diff --git a/docs/pro-runtime-hardening-workboard.md b/docs/pro-runtime-hardening-workboard.md
index 8fb6a52..e0f5f3b 100644
--- a/docs/pro-runtime-hardening-workboard.md
+++ b/docs/pro-runtime-hardening-workboard.md
@@ -382,10 +382,14 @@ Vollständige Sichtbarkeit auf Runtime, Queue, Writer, Generator, RF-Selbsttests
 - `rf_selftest_rds_57k_db`
 
 ## WS-04 Entscheidungslog
-- Noch leer
+| Datum | Entscheidung | Notiz |
+| --- | --- | --- |
+| 2026-04-06 | High-watermark trend sparkline | Captured audio high-watermark duration history and surface it as a new Health-panel sparkline for queue pressure visibility. |
 
 ## WS-04 Verifikation
-- Noch leer
+| Datum | Fokus | Ergebnis |
+| --- | --- | --- |
+| 2026-04-06 | High-watermark trend sparkline | `go test ./...` plus manual UI check confirm the new sparkline updates with runtime audio stats. |
 
 ---
 
diff --git a/internal/control/ui.html b/internal/control/ui.html
index e1a1eaa..8764bff 100644
--- a/internal/control/ui.html
+++ b/internal/control/ui.html
@@ -770,6 +770,16 @@ input.input-error {
 .health-line .val.good { color: var(--green); }
 .health-line .val.warn { color: var(--amber); }
 .health-line .val.err { color: var(--accent); }
+.health-trend {
+  margin-top: 10px;
+}
+.health-trend-label {
+  font-size: 10px;
+  text-transform: uppercase;
+  letter-spacing: 1px;
+  color: var(--text-muted);
+  margin-bottom: 6px;
+}
 
 .fault-history {
   margin-top: 12px;
@@ -1170,6 +1180,10 @@ input.input-error {
           <div class="health-line"><div class="name">Buffer Duration</div><div class="val" id="health-buffer-duration">--</div></div>
           <div class="health-line"><div class="name">High Watermark</div><div class="val" id="health-buffer-highwater">--</div></div>
           <div class="health-line"><div class="name">Last Update</div><div class="val" id="health-last">--</div></div>
+          <div class="health-trend">
+            <div class="health-trend-label">High Watermark Trend</div>
+            <svg class="spark warn" id="spark-high-watermark" viewBox="0 0 160 34" preserveAspectRatio="none"></svg>
+          </div>
         </div>
       </div>
 
@@ -1304,6 +1318,7 @@ const state = {
     audio: [],
     underruns: [],
     tx: [],
+    highWatermark: [],
   },
   runtimeTransitions: [],
   freqPresetIndex: 0,
@@ -1479,6 +1494,9 @@ function pushHistory(runtime) {
   const driver = runtime.driver || {};
   const audio = runtime.audioStream || {};
   pushChart(state.charts.audio, typeof audio.buffered === 'number' ? audio.buffered : 0);
+  const highWatermarkDurationSeconds = Number(audio.highWatermarkDurationSeconds);
+  const normalizedHighWatermark = Number.isFinite(highWatermarkDurationSeconds) ? highWatermarkDurationSeconds : 0;
+  pushChart(state.charts.highWatermark, normalizedHighWatermark);
   pushChart(state.charts.underruns, Number(engine.underruns ?? driver.underruns ?? 0));
   const txState = String(engine.state || 'idle').toLowerCase();
   pushChart(state.charts.tx, txState === 'running' ? 1 : state.txBusy ? 0.55 : 0.05);
@@ -1951,7 +1969,27 @@ function render() {
   updateTransitionHistory();
   updateResetHint(engine);
   updateMeters(engine, driver, audioStream);
+  const highWatermarkDurationSecondsRaw = audioStream?.highWatermarkDurationSeconds;
+  const highWatermarkDurationSeconds = Number(highWatermarkDurationSecondsRaw);
+  const highWatermarkFramesRaw = audioStream?.highWatermark;
+  const highWatermarkFrames = Number.isFinite(Number(highWatermarkFramesRaw)) ? Number(highWatermarkFramesRaw) : 0;
+  const capacityRaw = audioStream?.capacity;
+  const capacity = Number.isFinite(Number(capacityRaw)) ? Number(capacityRaw) : 0;
+  const bufferedDurationSecondsRaw = audioStream?.bufferedDurationSeconds;
+  const bufferedDurationSeconds = Number(bufferedDurationSecondsRaw);
+  const hasBufferedDuration = Number.isFinite(bufferedDurationSeconds);
+  const hasHighWatermarkDuration = Number.isFinite(highWatermarkDurationSeconds);
+  const highWatermarkRatio = capacity > 0 ? Math.min(1, highWatermarkFrames / capacity) : 0;
+  let highWatermarkMode = 'good';
+  if (highWatermarkRatio >= 0.95) highWatermarkMode = 'err';
+  else if (highWatermarkRatio >= 0.65) highWatermarkMode = 'warn';
+  const sparkHighWatermarkMax = Math.max(
+    1,
+    hasHighWatermarkDuration ? highWatermarkDurationSeconds : 0,
+    hasBufferedDuration ? bufferedDurationSeconds : 0
+  );
   drawSparkline('spark-audio', state.charts.audio, 'good', 1);
+  drawSparkline('spark-high-watermark', state.charts.highWatermark, highWatermarkMode, sparkHighWatermarkMax);
   drawSparkline('spark-underruns', state.charts.underruns, underruns > 0 ? 'err' : 'warn');
   drawSparkline('spark-tx', state.charts.tx, txStateValue === 'running' ? 'good' : 'warn', 1);
   applyMobilePanelDefaults();