feat: alerts (M8), notifications config page, and app icon (0.4.0)

- feat(alerts): desktop notifications (notify-send) for overheat (GPU/CPU past a
  configurable threshold), GPU-lost, and a new-version-available alert (once per
  version). Edge-triggered with cooldown so it doesn't spam (core/alerts.py)
- feat(gui): Notifications page to configure alerts (enable, GPU/CPU thresholds,
  Send test); changes apply live and persist via config.save_config/update_config
- feat(gui): ship a RigDoctor icon; the GUI self-registers the icon + .desktop on
  launch and sets the Wayland app-id, so the dock shows it after an update + relaunch
  (no installer re-run); installer/uninstaller updated to manage the icon
- config: alerts_enabled, gpu_temp_alert, cpu_temp_alert; flat-TOML writer
- tests for the alert monitor and config round-trip

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -5,6 +5,18 @@ All notable changes to RigDoctor are recorded here. Format follows
 (`MAJOR.MINOR.PATCH`, pre-1.0). `__version__` and `pyproject.toml` must match the git
 release tag (so the auto-updater, D18, can compare versions).
 
+## [0.4.0] - 2026-05-21
+### Added
+- **Alerts (M8)**: desktop notifications (via `notify-send`) for **overheat** (GPU/CPU past a
+  threshold), **GPU-lost** (nvidia-smi timeout), and a **new version available** (fired once
+  per version). Edge-triggered with a cooldown so it doesn't spam. Degrades gracefully if
+  `notify-send` isn't installed.
+- **Notifications page**: configure alerts (enable/disable, GPU/CPU temperature thresholds)
+  with a "Send test" button; changes apply live and persist to `config.toml`.
+- **App icon**: ships a RigDoctor icon and shows it in the dock/launcher. The GUI
+  **self-registers** the icon + `.desktop` on launch (and sets the Wayland app-id), so a
+  self-update + relaunch picks it up — no need to re-run the installer.
+
 ## [0.3.2] - 2026-05-21
 ### Changed
 - Replaced the per-page "Run with admin" buttons with a **single password prompt at launch**

docs/MODULES.md

@@ -12,7 +12,7 @@ Status: ⬜ not started · 🟦 designing · 🟨 in progress · ✅ done
 | M3 | Crash-capture logger | Essential | none (opt: smartmontools) | all (NVIDIA first) | P0 | 🟨 |
 | M4 | Health report (log scan) | Essential | none (opt: smartmontools) | all (NVIDIA first) | P0 | 🟨 |
 | M2 | Live monitor (TUI) | Monitoring | none (stdlib curses) | all | P1 | ⬜ |
-| M8 | Alerting | Monitoring | libnotify (opt) | all | P2 | ⬜ |
+| M8 | Alerting | Monitoring | libnotify (opt) | all | P2 | 🟨 |
 | M5 | System inventory | Diagnostics | none (opt: lm-sensors, dmidecode) | all | P1 | 🟨 |
 | M6 | Gaming env checks | Diagnostics | none | all | P2 | ⬜ |
 | M10 | Desktop GUI | Desktop UI | **python3-pyside6** | all | P2 | 🟨 |

install.sh

@@ -16,7 +16,8 @@ SCRIPT_DIR=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
 uninstall() {
     echo "Removing RigDoctor user-local install…"
     rm -rf "$VENV"
-    rm -f "$BIN_DIR/rigdoctor" "$BIN_DIR/rigdoctor-gui" "$DESKTOP_FILE"
+    rm -f "$BIN_DIR/rigdoctor" "$BIN_DIR/rigdoctor-gui" "$DESKTOP_FILE" \
+          "$DATA_HOME/icons/hicolor/scalable/apps/rigdoctor.svg"
     echo "Done. (Config and logs under ~/.config/rigdoctor and ~/.local/share/rigdoctor were kept.)"
 }
 
@@ -81,6 +82,17 @@ mkdir -p "$BIN_DIR"
 ln -sf "$VENV/bin/rigdoctor" "$BIN_DIR/rigdoctor"
 ln -sf "$VENV/bin/rigdoctor-gui" "$BIN_DIR/rigdoctor-gui"
 
+# Install the app icon (for the dock/launcher); fall back to a stock icon.
+ICON_NAME=utilities-system-monitor
+ICON_SRC=$("$VENV/bin/python" -c "import os, rigdoctor.gui as g; print(os.path.join(os.path.dirname(g.__file__), 'assets', 'rigdoctor.svg'))" 2>/dev/null || true)
+if [ -n "$ICON_SRC" ] && [ -f "$ICON_SRC" ]; then
+    ICON_DST="$DATA_HOME/icons/hicolor/scalable/apps/rigdoctor.svg"
+    mkdir -p "$(dirname "$ICON_DST")"
+    cp "$ICON_SRC" "$ICON_DST"
+    ICON_NAME=rigdoctor
+    command -v gtk-update-icon-cache >/dev/null 2>&1 && gtk-update-icon-cache -qtf "$DATA_HOME/icons/hicolor" 2>/dev/null || true
+fi
+
 mkdir -p "$DESKTOP_DIR"
 cat > "$DESKTOP_FILE" <<EOF
 [Desktop Entry]
@@ -88,10 +100,12 @@ Type=Application
 Name=RigDoctor
 Comment=Hardware monitoring & crash diagnostics for Linux gamers
 Exec=$VENV/bin/rigdoctor-gui
-Icon=utilities-system-monitor
+Icon=$ICON_NAME
 Terminal=false
 Categories=System;Monitor;Utility;
+StartupWMClass=rigdoctor
 EOF
+command -v update-desktop-database >/dev/null 2>&1 && update-desktop-database "$DESKTOP_DIR" 2>/dev/null || true
 
 echo
 echo "RigDoctor $("$VENV/bin/rigdoctor" --version 2>/dev/null | awk '{print $2}') installed."

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "rigdoctor"
-version = "0.3.2"
+version = "0.4.0"
 description = "Modular hardware monitoring & crash diagnostics for Linux gamers."
 readme = "README.md"
 requires-python = ">=3.11"
@@ -21,3 +21,6 @@ rigdoctor-gui = "rigdoctor.gui.app:main"
 
 [tool.setuptools.packages.find]
 where = ["src"]
+
+[tool.setuptools.package-data]
+rigdoctor = ["gui/assets/*.svg"]

src/rigdoctor/__init__.py

@@ -1,3 +1,3 @@
 """RigDoctor — modular hardware monitoring & crash diagnostics for Linux gamers."""
 
-__version__ = "0.3.2"
+__version__ = "0.4.0"

src/rigdoctor/config.py

@@ -139,6 +139,9 @@ DEFAULTS: dict = {
     "log_backups": 10,            # keep this many rotated segments (bounds disk use)
     "update_check_minutes": 30,   # re-check for updates this often while running (0 = off)
     "elevate_on_launch": True,    # GUI asks for the password once at launch (SMART/dmidecode)
+    "alerts_enabled": True,       # desktop notifications on overheat / GPU-lost / new version
+    "gpu_temp_alert": 90.0,       # °C — alert when GPU reaches this
+    "cpu_temp_alert": 95.0,       # °C — alert when CPU reaches this
 }
 
 
@@ -154,3 +157,27 @@ def load_config() -> dict:
     except Exception:
         pass
     return cfg
+
+
+def _toml_value(value) -> str:
+    if isinstance(value, bool):
+        return "true" if value else "false"
+    if isinstance(value, (int, float)):
+        return repr(value)
+    return '"' + str(value).replace("\\", "\\\\").replace('"', '\\"') + '"'
+
+
+def save_config(values: dict) -> None:
+    """Write a flat config.toml (stdlib has no TOML writer)."""
+    CONFIG_DIR.mkdir(parents=True, exist_ok=True)
+    lines = ["# RigDoctor config — edit in the app (Notifications) or here."]
+    lines += [f"{key} = {_toml_value(value)}" for key, value in values.items()]
+    CONFIG_FILE.write_text("\n".join(lines) + "\n")
+
+
+def update_config(**changes) -> dict:
+    """Merge changes into the current effective config and persist them."""
+    cfg = load_config()
+    cfg.update(changes)
+    save_config(cfg)
+    return cfg

src/rigdoctor/core/alerts.py

@@ -0,0 +1,91 @@
+"""Desktop alerts (M8): notify on overheat / GPU-lost / new version via notify-send.
+
+Edge-triggered: an alert fires when a condition becomes true (not every sample), and
+can fire again only after it has cleared and a cooldown has passed — so a hot GPU or a
+1-Hz sample loop doesn't spam notifications. Degrades to a no-op if notify-send is absent.
+"""
+
+from __future__ import annotations
+
+import shutil
+import subprocess
+import time
+
+from .sample import Sample
+
+APP_NAME = "RigDoctor"
+_ICON = "utilities-system-monitor"
+
+
+def available() -> bool:
+    return shutil.which("notify-send") is not None
+
+
+def notify(title: str, message: str, urgency: str = "normal") -> bool:
+    """Send a desktop notification (best-effort). urgency: low|normal|critical."""
+    if not available():
+        return False
+    try:
+        subprocess.run(
+            ["notify-send", "-a", APP_NAME, "-u", urgency, "-i", _ICON, title, message],
+            timeout=10,
+            check=False,
+        )
+        return True
+    except (subprocess.SubprocessError, OSError):
+        return False
+
+
+class AlertMonitor:
+    """Evaluate samples and raise edge-triggered desktop alerts."""
+
+    def __init__(self, gpu_temp: float = 90.0, cpu_temp: float = 95.0, cooldown: float = 300.0):
+        self.gpu_temp = gpu_temp
+        self.cpu_temp = cpu_temp
+        self.cooldown = cooldown
+        self.enabled = True
+        self._active: dict[str, bool] = {}
+        self._last: dict[str, float] = {}
+
+    def _fire(self, key: str, title: str, message: str, urgency: str = "critical") -> None:
+        if self._active.get(key):
+            return  # already alerting; wait until it clears
+        now = time.time()
+        if now - self._last.get(key, 0.0) < self.cooldown:
+            return
+        self._active[key] = True
+        self._last[key] = now
+        notify(title, message, urgency)
+
+    def _clear(self, key: str) -> None:
+        self._active[key] = False
+
+    def check(self, sample: Sample) -> None:
+        if not self.enabled:
+            return
+        gpu_t = next(
+            (r.value for r in sample.readings
+             if r.source == "gpu" and r.metric == "temp" and r.label == "" and r.value is not None),
+            None,
+        )
+        if gpu_t is not None:
+            if gpu_t >= self.gpu_temp:
+                self._fire("gpu_temp", "GPU overheating", f"GPU at {gpu_t:.0f} °C")
+            else:
+                self._clear("gpu_temp")
+
+        cpu_temps = [r.value for r in sample.readings
+                     if r.source == "cpu" and r.metric == "temp" and r.value is not None]
+        if cpu_temps:
+            cpu_t = max(cpu_temps)
+            if cpu_t >= self.cpu_temp:
+                self._fire("cpu_temp", "CPU overheating", f"CPU at {cpu_t:.0f} °C")
+            else:
+                self._clear("cpu_temp")
+
+        lost = any(r.source == "gpu" and r.metric == "status" and r.label == "query-timeout"
+                   for r in sample.readings)
+        if lost:
+            self._fire("gpu_lost", "GPU not responding", "nvidia-smi query timed out — the GPU may have dropped")
+        else:
+            self._clear("gpu_lost")

src/rigdoctor/core/uninstall.py

@@ -23,6 +23,7 @@ def targets(purge: bool = False) -> list[Path]:
         home / ".local" / "bin" / "rigdoctor",
         home / ".local" / "bin" / "rigdoctor-gui",
         share / "applications" / "rigdoctor.desktop",
+        share / "icons" / "hicolor" / "scalable" / "apps" / "rigdoctor.svg",
     ]
     if purge:
         items += [config.CONFIG_DIR, config.STATE_DIR, config.DATA_DIR]

src/rigdoctor/gui/app.py

@@ -3,18 +3,28 @@
 from __future__ import annotations
 
 import sys
+from pathlib import Path
 
+from PySide6.QtGui import QIcon
 from PySide6.QtWidgets import QApplication
 
 from ..config import load_config
+from . import desktop
 from .main_window import MainWindow
 from .theme import STYLESHEET
 
+ICON = Path(__file__).parent / "assets" / "rigdoctor.svg"
+
 
 def main(argv: list[str] | None = None) -> int:
+    desktop.ensure()  # self-register icon + .desktop so updates show it without re-installing
     app = QApplication(argv if argv is not None else sys.argv)
     app.setApplicationName("RigDoctor")
     app.setApplicationDisplayName("RigDoctor")
+    # Match the installed rigdoctor.desktop so the dock/launcher shows our icon (Wayland app-id).
+    app.setDesktopFileName("rigdoctor")
+    if ICON.exists():
+        app.setWindowIcon(QIcon(str(ICON)))
     app.setStyle("Fusion")
     app.setStyleSheet(STYLESHEET)
 

src/rigdoctor/gui/assets/rigdoctor.svg

@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="256" height="256" viewBox="0 0 256 256">
+  <rect x="8" y="8" width="240" height="240" rx="52" fill="#15181e"/>
+  <circle cx="128" cy="128" r="84" fill="none" stroke="#2a2f39" stroke-width="14"/>
+  <path d="M128 44 a84 84 0 1 1 -59.4 24.6" fill="none" stroke="#38bdf8"
+        stroke-width="14" stroke-linecap="round"/>
+  <path d="M60 132 H100 L116 96 L140 168 L156 132 H196" fill="none" stroke="#e6e8eb"
+        stroke-width="14" stroke-linecap="round" stroke-linejoin="round"/>
+</svg>

src/rigdoctor/gui/desktop.py

@@ -0,0 +1,51 @@
+"""Best-effort desktop integration: install our icon + .desktop so the dock shows it.
+
+Runs at GUI launch (idempotent), so a self-update + relaunch refreshes the icon without
+re-running install.sh. No-op for non-installed (dev) runs where the launcher is absent.
+"""
+
+from __future__ import annotations
+
+import shutil
+import sys
+from pathlib import Path
+
+from .. import config
+
+_ICON_SRC = Path(__file__).parent / "assets" / "rigdoctor.svg"
+
+_DESKTOP = """[Desktop Entry]
+Type=Application
+Name=RigDoctor
+Comment=Hardware monitoring & crash diagnostics for Linux gamers
+Exec={exec}
+Icon=rigdoctor
+Terminal=false
+Categories=System;Monitor;Utility;
+StartupWMClass=rigdoctor
+"""
+
+
+def ensure() -> None:
+    share = config.DATA_DIR.parent  # ~/.local/share
+
+    try:
+        if _ICON_SRC.exists():
+            icon_dst = share / "icons" / "hicolor" / "scalable" / "apps" / "rigdoctor.svg"
+            icon_dst.parent.mkdir(parents=True, exist_ok=True)
+            if not icon_dst.exists() or icon_dst.read_bytes() != _ICON_SRC.read_bytes():
+                shutil.copyfile(_ICON_SRC, icon_dst)
+    except OSError:
+        pass
+
+    gui_exec = Path(sys.executable).with_name("rigdoctor-gui")
+    if not gui_exec.exists():  # dev / not a normal install — don't fabricate a .desktop
+        return
+    try:
+        desktop = share / "applications" / "rigdoctor.desktop"
+        content = _DESKTOP.format(exec=gui_exec)
+        desktop.parent.mkdir(parents=True, exist_ok=True)
+        if not desktop.exists() or desktop.read_text() != content:
+            desktop.write_text(content)
+    except OSError:
+        pass

src/rigdoctor/gui/main_window.py

@@ -26,16 +26,17 @@ from PySide6.QtWidgets import (
 
 from .. import __version__
 from ..config import load_config
-from ..core import elevation, updates
+from ..core import alerts, elevation, updates
 from .dashboard import Dashboard
 from .health_page import HealthPage
 from .inventory_page import InventoryPage
+from .notifications_page import NotificationsPage
 from .recorder_page import RecorderPage
 from .setup_page import SetupPage
 from .theme import ACCENT, GOOD, MUTED
 from .worker import SamplerWorker
 
-_NAV_ITEMS = ["Dashboard", "Logs", "Health", "Setup", "Inventory"]
+_NAV_ITEMS = ["Dashboard", "Logs", "Health", "Setup", "Inventory", "Notifications"]
 
 
 class MainWindow(QMainWindow):
@@ -67,11 +68,14 @@ class MainWindow(QMainWindow):
         self.health_page = HealthPage()
         self.setup_page = SetupPage()
         self.inventory_page = InventoryPage()
+        self.notifications_page = NotificationsPage()
+        self.notifications_page.changed.connect(self._apply_alert_settings)
         self._stack.addWidget(self.dashboard)            # 0 Dashboard
         self._stack.addWidget(self.recorder_page)        # 1 Logs
         self._stack.addWidget(self.health_page)          # 2 Health
         self._stack.addWidget(self.setup_page)           # 3 Setup
         self._stack.addWidget(self.inventory_page)       # 4 Inventory
+        self._stack.addWidget(self.notifications_page)   # 5 Notifications
         content_layout.addWidget(self._stack)
 
         layout.addWidget(self._build_sidebar())
@@ -79,6 +83,15 @@ class MainWindow(QMainWindow):
 
         self._worker = SamplerWorker(interval=interval)
         self._worker.sampled.connect(self.dashboard.update_sample)
+        # Desktop alerts (M8): overheat / GPU-lost from the sample stream, new-version below.
+        # Configurable on the Notifications page; gated by AlertMonitor.enabled.
+        self._notified_update_tag = None
+        self._alert_monitor = alerts.AlertMonitor(
+            gpu_temp=float(cfg.get("gpu_temp_alert", 90.0)),
+            cpu_temp=float(cfg.get("cpu_temp_alert", 95.0)),
+        )
+        self._alert_monitor.enabled = bool(cfg.get("alerts_enabled", True))
+        self._worker.sampled.connect(self._alert_monitor.check)
         self._worker.start()
 
         # Ask for the password once at launch and collect root-only data (SMART +
@@ -216,6 +229,12 @@ class MainWindow(QMainWindow):
         self.health_page._run()
         self.inventory_page._run()
 
+    def _apply_alert_settings(self) -> None:
+        cfg = load_config()
+        self._alert_monitor.enabled = bool(cfg.get("alerts_enabled", True))
+        self._alert_monitor.gpu_temp = float(cfg.get("gpu_temp_alert", 90.0))
+        self._alert_monitor.cpu_temp = float(cfg.get("cpu_temp_alert", 95.0))
+
     def _manual_check(self) -> None:
         if self._applied:
             return
@@ -279,6 +298,9 @@ class MainWindow(QMainWindow):
             self._update_label.setText(f'<span style="color:{GOOD};">{tag} available</span>')
             self._update_btn.setText(f"Update to {tag}")
             self._update_btn.setVisible(True)
+            if self._alert_monitor.enabled and tag != self._notified_update_tag:
+                self._notified_update_tag = tag  # once per version, not every poll
+                alerts.notify("Update available", f"RigDoctor {tag} is available — open RigDoctor to update.")
         else:  # UP_TO_DATE
             self._update_label.setText("up-to-date")
 

src/rigdoctor/gui/notifications_page.py

@@ -0,0 +1,108 @@
+"""Notifications page (M8 config): user-configurable alert settings."""
+
+from __future__ import annotations
+
+from PySide6.QtCore import Qt, Signal
+from PySide6.QtWidgets import (
+    QCheckBox,
+    QDoubleSpinBox,
+    QFrame,
+    QGridLayout,
+    QHBoxLayout,
+    QLabel,
+    QPushButton,
+    QVBoxLayout,
+    QWidget,
+)
+
+from ..config import load_config, update_config
+from ..core import alerts
+
+
+class NotificationsPage(QWidget):
+    changed = Signal()  # settings saved — main window re-applies them live
+
+    def __init__(self) -> None:
+        super().__init__()
+        self.setObjectName("Page")
+        root = QVBoxLayout(self)
+        root.setContentsMargins(20, 18, 20, 18)
+        root.setSpacing(16)
+
+        title = QLabel("Notifications")
+        title.setObjectName("PageTitle")
+        root.addWidget(title)
+
+        card = QFrame()
+        card.setObjectName("Card")
+        v = QVBoxLayout(card)
+        v.setContentsMargins(16, 14, 16, 14)
+        v.setSpacing(10)
+        head = QLabel("Alerts")
+        head.setStyleSheet("font-weight: 700; background: transparent;")
+        v.addWidget(head)
+
+        self._enabled = QCheckBox("Enable desktop notifications")
+        v.addWidget(self._enabled)
+
+        grid = QGridLayout()
+        grid.setHorizontalSpacing(12)
+        grid.setColumnStretch(2, 1)
+        self._gpu = self._spin()
+        self._cpu = self._spin()
+        grid.addWidget(QLabel("GPU temperature alert"), 0, 0)
+        grid.addWidget(self._gpu, 0, 1)
+        grid.addWidget(QLabel("CPU temperature alert"), 1, 0)
+        grid.addWidget(self._cpu, 1, 1)
+        v.addLayout(grid)
+
+        note = QLabel("GPU-lost and new-version alerts are included whenever notifications are enabled.")
+        note.setObjectName("Muted")
+        note.setWordWrap(True)
+        v.addWidget(note)
+
+        buttons = QHBoxLayout()
+        save = QPushButton("Save")
+        save.setObjectName("PrimaryButton")
+        save.clicked.connect(self._save)
+        test = QPushButton("Send test")
+        test.clicked.connect(self._test)
+        buttons.addWidget(save)
+        buttons.addWidget(test)
+        buttons.addStretch(1)
+        v.addLayout(buttons)
+        self._status = QLabel("")
+        self._status.setObjectName("Muted")
+        v.addWidget(self._status)
+
+        root.addWidget(card)
+        root.addStretch(1)
+        self._load()
+
+    @staticmethod
+    def _spin() -> QDoubleSpinBox:
+        spin = QDoubleSpinBox()
+        spin.setRange(40, 110)
+        spin.setDecimals(0)
+        spin.setSingleStep(1)
+        spin.setSuffix(" °C")
+        return spin
+
+    def _load(self) -> None:
+        cfg = load_config()
+        self._enabled.setChecked(bool(cfg.get("alerts_enabled", True)))
+        self._gpu.setValue(float(cfg.get("gpu_temp_alert", 90.0)))
+        self._cpu.setValue(float(cfg.get("cpu_temp_alert", 95.0)))
+
+    def _save(self) -> None:
+        update_config(
+            alerts_enabled=self._enabled.isChecked(),
+            gpu_temp_alert=self._gpu.value(),
+            cpu_temp_alert=self._cpu.value(),
+        )
+        self.changed.emit()
+        self._status.setText("Saved.")
+
+    def _test(self) -> None:
+        ok = alerts.notify("RigDoctor", "Test notification — alerts are working.")
+        self._status.setText("Test notification sent." if ok else "notify-send not found — install libnotify-bin (Setup).")

tests/test_alerts.py

@@ -0,0 +1,38 @@
+"""Tests for the M8 alert monitor (edge-triggered; notify mocked)."""
+
+import unittest
+from unittest import mock
+
+from rigdoctor.core import alerts
+from rigdoctor.core.sample import Reading, Sample
+
+
+def _gpu(temp):
+    return Sample(readings=[Reading("gpu", "temp", temp, "°C")])
+
+
+class AlertTests(unittest.TestCase):
+    @mock.patch.object(alerts, "notify")
+    def test_edge_triggered_no_repeat(self, m):
+        mon = alerts.AlertMonitor(gpu_temp=90.0, cooldown=0.0)
+        mon.check(_gpu(95))   # fires
+        mon.check(_gpu(96))   # still hot — no repeat while active
+        self.assertEqual(m.call_count, 1)
+        mon.check(_gpu(50))   # clears
+        mon.check(_gpu(95))   # hot again — fires
+        self.assertEqual(m.call_count, 2)
+
+    @mock.patch.object(alerts, "notify")
+    def test_no_alert_below_threshold(self, m):
+        alerts.AlertMonitor(gpu_temp=90.0).check(_gpu(70))
+        m.assert_not_called()
+
+    @mock.patch.object(alerts, "notify")
+    def test_gpu_lost(self, m):
+        mon = alerts.AlertMonitor()
+        mon.check(Sample(readings=[Reading("gpu", "status", None, "", "query-timeout")]))
+        m.assert_called_once()
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_config.py

@@ -0,0 +1,32 @@
+"""Tests for config save/load (flat TOML writer)."""
+
+import tempfile
+import unittest
+from pathlib import Path
+from unittest import mock
+
+from rigdoctor import config
+
+
+class ConfigTests(unittest.TestCase):
+    def test_save_load_round_trip(self):
+        with tempfile.TemporaryDirectory() as d:
+            cf = Path(d) / "config.toml"
+            with mock.patch.object(config, "CONFIG_FILE", cf), mock.patch.object(config, "CONFIG_DIR", Path(d)):
+                config.save_config({"alerts_enabled": False, "gpu_temp_alert": 88.0, "update_check_minutes": 5})
+                loaded = config.load_config()
+                self.assertIs(loaded["alerts_enabled"], False)
+                self.assertEqual(loaded["gpu_temp_alert"], 88.0)
+                self.assertEqual(loaded["update_check_minutes"], 5)
+
+    def test_update_config_merges_and_keeps_defaults(self):
+        with tempfile.TemporaryDirectory() as d:
+            cf = Path(d) / "config.toml"
+            with mock.patch.object(config, "CONFIG_FILE", cf), mock.patch.object(config, "CONFIG_DIR", Path(d)):
+                config.update_config(cpu_temp_alert=70.0)
+                self.assertEqual(config.load_config()["cpu_temp_alert"], 70.0)
+                self.assertEqual(config.load_config()["gpu_temp_alert"], 90.0)  # default preserved
+
+
+if __name__ == "__main__":
+    unittest.main()