diff --git a/muxplex/frontend/app.js b/muxplex/frontend/app.js
index 771bdbf..9acb4ca 100644
--- a/muxplex/frontend/app.js
+++ b/muxplex/frontend/app.js
@@ -248,6 +248,7 @@ async function pollSessions() {
     renderSidebar(sessions, _viewingSession);
     handleBellTransitions(prev, sessions);
     updateSessionPill(sessions);
+    updateFaviconBadge();
   } catch (err) {
     _pollFailCount++;
     setConnectionStatus(_pollFailCount <= 2 ? 'warn' : 'err');
@@ -815,6 +816,61 @@ function updatePillBell() {
   if (hasBell) el.classList.remove('hidden'); else el.classList.add('hidden');
 }
 
+// ---------------------------------------------------------------------------
+// Dynamic favicon — activity dot overlay
+// ---------------------------------------------------------------------------
+
+var _originalFavicon = null; // cached original favicon href
+
+/**
+ * Update the favicon with an activity dot if any session has unseen bells.
+ * Uses a 32x32 canvas to draw the original favicon + a colored circle overlay.
+ * Restores the original favicon when there are no unseen bells.
+ */
+function updateFaviconBadge() {
+  var hasActivity = _currentSessions && _currentSessions.some(function (s) {
+    return s.bell && s.bell.unseen_count > 0;
+  });
+
+  var link = document.querySelector('link[rel="icon"][sizes="32x32"]') ||
+             document.querySelector('link[rel="icon"]');
+  if (!link) return;
+
+  // Cache the original favicon on first call
+  if (!_originalFavicon) _originalFavicon = link.href;
+
+  if (!hasActivity) {
+    // Restore original favicon when no activity
+    if (link.href !== _originalFavicon) link.href = _originalFavicon;
+    return;
+  }
+
+  // Draw favicon + activity dot on canvas
+  var canvas = document.createElement('canvas');
+  canvas.width = 32;
+  canvas.height = 32;
+  var ctx = canvas.getContext('2d');
+  if (!ctx) return;
+
+  var img = new Image();
+  img.crossOrigin = 'anonymous';
+  img.onload = function () {
+    ctx.drawImage(img, 0, 0, 32, 32);
+
+    // Activity dot — brand amber (same as bell indicator)
+    ctx.beginPath();
+    ctx.arc(24, 8, 7, 0, 2 * Math.PI); // top-right area
+    ctx.fillStyle = '#F1A640';           // var(--bell-color)
+    ctx.fill();
+    ctx.strokeStyle = '#0D1117';         // var(--bg) — border for contrast
+    ctx.lineWidth = 2;
+    ctx.stroke();
+
+    link.href = canvas.toDataURL('image/png');
+  };
+  img.src = _originalFavicon;
+}
+
 // ─── Session open / close ────────────────────────────────────────────────────
 
 /**
diff --git a/muxplex/frontend/tests/test_app.mjs b/muxplex/frontend/tests/test_app.mjs
index f0dc75f..11918b5 100644
--- a/muxplex/frontend/tests/test_app.mjs
+++ b/muxplex/frontend/tests/test_app.mjs
@@ -2040,3 +2040,26 @@ test('applyDisplaySettings calls window._setTerminalFontSize when available', ()
 });
 
 
+
+// --- Issue: Dynamic favicon badge with activity dot ---
+
+test('updateFaviconBadge function exists in app.js', () => {
+  const source = fs.readFileSync(new URL('../app.js', import.meta.url), 'utf8');
+  assert.ok(
+    source.includes('function updateFaviconBadge'),
+    'app.js must define updateFaviconBadge function'
+  );
+});
+
+test('pollSessions calls updateFaviconBadge', () => {
+  const source = fs.readFileSync(new URL('../app.js', import.meta.url), 'utf8');
+  const pollStart = source.indexOf('async function pollSessions()');
+  assert.ok(pollStart !== -1, 'pollSessions must exist');
+  // Find the closing brace of pollSessions (next line starting with "}")
+  const pollEnd = source.indexOf('\n}', pollStart);
+  const pollBody = source.substring(pollStart, pollEnd + 2);
+  assert.ok(
+    pollBody.includes('updateFaviconBadge'),
+    'pollSessions must call updateFaviconBadge — update favicon on every poll cycle'
+  );
+});