diff --git a/FILE_MANIFEST.sha256 b/FILE_MANIFEST.sha256
index 986e6fe..9b99e85 100644
--- a/FILE_MANIFEST.sha256
+++ b/FILE_MANIFEST.sha256
@@ -197,13 +197,13 @@ d4aea1d6ec595000eaddca3b6f0e3d4003901365ece7788147a6ed207cffcc78  ./web/js/flows
 f06557c6d338259059b990f8f79c91d68ac8ec1f245c302468f08929b5506901  ./web/js/forms.js
 dbf36223863ba882c03eccea4516ba8db7acf0c2e72c6c64490cb994f1e20f96  ./web/js/history.js
 7eaa04992ea828dc89f5eaebf674cbbfd160f53eb8d0d6ef0d4e47bd8c28c435  ./web/js/main.js
-a0959f9caf84f1873e3549261de8b1a069f4df8326b17bfe1f8c3de120299875  ./web/js/navigation.js
+733fcc595ed9c03c9639acc6caba46f0588f29e0b95bf72891e34443e7aa9db8  ./web/js/navigation.js
 9ba3f6fa05b72aa989139b2a909982571b2a02055052e4c40104f1e81a9aa7eb  ./web/js/README.md
 2bc9cfa306cdeafff39a7bfc8c5744568e0130d88432351cba8b062178aefce3  ./web/js/realtime.js
 c8c82e88c3715b1bfabf155e36266a4c94f5e2fc03eb39dcdd9d08a1985a997c  ./web/js/router.js
 3c4a96bbc73cdfaf2f76798201f88ef43776875dce42f2b75d6a1808cef496d9  ./web/js/settings.js
 bdeb55546a1dff5e5bdfde4b114d6330f025df1b62e528bf18a93ad6dd4c3e83  ./web/js/settings-ui.js
 6b653e4fe2d4db4ffae6ff8f39b8ce57a10a990dc0000ee4aae51d949afadd52  ./web/manifest.webmanifest
-c5d515b987d96ebfbc7593e9bac9aff64c8d54420f23cc8df5e2c84b14a69852  ./web/styles.css
+a4f8a8ba9cfb29cb49db1d465d81e4d98a05165de17709ea0523c49fc45cfddf  ./web/styles.css
 ae1b03f30b494f474a781a5d32072f1e73eba2b7c768109fc1cc8028cb6662a4  ./web/sw.js
 d505d793ce7cc9485b45b78bba1c0d51887adc7451ab59a42702946e5b991382  ./web/theme-init.js
diff --git a/web/js/navigation.js b/web/js/navigation.js
index 544c5e5..19d22b7 100644
--- a/web/js/navigation.js
+++ b/web/js/navigation.js
@@ -54,22 +54,54 @@ function addPingSample(id, value, error = '') {
 
 function pingSparkline(samples) {
   const width = 360, height = 92, padX = 8, padY = 9;
+  if (!samples.length) return `<div class="ping-empty">${esc(tr('devices.pingNoSamples'))}</div>`;
+
   const valid = samples.map((sample, index) => ({ index, value: sample.value == null ? NaN : Number(sample.value) })).filter(item => Number.isFinite(item.value));
-  if (!valid.length) return `<div class="ping-empty">${esc(tr('devices.pingNoSamples'))}</div>`;
   const values = valid.map(item => item.value);
-  const min = Math.min(...values);
-  const max = Math.max(...values);
+  const min = values.length ? Math.min(...values) : 0;
+  const max = values.length ? Math.max(...values) : 10;
   const ceiling = Math.max(max, 10);
   const floor = Math.min(min, 0);
   const range = Math.max(1, ceiling - floor);
   const lastIndex = Math.max(1, samples.length - 1);
-  const points = valid.map(item => {
-    const x = padX + (item.index / lastIndex) * (width - padX * 2);
-    const y = height - padY - ((item.value - floor) / range) * (height - padY * 2);
+  const pointFor = (index, value) => {
+    const x = padX + (index / lastIndex) * (width - padX * 2);
+    const y = height - padY - ((value - floor) / range) * (height - padY * 2);
     return `${x.toFixed(1)},${y.toFixed(1)}`;
-  }).join(' ');
+  };
+
+  // Keep successful ping runs separate so a packet loss never gets hidden by a line
+  // connecting the samples before and after the failed request.
+  const runs = [];
+  let currentRun = [];
+  samples.forEach((sample, index) => {
+    const value = sample.value == null ? NaN : Number(sample.value);
+    if (Number.isFinite(value)) {
+      currentRun.push(pointFor(index, value));
+    } else if (currentRun.length) {
+      runs.push(currentRun);
+      currentRun = [];
+    }
+  });
+  if (currentRun.length) runs.push(currentRun);
+
+  const lineRuns = runs.map(points => points.length === 1
+    ? `<circle class="ping-success-point" cx="${points[0].split(',')[0]}" cy="${points[0].split(',')[1]}" r="1.8"></circle>`
+    : `<polyline class="ping-success-line" points="${points.join(' ')}"></polyline>`
+  ).join('');
+
+  // Failed requests are packet-loss / unavailability samples. Draw a red band and
+  // an X at each failed position so even a single loss is immediately visible.
+  const losses = samples.map((sample, index) => ({ sample, index })).filter(({ sample }) => sample.value == null).map(({ index }) => {
+    const x = padX + (index / lastIndex) * (width - padX * 2);
+    const bandWidth = Math.max(4, Math.min(10, (width - padX * 2) / Math.max(samples.length, 12)));
+    const left = Math.max(0, x - bandWidth / 2);
+    const markerY = height - padY - 5;
+    return `<g class="ping-loss-marker"><rect x="${left.toFixed(1)}" y="${padY}" width="${bandWidth.toFixed(1)}" height="${height - padY * 2}" rx="2"></rect><path d="M ${(x - 3).toFixed(1)} ${(markerY - 3).toFixed(1)} L ${(x + 3).toFixed(1)} ${(markerY + 3).toFixed(1)} M ${(x + 3).toFixed(1)} ${(markerY - 3).toFixed(1)} L ${(x - 3).toFixed(1)} ${(markerY + 3).toFixed(1)}"></path></g>`;
+  }).join('');
+
   const guide = [0.25, 0.5, 0.75].map(ratio => `<line x1="${padX}" y1="${(height * ratio).toFixed(1)}" x2="${width - padX}" y2="${(height * ratio).toFixed(1)}"></line>`).join('');
-  return `<svg class="ping-sparkline" viewBox="0 0 ${width} ${height}" preserveAspectRatio="none" role="img" aria-label="${esc(tr('devices.pingLive'))}"><g class="ping-grid-lines">${guide}</g><polyline points="${points}"></polyline></svg>`;
+  return `<svg class="ping-sparkline" viewBox="0 0 ${width} ${height}" preserveAspectRatio="none" role="img" aria-label="${esc(tr('devices.pingLive'))}"><g class="ping-grid-lines">${guide}</g>${lineRuns}${losses}</svg>`;
 }
 
 function pingStats(samples) {
diff --git a/web/styles.css b/web/styles.css
index 346d069..fab6e97 100644
--- a/web/styles.css
+++ b/web/styles.css
@@ -7141,3 +7141,34 @@ body.chart-fullscreen-open::before { content:""; position:fixed; inset:0; z-inde
 @media (max-width: 640px) {
   .technical-config-actions button { flex: 1 1 100%; }
 }
+
+/* Ping diagnostics: make packet loss and device unavailability explicit on the chart. */
+.ping-sparkline .ping-success-line {
+  fill: none;
+  stroke: var(--accent);
+  stroke-width: 2;
+  stroke-linejoin: round;
+  stroke-linecap: round;
+  vector-effect: non-scaling-stroke;
+}
+
+.ping-sparkline .ping-success-point {
+  fill: var(--accent);
+  stroke: var(--accent);
+  vector-effect: non-scaling-stroke;
+}
+
+.ping-sparkline .ping-loss-marker rect {
+  fill: var(--danger-soft);
+  stroke: var(--danger);
+  stroke-width: 1;
+  vector-effect: non-scaling-stroke;
+}
+
+.ping-sparkline .ping-loss-marker path {
+  fill: none;
+  stroke: var(--danger);
+  stroke-width: 2;
+  stroke-linecap: round;
+  vector-effect: non-scaling-stroke;
+}