Use one relay listener lane by default

resources/scripts/napseer_mcp_server.py

@@ -2839,9 +2839,9 @@ def gateway_listener_min_lanes():
 
 def gateway_listener_max_lanes():
     try:
-        configured = int(os.environ.get("NAPSEER_GATEWAY_RELAY_LISTENER_MAX_LANES", "3"))
+        configured = int(os.environ.get("NAPSEER_GATEWAY_RELAY_LISTENER_MAX_LANES", "1"))
     except ValueError:
-        configured = 3
+        configured = 1
     return max(gateway_listener_min_lanes(), min(5, configured))
 
 
@@ -4567,6 +4567,11 @@ def handle_gateway_relay_session(connect_request, listener_sock=None):
                         "snapshot_truncated": len(snapshot_data) >= max_snapshot_bytes,
                         "sent_at": iso_now(),
                     })
+            elif gateway_remote_should_run():
+                # An explicitly configured spare lane stays silent while it is
+                # outside the current target. It is not a readiness failure.
+                closed_by_relay_streak = 0
+                failure_streak = 0
             else:
                 for chunk in attach.chunks:
                     send_gateway_payload({

tests/test_gateway_listener_lanes.py

@@ -0,0 +1,30 @@
+import importlib.util
+import pathlib
+
+
+def load_module():
+    script_path = pathlib.Path(__file__).resolve().parents[1] / "resources" / "scripts" / "napseer_mcp_server.py"
+    spec = importlib.util.spec_from_file_location("napseer_gateway_listener_lanes_test", script_path)
+    module = importlib.util.module_from_spec(spec)
+    assert spec and spec.loader
+    spec.loader.exec_module(module)
+    return module
+
+
+def test_gateway_relay_uses_one_listener_lane_by_default(monkeypatch):
+    mod = load_module()
+    monkeypatch.delenv("NAPSEER_GATEWAY_RELAY_LISTENER_MIN_LANES", raising=False)
+    monkeypatch.delenv("NAPSEER_GATEWAY_RELAY_LISTENER_MAX_LANES", raising=False)
+
+    assert mod.gateway_listener_min_lanes() == 1
+    assert mod.gateway_listener_max_lanes() == 1
+    assert mod.gateway_listener_target_lanes() == 1
+    assert mod.gateway_listener_lane_ids() == ["lane-1"]
+
+
+def test_gateway_relay_extra_lanes_require_explicit_configuration(monkeypatch):
+    mod = load_module()
+    monkeypatch.setenv("NAPSEER_GATEWAY_RELAY_LISTENER_MIN_LANES", "1")
+    monkeypatch.setenv("NAPSEER_GATEWAY_RELAY_LISTENER_MAX_LANES", "3")
+
+    assert mod.gateway_listener_lane_ids() == ["lane-1", "lane-2", "lane-3"]