working version

python_app/hardware_full/librevna_multi_device_driver/controller.py

@@ -93,6 +93,14 @@ class MultiDeviceVnaController:
         if not self._reference_configuration_applied:
             self._configure_reference_clocks()
 
+        # Even when the device-side configuration matches and we skip reconfiguration,
+        # the host-side packet queue has been accumulating datapoints from cycles that
+        # ran between calls. Draining here guarantees the next collect_running_sweep_cycles
+        # returns a freshly-arriving cycle (the cycle tracker waits for point_index==0).
+        # Without this drain, callers would receive whichever stale cycle happened to be
+        # at the head of the queue — e.g. data from before a manual cable swap.
+        self._drain_all_received_packets()
+
         if (
             self._sweep_is_running
             and self._last_applied_sweep_configuration == sweep_configuration
@@ -104,7 +112,6 @@ class MultiDeviceVnaController:
             self._send_idle_to_all_devices()
             time.sleep(self._reconfigure_delay_s)
 
-        self._drain_all_received_packets()
         self._configure_sweep_on_all_devices(
             sweep_configuration,
             master_stimulus_ports=stimulus_ports,