feat(backend): introduce session controller and status models

Implement DeviceController and SessionController to bridge QML requests with backend state, supporting playback replay tracking, cluster averaging, and slot error boundaries.

src/pygui/backend/comparison.py

@@ -17,8 +17,14 @@ Returns:
     x = np.array(series_a, dtype=float)
     y = np.array(series_b, dtype=float)
 
-    if x.size == 0 or y.size == 0:
+    # Filter out NaN/Inf values so dtw doesn't choke on them.
-        return {"distance": float('inf'), "index_a": [],"index_b": [], "warping_path": []}
+    mask_x = np.isfinite(x)
+    mask_y = np.isfinite(y)
+    if not mask_x.any() or not mask_y.any():
+        return {"distance": float('inf'), "index_a": [], "index_b": [], "warping_path": []}
+
+    x = x[mask_x]
+    y = y[mask_y]
 
     alignment = dtw(x, y, keep_internals=True)
     return {

src/pygui/backend/controllers/device_controller.py

@@ -58,8 +58,8 @@ class DeviceController(QObject):
         self._data_dir = data_dir
         self._service = DeviceService(settings)
 
-        # Initialize status from persisted settings (with defaults for new installations)
+        # Always start fresh — never restore connection status from a prior session
-        self._connection_status = getattr(settings, 'connection_status', "Disconnected")
+        self._connection_status = "Disconnected"
         self._operation_in_progress = False
         self._activity_log: list[str] = getattr(settings, 'activity_log', [])
         self._raw_bytes: Optional[bytes] = None
@@ -87,6 +87,9 @@ class DeviceController(QObject):
                 self._append_log(f"Last wafer: {info.get('serialNumber', 'Unknown')} ({info.get('familyCode', 'Unknown')})")
             self.statusRestored.emit()
 
+        # Reset connection status on fresh start
+        self._connection_status = "Disconnected"
+
         # Marshal worker-thread results onto the Qt main thread.
         self._detectFinished.connect(self._handle_detect_finished, Qt.ConnectionType.QueuedConnection)
         self._readFinished.connect(self._handle_read_finished, Qt.ConnectionType.QueuedConnection)
@@ -101,6 +104,12 @@ class DeviceController(QObject):
         """Currently available serial port names."""
         return self._service.enumerate_ports()
 
+    def _set_connection_status(self, status: str) -> None:
+        """Update connection status and notify QML."""
+        if self._connection_status != status:
+            self._connection_status = status
+            self.portsUpdated.emit(self.availablePorts)
+
     @Property(str, notify=portsUpdated)
     def connectionStatus(self) -> str:
         """Current connection status string for display."""
@@ -223,7 +232,7 @@ class DeviceController(QObject):
     @slot_error_boundary
     def clearSession(self) -> None:
         """Clear the current session state, allowing a clean detect."""
-        self._connection_status = "Disconnected"
+        self._set_connection_status("Disconnected")
         self._selected_port = ""
         self._last_wafer_info = {}
         self._data_row_count = 0
@@ -235,6 +244,7 @@ class DeviceController(QObject):
         self._append_log("Session refreshed/cleared")
         self._save_status()
 
+
     def _set_operation_progress(self, in_progress: bool) -> None:
         """Set operation progress state and notify QML.
 
@@ -252,7 +262,7 @@ class DeviceController(QObject):
     def refreshPorts(self) -> None:
         """Scan for available serial ports and emit updated list."""
         ports = self._service.enumerate_ports()
-        self._connection_status = "Disconnected"
+        self._set_connection_status("Disconnected")
         self.portsUpdated.emit(ports)
         self._append_log(f"Scanned {len(ports)} serial port(s)")
         self._save_status()
@@ -271,7 +281,7 @@ class DeviceController(QObject):
             return
 
         self._set_operation_progress(True)
-        self._connection_status = "Detecting..."
+        self._set_connection_status("Detecting...")
         self.portsUpdated.emit(self._service.enumerate_ports())
         self._append_log("Scanning all ports for wafer ...")
 
@@ -295,7 +305,7 @@ class DeviceController(QObject):
         """Main-thread completion handler for detectWafer."""
         if info is not None:
             self._selected_port = port or ""
-            self._connection_status = "Connected"
+            self._set_connection_status("Connected")
             self._append_log(
                 f"Detected: {info.serial_number} (family={info.family_code}, "
                 f"port={port}, runtime={info.runtime}s, cycles={info.cycle_count})"
@@ -306,7 +316,7 @@ class DeviceController(QObject):
             self._save_status()
         else:
             self._selected_port = ""
-            self._connection_status = "Disconnected"
+            self._set_connection_status("Disconnected")
             self._append_log("No wafer detected on any port")
             self._last_wafer_info = {}
             self.detectResult.emit(None)
@@ -334,7 +344,7 @@ class DeviceController(QObject):
         family_code = self._last_wafer_info.get("familyCode", "")
 
         self._set_operation_progress(True)
-        self._connection_status = "Reading..."
+        self._set_connection_status("Reading...")
         self.portsUpdated.emit(self._service.enumerate_ports())
         self._append_log(
             f"Reading memory on {port} (family={family_code or 'auto'}) ..."
@@ -362,7 +372,7 @@ class DeviceController(QObject):
     ) -> None:
         """Main-thread completion handler for readMemoryAsync."""
         if data is not None:
-            self._connection_status = "Connected"
+            self._set_connection_status("Connected")
             self._append_log(f"Read {len(data)} bytes")
             self._raw_bytes = data
             self.readResult.emit({"success": True, "bytes": len(data)})
@@ -370,7 +380,7 @@ class DeviceController(QObject):
             self._append_log("Memory read complete - choose save directory to save CSV")
             self._save_status()
             return
-        self._connection_status = "Disconnected"
+        self._set_connection_status("Disconnected")
         self._append_log("Read returned no data")
         self._raw_bytes = None
         self.readResult.emit({"error": "Read returned no data"})
@@ -382,16 +392,16 @@ class DeviceController(QObject):
     def eraseMemory(self, port: str) -> None:
         """Send p1 erase command."""
         self._set_operation_progress(True)
-        self._connection_status = "Erasing..."
+        self._set_connection_status("Erasing...")
         self.portsUpdated.emit(self._service.enumerate_ports())
         self._append_log(f"Erase command sent to {port} (wafer takes ~15s) ...")
 
         ok = self._service.erase_wafer(port)
         if ok:
-            self._connection_status = "Connected"
+            self._set_connection_status("Connected")
             self._append_log("Erase command accepted — wait ~15 seconds")
         else:
-            self._connection_status = "Disconnected"
+            self._set_connection_status("Disconnected")
             self._append_log("Erase command failed")
         self.eraseResult.emit({"success": ok})
         self._set_operation_progress(False)
@@ -404,14 +414,14 @@ class DeviceController(QObject):
         Emits debugResult with counts on success.
         """
         self._set_operation_progress(True)
-        self._connection_status = "Reading debug..."
+        self._set_connection_status("Reading debug...")
         self.portsUpdated.emit(self._service.enumerate_ports())
         self._append_log(f"Reading debug data on {port} ...")
 
         # Step 1: D1 sensor data
         sensor_data = self._service.read_wafer_data(port, family_code="")
         if sensor_data is None:
-            self._connection_status = "Disconnected"
+            self._set_connection_status("Disconnected")
             self._append_log("D1 read failed — aborting debug read")
             self.debugResult.emit({"error": "D1 read failed"})
             self._set_operation_progress(False)
@@ -422,13 +432,13 @@ class DeviceController(QObject):
         # Step 2: F1 debug data
         debug_data = self._service.read_wafer_data(port, family_code="", cmd="F1")
         if debug_data is None:
-            self._connection_status = "Disconnected"
+            self._set_connection_status("Disconnected")
             self._append_log("F1 read failed")
             self.debugResult.emit({"error": "F1 read failed"})
             self._set_operation_progress(False)
             return
 
-        self._connection_status = "Connected"
+        self._set_connection_status("Connected")
         self._append_log(
             f"Debug read complete: {len(sensor_data)} sensor bytes, "
             f"{len(debug_data)} debug bytes"

src/pygui/backend/controllers/session_controller.py

@@ -87,12 +87,7 @@ class SessionController(QObject):
 
     def _load_settings(self, settings: dict) -> None:
         """Restore session state from persisted settings dict."""
-        last_file = settings.get("session_last_file", "")
+        # Do NOT auto-restore the last session file — always start fresh.
-        if last_file:
-            try:
-                self.loadFile(last_file)
-            except Exception:
-                log.warning("Could not restore last session file: %s", last_file)
 
     def collect_settings(self) -> dict:
         """Return a dict of session state to persist."""

src/pygui/backend/models/replay_stats.py

@@ -2,14 +2,14 @@ import numpy as np
 
 
 class ReplayStatsTracker:
-    """Accumulates per-frames statistic acrossa replay session."""
+    """Accumulates per-frame statistics across a replay session."""
 
     def __init__(self) -> None:
         self.history: list[dict] = []
         self.running_avg: float = 0.0
 
     def track(self, frame_index: int, temperatures: list[float]) -> dict:
-        arr = np.array(temperatures, dtype = np.float32)
+        arr = np.array(temperatures, dtype=np.float32)
         clean_arr = arr[np.isfinite(arr)]
 
         if clean_arr.size == 0:
@@ -24,12 +24,11 @@ class ReplayStatsTracker:
             }
 
         self.history.append(stats)
-        if self.history:
         self.running_avg = float(np.mean([s["avg"] for s in self.history]))
         return stats
 
     def get_trend(self) -> list[float]:
-        """Return list of per-frame average for trend chat"""
+        """Return list of per-frame averages for the trend chart."""
         return [s["avg"] for s in self.history]
 
     def reset(self) -> None: