some fixes again

python_app/gui/app_window.py

@@ -140,8 +140,17 @@ class AppWindow(
         try:
             value = int(raw)
         except ValueError:
-            return 50
-        return value if value >= 1 else 50
+            value = 0
+        if value >= 1:
+            return value
+        # A non-empty but invalid value is an operator mistake — say so instead of
+        # silently swallowing it (stderr is captured by journald in headless mode).
+        print(
+            f"[radar] Ignoring invalid RADAR_SYSTEM_METRICS_REPORT_EVERY={raw!r}; using default 50.",
+            file=sys.stderr,
+            flush=True,
+        )
+        return 50
 
     def _init_config_profile_state(self) -> None:
         """Resolve startup profile path, load active profile, and queue fallback notices."""

python_app/gui/controllers/app_window_config/state_builders.py

@@ -453,6 +453,7 @@ class AppWindowConfigStateBuildersMixin:
             config.gpr,
             input_switch_positions=config.input_switch.positions,
             output_switch_positions=config.output_switch.positions,
+            sweep=config.radar.sweep,
         )
         return config
 

python_app/gui/controllers/app_window_control_button_mixin.py

@@ -72,17 +72,11 @@ class AppWindowControlButtonMixin:
         Delivered as a queued signal from the watcher thread, so this executes
         on the GUI thread exactly like a click on "Capture Tmp Reference".
         """
-        # Ignore a re-entrant press: the capture flow spins the event loop (stop/
-        # start run, dialogs), so a second queued press must not start a nested capture.
-        if self._control_button_busy:
-            self._log("GPIO control button press ignored: capture already in progress.")
-            return
-        self._control_button_busy = True
-        try:
-            self._log("GPIO control button pressed: capturing tmp reference.")
-            self._capture_tmp_reference()
-        finally:
-            self._control_button_busy = False
+        # The shared re-entrancy guard lives in _capture_tmp_reference, so this GPIO
+        # trigger and the GUI "Capture Tmp Reference" button are protected by one
+        # mechanism (a press during an in-progress capture is ignored there).
+        self._log("GPIO control button pressed: capturing tmp reference.")
+        self._capture_tmp_reference()
 
     def _on_control_button_failed(self, message: str) -> None:
         """Log an unrecoverable watcher error reported from the background thread."""

python_app/gui/controllers/app_window_pipeline_mixin.py

@@ -469,8 +469,8 @@ class AppWindowPipelineMixin:
             if collection is None:
                 break
             self._pipeline_metrics.record("processing", int(collection.processing_duration_ns))
-            if record_result_history(self._result_history, collection):
-                latest = collection
+            record_result_history(self._result_history, collection)
+            latest = collection
         return latest
 
     def _pump_events_during_drain(self, pause_s: float) -> None:

python_app/gui/controllers/app_window_plot/trace_plot_mixin.py

@@ -43,7 +43,9 @@ class AppWindowTracePlotMixin:
                 details=f"{exc}\nExpected format: input:output,input:output",
                 once_key=f"pass_through_combo_filter_invalid_{text}",
             )
-            return set()
+            # Fail open: an unparseable filter is ignored (all traces stay visible),
+            # not turned into an empty allow-set that silently hides every trace.
+            return None
 
     def _configure_pass_through_magnitude_axis(self, plot: pg.PlotWidget) -> None:
         """Apply pass-through magnitude-axis autorange or fixed Y window."""

python_app/gui/controllers/app_window_preprocess_mixin.py

@@ -117,6 +117,13 @@ class AppWindowPreprocessMixin:
                 details=self._capture_state_details(),
             )
             return
+        # One shared re-entrancy guard for BOTH the GUI button and the GPIO trigger:
+        # this capture spins the Qt event loop (stop/start run, dialogs), so a second
+        # request from either source must not start a nested capture.
+        if self._control_button_busy:
+            self._log("Tmp reference capture already in progress; ignoring duplicate request.")
+            return
+        self._control_button_busy = True
 
         pipeline_was_running = self._supervisor.is_running()
         pipeline_was_paused = False
@@ -178,6 +185,7 @@ class AppWindowPreprocessMixin:
         finally:
             if pipeline_was_paused:
                 self._start_run()
+            self._control_button_busy = False
 
     def _ensure_preprocess_dialog(self) -> PreprocessDialog:
         """Create preprocessing dialog lazily and wire its signals once."""

python_app/gui/controllers/app_window_ui_mixin.py

@@ -160,7 +160,7 @@ class AppWindowUiMixin:
 
         self._status_label = QLabel("Status: idle", self._settings_panel)
         self._status_label.setObjectName("statusLabel")
-        self._status_label.hide()
+        right_layout.addWidget(self._status_label)
 
         self._history_label = QLabel("History: raw=0, preprocessed=0, results=0", self._settings_panel)
         self._history_label.setObjectName("hintLabel")

python_app/gui/controllers/sections/data_actions_section.py

@@ -25,7 +25,10 @@ def build_data_actions_group(owner) -> QGroupBox:
     save_button = QPushButton("Save Dataset")
     save_button.clicked.connect(owner._save_snapshot)
     save_button.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Fixed)
-    save_vna_json_button = QPushButton("Save JSON")
+    save_vna_json_button = QPushButton("Save S21 JSON")
+    save_vna_json_button.setToolTip(
+        "Export one S21 VNA-history JSON per combo from the preprocessed stage (S11 is not included)."
+    )
     save_vna_json_button.clicked.connect(owner._save_vna_history_json)
     save_vna_json_button.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Fixed)
     remove_last_button = QPushButton("Remove Last Measurement")

python_app/gui/runtime/history.py

@@ -15,8 +15,8 @@ THistoryCollection = TypeVar("THistoryCollection", SweepCollection, ResultCollec
 def record_result_history(
     result_history: deque[ResultCollection],
     collection: ResultCollection,
-) -> bool:
-    """Append new result or replace existing entry by stable collection key."""
+) -> None:
+    """Append a new result, or replace the existing entry with the same stable key."""
     for index in range(len(result_history) - 1, -1, -1):
         existing = result_history[index]
         if (
@@ -24,10 +24,9 @@ def record_result_history(
             and existing.monotonic_ns == collection.monotonic_ns
         ):
             result_history[index] = collection
-            return True
+            return
 
     result_history.append(collection)
-    return True
 
 
 def remove_last_aligned_histories(