diff --git a/requirements.txt b/requirements.txt
index cb05331..6b9fdfb 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -44,3 +44,6 @@ cryptography>=41.0.0
 # WebSocket support for in-app audio streaming (KiwiSDR, Listening Post)
 flask-sock
 websocket-client>=1.6.0
+
+# System health monitoring (optional - graceful fallback if unavailable)
+psutil>=5.9.0
diff --git a/routes/__init__.py b/routes/__init__.py
index e1e1319..3a00b91 100644
--- a/routes/__init__.py
+++ b/routes/__init__.py
@@ -30,6 +30,7 @@ def register_blueprints(app):
     from .sstv import sstv_bp
     from .sstv_general import sstv_general_bp
     from .subghz import subghz_bp
+    from .system import system_bp
     from .tscm import init_tscm_state, tscm_bp
     from .updater import updater_bp
     from .vdl2 import vdl2_bp
@@ -75,6 +76,7 @@ def register_blueprints(app):
     app.register_blueprint(signalid_bp)  # External signal ID enrichment
     app.register_blueprint(wefax_bp)  # WeFax HF weather fax decoder
     app.register_blueprint(morse_bp)  # CW/Morse code decoder
+    app.register_blueprint(system_bp)  # System health monitoring
 
     # Initialize TSCM state with queue and lock from app
     import app as app_module
diff --git a/routes/system.py b/routes/system.py
new file mode 100644
index 0000000..839899d
--- /dev/null
+++ b/routes/system.py
@@ -0,0 +1,323 @@
+"""System Health monitoring blueprint.
+
+Provides real-time system metrics (CPU, memory, disk, temperatures),
+active process status, and SDR device enumeration via SSE streaming.
+"""
+
+from __future__ import annotations
+
+import contextlib
+import os
+import platform
+import queue
+import socket
+import threading
+import time
+from typing import Any
+
+from flask import Blueprint, Response, jsonify
+
+from utils.constants import SSE_KEEPALIVE_INTERVAL, SSE_QUEUE_TIMEOUT
+from utils.logging import sensor_logger as logger
+from utils.sse import sse_stream_fanout
+
+try:
+    import psutil
+
+    _HAS_PSUTIL = True
+except ImportError:
+    psutil = None  # type: ignore[assignment]
+    _HAS_PSUTIL = False
+
+system_bp = Blueprint('system', __name__, url_prefix='/system')
+
+# ---------------------------------------------------------------------------
+# Background metrics collector
+# ---------------------------------------------------------------------------
+
+_metrics_queue: queue.Queue = queue.Queue(maxsize=500)
+_collector_started = False
+_collector_lock = threading.Lock()
+_app_start_time: float | None = None
+
+
+def _get_app_start_time() -> float:
+    """Return the application start timestamp from the main app module."""
+    global _app_start_time
+    if _app_start_time is None:
+        try:
+            import app as app_module
+
+            _app_start_time = getattr(app_module, '_app_start_time', time.time())
+        except Exception:
+            _app_start_time = time.time()
+    return _app_start_time
+
+
+def _get_app_version() -> str:
+    """Return the application version string."""
+    try:
+        from config import VERSION
+
+        return VERSION
+    except Exception:
+        return 'unknown'
+
+
+def _format_uptime(seconds: float) -> str:
+    """Format seconds into a human-readable uptime string."""
+    days = int(seconds // 86400)
+    hours = int((seconds % 86400) // 3600)
+    minutes = int((seconds % 3600) // 60)
+    parts = []
+    if days > 0:
+        parts.append(f'{days}d')
+    if hours > 0:
+        parts.append(f'{hours}h')
+    parts.append(f'{minutes}m')
+    return ' '.join(parts)
+
+
+def _collect_process_status() -> dict[str, bool]:
+    """Return running/stopped status for each decoder process.
+
+    Mirrors the logic in app.py health_check().
+    """
+    try:
+        import app as app_module
+
+        def _alive(attr: str) -> bool:
+            proc = getattr(app_module, attr, None)
+            if proc is None:
+                return False
+            try:
+                return proc.poll() is None
+            except Exception:
+                return False
+
+        processes: dict[str, bool] = {
+            'pager': _alive('current_process'),
+            'sensor': _alive('sensor_process'),
+            'adsb': _alive('adsb_process'),
+            'ais': _alive('ais_process'),
+            'acars': _alive('acars_process'),
+            'vdl2': _alive('vdl2_process'),
+            'aprs': _alive('aprs_process'),
+            'dsc': _alive('dsc_process'),
+            'morse': _alive('morse_process'),
+        }
+
+        # WiFi
+        try:
+            from app import _get_wifi_health
+
+            wifi_active, _, _ = _get_wifi_health()
+            processes['wifi'] = wifi_active
+        except Exception:
+            processes['wifi'] = False
+
+        # Bluetooth
+        try:
+            from app import _get_bluetooth_health
+
+            bt_active, _ = _get_bluetooth_health()
+            processes['bluetooth'] = bt_active
+        except Exception:
+            processes['bluetooth'] = False
+
+        # SubGHz
+        try:
+            from app import _get_subghz_active
+
+            processes['subghz'] = _get_subghz_active()
+        except Exception:
+            processes['subghz'] = False
+
+        return processes
+    except Exception:
+        return {}
+
+
+def _collect_metrics() -> dict[str, Any]:
+    """Gather a snapshot of system metrics."""
+    now = time.time()
+    start = _get_app_start_time()
+    uptime_seconds = round(now - start, 2)
+
+    metrics: dict[str, Any] = {
+        'type': 'system_metrics',
+        'timestamp': now,
+        'system': {
+            'hostname': socket.gethostname(),
+            'platform': platform.platform(),
+            'python': platform.python_version(),
+            'version': _get_app_version(),
+            'uptime_seconds': uptime_seconds,
+            'uptime_human': _format_uptime(uptime_seconds),
+        },
+        'processes': _collect_process_status(),
+    }
+
+    if _HAS_PSUTIL:
+        # CPU
+        cpu_percent = psutil.cpu_percent(interval=None)
+        cpu_count = psutil.cpu_count() or 1
+        try:
+            load_1, load_5, load_15 = os.getloadavg()
+        except (OSError, AttributeError):
+            load_1 = load_5 = load_15 = 0.0
+
+        metrics['cpu'] = {
+            'percent': cpu_percent,
+            'count': cpu_count,
+            'load_1': round(load_1, 2),
+            'load_5': round(load_5, 2),
+            'load_15': round(load_15, 2),
+        }
+
+        # Memory
+        mem = psutil.virtual_memory()
+        metrics['memory'] = {
+            'total': mem.total,
+            'used': mem.used,
+            'available': mem.available,
+            'percent': mem.percent,
+        }
+
+        swap = psutil.swap_memory()
+        metrics['swap'] = {
+            'total': swap.total,
+            'used': swap.used,
+            'percent': swap.percent,
+        }
+
+        # Disk
+        try:
+            disk = psutil.disk_usage('/')
+            metrics['disk'] = {
+                'total': disk.total,
+                'used': disk.used,
+                'free': disk.free,
+                'percent': disk.percent,
+                'path': '/',
+            }
+        except Exception:
+            metrics['disk'] = None
+
+        # Temperatures
+        try:
+            temps = psutil.sensors_temperatures()
+            if temps:
+                temp_data: dict[str, list[dict[str, Any]]] = {}
+                for chip, entries in temps.items():
+                    temp_data[chip] = [
+                        {
+                            'label': e.label or chip,
+                            'current': e.current,
+                            'high': e.high,
+                            'critical': e.critical,
+                        }
+                        for e in entries
+                    ]
+                metrics['temperatures'] = temp_data
+            else:
+                metrics['temperatures'] = None
+        except (AttributeError, Exception):
+            metrics['temperatures'] = None
+    else:
+        metrics['cpu'] = None
+        metrics['memory'] = None
+        metrics['swap'] = None
+        metrics['disk'] = None
+        metrics['temperatures'] = None
+
+    return metrics
+
+
+def _collector_loop() -> None:
+    """Background thread that pushes metrics onto the queue every 3 seconds."""
+    # Seed psutil's CPU measurement so the first real read isn't 0%.
+    if _HAS_PSUTIL:
+        with contextlib.suppress(Exception):
+            psutil.cpu_percent(interval=None)
+
+    while True:
+        try:
+            metrics = _collect_metrics()
+            # Non-blocking put — drop oldest if full
+            try:
+                _metrics_queue.put_nowait(metrics)
+            except queue.Full:
+                with contextlib.suppress(queue.Empty):
+                    _metrics_queue.get_nowait()
+                _metrics_queue.put_nowait(metrics)
+        except Exception as exc:
+            logger.debug('system metrics collection error: %s', exc)
+        time.sleep(3)
+
+
+def _ensure_collector() -> None:
+    """Start the background collector thread once."""
+    global _collector_started
+    if _collector_started:
+        return
+    with _collector_lock:
+        if _collector_started:
+            return
+        t = threading.Thread(target=_collector_loop, daemon=True, name='system-metrics-collector')
+        t.start()
+        _collector_started = True
+        logger.info('System metrics collector started')
+
+
+# ---------------------------------------------------------------------------
+# Routes
+# ---------------------------------------------------------------------------
+
+
+@system_bp.route('/metrics')
+def get_metrics() -> Response:
+    """REST snapshot of current system metrics."""
+    _ensure_collector()
+    return jsonify(_collect_metrics())
+
+
+@system_bp.route('/stream')
+def stream_system() -> Response:
+    """SSE stream for real-time system metrics."""
+    _ensure_collector()
+
+    response = Response(
+        sse_stream_fanout(
+            source_queue=_metrics_queue,
+            channel_key='system',
+            timeout=SSE_QUEUE_TIMEOUT,
+            keepalive_interval=SSE_KEEPALIVE_INTERVAL,
+        ),
+        mimetype='text/event-stream',
+    )
+    response.headers['Cache-Control'] = 'no-cache'
+    response.headers['X-Accel-Buffering'] = 'no'
+    return response
+
+
+@system_bp.route('/sdr_devices')
+def get_sdr_devices() -> Response:
+    """Enumerate all connected SDR devices (on-demand, not every tick)."""
+    try:
+        from utils.sdr.detection import detect_all_devices
+
+        devices = detect_all_devices()
+        result = []
+        for d in devices:
+            result.append({
+                'type': d.sdr_type.value if hasattr(d.sdr_type, 'value') else str(d.sdr_type),
+                'index': d.index,
+                'name': d.name,
+                'serial': d.serial or '',
+                'driver': d.driver or '',
+            })
+        return jsonify({'devices': result})
+    except Exception as exc:
+        logger.warning('SDR device detection failed: %s', exc)
+        return jsonify({'devices': [], 'error': str(exc)})
diff --git a/static/css/modes/system.css b/static/css/modes/system.css
new file mode 100644
index 0000000..3efd245
--- /dev/null
+++ b/static/css/modes/system.css
@@ -0,0 +1,215 @@
+/* System Health Mode Styles */
+
+.sys-dashboard {
+    display: grid;
+    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
+    gap: 16px;
+    padding: 16px;
+    width: 100%;
+    box-sizing: border-box;
+}
+
+.sys-card {
+    background: var(--bg-card, #1a1a2e);
+    border: 1px solid var(--border-color, #2a2a4a);
+    border-radius: 6px;
+    padding: 16px;
+    min-height: 120px;
+}
+
+.sys-card-header {
+    font-size: 11px;
+    font-weight: 700;
+    text-transform: uppercase;
+    letter-spacing: 0.05em;
+    color: var(--text-dim, #8888aa);
+    margin-bottom: 12px;
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+}
+
+.sys-card-body {
+    font-size: 12px;
+    color: var(--text-primary, #e0e0ff);
+    font-family: var(--font-mono, 'JetBrains Mono', monospace);
+}
+
+.sys-card-detail {
+    font-size: 11px;
+    color: var(--text-dim, #8888aa);
+    margin-top: 4px;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+}
+
+/* Metric Bars */
+.sys-metric-bar-wrap {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    margin-bottom: 6px;
+}
+
+.sys-metric-bar-label {
+    font-size: 10px;
+    color: var(--text-dim, #8888aa);
+    min-width: 40px;
+    text-transform: uppercase;
+}
+
+.sys-metric-bar {
+    flex: 1;
+    height: 8px;
+    background: var(--bg-primary, #0d0d1a);
+    border-radius: 4px;
+    overflow: hidden;
+}
+
+.sys-metric-bar-fill {
+    height: 100%;
+    border-radius: 4px;
+    transition: width 0.4s ease;
+}
+
+.sys-metric-bar-fill.ok {
+    background: var(--accent-green, #00ff88);
+}
+
+.sys-metric-bar-fill.warn {
+    background: var(--accent-yellow, #ffcc00);
+}
+
+.sys-metric-bar-fill.crit {
+    background: var(--accent-red, #ff3366);
+}
+
+.sys-metric-bar-value {
+    font-size: 12px;
+    font-weight: 700;
+    min-width: 36px;
+    text-align: right;
+    font-family: var(--font-mono, 'JetBrains Mono', monospace);
+}
+
+.sys-metric-na {
+    color: var(--text-dim, #8888aa);
+    font-style: italic;
+    font-size: 11px;
+}
+
+/* Process items */
+.sys-process-item {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    padding: 3px 0;
+}
+
+.sys-process-name {
+    font-size: 12px;
+}
+
+.sys-process-dot {
+    display: inline-block;
+    width: 7px;
+    height: 7px;
+    border-radius: 50%;
+    flex-shrink: 0;
+}
+
+.sys-process-dot.running {
+    background: var(--accent-green, #00ff88);
+    box-shadow: 0 0 4px rgba(0, 255, 136, 0.4);
+}
+
+.sys-process-dot.stopped {
+    background: var(--text-dim, #555);
+}
+
+/* SDR Devices */
+.sys-sdr-device {
+    padding: 6px 0;
+    border-bottom: 1px solid var(--border-color, #2a2a4a);
+}
+
+.sys-sdr-device:last-child {
+    border-bottom: none;
+}
+
+.sys-rescan-btn {
+    font-size: 9px;
+    padding: 2px 8px;
+    background: transparent;
+    border: 1px solid var(--border-color, #2a2a4a);
+    color: var(--accent-cyan, #00d4ff);
+    border-radius: 3px;
+    cursor: pointer;
+    text-transform: uppercase;
+    letter-spacing: 0.04em;
+}
+
+.sys-rescan-btn:hover {
+    background: var(--bg-primary, #0d0d1a);
+}
+
+/* Sidebar Quick Grid */
+.sys-quick-grid {
+    display: grid;
+    grid-template-columns: 1fr 1fr;
+    gap: 6px;
+}
+
+.sys-quick-item {
+    padding: 6px 8px;
+    background: var(--bg-primary, #0d0d1a);
+    border: 1px solid var(--border-color, #2a2a4a);
+    border-radius: 4px;
+    text-align: center;
+}
+
+.sys-quick-label {
+    display: block;
+    font-size: 9px;
+    color: var(--text-dim, #8888aa);
+    text-transform: uppercase;
+    letter-spacing: 0.05em;
+    margin-bottom: 2px;
+}
+
+.sys-quick-value {
+    display: block;
+    font-size: 14px;
+    font-weight: 700;
+    font-family: var(--font-mono, 'JetBrains Mono', monospace);
+    color: var(--text-primary, #e0e0ff);
+}
+
+/* Color-coded quick values */
+.sys-val-ok {
+    color: var(--accent-green, #00ff88) !important;
+}
+
+.sys-val-warn {
+    color: var(--accent-yellow, #ffcc00) !important;
+}
+
+.sys-val-crit {
+    color: var(--accent-red, #ff3366) !important;
+}
+
+/* Responsive */
+@media (max-width: 768px) {
+    .sys-dashboard {
+        grid-template-columns: 1fr;
+        padding: 8px;
+        gap: 10px;
+    }
+}
+
+@media (max-width: 1024px) and (min-width: 769px) {
+    .sys-dashboard {
+        grid-template-columns: repeat(2, 1fr);
+    }
+}
diff --git a/static/js/modes/system.js b/static/js/modes/system.js
new file mode 100644
index 0000000..1aab9aa
--- /dev/null
+++ b/static/js/modes/system.js
@@ -0,0 +1,300 @@
+/**
+ * System Health – IIFE module
+ *
+ * Always-on monitoring that auto-connects when the mode is entered.
+ * Streams real-time system metrics via SSE and provides SDR device enumeration.
+ */
+const SystemHealth = (function () {
+    'use strict';
+
+    let eventSource = null;
+    let connected = false;
+    let lastMetrics = null;
+
+    // -----------------------------------------------------------------------
+    // Helpers
+    // -----------------------------------------------------------------------
+
+    function formatBytes(bytes) {
+        if (bytes == null) return '--';
+        const units = ['B', 'KB', 'MB', 'GB', 'TB'];
+        let i = 0;
+        let val = bytes;
+        while (val >= 1024 && i < units.length - 1) { val /= 1024; i++; }
+        return val.toFixed(1) + ' ' + units[i];
+    }
+
+    function barClass(pct) {
+        if (pct >= 85) return 'crit';
+        if (pct >= 60) return 'warn';
+        return 'ok';
+    }
+
+    function barHtml(pct, label) {
+        if (pct == null) return '<span class="sys-metric-na">N/A</span>';
+        const cls = barClass(pct);
+        const rounded = Math.round(pct);
+        return '<div class="sys-metric-bar-wrap">' +
+            (label ? '<span class="sys-metric-bar-label">' + label + '</span>' : '') +
+            '<div class="sys-metric-bar"><div class="sys-metric-bar-fill ' + cls + '" style="width:' + rounded + '%"></div></div>' +
+            '<span class="sys-metric-bar-value">' + rounded + '%</span>' +
+            '</div>';
+    }
+
+    // -----------------------------------------------------------------------
+    // Rendering
+    // -----------------------------------------------------------------------
+
+    function renderCpuCard(m) {
+        const el = document.getElementById('sysCardCpu');
+        if (!el) return;
+        const cpu = m.cpu;
+        if (!cpu) { el.innerHTML = '<div class="sys-card-body"><span class="sys-metric-na">psutil not available</span></div>'; return; }
+        el.innerHTML =
+            '<div class="sys-card-header">CPU</div>' +
+            '<div class="sys-card-body">' +
+            barHtml(cpu.percent, '') +
+            '<div class="sys-card-detail">Load: ' + cpu.load_1 + ' / ' + cpu.load_5 + ' / ' + cpu.load_15 + '</div>' +
+            '<div class="sys-card-detail">Cores: ' + cpu.count + '</div>' +
+            '</div>';
+    }
+
+    function renderMemoryCard(m) {
+        const el = document.getElementById('sysCardMemory');
+        if (!el) return;
+        const mem = m.memory;
+        if (!mem) { el.innerHTML = '<div class="sys-card-body"><span class="sys-metric-na">N/A</span></div>'; return; }
+        const swap = m.swap || {};
+        el.innerHTML =
+            '<div class="sys-card-header">Memory</div>' +
+            '<div class="sys-card-body">' +
+            barHtml(mem.percent, '') +
+            '<div class="sys-card-detail">' + formatBytes(mem.used) + ' / ' + formatBytes(mem.total) + '</div>' +
+            '<div class="sys-card-detail">Swap: ' + formatBytes(swap.used) + ' / ' + formatBytes(swap.total) + '</div>' +
+            '</div>';
+    }
+
+    function renderDiskCard(m) {
+        const el = document.getElementById('sysCardDisk');
+        if (!el) return;
+        const disk = m.disk;
+        if (!disk) { el.innerHTML = '<div class="sys-card-body"><span class="sys-metric-na">N/A</span></div>'; return; }
+        el.innerHTML =
+            '<div class="sys-card-header">Disk</div>' +
+            '<div class="sys-card-body">' +
+            barHtml(disk.percent, '') +
+            '<div class="sys-card-detail">' + formatBytes(disk.used) + ' / ' + formatBytes(disk.total) + '</div>' +
+            '<div class="sys-card-detail">Path: ' + (disk.path || '/') + '</div>' +
+            '</div>';
+    }
+
+    function _extractPrimaryTemp(temps) {
+        if (!temps) return null;
+        // Prefer common chip names
+        const preferred = ['cpu_thermal', 'coretemp', 'k10temp', 'acpitz', 'soc_thermal'];
+        for (const name of preferred) {
+            if (temps[name] && temps[name].length) return temps[name][0];
+        }
+        // Fall back to first available
+        for (const key of Object.keys(temps)) {
+            if (temps[key] && temps[key].length) return temps[key][0];
+        }
+        return null;
+    }
+
+    function renderSdrCard(devices) {
+        const el = document.getElementById('sysCardSdr');
+        if (!el) return;
+        let html = '<div class="sys-card-header">SDR Devices <button class="sys-rescan-btn" onclick="SystemHealth.refreshSdr()">Rescan</button></div>';
+        html += '<div class="sys-card-body">';
+        if (!devices || !devices.length) {
+            html += '<span class="sys-metric-na">No devices found</span>';
+        } else {
+            devices.forEach(function (d) {
+                html += '<div class="sys-sdr-device">' +
+                    '<span class="sys-process-dot running"></span> ' +
+                    '<strong>' + d.type + ' #' + d.index + '</strong>' +
+                    '<div class="sys-card-detail">' + (d.name || 'Unknown') + '</div>' +
+                    (d.serial ? '<div class="sys-card-detail">S/N: ' + d.serial + '</div>' : '') +
+                    '</div>';
+            });
+        }
+        html += '</div>';
+        el.innerHTML = html;
+    }
+
+    function renderProcessCard(m) {
+        const el = document.getElementById('sysCardProcesses');
+        if (!el) return;
+        const procs = m.processes || {};
+        const keys = Object.keys(procs).sort();
+        let html = '<div class="sys-card-header">Processes</div><div class="sys-card-body">';
+        if (!keys.length) {
+            html += '<span class="sys-metric-na">No data</span>';
+        } else {
+            keys.forEach(function (k) {
+                const running = procs[k];
+                const dotCls = running ? 'running' : 'stopped';
+                const label = k.charAt(0).toUpperCase() + k.slice(1);
+                html += '<div class="sys-process-item">' +
+                    '<span class="sys-process-dot ' + dotCls + '"></span> ' +
+                    '<span class="sys-process-name">' + label + '</span>' +
+                    '</div>';
+            });
+        }
+        html += '</div>';
+        el.innerHTML = html;
+    }
+
+    function renderSystemInfoCard(m) {
+        const el = document.getElementById('sysCardInfo');
+        if (!el) return;
+        const sys = m.system || {};
+        const temp = _extractPrimaryTemp(m.temperatures);
+        let html = '<div class="sys-card-header">System Info</div><div class="sys-card-body">';
+        html += '<div class="sys-card-detail">Host: ' + (sys.hostname || '--') + '</div>';
+        html += '<div class="sys-card-detail">OS: ' + (sys.platform || '--') + '</div>';
+        html += '<div class="sys-card-detail">Python: ' + (sys.python || '--') + '</div>';
+        html += '<div class="sys-card-detail">App: v' + (sys.version || '--') + '</div>';
+        html += '<div class="sys-card-detail">Uptime: ' + (sys.uptime_human || '--') + '</div>';
+        if (temp) {
+            html += '<div class="sys-card-detail">Temp: ' + Math.round(temp.current) + '&deg;C';
+            if (temp.high) html += ' / ' + Math.round(temp.high) + '&deg;C max';
+            html += '</div>';
+        }
+        html += '</div>';
+        el.innerHTML = html;
+    }
+
+    function updateSidebarQuickStats(m) {
+        const cpuEl = document.getElementById('sysQuickCpu');
+        const tempEl = document.getElementById('sysQuickTemp');
+        const ramEl = document.getElementById('sysQuickRam');
+        const diskEl = document.getElementById('sysQuickDisk');
+
+        if (cpuEl) cpuEl.textContent = m.cpu ? Math.round(m.cpu.percent) + '%' : '--';
+        if (ramEl) ramEl.textContent = m.memory ? Math.round(m.memory.percent) + '%' : '--';
+        if (diskEl) diskEl.textContent = m.disk ? Math.round(m.disk.percent) + '%' : '--';
+
+        const temp = _extractPrimaryTemp(m.temperatures);
+        if (tempEl) tempEl.innerHTML = temp ? Math.round(temp.current) + '&deg;C' : '--';
+
+        // Color-code values
+        [cpuEl, ramEl, diskEl].forEach(function (el) {
+            if (!el) return;
+            const val = parseInt(el.textContent);
+            el.classList.remove('sys-val-ok', 'sys-val-warn', 'sys-val-crit');
+            if (!isNaN(val)) el.classList.add('sys-val-' + barClass(val));
+        });
+    }
+
+    function updateSidebarProcesses(m) {
+        const el = document.getElementById('sysProcessList');
+        if (!el) return;
+        const procs = m.processes || {};
+        const keys = Object.keys(procs).sort();
+        if (!keys.length) { el.textContent = 'No data'; return; }
+        const running = keys.filter(function (k) { return procs[k]; });
+        const stopped = keys.filter(function (k) { return !procs[k]; });
+        el.innerHTML =
+            (running.length ? '<span style="color: var(--accent-green, #00ff88);">' + running.length + ' running</span>' : '') +
+            (running.length && stopped.length ? ' &middot; ' : '') +
+            (stopped.length ? '<span style="color: var(--text-dim);">' + stopped.length + ' stopped</span>' : '');
+    }
+
+    function renderAll(m) {
+        renderCpuCard(m);
+        renderMemoryCard(m);
+        renderDiskCard(m);
+        renderProcessCard(m);
+        renderSystemInfoCard(m);
+        updateSidebarQuickStats(m);
+        updateSidebarProcesses(m);
+    }
+
+    // -----------------------------------------------------------------------
+    // SSE Connection
+    // -----------------------------------------------------------------------
+
+    function connect() {
+        if (eventSource) return;
+        eventSource = new EventSource('/system/stream');
+        eventSource.onmessage = function (e) {
+            try {
+                var data = JSON.parse(e.data);
+                if (data.type === 'keepalive') return;
+                lastMetrics = data;
+                renderAll(data);
+            } catch (_) { /* ignore parse errors */ }
+        };
+        eventSource.onopen = function () {
+            connected = true;
+        };
+        eventSource.onerror = function () {
+            connected = false;
+        };
+    }
+
+    function disconnect() {
+        if (eventSource) {
+            eventSource.close();
+            eventSource = null;
+        }
+        connected = false;
+    }
+
+    // -----------------------------------------------------------------------
+    // SDR Devices
+    // -----------------------------------------------------------------------
+
+    function refreshSdr() {
+        var sidebarEl = document.getElementById('sysSdrList');
+        if (sidebarEl) sidebarEl.innerHTML = 'Scanning&hellip;';
+
+        var cardEl = document.getElementById('sysCardSdr');
+        if (cardEl) cardEl.innerHTML = '<div class="sys-card-header">SDR Devices</div><div class="sys-card-body">Scanning&hellip;</div>';
+
+        fetch('/system/sdr_devices')
+            .then(function (r) { return r.json(); })
+            .then(function (data) {
+                var devices = data.devices || [];
+                renderSdrCard(devices);
+                // Update sidebar
+                if (sidebarEl) {
+                    if (!devices.length) {
+                        sidebarEl.innerHTML = '<span style="color: var(--text-dim);">No SDR devices found</span>';
+                    } else {
+                        var html = '';
+                        devices.forEach(function (d) {
+                            html += '<div style="margin-bottom: 4px;"><span class="sys-process-dot running"></span> ' +
+                                d.type + ' #' + d.index + ' &mdash; ' + (d.name || 'Unknown') + '</div>';
+                        });
+                        sidebarEl.innerHTML = html;
+                    }
+                }
+            })
+            .catch(function () {
+                if (sidebarEl) sidebarEl.innerHTML = '<span style="color: var(--accent-red, #ff3366);">Detection failed</span>';
+                renderSdrCard([]);
+            });
+    }
+
+    // -----------------------------------------------------------------------
+    // Public API
+    // -----------------------------------------------------------------------
+
+    function init() {
+        connect();
+        refreshSdr();
+    }
+
+    function destroy() {
+        disconnect();
+    }
+
+    return {
+        init: init,
+        destroy: destroy,
+        refreshSdr: refreshSdr,
+    };
+})();
diff --git a/templates/index.html b/templates/index.html
index 6e16d15..ddc1b96 100644
--- a/templates/index.html
+++ b/templates/index.html
@@ -82,7 +82,8 @@
             bt_locate: "{{ url_for('static', filename='css/modes/bt_locate.css') }}?v={{ version }}&r=btlocate4",
             spaceweather: "{{ url_for('static', filename='css/modes/space-weather.css') }}",
             wefax: "{{ url_for('static', filename='css/modes/wefax.css') }}",
-            morse: "{{ url_for('static', filename='css/modes/morse.css') }}"
+            morse: "{{ url_for('static', filename='css/modes/morse.css') }}",
+            system: "{{ url_for('static', filename='css/modes/system.css') }}"
         };
         window.INTERCEPT_MODE_STYLE_LOADED = {};
         window.INTERCEPT_MODE_STYLE_PROMISES = {};
@@ -705,6 +706,7 @@
 
                 {% include 'partials/modes/bt_locate.html' %}
                 {% include 'partials/modes/waterfall.html' %}
+                {% include 'partials/modes/system.html' %}
 
 
 
@@ -3125,6 +3127,36 @@
                     </div>
                 </div>
 
+                <!-- System Health Visuals -->
+                <div id="systemVisuals" class="sys-visuals-container" style="display: none;">
+                    <div class="sys-dashboard">
+                        <div class="sys-card" id="sysCardCpu">
+                            <div class="sys-card-header">CPU</div>
+                            <div class="sys-card-body"><span class="sys-metric-na">Connecting&hellip;</span></div>
+                        </div>
+                        <div class="sys-card" id="sysCardMemory">
+                            <div class="sys-card-header">Memory</div>
+                            <div class="sys-card-body"><span class="sys-metric-na">Connecting&hellip;</span></div>
+                        </div>
+                        <div class="sys-card" id="sysCardDisk">
+                            <div class="sys-card-header">Disk</div>
+                            <div class="sys-card-body"><span class="sys-metric-na">Connecting&hellip;</span></div>
+                        </div>
+                        <div class="sys-card" id="sysCardSdr">
+                            <div class="sys-card-header">SDR Devices</div>
+                            <div class="sys-card-body"><span class="sys-metric-na">Scanning&hellip;</span></div>
+                        </div>
+                        <div class="sys-card" id="sysCardProcesses">
+                            <div class="sys-card-header">Processes</div>
+                            <div class="sys-card-body"><span class="sys-metric-na">Connecting&hellip;</span></div>
+                        </div>
+                        <div class="sys-card" id="sysCardInfo">
+                            <div class="sys-card-header">System Info</div>
+                            <div class="sys-card-body"><span class="sys-metric-na">Connecting&hellip;</span></div>
+                        </div>
+                    </div>
+                </div>
+
                 <div class="output-content signal-feed" id="output">
                     <div class="placeholder signal-empty-state">
                         <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5">
@@ -3196,6 +3228,7 @@
     <script src="{{ url_for('static', filename='js/modes/wefax.js') }}"></script>
     <script src="{{ url_for('static', filename='js/modes/morse.js') }}?v={{ version }}&r=morse_iq12"></script>
     <script src="{{ url_for('static', filename='js/modes/space-weather.js') }}"></script>
+    <script src="{{ url_for('static', filename='js/modes/system.js') }}"></script>
     <script src="{{ url_for('static', filename='js/core/voice-alerts.js') }}?v={{ version }}&r=voicefix2"></script>
     <script src="{{ url_for('static', filename='js/core/keyboard-shortcuts.js') }}"></script>
     <script src="{{ url_for('static', filename='js/core/cheat-sheets.js') }}"></script>
@@ -3349,6 +3382,7 @@
             websdr: { label: 'WebSDR', indicator: 'WEBSDR', outputTitle: 'HF/Shortwave WebSDR', group: 'intel' },
             waterfall: { label: 'Waterfall', indicator: 'WATERFALL', outputTitle: 'Spectrum Waterfall', group: 'signals' },
             morse: { label: 'Morse', indicator: 'MORSE', outputTitle: 'CW/Morse Decoder', group: 'signals' },
+            system: { label: 'System', indicator: 'SYSTEM', outputTitle: 'System Health Monitor', group: 'system' },
         };
         const validModes = new Set(Object.keys(modeCatalog));
         window.interceptModeCatalog = Object.assign({}, modeCatalog);
@@ -4128,6 +4162,7 @@
             document.getElementById('spaceWeatherMode')?.classList.toggle('active', mode === 'spaceweather');
             document.getElementById('waterfallMode')?.classList.toggle('active', mode === 'waterfall');
             document.getElementById('morseMode')?.classList.toggle('active', mode === 'morse');
+            document.getElementById('systemMode')?.classList.toggle('active', mode === 'system');
 
 
             const pagerStats = document.getElementById('pagerStats');
@@ -4169,6 +4204,7 @@
             const wefaxVisuals = document.getElementById('wefaxVisuals');
             const spaceWeatherVisuals = document.getElementById('spaceWeatherVisuals');
             const waterfallVisuals = document.getElementById('waterfallVisuals');
+            const systemVisuals = document.getElementById('systemVisuals');
             if (wifiLayoutContainer) wifiLayoutContainer.style.display = mode === 'wifi' ? 'flex' : 'none';
             if (btLayoutContainer) btLayoutContainer.style.display = mode === 'bluetooth' ? 'flex' : 'none';
             if (satelliteVisuals) satelliteVisuals.style.display = mode === 'satellite' ? 'block' : 'none';
@@ -4186,6 +4222,7 @@
             if (wefaxVisuals) wefaxVisuals.style.display = mode === 'wefax' ? 'flex' : 'none';
             if (spaceWeatherVisuals) spaceWeatherVisuals.style.display = mode === 'spaceweather' ? 'flex' : 'none';
             if (waterfallVisuals) waterfallVisuals.style.display = mode === 'waterfall' ? 'flex' : 'none';
+            if (systemVisuals) systemVisuals.style.display = mode === 'system' ? 'flex' : 'none';
 
             // Prevent Leaflet heatmap redraws on hidden BT Locate map containers.
             if (typeof BtLocate !== 'undefined' && BtLocate.setActiveMode) {
@@ -4242,11 +4279,16 @@
                 if (typeof WeFax !== 'undefined' && WeFax.destroy) WeFax.destroy();
             }
 
+            // Disconnect System Health SSE when leaving the mode
+            if (mode !== 'system') {
+                if (typeof SystemHealth !== 'undefined' && SystemHealth.destroy) SystemHealth.destroy();
+            }
+
             // Show/hide Device Intelligence for modes that use it (not for satellite/aircraft/tscm)
             const reconBtn = document.getElementById('reconBtn');
             const intelBtn = document.querySelector('[onclick="exportDeviceDB()"]');
             const reconPanel = document.getElementById('reconPanel');
-            if (mode === 'satellite' || mode === 'sstv' || mode === 'weathersat' || mode === 'sstv_general' || mode === 'wefax' || mode === 'gps' || mode === 'aprs' || mode === 'tscm' || mode === 'spystations' || mode === 'meshtastic' || mode === 'websdr' || mode === 'subghz' || mode === 'spaceweather' || mode === 'waterfall') {
+            if (mode === 'satellite' || mode === 'sstv' || mode === 'weathersat' || mode === 'sstv_general' || mode === 'wefax' || mode === 'gps' || mode === 'aprs' || mode === 'tscm' || mode === 'spystations' || mode === 'meshtastic' || mode === 'websdr' || mode === 'subghz' || mode === 'spaceweather' || mode === 'waterfall' || mode === 'system') {
                 if (reconPanel) reconPanel.style.display = 'none';
                 if (reconBtn) reconBtn.style.display = 'none';
                 if (intelBtn) intelBtn.style.display = 'none';
@@ -4297,8 +4339,8 @@
             // Hide output console for modes with their own visualizations
             const outputEl = document.getElementById('output');
             const statusBar = document.querySelector('.status-bar');
-            if (outputEl) outputEl.style.display = (mode === 'satellite' || mode === 'sstv' || mode === 'weathersat' || mode === 'sstv_general' || mode === 'wefax' || mode === 'aprs' || mode === 'wifi' || mode === 'bluetooth' || mode === 'tscm' || mode === 'spystations' || mode === 'meshtastic' || mode === 'websdr' || mode === 'subghz' || mode === 'spaceweather' || mode === 'bt_locate' || mode === 'waterfall' || mode === 'morse') ? 'none' : 'block';
-            if (statusBar) statusBar.style.display = (mode === 'satellite' || mode === 'websdr' || mode === 'subghz' || mode === 'spaceweather' || mode === 'waterfall' || mode === 'morse') ? 'none' : 'flex';
+            if (outputEl) outputEl.style.display = (mode === 'satellite' || mode === 'sstv' || mode === 'weathersat' || mode === 'sstv_general' || mode === 'wefax' || mode === 'aprs' || mode === 'wifi' || mode === 'bluetooth' || mode === 'tscm' || mode === 'spystations' || mode === 'meshtastic' || mode === 'websdr' || mode === 'subghz' || mode === 'spaceweather' || mode === 'bt_locate' || mode === 'waterfall' || mode === 'morse' || mode === 'system') ? 'none' : 'block';
+            if (statusBar) statusBar.style.display = (mode === 'satellite' || mode === 'websdr' || mode === 'subghz' || mode === 'spaceweather' || mode === 'waterfall' || mode === 'morse' || mode === 'system') ? 'none' : 'flex';
 
             // Restore sidebar when leaving Meshtastic mode (user may have collapsed it)
             if (mode !== 'meshtastic') {
@@ -4372,6 +4414,8 @@
                 if (typeof Waterfall !== 'undefined') Waterfall.init();
             } else if (mode === 'morse') {
                 MorseMode.init();
+            } else if (mode === 'system') {
+                SystemHealth.init();
             }
 
             // Destroy Waterfall WebSocket when leaving SDR receiver modes
diff --git a/templates/partials/modes/system.html b/templates/partials/modes/system.html
new file mode 100644
index 0000000..a750e11
--- /dev/null
+++ b/templates/partials/modes/system.html
@@ -0,0 +1,52 @@
+<!-- SYSTEM HEALTH MODE -->
+<div id="systemMode" class="mode-content">
+    <div class="section">
+        <h3>System Health</h3>
+        <p class="info-text" style="font-size: 11px; color: var(--text-dim); margin-bottom: 12px;">
+            Real-time monitoring of host resources, active decoders, and SDR hardware.
+            Auto-connects when entering this mode.
+        </p>
+    </div>
+
+    <!-- Quick Status Grid -->
+    <div class="section">
+        <h3>Quick Status</h3>
+        <div class="sys-quick-grid">
+            <div class="sys-quick-item">
+                <span class="sys-quick-label">CPU</span>
+                <span class="sys-quick-value" id="sysQuickCpu">--%</span>
+            </div>
+            <div class="sys-quick-item">
+                <span class="sys-quick-label">Temp</span>
+                <span class="sys-quick-value" id="sysQuickTemp">--&deg;C</span>
+            </div>
+            <div class="sys-quick-item">
+                <span class="sys-quick-label">RAM</span>
+                <span class="sys-quick-value" id="sysQuickRam">--%</span>
+            </div>
+            <div class="sys-quick-item">
+                <span class="sys-quick-label">Disk</span>
+                <span class="sys-quick-value" id="sysQuickDisk">--%</span>
+            </div>
+        </div>
+    </div>
+
+    <!-- SDR Devices -->
+    <div class="section">
+        <h3>SDR Devices</h3>
+        <div id="sysSdrList" style="font-size: 11px; color: var(--text-dim);">
+            Scanning&hellip;
+        </div>
+        <button class="run-btn" style="width: 100%; margin-top: 8px;" onclick="SystemHealth.refreshSdr()">
+            Rescan SDR
+        </button>
+    </div>
+
+    <!-- Active Processes -->
+    <div class="section">
+        <h3>Active Processes</h3>
+        <div id="sysProcessList" style="font-size: 11px; color: var(--text-dim);">
+            Waiting for data&hellip;
+        </div>
+    </div>
+</div>
diff --git a/templates/partials/nav.html b/templates/partials/nav.html
index 7cc4fff..68a6d6c 100644
--- a/templates/partials/nav.html
+++ b/templates/partials/nav.html
@@ -140,6 +140,19 @@
         </div>
     </div>
 
+    {# System Group #}
+    <div class="mode-nav-dropdown" data-group="system">
+        <button type="button" class="mode-nav-dropdown-btn"{% if is_index_page %} onclick="toggleNavDropdown('system')"{% endif %}>
+            <span class="nav-icon icon"><svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><rect x="2" y="2" width="20" height="8" rx="2" ry="2"/><rect x="2" y="14" width="20" height="8" rx="2" ry="2"/><line x1="6" y1="6" x2="6.01" y2="6"/><line x1="6" y1="18" x2="6.01" y2="18"/></svg></span>
+            <span class="nav-label">System</span>
+            <span class="dropdown-arrow icon"><svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><polyline points="6 9 12 15 18 9"/></svg></span>
+        </button>
+
+        <div class="mode-nav-dropdown-menu">
+            {{ mode_item('system', 'Health', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M22 12h-4l-3 9L9 3l-3 9H2"/></svg>') }}
+        </div>
+    </div>
+
     {# Dynamic dashboard button (shown when in satellite mode) #}
     <div class="mode-nav-actions">
         <a href="/satellite/dashboard" target="_blank" class="nav-action-btn" id="satelliteDashboardBtn" style="display: none;">
@@ -230,6 +243,8 @@
     {{ mobile_item('websdr', 'WebSDR', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><circle cx="12" cy="12" r="10"/><line x1="2" y1="12" x2="22" y2="12"/><path d="M12 2a15.3 15.3 0 0 1 4 10 15.3 15.3 0 0 1-4 10 15.3 15.3 0 0 1-4-10 15.3 15.3 0 0 1 4-10z"/></svg>') }}
     {# New modes #}
     {{ mobile_item('waterfall', 'Waterfall', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M2 12h4l3-8 3 16 3-8h4"/></svg>') }}
+    {# System #}
+    {{ mobile_item('system', 'System', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><rect x="2" y="2" width="20" height="8" rx="2" ry="2"/><rect x="2" y="14" width="20" height="8" rx="2" ry="2"/><line x1="6" y1="6" x2="6.01" y2="6"/><line x1="6" y1="18" x2="6.01" y2="18"/></svg>') }}
 </nav>
 
 {# JavaScript stub for pages that don't have switchMode defined #}
diff --git a/tests/test_system.py b/tests/test_system.py
new file mode 100644
index 0000000..6d2ea59
--- /dev/null
+++ b/tests/test_system.py
@@ -0,0 +1,89 @@
+"""Tests for the System Health monitoring blueprint."""
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock, patch
+
+
+def _login(client):
+    """Mark the Flask test session as authenticated."""
+    with client.session_transaction() as sess:
+        sess['logged_in'] = True
+        sess['username'] = 'test'
+        sess['role'] = 'admin'
+
+
+def test_metrics_returns_expected_keys(client):
+    """GET /system/metrics returns top-level metric keys."""
+    _login(client)
+    resp = client.get('/system/metrics')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert 'system' in data
+    assert 'processes' in data
+    assert 'cpu' in data
+    assert 'memory' in data
+    assert 'disk' in data
+    assert data['system']['hostname']
+    assert 'version' in data['system']
+    assert 'uptime_seconds' in data['system']
+    assert 'uptime_human' in data['system']
+
+
+def test_metrics_without_psutil(client):
+    """Metrics degrade gracefully when psutil is unavailable."""
+    _login(client)
+    import routes.system as mod
+
+    orig = mod._HAS_PSUTIL
+    mod._HAS_PSUTIL = False
+    try:
+        resp = client.get('/system/metrics')
+        assert resp.status_code == 200
+        data = resp.get_json()
+        # These fields should be None without psutil
+        assert data['cpu'] is None
+        assert data['memory'] is None
+        assert data['disk'] is None
+    finally:
+        mod._HAS_PSUTIL = orig
+
+
+def test_sdr_devices_returns_list(client):
+    """GET /system/sdr_devices returns a devices list."""
+    _login(client)
+    mock_device = MagicMock()
+    mock_device.sdr_type = MagicMock()
+    mock_device.sdr_type.value = 'rtlsdr'
+    mock_device.index = 0
+    mock_device.name = 'Generic RTL2832U'
+    mock_device.serial = '00000001'
+    mock_device.driver = 'rtlsdr'
+
+    with patch('utils.sdr.detection.detect_all_devices', return_value=[mock_device]):
+        resp = client.get('/system/sdr_devices')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert 'devices' in data
+    assert len(data['devices']) == 1
+    assert data['devices'][0]['type'] == 'rtlsdr'
+    assert data['devices'][0]['name'] == 'Generic RTL2832U'
+
+
+def test_sdr_devices_handles_detection_failure(client):
+    """SDR detection failure returns empty list with error."""
+    _login(client)
+    with patch('utils.sdr.detection.detect_all_devices', side_effect=RuntimeError('no devices')):
+        resp = client.get('/system/sdr_devices')
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data['devices'] == []
+    assert 'error' in data
+
+
+def test_stream_returns_sse_content_type(client):
+    """GET /system/stream returns text/event-stream."""
+    _login(client)
+    resp = client.get('/system/stream')
+    assert resp.status_code == 200
+    assert 'text/event-stream' in resp.content_type