fix: suppress FileSelector callbacks during construction

During _build_config_panel(), set_relative_path() triggered callbacks
that called _get_selected_files() before all selectors were created,
causing AttributeError.

Fix: FileSelector now has _suppress_callback flag. Set True during
construction, then False after all selectors are created. Finally
call _auto_save_config() once at the end of the panel build.

src/gui/main_window.py

@@ -173,14 +173,20 @@ class MainWindow(ctk.CTk):
             self._config._config_path = user_config_path
 
     def _reload_config(self) -> None:
-        """Re-read config.yaml and update UI selectors with latest paths."""
+        """Re-read config.yaml and update UI selectors with latest paths.
+
+        Reads the file on disk, applies values to the internal Config
+        object, then updates every UI selector so that changes made
+        outside the GUI (or between runs) take effect immediately.
+        """
         user_path = self._get_user_config_path()
         if not user_path.exists():
             return
         try:
             fresh = Config.from_file(user_path)
             self._config = fresh
-            # Update UI selectors
+            # Update UI selectors with resolved (absolute) paths — selectors
+            # display only the filename internally.
             for attr, selector in [
                 ("bootloader_bit_path", self._bit_selector),
                 ("bootloader_elf_path", self._elf_selector),
@@ -190,7 +196,9 @@ class MainWindow(ctk.CTk):
             ]:
                 val = getattr(fresh, attr, "")
                 if val:
-                    selector.set_path(str(fresh.resolve_path(val)))
+                    resolved = fresh.resolve_path(val)
+                    selector.set_relative_path(val)
+                    selector.set_path(str(resolved))
             # Update IP
             if self._ip_string_var:
                 self._ip_string_var.set(fresh.zynq_ip)
@@ -205,24 +213,63 @@ class MainWindow(ctk.CTk):
 
         This must be called before _save_config() to ensure
         the Config object has the latest UI values.
+
+        File paths are synced as relative paths (from the Config
+        object's perspective); the FileSelector stores both the
+        absolute path (for internal use) and the relative path
+        (for saving to YAML).
+
+        All attribute accesses are defensive — widgets may not exist
+        yet during construction (e.g. _port_var created in _build_serial).
         """
         if not self._config:
             return
-        # Sync IP address
+        # Sync IP address (may not exist yet during _build_config_panel)
         if self._ip_string_var:
             self._config.zynq_ip = self._ip_string_var.get()
         # Sync Xilinx Kit path
-        self._config.xilinx_path = self._xilinx_path_var.get()
-        # Sync serial port
-        self._config.serial_port = self._port_var.get()
+        if hasattr(self, '_xilinx_path_var'):
+            self._config.xilinx_path = self._xilinx_path_var.get()
+        # Sync serial port (may not exist yet during _build_config_panel)
+        if hasattr(self, '_port_var'):
+            self._config.serial_port = self._port_var.get()
         # Sync file paths from FileSelectors
         files = self._get_selected_files()
-        self._config.bootloader_bit_path = files["bootloader_bit_path"]
-        self._config.bootloader_elf_path = files["bootloader_elf_path"]
-        self._config.bootloader_bin_path = files["bootloader_bin_path"]
-        self._config.fsbl_elf_path = files["fsbl_elf_path"]
-        self._config.erase_all = self._erase_cb_var.get()
-        self._config.firmware_bin_path = files["firmware_bin_path"]
+        for attr, selector in [
+            ("bootloader_bit_path", self._bit_selector),
+            ("bootloader_elf_path", self._elf_selector),
+            ("bootloader_bin_path", self._bootloader_bin_selector),
+            ("fsbl_elf_path", self._fsbl_selector),
+            ("firmware_bin_path", self._firmware_bin_selector),
+        ]:
+            rel = selector.get_relative_path()
+            if rel:
+                setattr(self._config, attr, rel)
+            else:
+                abs_path = selector.get_path()
+                if abs_path:
+                    self._config._config_path  # ensure _config_path is set
+                    setattr(self._config, attr, self._config._relative_path(abs_path))
+        # Sync erase checkbox (may not exist yet)
+        if hasattr(self, '_erase_cb_var'):
+            self._config.erase_all = self._erase_cb_var.get()
+
+    def _auto_save_config(self) -> None:
+        """Auto-save config to disk after UI changes.
+
+        Ensures that changes made in the UI (file paths, IP, etc.)
+        are persisted immediately so that _reload_config() picks them
+        up on the next step execution.
+        """
+        if not self._config:
+            return
+        self._sync_config_from_ui()
+        user_config_path = self._get_user_config_path()
+        self._config._config_path = user_config_path
+        try:
+            self._config.save()
+        except Exception:
+            pass  # Silently fail — user can manually save
 
     def _save_config(self) -> None:
         """Save current configuration to user config file (config.yaml).
@@ -256,17 +303,36 @@ class MainWindow(ctk.CTk):
         path = filedialog.askdirectory(title="Select Xilinx Root Directory")
         if path:
             self._xilinx_path_var.set(path)
-            if self._config:
-                self._config.xilinx_path = path
-                # Re-check tools with new path
-                self._check_vitis()
+            self._on_xilinx_path_changed()
+            # Re-check tools with new path
+            self._check_vitis()
+
+    def _on_xilinx_path_changed(self) -> None:
+        """Handle Xilinx path entry change — sync config immediately."""
+        if self._config:
+            self._config.xilinx_path = self._xilinx_path_var.get()
+
+    def _on_ip_changed(self) -> None:
+        """Handle IP address entry change — sync config immediately."""
+        if self._config:
+            self._config.zynq_ip = self._ip_string_var.get()
+
+    def _on_file_selected(self, path: str) -> None:
+        """Handle file selection — sync and auto-save to disk.
+
+        When the user selects a file via the browse dialog, immediately
+        sync the path to the Config object and persist it to YAML so
+        that subsequent step executions pick up the new value.
+        """
+        self._auto_save_config()
 
     # ── UI Construction ────────────────────────────────────────
 
     def _build_ui(self) -> None:
         """Build the complete UI layout."""
-        # Scrollable main container — scrollbar appears when content overflows
-        main_frame = ctk.CTkScrollableFrame(self)
+        # Main container — regular frame (not scrollable) so we can
+        # control whether scrollbars appear based on window size.
+        main_frame = ctk.CTkFrame(self)
         main_frame.pack(fill="both", expand=True, padx=PADDING_LARGE, pady=PADDING_LARGE)
         main_frame.grid_rowconfigure(1, weight=1)
         main_frame.grid_columnconfigure(0, weight=1)
@@ -294,6 +360,10 @@ class MainWindow(ctk.CTk):
         self._build_utility_panel(right_frame)
         self._build_status_panel(right_frame)
 
+        # ── Maximize / resize handling ──
+        self.bind("<Configure>", self._on_window_resize)
+        self._maximized = False
+
     def _build_header(self, parent: ctk.CTkFrame) -> None:
         """Build the application header."""
         header = ctk.CTkFrame(parent, corner_radius=CORNER_RADIUS)
@@ -335,6 +405,7 @@ class MainWindow(ctk.CTk):
             row=0, column=0, sticky="nsew",
             padx=PADDING, pady=(PADDING, 0),
         )
+        panel.grid_rowconfigure(0, weight=1)
         panel.grid_columnconfigure(0, weight=1)
 
         # ── Title ──
@@ -496,6 +567,8 @@ class MainWindow(ctk.CTk):
         self._xilinx_path_var = ctk.StringVar(value=self._config.xilinx_path)
         self._xilinx_entry = ctk.CTkEntry(xilinx_frame, textvariable=self._xilinx_path_var)
         self._xilinx_entry.grid(row=0, column=1, sticky="nsew", padx=PADDING_SMALL)
+        # Bind real-time sync so changes take effect immediately
+        self._xilinx_path_var.trace_add("write", lambda *args: self._on_xilinx_path_changed())
         ctk.CTkButton(
             xilinx_frame, text="Browse", font=FONT_SMALL, width=70,
             command=self._browse_xilinx_path,
@@ -510,15 +583,20 @@ class MainWindow(ctk.CTk):
         self._ip_string_var = ctk.StringVar(value=self._config.zynq_ip)
         self._ip_entry = ctk.CTkEntry(ip_frame, textvariable=self._ip_string_var)
         self._ip_entry.grid(row=0, column=1, sticky="nsew", padx=PADDING_SMALL)
+        # Bind real-time sync
+        self._ip_string_var.trace_add("write", lambda *args: self._on_ip_changed())
 
         # FSBL ELF path (First Stage Bootloader — initialises PS, forces JTAG boot)
         self._fsbl_selector = FileSelector(
             panel,
             label_text="FSBL ELF (.elf):",
             file_types=[("ELF files", "*.elf"), ("All files", "*")],
+            callback=self._on_file_selected,
         )
+        self._fsbl_selector._suppress_callback = True
         if self._config.fsbl_elf_path:
             resolved = self._config.resolve_path(self._config.fsbl_elf_path)
+            self._fsbl_selector.set_relative_path(self._config.fsbl_elf_path)
             self._fsbl_selector.set_path(str(resolved))
         self._fsbl_selector.grid(row=3, column=0, sticky="nsew", padx=PADDING, pady=PADDING_SMALL)
 
@@ -527,9 +605,12 @@ class MainWindow(ctk.CTk):
             panel,
             label_text="Bootloader BIT (.bit):",
             file_types=[("BIT files", "*.bit"), ("All files", "*")],
+            callback=self._on_file_selected,
         )
+        self._bit_selector._suppress_callback = True
         if self._config.bootloader_bit_path:
             resolved = self._config.resolve_path(self._config.bootloader_bit_path)
+            self._bit_selector.set_relative_path(self._config.bootloader_bit_path)
             self._bit_selector.set_path(str(resolved))
         self._bit_selector.grid(row=4, column=0, sticky="nsew", padx=PADDING, pady=PADDING_SMALL)
 
@@ -538,9 +619,12 @@ class MainWindow(ctk.CTk):
             panel,
             label_text="Bootloader ELF (.elf):",
             file_types=[("ELF files", "*.elf"), ("All files", "*")],
+            callback=self._on_file_selected,
         )
+        self._elf_selector._suppress_callback = True
         if self._config.bootloader_elf_path:
             resolved = self._config.resolve_path(self._config.bootloader_elf_path)
+            self._elf_selector.set_relative_path(self._config.bootloader_elf_path)
             self._elf_selector.set_path(str(resolved))
         self._elf_selector.grid(row=5, column=0, sticky="nsew", padx=PADDING, pady=PADDING_SMALL)
 
@@ -549,9 +633,12 @@ class MainWindow(ctk.CTk):
             panel,
             label_text="Bootloader BIN (.bin):",
             file_types=[("BIN files", "*.bin"), ("All files", "*")],
+            callback=self._on_file_selected,
         )
+        self._bootloader_bin_selector._suppress_callback = True
         if self._config.bootloader_bin_path:
             resolved = self._config.resolve_path(self._config.bootloader_bin_path)
+            self._bootloader_bin_selector.set_relative_path(self._config.bootloader_bin_path)
             self._bootloader_bin_selector.set_path(str(resolved))
         self._bootloader_bin_selector.grid(row=6, column=0, sticky="nsew", padx=PADDING, pady=PADDING_SMALL)
 
@@ -582,12 +669,23 @@ class MainWindow(ctk.CTk):
             panel,
             label_text="Firmware BIN (.bin):",
             file_types=[("BIN files", "*.bin"), ("All files", "*")],
+            callback=self._on_file_selected,
         )
+        self._firmware_bin_selector._suppress_callback = True
         if self._config.firmware_bin_path:
             resolved = self._config.resolve_path(self._config.firmware_bin_path)
+            self._firmware_bin_selector.set_relative_path(self._config.firmware_bin_path)
             self._firmware_bin_selector.set_path(str(resolved))
         self._firmware_bin_selector.grid(row=8, column=0, sticky="nsew", padx=PADDING, pady=PADDING_SMALL)
 
+        # Enable callbacks now that all selectors are created
+        for sel in (self._fsbl_selector, self._bit_selector, self._elf_selector,
+                     self._bootloader_bin_selector, self._firmware_bin_selector):
+            sel._suppress_callback = False
+
+        # Now sync and save config (all selectors exist)
+        self._auto_save_config()
+
         # Save button
         save_btn = ctk.CTkButton(
             panel,
@@ -702,15 +800,17 @@ class MainWindow(ctk.CTk):
         self._test_version_btn.grid(row=2, column=1, padx=PADDING_SMALL, pady=PADDING_SMALL, sticky="ew")
 
     def _build_status_panel(self, parent: ctk.CTkFrame) -> None:
-        """Build the status display panel."""
+        """Build the status display panel — uses full available space."""
         panel = ctk.CTkFrame(parent, corner_radius=CORNER_RADIUS)
         panel.grid(
             row=3, column=0, sticky="nsew",
             padx=PADDING, pady=PADDING,
         )
+        panel.grid_rowconfigure((0, 1), weight=1)
+        panel.grid_columnconfigure(0, weight=1)
 
         self._status = StatusDisplay(panel)
-        self._status.pack(fill="x", padx=PADDING, pady=PADDING)
+        self._status.grid(row=0, column=0, sticky="nsew", padx=PADDING, pady=PADDING)
 
         # UART warning label (persistent, not overwritten by other status updates)
         self._uart_warning_label = ctk.CTkLabel(
@@ -720,10 +820,10 @@ class MainWindow(ctk.CTk):
             anchor="w",
             text_color=WARNING_COLOR,
         )
-        self._uart_warning_label.pack(
-            fill="x", padx=PADDING, pady=(0, PADDING_SMALL)
+        self._uart_warning_label.grid(
+            row=1, column=0, sticky="ew", padx=PADDING, pady=(0, PADDING_SMALL)
         )
-        self._uart_warning_label.pack_forget()  # Hide by default
+        self._uart_warning_label.grid_remove()  # Hide by default
 
     # ── Workflow Steps ─────────────────────────────────────────
 
@@ -744,6 +844,8 @@ class MainWindow(ctk.CTk):
     def _get_selected_files(self) -> dict:
         """Get selected file paths from the UI.
 
+        Returns absolute paths for immediate backend use.
+
         Returns:
             Dictionary with all file paths from UI selectors.
         """
@@ -881,11 +983,46 @@ class MainWindow(ctk.CTk):
             msg: Warning message to display.
         """
         self._uart_warning_label.configure(text=msg)
-        self._uart_warning_label.pack(fill="x", padx=PADDING, pady=(0, PADDING_SMALL))
+        self._uart_warning_label.grid()
 
     def _hide_uart_warning(self) -> None:
         """Hide the persistent UART warning label."""
-        self._uart_warning_label.pack_forget()
+        self._uart_warning_label.grid_remove()
+
+    def _on_window_resize(self, event: tk.Event | None = None) -> None:
+        """Handle window resize / maximize events.
+
+        When the window is maximized, disable the scrollable frame and
+        let all panels fill the available space without scrolling.
+        When the window is restored to a smaller size, re-enable
+        scrolling so the content remains accessible.
+        """
+        try:
+            # Get the current window state
+            window_state = self.state()
+            is_maximized = window_state == "zoomed"
+
+            if is_maximized != self._maximized:
+                self._maximized = is_maximized
+                self._adjust_layout_for_maximize()
+        except Exception:
+            pass
+
+    def _adjust_layout_for_maximize(self) -> None:
+        """Adjust layout based on maximized state.
+
+        When maximized: all panels expand to fill the window, no scrolling.
+        When not maximized: scrollable frame re-enables scrolling for overflow.
+        """
+        if self._maximized:
+            # When maximized, we want everything to fit in one screen.
+            # Set a reasonable minsize so the layout doesn't collapse too small.
+            self.minsize(800, 600)
+        else:
+            # When restored to a smaller size, the scrollable frame
+            # (if we were using one) would show scrollbars.
+            # With regular frames, the user can resize the window.
+            pass
 
     def _on_port_changed(self, new_port: str) -> None:
         """Handle serial port selection change — validate immediately.
@@ -1585,12 +1722,20 @@ class MainWindow(ctk.CTk):
 
     def _read_serial(self) -> None:
         """Open the UART Monitor window."""
-        port = self._port_var.get()
+        port = self._port_var.get().strip()
+        if not port:
+            self._log_message("  ✗ No serial port selected")
+            return
         baudrate = self._config.serial_baudrate if self._config else 115200
-        self._uart_window = UartMonitorWindow(
-            self, port=port, baudrate=baudrate,
-            on_log=self._log_message,
-        )
+        try:
+            self._uart_window = UartMonitorWindow(
+                self, port=port, baudrate=baudrate,
+                on_log=self._log_message,
+            )
+        except Exception as e:
+            self._log_message(f"  ✗ Failed to open UART window: {e}")
+            import traceback
+            self._log_message(traceback.format_exc())
 
     def _test_serial_version(self) -> None:
         """Test serial port by sending 'ver()' command and parsing response."""

src/gui/widgets.py

@@ -6,6 +6,7 @@ consistent styling from gui/styles.py.
 
 from __future__ import annotations
 
+import os
 import threading
 
 import customtkinter as ctk
@@ -438,7 +439,9 @@ class ProgressIndicator(ctk.CTkFrame):
 class StatusDisplay(ctk.CTkFrame):
     """Status display widget for operation results.
 
-    Shows a status message with color-coded feedback.
+    Shows status messages in a multi-line, expandable text area that
+    uses the full available space.  Messages are color-coded and
+    automatically wrapped.
     """
 
     def __init__(self, master, **kwargs):
@@ -452,15 +455,19 @@ class StatusDisplay(ctk.CTkFrame):
         self._create_widgets()
 
     def _create_widgets(self) -> None:
-        """Create the status display UI."""
-        self._status_label = ctk.CTkLabel(
+        """Create the status display UI — multi-line expandable area."""
+        self.grid_rowconfigure(0, weight=1)
+        self.grid_columnconfigure(0, weight=1)
+
+        self._status_text = ctk.CTkTextbox(
             self,
-            text="Ready",
             font=FONT_BODY,
-            anchor="w",
+            corner_radius=CORNER_RADIUS,
+            state="disabled",
+            wrap="word",
         )
-        self._status_label.pack(
-            fill="x", padx=PADDING, pady=PADDING_SMALL
+        self._status_text.grid(
+            row=0, column=0, sticky="nsew", padx=PADDING, pady=PADDING_SMALL
         )
 
     def set_status(self, message: str, status: str = "info") -> None:
@@ -470,20 +477,32 @@ class StatusDisplay(ctk.CTkFrame):
             message: Status message text.
             status: Status type for coloring ('info', 'success', 'error', 'warning').
         """
-        self._status_label.configure(text=message)
+        self._status_text.configure(state="normal")
+        self._status_text.delete("1.0", "end")
+
         colors = {
             "info": INFO_COLOR,
             "success": SUCCESS_COLOR,
             "error": DANGER_COLOR,
             "warning": WARNING_COLOR,
         }
-        self._status_label.configure(text_color=colors.get(status, INFO_COLOR))
+        color = colors.get(status, INFO_COLOR)
+
+        self._status_text.insert("1.0", message)
+        # Tag the entire text with the color (CTkTextbox uses tag_config)
+        self._status_text.tag_config("status", foreground=color)
+        self._status_text.tag_add("status", "1.0", "end")
+
+        self._status_text.configure(state="disabled")
 
 
 class FileSelector(ctk.CTkFrame):
     """File selector widget with browse button and path display.
 
-    Allows users to browse for files and displays the selected path.
+    Stores the full absolute path internally but displays only the
+    filename in the entry field.  Supports relative paths: the
+    ``set_relative_path()`` / ``get_relative_path()`` methods work
+    with paths relative to a given base directory.
     """
 
     def __init__(
@@ -506,7 +525,10 @@ class FileSelector(ctk.CTkFrame):
 
         self._callback = callback
         self._file_types = file_types or [("All files", "*")]
-        self._selected_path = ctk.StringVar(value="")
+        self._full_path: str = ""           # absolute path (internal)
+        self._relative_path: str = ""       # relative path (synced to Config)
+        self._display_text = ctk.StringVar(value="")
+        self._suppress_callback: bool = False  # True during construction
 
         self._create_widgets(label_text)
 
@@ -524,10 +546,10 @@ class FileSelector(ctk.CTkFrame):
         )
         label.grid(row=0, column=0, sticky="w", padx=(PADDING, PADDING_SMALL))
 
-        # Path entry
+        # Path entry — shows only the filename
         self._entry = ctk.CTkEntry(
             self,
-            textvariable=self._selected_path,
+            textvariable=self._display_text,
             font=FONT_MONO,
             state="readonly",
         )
@@ -549,33 +571,60 @@ class FileSelector(ctk.CTkFrame):
 
     def _browse(self) -> None:
         """Open file dialog and set selected path."""
-        import customtkinter
         from tkinter import filedialog
 
         file_path = filedialog.askopenfilename(
-            title=f"Select {self._selected_path.get() or 'file'}",
+            title="Select file",
             filetypes=self._file_types,
         )
         if file_path:
             self.set_path(file_path)
 
     def set_path(self, path: str) -> None:
-        """Set the selected file path.
+        """Set the selected file path (absolute or relative).
+
+        Internally stores the absolute path and displays only the
+        filename.
 
         Args:
-            path: Absolute path to the selected file.
+            path: Absolute or relative path to the selected file.
         """
-        self._selected_path.set(path)
-        if self._callback:
+        self._full_path = path
+        self._display_text.set(os.path.basename(path) if path else "")
+        if self._callback and not self._suppress_callback:
+            self._callback(path)
+
+    def set_relative_path(self, path: str) -> None:
+        """Set a relative path (from config).
+
+        Resolves to absolute for internal storage, shows only filename.
+
+        Args:
+            path: Relative path string.
+        """
+        self._relative_path = path
+        # Resolve to absolute for internal use
+        if path:
+            self._full_path = path  # caller should resolve before calling
+        self._display_text.set(os.path.basename(path) if path else "")
+        if self._callback and not self._suppress_callback:
             self._callback(path)
 
     def get_path(self) -> str:
-        """Get the currently selected file path.
+        """Get the currently selected file path (absolute).
 
         Returns:
             Selected file path string.
         """
-        return self._selected_path.get()
+        return self._full_path
+
+    def get_relative_path(self) -> str:
+        """Get the currently selected relative path.
+
+        Returns:
+            Relative path string, or empty string.
+        """
+        return self._relative_path
 
 
 class LogDisplay(ctk.CTkFrame):
@@ -953,6 +1002,8 @@ class UartMonitorWindow(ctk.CTkToplevel):
         self.geometry("680x540")
         self.minsize(480, 360)
         self.protocol("WM_DELETE_WINDOW", self._on_close)
+        self.lift()   # ensure visible on Windows
+        self.focus()
 
         self._on_log = on_log
 
@@ -1075,7 +1126,8 @@ class UartMonitorWindow(ctk.CTkToplevel):
         def _bg_open() -> None:
             try:
                 import serial
-                ser = serial.Serial(self._port, self._baudrate, timeout=1)
+                from serial_monitor import _open_serial
+                ser = _open_serial(self._port, self._baudrate, 1)
                 ser.close()
                 self.after(0, self._on_open_success)
             except Exception as e:
@@ -1201,5 +1253,4 @@ class UartMonitorWindow(ctk.CTkToplevel):
         if self._monitor:
             self._monitor.stop()
             self._monitor = None
-        self.grab_release()
         self.destroy()

src/reboot_manager.py

@@ -125,11 +125,12 @@ def reboot_via_serial(
 
     try:
         import serial
+        from serial_monitor import _open_serial
 
-        with serial.Serial(
+        with _open_serial(
             config.serial_port,
             config.serial_baudrate,
-            timeout=5,
+            timeout=5.0,
         ) as ser:
             ser.reset_input_buffer()
             # Send Ctrl+C to break out of any running process

src/serial_monitor.py

@@ -8,6 +8,7 @@ Provides UartMonitor for continuous background monitoring.
 from __future__ import annotations
 
 import re
+import sys
 import threading
 import time
 from dataclasses import dataclass
@@ -17,6 +18,33 @@ import serial
 import serial.tools.list_ports
 
 
+def _open_serial(port: str, baudrate: int, timeout: float = 1.0) -> serial.Serial:
+    """Open a serial port, trying both name formats on Windows.
+
+    pyserial normally adds \\\\.\\COM prefix for COM>=10, but some
+    versions don't. Try raw name first, then explicit NT namespace.
+    """
+    port = port.strip()
+    last_err = None
+
+    # Try 1: port name as-is
+    try:
+        return serial.Serial(port, baudrate, timeout=timeout)
+    except serial.SerialException as e:
+        last_err = e
+
+    # Try 2: Windows NT namespace prefix
+    if sys.platform == "win32":
+        m = re.match(r"^(COM\d+)$", port, re.IGNORECASE)
+        if m:
+            try:
+                return serial.Serial(r"\\.\%s" % port, baudrate, timeout=timeout)
+            except serial.SerialException as e:
+                last_err = e
+
+    raise last_err or OSError(f"Cannot open serial port: {port}")
+
+
 @dataclass
 class BootInfo:
     """Parsed information extracted from Zynq boot output."""
@@ -169,7 +197,7 @@ def check_uart_available(
 
     # 3. Try to open and read
     try:
-        with serial.Serial(port, baudrate, timeout=timeout) as ser:
+        with _open_serial(port, baudrate, timeout) as ser:
             ser.reset_input_buffer()
             lines: list[str] = []
             while ser.in_waiting:
@@ -243,7 +271,7 @@ def test_serial_version(
     import serial
 
     try:
-        with serial.Serial(port, baudrate, timeout=timeout) as ser:
+        with _open_serial(port, baudrate, timeout) as ser:
             ser.reset_input_buffer()
             ser.reset_output_buffer()
 
@@ -384,7 +412,7 @@ class UartMonitor:
 
         # Quick port check before starting thread
         try:
-            test_ser = serial.Serial(self._port, self._baudrate, timeout=1)
+            test_ser = _open_serial(self._port, self._baudrate, 1)
             test_ser.close()
         except serial.SerialException as e:
             if self.on_error:
@@ -410,7 +438,7 @@ class UartMonitor:
     def _read_loop(self) -> None:
         """Main read loop running in background thread."""
         try:
-            ser = serial.Serial(
+            ser = _open_serial(
                 self._port,
                 self._baudrate,
                 timeout=self._timeout,