diff --git a/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Runtime/UserSidResolverTests.cs b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Runtime/UserSidResolverTests.cs
new file mode 100644
index 00000000..aea0ecd0
--- /dev/null
+++ b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Runtime/UserSidResolverTests.cs
@@ -0,0 +1,41 @@
+using AutopilotMonitor.Agent.V2.Core.Monitoring.Runtime;
+using Xunit;
+
+namespace AutopilotMonitor.Agent.V2.Core.Tests.Monitoring.Runtime
+{
+    public sealed class UserSidResolverTests
+    {
+        [Fact]
+        public void Resolves_well_known_builtin_administrators_to_canonical_sid()
+        {
+            // BUILTIN\Administrators is a well-known local group with a deterministic SID on
+            // every Windows installation. Using it as the round-trip oracle avoids any
+            // environment-specific user-database dependency.
+            Assert.True(UserSidResolver.TryResolveSid("BUILTIN\\Administrators", out var sid));
+            Assert.Equal("S-1-5-32-544", sid);
+        }
+
+        [Fact]
+        public void Resolves_bare_user_form_for_well_known_account()
+        {
+            // SYSTEM ("NT AUTHORITY\SYSTEM") is well-known with SID S-1-5-18. The resolver
+            // must accept the qualified form on every Windows installation.
+            Assert.True(UserSidResolver.TryResolveSid("NT AUTHORITY\\SYSTEM", out var sid));
+            Assert.Equal("S-1-5-18", sid);
+        }
+
+        [Fact]
+        public void Returns_false_for_obviously_invalid_account()
+        {
+            Assert.False(UserSidResolver.TryResolveSid("CONTOSO\\definitely-not-a-real-user-7f3e2c9a", out var sid));
+            Assert.Null(sid);
+        }
+
+        [Fact]
+        public void Returns_false_for_empty_input()
+        {
+            Assert.False(UserSidResolver.TryResolveSid(string.Empty, out var sid));
+            Assert.Null(sid);
+        }
+    }
+}
diff --git a/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/SignalAdapters/RealmJoinWatcherAdapterTests.cs b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/SignalAdapters/RealmJoinWatcherAdapterTests.cs
new file mode 100644
index 00000000..2c23887f
--- /dev/null
+++ b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/SignalAdapters/RealmJoinWatcherAdapterTests.cs
@@ -0,0 +1,190 @@
+using System;
+using System.Linq;
+using AutopilotMonitor.Agent.V2.Core.Logging;
+using AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.SystemSignals;
+using AutopilotMonitor.Agent.V2.Core.SignalAdapters;
+using AutopilotMonitor.Agent.V2.Core.Tests.Harness;
+using AutopilotMonitor.Agent.V2.Core.Tests.Orchestration;
+using AutopilotMonitor.DecisionCore.Engine;
+using AutopilotMonitor.DecisionCore.Signals;
+using AutopilotMonitor.DecisionCore.State;
+using SharedEventTypes = AutopilotMonitor.Shared.Constants.EventTypes;
+using Xunit;
+
+namespace AutopilotMonitor.Agent.V2.Core.Tests.SignalAdapters
+{
+    public sealed class RealmJoinWatcherAdapterTests
+    {
+        private static readonly DateTime Fixed = new DateTime(2026, 5, 21, 10, 0, 0, DateTimeKind.Utc);
+
+        private sealed class Fixture : IDisposable
+        {
+            public TempDirectory Tmp { get; } = new TempDirectory();
+            public AgentLogger Logger { get; }
+            public RealmJoinWatcher Watcher { get; }
+            public FakeSignalIngressSink Ingress { get; } = new FakeSignalIngressSink();
+            public VirtualClock Clock { get; } = new VirtualClock(Fixed);
+
+            public Fixture()
+            {
+                Logger = new AgentLogger(Tmp.Path, AgentLogLevel.Info);
+                Watcher = new RealmJoinWatcher(Logger);
+            }
+
+            public void Dispose()
+            {
+                Watcher.Dispose();
+                Tmp.Dispose();
+            }
+        }
+
+        [Fact]
+        public void TriggerDetectedFromTest_emits_RealmJoinDetected_signal_and_informational_event()
+        {
+            using var f = new Fixture();
+            using var adapter = new RealmJoinWatcherAdapter(f.Watcher, f.Ingress, f.Clock);
+
+            adapter.TriggerDetectedFromTest(phase: 100);
+
+            // 1) Decision signal that mutates engine state.
+            var decision = f.Ingress.Posted.Single(p => p.Kind == DecisionSignalKind.RealmJoinDetected);
+            Assert.Equal("RealmJoinWatcher", decision.SourceOrigin);
+            Assert.Equal("100", decision.Payload![DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase]);
+
+            // 2) Dual-emit informational event so the timeline shows realmjoin_detected.
+            var info = f.Ingress.Posted.Single(p =>
+                p.Kind == DecisionSignalKind.InformationalEvent
+                && p.Payload != null
+                && p.Payload.TryGetValue(SignalPayloadKeys.EventType, out var et)
+                && et == SharedEventTypes.RealmJoinDetected);
+            Assert.Equal("RealmJoinWatcher", info.Payload![SignalPayloadKeys.Source]);
+            Assert.Equal("true", info.Payload[SignalPayloadKeys.ImmediateUpload]);
+            Assert.Equal("100", info.Payload["deploymentPhase"]);
+            Assert.Contains("HKLM", info.Payload["registryKey"]);
+        }
+
+        [Fact]
+        public void TriggerResolvedFromTest_emits_RealmJoinResolved_signal_and_informational_event()
+        {
+            using var f = new Fixture();
+            using var adapter = new RealmJoinWatcherAdapter(f.Watcher, f.Ingress, f.Clock);
+
+            adapter.TriggerResolvedFromTest(phase: 110);
+
+            var decision = f.Ingress.Posted.Single(p => p.Kind == DecisionSignalKind.RealmJoinResolved);
+            Assert.Equal("110", decision.Payload![DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase]);
+
+            var info = f.Ingress.Posted.Single(p =>
+                p.Kind == DecisionSignalKind.InformationalEvent
+                && p.Payload != null
+                && p.Payload.TryGetValue(SignalPayloadKeys.EventType, out var et)
+                && et == SharedEventTypes.RealmJoinResolved);
+            Assert.Equal("RealmJoinWatcher", info.Payload![SignalPayloadKeys.Source]);
+            Assert.Equal("110", info.Payload["deploymentPhase"]);
+        }
+
+        [Fact]
+        public void TriggerPhaseChangedFromTest_emits_informational_only_no_decision_signal()
+        {
+            using var f = new Fixture();
+            using var adapter = new RealmJoinWatcherAdapter(f.Watcher, f.Ingress, f.Clock);
+
+            adapter.TriggerPhaseChangedFromTest(prev: 100, curr: 200);
+
+            // Phase change is observability-only. There is no DecisionSignalKind.RealmJoinPhaseChanged.
+            Assert.DoesNotContain(f.Ingress.Posted, p => p.Kind == DecisionSignalKind.RealmJoinDetected);
+            Assert.DoesNotContain(f.Ingress.Posted, p => p.Kind == DecisionSignalKind.RealmJoinResolved);
+
+            var info = f.Ingress.Posted.Single(p =>
+                p.Kind == DecisionSignalKind.InformationalEvent
+                && p.Payload != null
+                && p.Payload.TryGetValue(SignalPayloadKeys.EventType, out var et)
+                && et == SharedEventTypes.RealmJoinPhaseChanged);
+            Assert.Equal("200", info.Payload!["deploymentPhase"]);
+            Assert.Equal("100", info.Payload["previousPhase"]);
+        }
+
+        [Fact]
+        public void TriggerPackageStartedFromTest_emits_signal_and_event_with_packageId_scope()
+        {
+            using var f = new Fixture();
+            using var adapter = new RealmJoinWatcherAdapter(f.Watcher, f.Ingress, f.Clock);
+
+            var snap = new RealmJoinPackageSnapshot(
+                packageId: "generic-vlc",
+                displayName: "VLC media player",
+                version: "3.0.21.0",
+                success: null,
+                lastExitCode: null);
+            adapter.TriggerPackageStartedFromTest(scope: RealmJoinPackageFact.ScopeMachine, snap: snap);
+
+            var decision = f.Ingress.Posted.Single(p => p.Kind == DecisionSignalKind.RealmJoinPackageStarted);
+            Assert.Equal("generic-vlc", decision.Payload![DecisionEngine.RealmJoinPayloadKeys.PackageId]);
+            Assert.Equal("VLC media player", decision.Payload[DecisionEngine.RealmJoinPayloadKeys.DisplayName]);
+            Assert.Equal("3.0.21.0", decision.Payload[DecisionEngine.RealmJoinPayloadKeys.Version]);
+            Assert.Equal("machine", decision.Payload[DecisionEngine.RealmJoinPayloadKeys.Scope]);
+
+            var info = f.Ingress.Posted.Single(p =>
+                p.Kind == DecisionSignalKind.InformationalEvent
+                && p.Payload != null
+                && p.Payload.TryGetValue(SignalPayloadKeys.EventType, out var et)
+                && et == SharedEventTypes.RealmJoinPackageStarted);
+            Assert.Equal("generic-vlc", info.Payload!["packageId"]);
+            Assert.Equal("machine", info.Payload["scope"]);
+        }
+
+        [Fact]
+        public void TriggerPackageCompletedFromTest_emits_signal_and_event_with_success_and_exit_code()
+        {
+            using var f = new Fixture();
+            using var adapter = new RealmJoinWatcherAdapter(f.Watcher, f.Ingress, f.Clock);
+
+            var snap = new RealmJoinPackageSnapshot(
+                packageId: "generic-vlc",
+                displayName: "VLC media player",
+                version: "3.0.21.0",
+                success: true,
+                lastExitCode: 0);
+            adapter.TriggerPackageCompletedFromTest(scope: RealmJoinPackageFact.ScopeMachine, snap: snap);
+
+            var decision = f.Ingress.Posted.Single(p => p.Kind == DecisionSignalKind.RealmJoinPackageCompleted);
+            Assert.Equal("true", decision.Payload![DecisionEngine.RealmJoinPayloadKeys.Success]);
+            Assert.Equal("0", decision.Payload[DecisionEngine.RealmJoinPayloadKeys.LastExitCode]);
+
+            var info = f.Ingress.Posted.Single(p =>
+                p.Kind == DecisionSignalKind.InformationalEvent
+                && p.Payload != null
+                && p.Payload.TryGetValue(SignalPayloadKeys.EventType, out var et)
+                && et == SharedEventTypes.RealmJoinPackageCompleted);
+            Assert.Equal("true", info.Payload!["success"]);
+            Assert.Equal("0", info.Payload["lastExitCode"]);
+        }
+
+        [Fact]
+        public void Overlong_display_name_is_truncated_to_256_characters()
+        {
+            using var f = new Fixture();
+            using var adapter = new RealmJoinWatcherAdapter(f.Watcher, f.Ingress, f.Clock);
+
+            var longName = new string('x', 1000);
+            var snap = new RealmJoinPackageSnapshot(
+                packageId: "generic-bigname",
+                displayName: longName,
+                version: null,
+                success: null,
+                lastExitCode: null);
+            adapter.TriggerPackageStartedFromTest(scope: RealmJoinPackageFact.ScopeUser, snap: snap);
+
+            var info = f.Ingress.Posted.Single(p =>
+                p.Kind == DecisionSignalKind.InformationalEvent
+                && p.Payload != null
+                && p.Payload.TryGetValue(SignalPayloadKeys.EventType, out var et)
+                && et == SharedEventTypes.RealmJoinPackageStarted);
+            // Adapter must clamp DisplayName before posting (PII / payload-size guard mirror of
+            // RealmJoinPackageFact.MaxDisplayNameLength = 256). The packageId stays intact.
+            Assert.Equal(256, info.Payload!["displayName"].Length);
+            Assert.Equal("generic-bigname", info.Payload["packageId"]);
+            Assert.Equal("user", info.Payload["scope"]);
+        }
+    }
+}
diff --git a/src/Agent/AutopilotMonitor.DecisionCore.Tests/RealmJoinGateTests.cs b/src/Agent/AutopilotMonitor.DecisionCore.Tests/RealmJoinGateTests.cs
new file mode 100644
index 00000000..7433f8d4
--- /dev/null
+++ b/src/Agent/AutopilotMonitor.DecisionCore.Tests/RealmJoinGateTests.cs
@@ -0,0 +1,284 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using AutopilotMonitor.DecisionCore.Engine;
+using AutopilotMonitor.DecisionCore.Signals;
+using AutopilotMonitor.DecisionCore.State;
+using AutopilotMonitor.Shared.Models;
+using Xunit;
+
+namespace AutopilotMonitor.DecisionCore.Tests
+{
+    /// <summary>
+    /// Reducer integration tests for the RealmJoin (RJ) completion-gate. The Classic and
+    /// SelfDeploying completion paths must defer terminal transitions while RJ is detected
+    /// and unresolved, and release them once <see cref="DecisionSignalKind.RealmJoinResolved"/>
+    /// arrives or the <see cref="DeadlineNames.RealmJoinTimeout"/> deadline fires.
+    /// </summary>
+    public sealed class RealmJoinGateTests
+    {
+        private static readonly DateTime T0 = new DateTime(2026, 5, 21, 10, 0, 0, DateTimeKind.Utc);
+
+        private static DecisionSignal MakeSignal(
+            long ordinal,
+            DecisionSignalKind kind,
+            DateTime occurredAtUtc,
+            IReadOnlyDictionary<string, string>? payload = null)
+        {
+            return new DecisionSignal(
+                sessionSignalOrdinal: ordinal,
+                sessionTraceOrdinal: ordinal,
+                kind: kind,
+                kindSchemaVersion: 1,
+                occurredAtUtc: occurredAtUtc,
+                sourceOrigin: "test",
+                evidence: new Evidence(EvidenceKind.Synthetic, $"t-{kind}-{ordinal}", $"synthetic {kind}"),
+                payload: payload);
+        }
+
+        private static DecisionState PrimeClassicAwaitingDesktop(DecisionEngine engine)
+        {
+            var state = DecisionState.CreateInitial("rj-sess", "rj-tenant", T0);
+            state = engine.Reduce(state, MakeSignal(0, DecisionSignalKind.SessionStarted, T0)).NewState;
+            state = engine.Reduce(state, MakeSignal(1, DecisionSignalKind.EspPhaseChanged, T0.AddMinutes(1),
+                new Dictionary<string, string> { [SignalPayloadKeys.EspPhase] = "DeviceSetup" })).NewState;
+            state = engine.Reduce(state, MakeSignal(2, DecisionSignalKind.EspPhaseChanged, T0.AddMinutes(2),
+                new Dictionary<string, string> { [SignalPayloadKeys.EspPhase] = "AccountSetup" })).NewState;
+            state = engine.Reduce(state, MakeSignal(3, DecisionSignalKind.EspExiting, T0.AddMinutes(3))).NewState;
+            state = engine.Reduce(state, MakeSignal(4, DecisionSignalKind.HelloResolved, T0.AddMinutes(4),
+                new Dictionary<string, string> { [SignalPayloadKeys.HelloOutcome] = "Success" })).NewState;
+            Assert.Equal(SessionStage.AwaitingDesktop, state.Stage);
+            return state;
+        }
+
+        // ============================================================== Classic flow
+
+        [Fact]
+        public void Baseline_without_realmjoin_detected_completes_normally()
+        {
+            // Regression guard — on devices where RJ is not installed (DetectedUtc stays null),
+            // the gate is open and the Hello+Desktop AND-gate must reach Finalizing exactly as
+            // before Phase A.
+            var engine = new DecisionEngine();
+            var state = PrimeClassicAwaitingDesktop(engine);
+            Assert.Null(state.RealmJoinFacts.DetectedUtc);
+
+            var step = engine.Reduce(state, MakeSignal(5, DecisionSignalKind.DesktopArrived, T0.AddMinutes(5)));
+
+            Assert.Equal(SessionStage.Finalizing, step.NewState.Stage);
+            Assert.Contains(step.NewState.Deadlines, d => d.Name == DeadlineNames.FinalizingGrace);
+        }
+
+        [Fact]
+        public void RealmJoinDetected_arms_the_60_min_hard_timeout_deadline()
+        {
+            var engine = new DecisionEngine();
+            var state = PrimeClassicAwaitingDesktop(engine);
+
+            var step = engine.Reduce(state, MakeSignal(5, DecisionSignalKind.RealmJoinDetected, T0.AddMinutes(5),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "100" }));
+
+            Assert.NotNull(step.NewState.RealmJoinFacts.DetectedUtc);
+            Assert.Equal(100, step.NewState.RealmJoinFacts.LastDeploymentPhase!.Value);
+
+            var deadline = Assert.Single(step.NewState.Deadlines, d => d.Name == DeadlineNames.RealmJoinTimeout);
+            // 60-min hard timeout from the post-PrimeClassic AgentBoot anchor (T0) — within rounding.
+            Assert.InRange(deadline.DueAtUtc, T0.AddMinutes(55), T0.AddMinutes(70));
+
+            // ScheduleDeadline effect emitted exactly once.
+            Assert.Single(step.Effects, e =>
+                e.Kind == DecisionEffectKind.ScheduleDeadline &&
+                e.Deadline != null &&
+                e.Deadline.Name == DeadlineNames.RealmJoinTimeout);
+        }
+
+        [Fact]
+        public void RealmJoinGate_closed_defers_finalizing_when_DesktopArrived_arrives_with_hello_already_resolved()
+        {
+            // Sequence: Hello + RealmJoinDetected before Desktop, then DesktopArrived. The AND-gate
+            // would normally TransitionToFinalizing — but the closed gate must keep the session
+            // out of Finalizing until RJ resolves.
+            var engine = new DecisionEngine();
+            var state = PrimeClassicAwaitingDesktop(engine);
+
+            state = engine.Reduce(state, MakeSignal(5, DecisionSignalKind.RealmJoinDetected, T0.AddMinutes(5),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "100" })).NewState;
+
+            var step = engine.Reduce(state, MakeSignal(6, DecisionSignalKind.DesktopArrived, T0.AddMinutes(6)));
+
+            Assert.NotEqual(SessionStage.Finalizing, step.NewState.Stage);
+            Assert.Null(step.NewState.Outcome);
+            Assert.DoesNotContain(step.NewState.Deadlines, d => d.Name == DeadlineNames.FinalizingGrace);
+            Assert.NotNull(step.NewState.DesktopArrivedUtc); // fact still recorded
+        }
+
+        [Fact]
+        public void RealmJoinResolved_after_hello_and_desktop_triggers_finalizing_via_classic_path()
+        {
+            // Same setup as the previous test, then RealmJoinResolved (phase 110) lands. The
+            // resolved handler routes through CompleteIfDeferredOrBookkeep → TransitionToFinalizing.
+            var engine = new DecisionEngine();
+            var state = PrimeClassicAwaitingDesktop(engine);
+            state = engine.Reduce(state, MakeSignal(5, DecisionSignalKind.RealmJoinDetected, T0.AddMinutes(5),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "100" })).NewState;
+            state = engine.Reduce(state, MakeSignal(6, DecisionSignalKind.DesktopArrived, T0.AddMinutes(6))).NewState;
+            Assert.NotEqual(SessionStage.Finalizing, state.Stage);
+
+            var step = engine.Reduce(state, MakeSignal(7, DecisionSignalKind.RealmJoinResolved, T0.AddMinutes(7),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "110" }));
+
+            Assert.Equal(SessionStage.Finalizing, step.NewState.Stage);
+            Assert.Contains(step.NewState.Deadlines, d => d.Name == DeadlineNames.FinalizingGrace);
+            // RealmJoinTimeout deadline got cancelled both in state and as a scheduler effect.
+            Assert.DoesNotContain(step.NewState.Deadlines, d => d.Name == DeadlineNames.RealmJoinTimeout);
+            Assert.Contains(step.Effects, e =>
+                e.Kind == DecisionEffectKind.CancelDeadline &&
+                e.CancelDeadlineName == DeadlineNames.RealmJoinTimeout);
+            Assert.Equal("Resolved", step.NewState.RealmJoinFacts.Outcome!.Value);
+        }
+
+        [Fact]
+        public void RealmJoinTimeout_with_hello_and_desktop_in_completes_with_timeout_outcome()
+        {
+            // Hard 60-min timeout fires while RJ is still incomplete but Hello+Desktop already
+            // landed. Handler routes through CompleteIfDeferredOrBookkeep → TransitionToFinalizing
+            // and records realmjoinOutcome="Timeout".
+            var engine = new DecisionEngine();
+            var state = PrimeClassicAwaitingDesktop(engine);
+            state = engine.Reduce(state, MakeSignal(5, DecisionSignalKind.RealmJoinDetected, T0.AddMinutes(5),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "100" })).NewState;
+            state = engine.Reduce(state, MakeSignal(6, DecisionSignalKind.DesktopArrived, T0.AddMinutes(6))).NewState;
+
+            var step = engine.Reduce(state, MakeSignal(7, DecisionSignalKind.DeadlineFired, T0.AddMinutes(65),
+                new Dictionary<string, string> { [SignalPayloadKeys.Deadline] = DeadlineNames.RealmJoinTimeout }));
+
+            Assert.Equal(SessionStage.Finalizing, step.NewState.Stage);
+            Assert.Equal("Timeout", step.NewState.RealmJoinFacts.Outcome!.Value);
+
+            // The reducer emitted a realmjoin_timeout timeline entry alongside the
+            // Finalizing-transition effects.
+            Assert.Contains(step.Effects, e =>
+                e.Kind == DecisionEffectKind.EmitEventTimelineEntry &&
+                e.Parameters != null &&
+                e.Parameters.TryGetValue("eventType", out var et) && et == "realmjoin_timeout");
+        }
+
+        // ============================================================== SelfDeploying flow
+
+        [Fact]
+        public void SelfDeploying_DeviceSetupProvisioningComplete_with_realmjoin_open_completes_immediately()
+        {
+            // Baseline — RJ never detected → SelfDeploying terminal path completes directly.
+            var engine = new DecisionEngine();
+            var state = DecisionState.CreateInitial("rj-sd", "rj-tenant", T0);
+            state = engine.Reduce(state, MakeSignal(0, DecisionSignalKind.SessionStarted, T0)).NewState;
+            state = engine.Reduce(state, MakeSignal(1, DecisionSignalKind.EspPhaseChanged, T0.AddMinutes(1),
+                new Dictionary<string, string> { [SignalPayloadKeys.EspPhase] = "DeviceSetup" })).NewState;
+
+            var step = engine.Reduce(state, MakeSignal(2, DecisionSignalKind.DeviceSetupProvisioningComplete, T0.AddMinutes(2)));
+
+            Assert.Equal(SessionStage.Completed, step.NewState.Stage);
+            Assert.Equal(SessionOutcome.EnrollmentComplete, step.NewState.Outcome);
+        }
+
+        [Fact]
+        public void SelfDeploying_with_realmjoin_detected_defers_terminal_until_resolved()
+        {
+            // SelfDeploying terminal handler observes the gate is closed → marks
+            // SelfDeployingDeferredCompletion on RealmJoinFacts, stays non-terminal, lets the
+            // RealmJoinResolved handler complete directly to Completed (not via Finalizing).
+            var engine = new DecisionEngine();
+            var state = DecisionState.CreateInitial("rj-sd-2", "rj-tenant", T0);
+            state = engine.Reduce(state, MakeSignal(0, DecisionSignalKind.SessionStarted, T0)).NewState;
+            state = engine.Reduce(state, MakeSignal(1, DecisionSignalKind.EspPhaseChanged, T0.AddMinutes(1),
+                new Dictionary<string, string> { [SignalPayloadKeys.EspPhase] = "DeviceSetup" })).NewState;
+            state = engine.Reduce(state, MakeSignal(2, DecisionSignalKind.RealmJoinDetected, T0.AddMinutes(2),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "100" })).NewState;
+
+            var deferred = engine.Reduce(state, MakeSignal(3, DecisionSignalKind.DeviceSetupProvisioningComplete, T0.AddMinutes(3))).NewState;
+            Assert.NotEqual(SessionStage.Completed, deferred.Stage);
+            Assert.True(deferred.RealmJoinFacts.SelfDeployingDeferredCompletion?.Value);
+
+            var step = engine.Reduce(deferred, MakeSignal(4, DecisionSignalKind.RealmJoinResolved, T0.AddMinutes(4),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "110" }));
+
+            Assert.Equal(SessionStage.Completed, step.NewState.Stage);
+            Assert.Equal(SessionOutcome.EnrollmentComplete, step.NewState.Outcome);
+            // Direct Completed path emits enrollment_complete inline; no FinalizingGrace deadline
+            // needed because the SelfDeploying handler clears deadlines.
+            Assert.DoesNotContain(step.NewState.Deadlines, d => d.Name == DeadlineNames.FinalizingGrace);
+            Assert.Contains(step.Effects, e =>
+                e.Kind == DecisionEffectKind.EmitEventTimelineEntry &&
+                e.Parameters != null &&
+                e.Parameters.TryGetValue("eventType", out var et) && et == "enrollment_complete");
+        }
+
+        // ============================================================== Per-package tracking
+
+        [Fact]
+        public void Per_package_started_and_completed_signals_update_RealmJoinFacts_packages()
+        {
+            var engine = new DecisionEngine();
+            var state = DecisionState.CreateInitial("rj-pkg", "rj-tenant", T0);
+            state = engine.Reduce(state, MakeSignal(0, DecisionSignalKind.SessionStarted, T0)).NewState;
+            state = engine.Reduce(state, MakeSignal(1, DecisionSignalKind.RealmJoinDetected, T0.AddMinutes(1),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "100" })).NewState;
+
+            state = engine.Reduce(state, MakeSignal(2, DecisionSignalKind.RealmJoinPackageStarted, T0.AddMinutes(2),
+                new Dictionary<string, string>
+                {
+                    [DecisionEngine.RealmJoinPayloadKeys.PackageId] = "generic-vlc",
+                    [DecisionEngine.RealmJoinPayloadKeys.DisplayName] = "VLC media player",
+                    [DecisionEngine.RealmJoinPayloadKeys.Version] = "3.0.21.0",
+                    [DecisionEngine.RealmJoinPayloadKeys.Scope] = RealmJoinPackageFact.ScopeMachine,
+                })).NewState;
+            Assert.Single(state.RealmJoinFacts.Packages, p => p.PackageId == "generic-vlc" && p.CompletedUtc == null);
+
+            state = engine.Reduce(state, MakeSignal(3, DecisionSignalKind.RealmJoinPackageCompleted, T0.AddMinutes(3),
+                new Dictionary<string, string>
+                {
+                    [DecisionEngine.RealmJoinPayloadKeys.PackageId] = "generic-vlc",
+                    [DecisionEngine.RealmJoinPayloadKeys.DisplayName] = "VLC media player",
+                    [DecisionEngine.RealmJoinPayloadKeys.Scope] = RealmJoinPackageFact.ScopeMachine,
+                    [DecisionEngine.RealmJoinPayloadKeys.Success] = "true",
+                    [DecisionEngine.RealmJoinPayloadKeys.LastExitCode] = "0",
+                })).NewState;
+            var completed = Assert.Single(state.RealmJoinFacts.Packages, p => p.PackageId == "generic-vlc");
+            Assert.True(completed.Success);
+            Assert.Equal(0, completed.LastExitCode);
+            Assert.NotNull(completed.CompletedUtc);
+        }
+
+        // ============================================================== Audit trail
+
+        [Fact]
+        public void Audit_trail_attaches_realmjoin_fields_when_enrollment_completes_after_resolved()
+        {
+            // After SelfDeploying + RealmJoinResolved, the enrollment_complete effect must carry
+            // the realmjoin* audit-trail fields built by DecisionAuditTrailBuilder.
+            var engine = new DecisionEngine();
+            var state = DecisionState.CreateInitial("rj-audit", "rj-tenant", T0);
+            state = engine.Reduce(state, MakeSignal(0, DecisionSignalKind.SessionStarted, T0)).NewState;
+            state = engine.Reduce(state, MakeSignal(1, DecisionSignalKind.EspPhaseChanged, T0.AddMinutes(1),
+                new Dictionary<string, string> { [SignalPayloadKeys.EspPhase] = "DeviceSetup" })).NewState;
+            state = engine.Reduce(state, MakeSignal(2, DecisionSignalKind.RealmJoinDetected, T0.AddMinutes(2),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "100" })).NewState;
+            state = engine.Reduce(state, MakeSignal(3, DecisionSignalKind.DeviceSetupProvisioningComplete, T0.AddMinutes(3))).NewState;
+
+            var step = engine.Reduce(state, MakeSignal(4, DecisionSignalKind.RealmJoinResolved, T0.AddMinutes(4),
+                new Dictionary<string, string> { [DecisionEngine.RealmJoinPayloadKeys.DeploymentPhase] = "110" }));
+
+            var completeEffect = Assert.Single(step.Effects, e =>
+                e.Kind == DecisionEffectKind.EmitEventTimelineEntry &&
+                e.Parameters != null &&
+                e.Parameters.TryGetValue("eventType", out var et) && et == "enrollment_complete");
+
+            Assert.NotNull(completeEffect.TypedPayload);
+            var data = Assert.IsType<Dictionary<string, object>>(completeEffect.TypedPayload);
+            Assert.Equal("Resolved", data["realmjoinOutcome"]);
+            Assert.Equal(110, data["realmjoinLastPhase"]);
+            Assert.True(data.ContainsKey("realmjoinDetectedUtc"));
+            Assert.True(data.ContainsKey("realmjoinResolvedUtc"));
+        }
+    }
+}
diff --git a/tests/fixtures/signal-kinds/realmjoin-detected-v1.json b/tests/fixtures/signal-kinds/realmjoin-detected-v1.json
new file mode 100644
index 00000000..d406fabd
--- /dev/null
+++ b/tests/fixtures/signal-kinds/realmjoin-detected-v1.json
@@ -0,0 +1,8 @@
+# RealmJoinDetected v1 — RealmJoin deployment tracking.
+# Posted by RealmJoinWatcherAdapter when HKLM\SYSTEM\CurrentControlSet\Services\realmjoin\
+# Parameters is first observed. Payload carries the current DeploymentPhase DWORD.
+# Reducer: HandleRealmJoinDetectedV1 → records RealmJoinFacts.DetectedUtc + LastDeploymentPhase,
+# arms the 60-min RealmJoinTimeout deadline. The V2 completion AND-gate now reads
+# RealmJoinFacts.DetectedUtc != null and defers Finalizing until RealmJoinResolved /
+# RealmJoinTimeout fires.
+{"SessionSignalOrdinal":1,"SessionTraceOrdinal":1,"Kind":"RealmJoinDetected","KindSchemaVersion":1,"OccurredAtUtc":"2026-05-21T10:00:00.0000000Z","SourceOrigin":"RealmJoinWatcher","Evidence":{"Kind":"Derived","Identifier":"realmjoin-detected-v1","Summary":"RealmJoin Parameters key observed (phase=100)","DerivationInputs":{"registryKey":"HKLM\\SYSTEM\\CurrentControlSet\\Services\\realmjoin\\Parameters"}},"Payload":{"deploymentPhase":"100"}}
diff --git a/tests/fixtures/signal-kinds/realmjoin-package-completed-v1.json b/tests/fixtures/signal-kinds/realmjoin-package-completed-v1.json
new file mode 100644
index 00000000..322692e5
--- /dev/null
+++ b/tests/fixtures/signal-kinds/realmjoin-package-completed-v1.json
@@ -0,0 +1,7 @@
+# RealmJoinPackageCompleted v1 — terminal per-package event.
+# Posted by RealmJoinWatcherAdapter when the matching <id> sub-key gains both Success and
+# LastExitCode values. Payload extends the started shape with success ("true"|"false") +
+# lastExitCode (decimal string of the DWORD).
+# Reducer: HandleRealmJoinPackageCompletedV1 → updates the matching RealmJoinPackageFact
+# row with CompletedUtc / Success / LastExitCode. Stage unchanged.
+{"SessionSignalOrdinal":12,"SessionTraceOrdinal":12,"Kind":"RealmJoinPackageCompleted","KindSchemaVersion":1,"OccurredAtUtc":"2026-05-21T10:08:00.0000000Z","SourceOrigin":"RealmJoinWatcher","Evidence":{"Kind":"Derived","Identifier":"realmjoin-package-completed:machine:generic-vlc","Summary":"RealmJoin package install completed (scope=machine, id=generic-vlc, success=True, exitCode=0)","DerivationInputs":{"registryKey":"HKLM\\SYSTEM\\CurrentControlSet\\Services\\realmjoin\\Parameters"}},"Payload":{"packageId":"generic-vlc","displayName":"VLC media player","version":"3.0.21.0","scope":"machine","success":"true","lastExitCode":"0"}}
diff --git a/tests/fixtures/signal-kinds/realmjoin-package-started-v1.json b/tests/fixtures/signal-kinds/realmjoin-package-started-v1.json
new file mode 100644
index 00000000..4fb96ee6
--- /dev/null
+++ b/tests/fixtures/signal-kinds/realmjoin-package-started-v1.json
@@ -0,0 +1,9 @@
+# RealmJoinPackageStarted v1 — observation-only per-package event.
+# Posted by RealmJoinWatcherAdapter when a HKLM\SOFTWARE\RealmJoin\Packages\<id> sub-key
+# (or its HKU\<sid>\... counterpart) is first observed with a DisplayName value.
+# Payload: packageId (mandatory), displayName (truncated to 256 chars), optional version,
+# scope ("machine"|"user").
+# Reducer: HandleRealmJoinPackageStartedV1 → appends a RealmJoinPackageFact row. Stage
+# unchanged. Dual emission as InformationalEvent realmjoin_package_started handles UI
+# timeline visibility.
+{"SessionSignalOrdinal":7,"SessionTraceOrdinal":7,"Kind":"RealmJoinPackageStarted","KindSchemaVersion":1,"OccurredAtUtc":"2026-05-21T10:05:00.0000000Z","SourceOrigin":"RealmJoinWatcher","Evidence":{"Kind":"Derived","Identifier":"realmjoin-package-started:machine:generic-vlc","Summary":"RealmJoin package install started (scope=machine, id=generic-vlc)","DerivationInputs":{"registryKey":"HKLM\\SYSTEM\\CurrentControlSet\\Services\\realmjoin\\Parameters"}},"Payload":{"packageId":"generic-vlc","displayName":"VLC media player","version":"3.0.21.0","scope":"machine"}}
diff --git a/tests/fixtures/signal-kinds/realmjoin-resolved-v1.json b/tests/fixtures/signal-kinds/realmjoin-resolved-v1.json
new file mode 100644
index 00000000..f6a4896f
--- /dev/null
+++ b/tests/fixtures/signal-kinds/realmjoin-resolved-v1.json
@@ -0,0 +1,8 @@
+# RealmJoinResolved v1 — RealmJoin first deployment completed.
+# Posted by RealmJoinWatcherAdapter when DeploymentPhase first reaches
+# CompletedFirstDeployment (110). Payload carries the observed phase.
+# Reducer: HandleRealmJoinResolvedV1 → records RealmJoinFacts.ResolvedUtc/LastPhase/Outcome,
+# cancels the RealmJoinTimeout deadline (scheduler + reducer view), and (if Hello + Desktop
+# already resolved OR SelfDeployingDeferredCompletion is set) routes through
+# CompleteIfDeferredOrBookkeep to TransitionToFinalizing / direct Completed.
+{"SessionSignalOrdinal":42,"SessionTraceOrdinal":42,"Kind":"RealmJoinResolved","KindSchemaVersion":1,"OccurredAtUtc":"2026-05-21T10:25:00.0000000Z","SourceOrigin":"RealmJoinWatcher","Evidence":{"Kind":"Derived","Identifier":"realmjoin-resolved-v1","Summary":"RealmJoin reached phase 110","DerivationInputs":{"registryKey":"HKLM\\SYSTEM\\CurrentControlSet\\Services\\realmjoin\\Parameters"}},"Payload":{"deploymentPhase":"110"}}
diff --git a/tests/fixtures/signal-kinds/realmjoin-timeout-v1.json b/tests/fixtures/signal-kinds/realmjoin-timeout-v1.json
new file mode 100644
index 00000000..fda41e44
--- /dev/null
+++ b/tests/fixtures/signal-kinds/realmjoin-timeout-v1.json
@@ -0,0 +1,8 @@
+# RealmJoin hard-timeout (60-min) deadline fire.
+# This kind is NOT posted by any adapter — it is dispatched by the DeadlineFiredV1 switch
+# (DecisionEngine.Shared.cs) when the RealmJoinTimeout ActiveDeadline armed by
+# HandleRealmJoinDetectedV1 elapses without DeploymentPhase reaching 110.
+# Reducer: HandleRealmJoinTimeoutDeadlineFired → sets RealmJoinFacts.Outcome="Timeout",
+# emits a realmjoin_timeout timeline event, and (if Hello+Desktop already resolved OR
+# SelfDeployingDeferredCompletion is set) routes through CompleteIfDeferredOrBookkeep.
+{"SessionSignalOrdinal":99,"SessionTraceOrdinal":99,"Kind":"DeadlineFired","KindSchemaVersion":1,"OccurredAtUtc":"2026-05-21T11:00:00.0000000Z","SourceOrigin":"DeadlineScheduler","Evidence":{"Kind":"Derived","Identifier":"deadline-realmjoin-timeout","Summary":"RealmJoin hard timeout fired"},"Payload":{"deadline":"realmjoin_timeout"}}