component",
+      source_component_id: "src1",
+      name: "R1",
+      ftype: "simple_resistor",
+    },
+    {
+      type: "pcb_courtyard_rect",
+      pcb_courtyard_rect_id: "cy1",
+      pcb_component_id: "comp1",
+      center: { x: 0, y: 0 },
+      width: 4,
+      height: 2,
+      layer: "top",
+    },
+    {
+      type: "pcb_component",
+      pcb_component_id: "comp2",
+      source_component_id: "src2",
+      center: { x: 0, y: 0 },
+      layer: "bottom",
+      rotation: 0,
+      width: 4,
+      height: 2,
+    },
+    {
+      type: "source_component",
+      source_component_id: "src2",
+      name: "R2",
+      ftype: "simple_resistor",
+    },
+    {
+      type: "pcb_courtyard_rect",
+      pcb_courtyard_rect_id: "cy2",
+      pcb_component_id: "comp2",
+      center: { x: 0, y: 0 },
+      width: 4,
+      height: 2,
+      layer: "bottom",
+    },
+  ]
+
+  const errors = checkCourtyardOverlap(circuitJson)
+  expect(errors).toHaveLength(0)
+})
+
+test("courtyards on same layer should still produce overlap error", () => {
+  const circuitJson: any[] = [
+    {
+      type: "pcb_component",
+      pcb_component_id: "comp1",
+      source_component_id: "src1",
+      center: { x: 0, y: 0 },
+      layer: "top",
+      rotation: 0,
+      width: 4,
+      height: 2,
+    },
+    {
+      type: "source_component",
+      source_component_id: "src1",
+      name: "R1",
+      ftype: "simple_resistor",
+    },
+    {
+      type: "pcb_courtyard_rect",
+      pcb_courtyard_rect_id: "cy1",
+      pcb_component_id: "comp1",
+      center: { x: 0, y: 0 },
+      width: 4,
+      height: 2,
+      layer: "top",
+    },
+    {
+      type: "pcb_component",
+      pcb_component_id: "comp2",
+      source_component_id: "src2",
+      center: { x: 1, y: 0 },
+      layer: "top",
+      rotation: 0,
+      width: 4,
+      height: 2,
+    },
+    {
+      type: "source_component",
+      source_component_id: "src2",
+      name: "R2",
+      ftype: "simple_resistor",
+    },
+    {
+      type: "pcb_courtyard_rect",
+      pcb_courtyard_rect_id: "cy2",
+      pcb_component_id: "comp2",
+      center: { x: 1, y: 0 },
+      width: 4,
+      height: 2,
+      layer: "top",
+    },
+  ]
+
+  const errors = checkCourtyardOverlap(circuitJson)
+  expect(errors).toHaveLength(1)
+  expect(errors[0].type).toBe("pcb_courtyard_overlap_error")
+})