diff --git a/src/TeamsISO.Engine/Discovery/ParticipantTracker.cs b/src/TeamsISO.Engine/Discovery/ParticipantTracker.cs
index 3b94340..df8b8b4 100644
--- a/src/TeamsISO.Engine/Discovery/ParticipantTracker.cs
+++ b/src/TeamsISO.Engine/Discovery/ParticipantTracker.cs
@@ -31,9 +31,15 @@ public sealed class ParticipantTracker
             case DiscoveryEvent.Added a when a.Source.Kind == NdiSourceKind.Participant:
                 HandleAdded(a.Source);
                 break;
+            case DiscoveryEvent.Added a when a.Source.Kind == NdiSourceKind.ActiveSpeaker:
+                HandleAutoMixAdded(a.Source);
+                break;
             case DiscoveryEvent.Removed r when r.Source.Kind == NdiSourceKind.Participant:
                 HandleRemoved(r.Source);
                 break;
+            case DiscoveryEvent.Removed r when r.Source.Kind == NdiSourceKind.ActiveSpeaker:
+                HandleRemoved(r.Source);
+                break;
         }
     }
 
@@ -61,6 +67,52 @@ public sealed class ParticipantTracker
             LastSeen: now));
     }
 
+    /// <summary>
+    /// Surfaces Teams' auto-mix output (the "Active Speaker" feed in current Teams,
+    /// or the legacy bare "(Teams)" source) as a special row in the participant list
+    /// with the synthetic display name "Active Speaker". The operator can then route
+    /// it to its own normalized ISO via the same enable toggle every other participant
+    /// uses. Id is deterministic from "auto-mix:&lt;machine&gt;" so the row's identity is
+    /// stable across discovery churn.
+    /// </summary>
+    private void HandleAutoMixAdded(NdiSource source)
+    {
+        var now = _now();
+        PruneRecentlyRemoved(now);
+
+        var stableId = DeterministicGuid("auto-mix:" + source.MachineName);
+        var existing = _participants.FirstOrDefault(p => p.Id == stableId);
+        if (existing is not null)
+        {
+            existing.CurrentSource = source;
+            existing.LastSeen = now;
+            return;
+        }
+
+        _participants.Add(new MutableParticipant(
+            Id: stableId,
+            DisplayName: "Active Speaker",
+            CurrentSource: source,
+            FirstSeen: now,
+            LastSeen: now));
+    }
+
+    /// <summary>
+    /// Stable Guid derived from a string. Used to give the auto-mix synthetic
+    /// participant a consistent Id across discovery cycles (so re-add doesn't
+    /// duplicate the row, and the operator's ISO assignment persists).
+    /// </summary>
+    private static Guid DeterministicGuid(string input)
+    {
+        var hash = System.Security.Cryptography.SHA1.HashData(System.Text.Encoding.UTF8.GetBytes(input));
+        var bytes = new byte[16];
+        Buffer.BlockCopy(hash, 0, bytes, 0, 16);
+        // Set the version (5) and variant bits per RFC 4122 so the value is a valid v5 GUID.
+        bytes[6] = (byte)((bytes[6] & 0x0F) | 0x50);
+        bytes[8] = (byte)((bytes[8] & 0x3F) | 0x80);
+        return new Guid(bytes);
+    }
+
     private void HandleRemoved(NdiSource source)
     {
         var now = _now();
diff --git a/src/tests/TeamsISO.Engine.Tests/Discovery/ParticipantTrackerTests.cs b/src/tests/TeamsISO.Engine.Tests/Discovery/ParticipantTrackerTests.cs
index 0892fab..c125685 100644
--- a/src/tests/TeamsISO.Engine.Tests/Discovery/ParticipantTrackerTests.cs
+++ b/src/tests/TeamsISO.Engine.Tests/Discovery/ParticipantTrackerTests.cs
@@ -100,4 +100,39 @@ public class ParticipantTrackerTests
 
         tracker.Participants.Should().BeEmpty();
     }
+
+    [Fact]
+    public void ActiveSpeaker_AppearsAsSyntheticAutoMixParticipant()
+    {
+        // The ActiveSpeaker kind (legacy "MACHINE (Teams)" or current
+        // "MACHINE (MS Teams - Active Speaker)") is now surfaced as a row in the
+        // participant list with a synthetic display name "Active Speaker", so the
+        // operator can route it to its own normalized ISO via the same toggle as
+        // any participant.
+        var tracker = new ParticipantTracker(TimeSpan.FromSeconds(5), () => T0);
+        var autoMix = new NdiSource("WOOGLIN (MS Teams - Active Speaker)", "WOOGLIN", NdiSourceKind.ActiveSpeaker, null);
+
+        tracker.Apply(new DiscoveryEvent.Added(autoMix));
+
+        tracker.Participants.Should().HaveCount(1);
+        tracker.Participants[0].DisplayName.Should().Be("Active Speaker");
+        tracker.Participants[0].CurrentSource!.FullName.Should().Be(autoMix.FullName);
+    }
+
+    [Fact]
+    public void ActiveSpeaker_ReAddOnSameMachine_PreservesId()
+    {
+        // The synthetic auto-mix participant must use a deterministic Id (derived
+        // from "auto-mix:<machine>") so a discovery cycle that re-adds the source
+        // doesn't duplicate the row and the operator's ISO assignment stays bound.
+        var tracker = new ParticipantTracker(TimeSpan.FromSeconds(5), () => T0);
+        var autoMix = new NdiSource("WOOGLIN (MS Teams - Active Speaker)", "WOOGLIN", NdiSourceKind.ActiveSpeaker, null);
+
+        tracker.Apply(new DiscoveryEvent.Added(autoMix));
+        var firstId = tracker.Participants[0].Id;
+        tracker.Apply(new DiscoveryEvent.Added(autoMix));
+
+        tracker.Participants.Should().HaveCount(1);
+        tracker.Participants[0].Id.Should().Be(firstId);
+    }
 }