diff --git a/src/Mod/FreeCADExchange/AutoRouting.py b/src/Mod/FreeCADExchange/AutoRouting.py
index 144a272..e259a9a 100644
--- a/src/Mod/FreeCADExchange/AutoRouting.py
+++ b/src/Mod/FreeCADExchange/AutoRouting.py
@@ -1098,6 +1098,18 @@ def _wire_item_value(item, *names):
     return ""
 
 
+def _route_lane_key(start_uuid, end_uuid):
+    endpoints = sorted(
+        value
+        for value in (
+            str(start_uuid or "").strip(),
+            str(end_uuid or "").strip(),
+        )
+        if value
+    )
+    return tuple(endpoints)
+
+
 def bind_wire_task_terminals_from_payload(doc, payload):
     """Bind local template terminals to QET terminal UUIDs without creating wires."""
     if doc is None:
@@ -1175,8 +1187,9 @@ def route_eplan_connections_from_payload(doc, payload, options=None, prepared_la
     if isinstance(prepared_layout, dict):
         report["prepared_layout"] = prepared_layout
     missing_endpoint_uuids = set()
+    lane_indexes_by_pair = {}
 
-    for index, item in enumerate(wires):
+    for item in wires:
         if not isinstance(item, dict):
             report["skipped_invalid"] += 1
             continue
@@ -1206,12 +1219,14 @@ def route_eplan_connections_from_payload(doc, payload, options=None, prepared_la
                     }
                 )
             continue
+        lane_key = _route_lane_key(start_uuid, end_uuid)
+        route_lane_index = lane_indexes_by_pair.get(lane_key, 0)
         try:
             result = route_eplan_connection_between_terminals(
                 doc,
                 start_terminal,
                 end_terminal,
-                route_index=index,
+                route_index=route_lane_index,
                 options=options,
                 wire_uuid=_wire_item_value(item, "wire_id", "wire_uuid", "id"),
                 wire_label=_wire_item_value(item, "wire_label", "wire_mark"),
@@ -1224,6 +1239,7 @@ def route_eplan_connections_from_payload(doc, payload, options=None, prepared_la
         except Exception as exc:
             report["errors"].append(str(exc))
             continue
+        lane_indexes_by_pair[lane_key] = route_lane_index + 1
         if result["route_status"] == "CollisionWarning":
             report["collision_warnings"] += 1
         route_collision_samples = []
diff --git a/tests/python/freecad_exchange_auto_routing_test.py b/tests/python/freecad_exchange_auto_routing_test.py
index f57050c..7648c1f 100644
--- a/tests/python/freecad_exchange_auto_routing_test.py
+++ b/tests/python/freecad_exchange_auto_routing_test.py
@@ -1241,6 +1241,59 @@ class AutoRoutingTest(unittest.TestCase):
         self.assertEqual(1, route["network"]["carriers"])
         self.assertEqual("WireDuct", route["route_track"]["segments"][0]["carrier"]["kind"])
 
+    def test_route_eplan_connections_lane_index_is_per_terminal_pair(self):
+        _install_fake_freecad()
+        terminal_objects, _wiring_objects, routing_network, auto_routing = _reload_modules()
+        app = sys.modules["FreeCAD"]
+        doc = FakeDocument()
+        terminal_objects.ensure_root_group(doc, "project-1")
+        _terminal(doc, terminal_objects, "TerminalStartA", "terminal-start-a", app.Vector(0, 0, 0))
+        _terminal(doc, terminal_objects, "TerminalEndA", "terminal-end-a", app.Vector(100, 0, 0))
+        _terminal(doc, terminal_objects, "TerminalStartB", "terminal-start-b", app.Vector(0, 100, 0))
+        _terminal(doc, terminal_objects, "TerminalEndB", "terminal-end-b", app.Vector(100, 100, 0))
+        routing_network.create_route_carrier(
+            doc,
+            [app.Vector(0, 0, 20), app.Vector(100, 0, 20)],
+            project_uuid="project-1",
+            kind="WireDuct",
+        )
+        routing_network.create_route_carrier(
+            doc,
+            [app.Vector(0, 100, 20), app.Vector(100, 100, 20)],
+            project_uuid="project-1",
+            kind="WireDuct",
+        )
+        payload = {
+            "project_uuid": "project-1",
+            "wires": [
+                {
+                    "wire_id": "wire-a",
+                    "start_terminal_uuid": "terminal-start-a",
+                    "end_terminal_uuid": "terminal-end-a",
+                },
+                {
+                    "wire_id": "wire-b",
+                    "start_terminal_uuid": "terminal-start-b",
+                    "end_terminal_uuid": "terminal-end-b",
+                },
+                {
+                    "wire_id": "wire-a-repeat",
+                    "start_terminal_uuid": "terminal-start-a",
+                    "end_terminal_uuid": "terminal-end-a",
+                },
+            ],
+        }
+
+        report = auto_routing.route_eplan_connections_from_payload(
+            doc,
+            payload,
+            options={"lane_spacing": 10.0, "lane_axis": "y"},
+        )
+
+        self.assertEqual(0, report["routes"][0]["lane"]["index"])
+        self.assertEqual(0, report["routes"][1]["lane"]["index"])
+        self.assertEqual(1, report["routes"][2]["lane"]["index"])
+
     def test_route_eplan_connections_report_includes_collision_samples(self):
         _install_fake_freecad()
         terminal_objects, _wiring_objects, routing_network, auto_routing = _reload_modules()