diff --git a/electron/main.js b/electron/main.js
index adc1f7b9..5da624af 100644
--- a/electron/main.js
+++ b/electron/main.js
@@ -1478,6 +1478,10 @@ function createWindow() {
   // Frozen-but-not-crashed is the silent class no crash log sees; Chromium's own unresponsive
   // signal costs nothing and the report fires from the renderer AFTER it recovers.
   let wedgeStartedAt = 0;
+  try {
+    const { startMemorySensor } = require('./memorySensor');
+    startMemorySensor(app, () => mainWindow);
+  } catch (e) { console.warn('[diag] memory sensor unavailable:', e && e.message); }
   mainWindow.webContents.on('unresponsive', () => {
     wedgeStartedAt = Date.now();
     console.error('[diag][main] renderer unresponsive');
diff --git a/electron/memorySensor.js b/electron/memorySensor.js
new file mode 100644
index 00000000..88b7f572
--- /dev/null
+++ b/electron/memorySensor.js
@@ -0,0 +1,69 @@
+// Memory/compute overload sensor: the quiet death nobody reports, where RSS climbs until macOS
+// kills a renderer or the fans spin up. Idle-scheduled, unref'd, and it EMITS ONLY on threshold
+// crossings, so a healthy session ships nothing at all.
+'use strict';
+
+const SAMPLE_MS = 60_000;
+// Crossed once, reported once: a leak is a trend, not a per-minute alarm.
+const TOTAL_MB_CAP = 3000;
+const GROWTH_MB_PER_MIN = 40;
+const GROWTH_WINDOW = 10;
+
+let p_timer = null;
+let p_history = [];
+let p_capReported = false;
+let p_growthReported = false;
+
+function totalMb(metrics) {
+  let kb = 0;
+  for (const m of metrics) kb += (m.memory && m.memory.workingSetSize) || 0;
+  return Math.round(kb / 1024);
+}
+
+/** Least-squares slope in MB/min over the sample window; a straight climb is the leak signature. */
+function slopeMbPerMin(history) {
+  const n = history.length;
+  if (n < 4) return 0;
+  const meanX = (n - 1) / 2;
+  const meanY = history.reduce((a, b) => a + b, 0) / n;
+  let num = 0;
+  let den = 0;
+  for (let i = 0; i < n; i += 1) {
+    num += (i - meanX) * (history[i] - meanY);
+    den += (i - meanX) * (i - meanX);
+  }
+  return den === 0 ? 0 : num / den;
+}
+
+function startMemorySensor(app, getMainWindow) {
+  if (p_timer) return;
+  p_timer = setInterval(() => {
+    let metrics;
+    try { metrics = app.getAppMetrics(); } catch (_) { return; }
+    const mb = totalMb(metrics);
+    p_history.push(mb);
+    if (p_history.length > GROWTH_WINDOW) p_history.shift();
+    const slope = slopeMbPerMin(p_history);
+    const send = (reason, extra) => {
+      const win = getMainWindow();
+      if (win && !win.isDestroyed()) {
+        try { win.webContents.send('diag:memory', { reason, total_mb: mb, procs: metrics.length, slope_mb_min: Math.round(slope), ...extra }); } catch (_) {}
+      }
+      console.error('[diag][memory]', reason, 'total_mb=' + mb, 'procs=' + metrics.length, 'slope=' + Math.round(slope));
+    };
+    if (!p_capReported && mb >= TOTAL_MB_CAP) { p_capReported = true; send('cap_crossed', {}); }
+    if (p_capReported && mb < TOTAL_MB_CAP * 0.8) p_capReported = false;
+    if (!p_growthReported && p_history.length >= GROWTH_WINDOW && slope >= GROWTH_MB_PER_MIN) {
+      p_growthReported = true;
+      send('growth_suspect', { window_min: GROWTH_WINDOW });
+    }
+  }, SAMPLE_MS);
+  p_timer.unref?.();
+}
+
+function stopMemorySensor() {
+  if (p_timer) { clearInterval(p_timer); p_timer = null; }
+  p_history = [];
+}
+
+module.exports = { startMemorySensor, stopMemorySensor, slopeMbPerMin, totalMb, TOTAL_MB_CAP, GROWTH_MB_PER_MIN };
diff --git a/electron/memorySensor.test.js b/electron/memorySensor.test.js
new file mode 100644
index 00000000..d4708c62
--- /dev/null
+++ b/electron/memorySensor.test.js
@@ -0,0 +1,27 @@
+// The leak detector's math, pinned: a flat session reports nothing, a straight climb is caught.
+const assert = require('node:assert/strict');
+const { test } = require('node:test');
+const { slopeMbPerMin, totalMb, GROWTH_MB_PER_MIN } = require('./memorySensor');
+
+test('a flat memory profile has no slope, so nothing is ever reported', () => {
+  assert.ok(Math.abs(slopeMbPerMin([900, 905, 898, 902, 900, 903, 899, 901, 900, 902])) < 1, 'jitter is not a trend');
+});
+
+test('a steady climb is caught above the growth threshold', () => {
+  const climbing = Array.from({ length: 10 }, (_, i) => 800 + i * 60);
+  assert.ok(slopeMbPerMin(climbing) >= GROWTH_MB_PER_MIN, 'a 60MB/min climb must exceed the threshold');
+});
+
+test('a single spike is not a leak', () => {
+  const spike = [900, 900, 900, 900, 2000, 900, 900, 900, 900, 900];
+  assert.ok(slopeMbPerMin(spike) < GROWTH_MB_PER_MIN, 'one spike must not read as a trend');
+});
+
+test('too few samples never guesses', () => {
+  assert.equal(slopeMbPerMin([900, 2000, 3000]), 0);
+});
+
+test('totals sum every process in MB', () => {
+  assert.equal(totalMb([{ memory: { workingSetSize: 1024 * 500 } }, { memory: { workingSetSize: 1024 * 300 } }]), 800);
+  assert.equal(totalMb([{}, { memory: {} }]), 0);
+});
diff --git a/electron/preload.js b/electron/preload.js
index b16e668b..a8011822 100644
--- a/electron/preload.js
+++ b/electron/preload.js
@@ -152,6 +152,12 @@ contextBridge.exposeInMainWorld('openswarm', {
   openApplication: (name) => ipcRenderer.invoke('open-application', name),
   getUpdateStatus: () => ipcRenderer.invoke('get-update-status'),
   getCrashRecoveryInfo: () => ipcRenderer.invoke('get-crash-recovery-info'),
+  // Threshold-crossing memory alerts (cap or leak-shaped growth); silent on a healthy session.
+  onMemoryAlert: (cb) => {
+    const listener = (_e, info) => cb(info);
+    ipcRenderer.on('diag:memory', listener);
+    return () => ipcRenderer.removeListener('diag:memory', listener);
+  },
   // Fires after the renderer RECOVERS from a Chromium-detected freeze, with how long it was wedged.
   onWedge: (cb) => {
     const listener = (_e, info) => cb(info);
diff --git a/frontend/src/shared/uxSignals.ts b/frontend/src/shared/uxSignals.ts
index 9a862060..5c9615d6 100644
--- a/frontend/src/shared/uxSignals.ts
+++ b/frontend/src/shared/uxSignals.ts
@@ -67,9 +67,13 @@ export function installUxSignals(): () => void {
     report('process', 'wedge_recovered', { wedge_ms: info?.ms ?? -1, source: 'chromium' });
   });
   const offObserver = installWedgeObserver();
+  const offMem = (bridge.openswarm as { onMemoryAlert?: (cb: (i: Record<string, number | string>) => void) => () => void } | undefined)?.onMemoryAlert?.((info) => {
+    report('process', 'memory_alert', info);
+  });
   return () => {
     window.removeEventListener('click', onClick, true);
     offWedge?.();
     offObserver();
+    offMem?.();
   };
 }