diff --git a/packages/cli/src/commands/metrics.ts b/packages/cli/src/commands/metrics.ts
index f4d2a8b..69cf920 100644
--- a/packages/cli/src/commands/metrics.ts
+++ b/packages/cli/src/commands/metrics.ts
@@ -98,6 +98,10 @@ function activeChannels(channels: DeviceChannel[]): DeviceChannel[] {
 	return channels.filter((ch) => ch.enabled !== false);
 }
 
+function ageSeconds(timestamp: Date): number {
+	return Math.max(0, Math.floor((Date.now() - timestamp.getTime()) / 1000));
+}
+
 function channelLabels(device: Device, channel: DeviceChannel): Record<string, string | null> {
 	return {
 		serial: device.serial,
@@ -119,8 +123,18 @@ export function renderMetrics(snapshot: MetricsSnapshot): string {
 	const alarmHigh: Sample[] = [];
 	const alarmLow: Sample[] = [];
 	const battery: Sample[] = [];
+	const deviceTelemetryAge: Sample[] = [];
+	const channelTelemetryAge: Sample[] = [];
 
 	for (const { device, channels } of snapshot.devices) {
+		const deviceTimestamp = device.latestReading ?? device.lastTelemetrySaved ?? device.lastSeen;
+		if (deviceTimestamp) {
+			deviceTelemetryAge.push({
+				labels: { serial: device.serial, device: device.label || device.serial },
+				value: ageSeconds(deviceTimestamp),
+			});
+		}
+
 		if (device.battery != null) {
 			battery.push({
 				labels: { serial: device.serial, device: device.label || device.serial },
@@ -133,6 +147,10 @@ export function renderMetrics(snapshot: MetricsSnapshot): string {
 			if (channel.value != null) {
 				temperature.push({ labels, value: channel.value });
 			}
+			const channelTimestamp = channel.lastTelemetrySaved ?? channel.lastSeen;
+			if (channelTimestamp) {
+				channelTelemetryAge.push({ labels, value: ageSeconds(channelTimestamp) });
+			}
 			if (channel.minimum?.value != null) {
 				minimum.push({ labels, value: channel.minimum.value });
 			}
@@ -197,6 +215,18 @@ export function renderMetrics(snapshot: MetricsSnapshot): string {
 			type: "gauge",
 			samples: battery,
 		},
+		{
+			name: "thermoworks_device_telemetry_age_seconds",
+			help: "Seconds since the newest device telemetry timestamp.",
+			type: "gauge",
+			samples: deviceTelemetryAge,
+		},
+		{
+			name: "thermoworks_channel_telemetry_age_seconds",
+			help: "Seconds since the newest channel telemetry timestamp.",
+			type: "gauge",
+			samples: channelTelemetryAge,
+		},
 	];
 
 	const lines = metrics.flatMap(renderMetric);
diff --git a/packages/cli/tests/metrics.test.ts b/packages/cli/tests/metrics.test.ts
index 612ec80..afe30c1 100644
--- a/packages/cli/tests/metrics.test.ts
+++ b/packages/cli/tests/metrics.test.ts
@@ -37,9 +37,9 @@ function makeDevice(overrides: Partial<Device> & { serial: string }): Device {
 		temperatureDeltaTrigger: null,
 		pendingLoad: null,
 		batteryAlertSent: null,
-		lastSeen: null,
-		lastTelemetrySaved: null,
-		latestReading: null,
+		lastSeen: overrides.lastSeen ?? null,
+		lastTelemetrySaved: overrides.lastTelemetrySaved ?? null,
+		latestReading: overrides.latestReading ?? null,
 		lastWifiConnection: null,
 		lastBluetoothConnection: null,
 		sessionStart: null,
@@ -70,8 +70,8 @@ function makeChannel(overrides: Partial<DeviceChannel> = {}): DeviceChannel {
 		number: overrides.number ?? null,
 		enabled: overrides.enabled ?? null,
 		color: null,
-		lastSeen: null,
-		lastTelemetrySaved: null,
+		lastSeen: overrides.lastSeen ?? null,
+		lastTelemetrySaved: overrides.lastTelemetrySaved ?? null,
 		lastEventId: null,
 		showAvgTemp: null,
 		estimatedAlarmStatus: null,
@@ -296,6 +296,54 @@ describe("renderMetrics", () => {
 	});
 });
 
+it("emits telemetry age metrics when timestamps are present", () => {
+	vi.useFakeTimers();
+	vi.setSystemTime(new Date("2026-01-15T12:10:00Z"));
+	try {
+		const devices: DeviceWithChannels[] = [
+			{
+				device: makeDevice({
+					serial: "S1",
+					label: "Smoker",
+					latestReading: new Date("2026-01-15T12:08:00Z"),
+				}),
+				channels: [
+					makeChannel({
+						label: "Pit",
+						number: "1",
+						lastTelemetrySaved: new Date("2026-01-15T12:09:30Z"),
+					}),
+				],
+			},
+		];
+
+		const text = renderMetrics({ up: true, scrapeErrors: 0, devices });
+
+		expect(text).toContain(
+			'thermoworks_device_telemetry_age_seconds{serial="S1",device="Smoker"} 120',
+		);
+		expect(text).toContain(
+			'thermoworks_channel_telemetry_age_seconds{serial="S1",device="Smoker",channel="1",label="Pit"} 30',
+		);
+	} finally {
+		vi.useRealTimers();
+	}
+});
+
+it("skips telemetry age metrics when timestamps are missing", () => {
+	const devices: DeviceWithChannels[] = [
+		{
+			device: makeDevice({ serial: "S1", label: "Smoker" }),
+			channels: [makeChannel({ label: "Pit", number: "1" })],
+		},
+	];
+
+	const text = renderMetrics({ up: true, scrapeErrors: 0, devices });
+
+	expect(text).not.toContain("thermoworks_device_telemetry_age_seconds{");
+	expect(text).not.toContain("thermoworks_channel_telemetry_age_seconds{");
+});
+
 // =============================================================================
 // createMetricsServer (real HTTP)
 // =============================================================================