diff --git a/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Gather/GatherRuleExecutorEmitModeTests.cs b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Gather/GatherRuleExecutorEmitModeTests.cs
new file mode 100644
index 00000000..5955c8a9
--- /dev/null
+++ b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Gather/GatherRuleExecutorEmitModeTests.cs
@@ -0,0 +1,249 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using AutopilotMonitor.Agent.V2.Core.Logging;
+using AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather;
+using AutopilotMonitor.Agent.V2.Core.Tests.Harness;
+using AutopilotMonitor.Shared.Models;
+using Xunit;
+
+namespace AutopilotMonitor.Agent.V2.Core.Tests.Monitoring.Gather
+{
+    /// <summary>
+    /// EmitMode "on_change" on <see cref="GatherRuleExecutor"/>: poll on the trigger cadence but
+    /// emit only when the collected result changes. The dedup state machine is asserted
+    /// synchronously via the internal <c>ShouldEmitOnChange</c> / <c>ComputeCanonicalHash</c>
+    /// (no timer races); the ExecuteRule wiring (hash-before-injection, empty-result no-op,
+    /// emitOnlyIfExists composition) through the public startup path.
+    /// </summary>
+    [Collection("SerialThreading")] // startup rules execute on the shared ThreadPool
+    public sealed class GatherRuleExecutorEmitModeTests : IDisposable
+    {
+        private readonly TempDirectory _tmp = new TempDirectory();
+        private readonly List<EnrollmentEvent> _events = new List<EnrollmentEvent>();
+        private readonly object _eventsGate = new object();
+        private readonly GatherRuleExecutor _executor;
+
+        private const string AbsentPath =
+            "HKLM\\SOFTWARE\\AutopilotMonitorTests\\DefinitelyAbsent_7e3a1f4b-0000-0000-0000-000000000000";
+
+        public GatherRuleExecutorEmitModeTests()
+        {
+            var logger = new AgentLogger(_tmp.Path, AgentLogLevel.Info);
+            _executor = new GatherRuleExecutor(
+                "sess", "tenant",
+                evt => { lock (_eventsGate) _events.Add(evt); },
+                logger)
+            {
+                UnrestrictedMode = true
+            };
+        }
+
+        public void Dispose()
+        {
+            _executor.Dispose();
+            _tmp.Dispose();
+        }
+
+        private int EventCount { get { lock (_eventsGate) return _events.Count; } }
+
+        private EnrollmentEvent SingleEvent()
+        {
+            lock (_eventsGate) return Assert.Single(_events);
+        }
+
+        private bool WaitForEventCount(int count, int timeoutMs = 10000)
+        {
+            var sw = Stopwatch.StartNew();
+            while (sw.ElapsedMilliseconds < timeoutMs)
+            {
+                if (EventCount >= count) return true;
+                Thread.Sleep(25);
+            }
+            return EventCount >= count;
+        }
+
+        private static GatherRule OnChangeRule(string id = "GATHER-OC-001") => new GatherRule
+        {
+            RuleId = id,
+            Title = id,
+            CollectorType = "registry",
+            Target = AbsentPath,
+            Trigger = "interval",
+            IntervalSeconds = 3600,
+            OutputEventType = "gather_test",
+            Enabled = true,
+            EmitMode = "on_change",
+        };
+
+        private static Dictionary<string, object> Result(params (string Key, object Value)[] pairs)
+        {
+            var d = new Dictionary<string, object>();
+            foreach (var (key, value) in pairs) d[key] = value;
+            return d;
+        }
+
+        // ── on_change state machine (synchronous) ──────────────────────────
+
+        [Fact]
+        public void FirstResult_AlwaysEmits_ThenUnchangedIsSuppressed_ThenChangeReemits()
+        {
+            var rule = OnChangeRule();
+
+            Assert.True(_executor.ShouldEmitOnChange(rule, Result(("exists", false))));   // first
+            Assert.False(_executor.ShouldEmitOnChange(rule, Result(("exists", false))));  // unchanged
+            Assert.False(_executor.ShouldEmitOnChange(rule, Result(("exists", false))));  // unchanged
+            Assert.True(_executor.ShouldEmitOnChange(rule, Result(("exists", true), ("Version", "1")))); // changed
+        }
+
+        [Fact]
+        public void EmitAfterSuppressionStreak_CarriesSuppressedPollCount_AndResets()
+        {
+            var rule = OnChangeRule();
+
+            Assert.True(_executor.ShouldEmitOnChange(rule, Result(("exists", false))));
+            Assert.False(_executor.ShouldEmitOnChange(rule, Result(("exists", false))));
+            Assert.False(_executor.ShouldEmitOnChange(rule, Result(("exists", false))));
+            Assert.False(_executor.ShouldEmitOnChange(rule, Result(("exists", false))));
+
+            var changed = Result(("exists", true));
+            Assert.True(_executor.ShouldEmitOnChange(rule, changed));
+            Assert.Equal(3, changed["suppressedPolls"]);
+            Assert.True(changed.ContainsKey("suppressedSinceUtc"));
+
+            // Counter must reset: the next change emits without a suppression payload.
+            var changedAgain = Result(("exists", false));
+            Assert.True(_executor.ShouldEmitOnChange(rule, changedAgain));
+            Assert.False(changedAgain.ContainsKey("suppressedPolls"));
+            Assert.False(changedAgain.ContainsKey("suppressedSinceUtc"));
+        }
+
+        [Fact]
+        public void SuppressionState_IsIsolatedPerRule()
+        {
+            var ruleA = OnChangeRule("GATHER-OC-A");
+            var ruleB = OnChangeRule("GATHER-OC-B");
+            var payload = Result(("exists", false));
+
+            Assert.True(_executor.ShouldEmitOnChange(ruleA, new Dictionary<string, object>(payload)));
+            // Same content, different rule: B has no hash yet — must emit.
+            Assert.True(_executor.ShouldEmitOnChange(ruleB, new Dictionary<string, object>(payload)));
+            Assert.False(_executor.ShouldEmitOnChange(ruleA, new Dictionary<string, object>(payload)));
+            Assert.False(_executor.ShouldEmitOnChange(ruleB, new Dictionary<string, object>(payload)));
+        }
+
+        [Fact]
+        public void DedupState_SurvivesUpdateRulesRefresh()
+        {
+            var rule = OnChangeRule();
+            Assert.True(_executor.ShouldEmitOnChange(rule, Result(("exists", false))));
+
+            // Config refresh mid-session must not reset the last-emitted hash (that would
+            // re-emit an unchanged result on every refresh).
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            Assert.False(_executor.ShouldEmitOnChange(rule, Result(("exists", false))));
+        }
+
+        // ── Canonical hashing ──────────────────────────────────────────────
+
+        [Fact]
+        public void CanonicalHash_IsKeyOrderInsensitive()
+        {
+            var a = new Dictionary<string, object> { ["alpha"] = 1, ["beta"] = "x" };
+            var b = new Dictionary<string, object> { ["beta"] = "x", ["alpha"] = 1 };
+
+            Assert.Equal(
+                GatherRuleExecutor.ComputeCanonicalHash(a),
+                GatherRuleExecutor.ComputeCanonicalHash(b));
+        }
+
+        [Fact]
+        public void CanonicalHash_DetectsValueChanges_IncludingNested()
+        {
+            var baseline = new Dictionary<string, object>
+            {
+                ["exists"] = true,
+                ["entries"] = new List<object> { new Dictionary<string, object> { ["id"] = 1 } },
+            };
+            var changedScalar = new Dictionary<string, object>
+            {
+                ["exists"] = false,
+                ["entries"] = new List<object> { new Dictionary<string, object> { ["id"] = 1 } },
+            };
+            var changedNested = new Dictionary<string, object>
+            {
+                ["exists"] = true,
+                ["entries"] = new List<object> { new Dictionary<string, object> { ["id"] = 2 } },
+            };
+
+            var baseHash = GatherRuleExecutor.ComputeCanonicalHash(baseline);
+            Assert.NotEqual(baseHash, GatherRuleExecutor.ComputeCanonicalHash(changedScalar));
+            Assert.NotEqual(baseHash, GatherRuleExecutor.ComputeCanonicalHash(changedNested));
+        }
+
+        [Fact]
+        public void CanonicalHash_DistinguishesTypeShapes()
+        {
+            // "1" (string) vs 1 (int) and null vs "<null>"-like strings must not collide.
+            Assert.NotEqual(
+                GatherRuleExecutor.ComputeCanonicalHash(new Dictionary<string, object> { ["v"] = "1" }),
+                GatherRuleExecutor.ComputeCanonicalHash(new Dictionary<string, object> { ["v"] = 1 }));
+            Assert.NotEqual(
+                GatherRuleExecutor.ComputeCanonicalHash(new Dictionary<string, object> { ["v"] = null }),
+                GatherRuleExecutor.ComputeCanonicalHash(new Dictionary<string, object> { ["v"] = "<null>" }));
+        }
+
+        // ── ExecuteRule wiring (async via startup path) ────────────────────
+
+        [Fact]
+        public void AlwaysMode_EmitsEveryCollection()
+        {
+            // EmitMode absent (legacy) — repeated identical results all emit. Two executions of
+            // the same collector via two rules sharing the target prove no dedup is applied.
+            var rule1 = OnChangeRule("GATHER-AL-1"); rule1.EmitMode = null; rule1.Trigger = "startup";
+            var rule2 = OnChangeRule("GATHER-AL-2"); rule2.EmitMode = null; rule2.Trigger = "startup";
+
+            _executor.UpdateRules(new List<GatherRule> { rule1, rule2 });
+
+            Assert.True(_executor.WaitForStartupRules(30));
+            Assert.True(WaitForEventCount(2));
+        }
+
+        [Fact]
+        public void OnChange_FirstInScopePoll_EmitsExistsFalse_AsPollingIndicator()
+        {
+            // The first result on an absent key IS the visible "we're polling now" indicator.
+            var rule = OnChangeRule();
+            rule.Trigger = "startup";
+
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            Assert.True(_executor.WaitForStartupRules(30));
+            Assert.True(WaitForEventCount(1));
+            var evt = SingleEvent();
+            Assert.Equal(false, evt.Data["exists"]);
+            Assert.Equal("GATHER-OC-001", evt.Data["ruleId"]); // injection happened after hashing
+        }
+
+        [Fact]
+        public void OnChange_ComposedWithEmitOnlyIfExists_EmptyResultDoesNotTouchHashState()
+        {
+            // emitOnlyIfExists miss → empty result → no emit AND no hash update: the eventual
+            // first real result must still count as "first emit".
+            var rule = OnChangeRule();
+            rule.Trigger = "startup";
+            rule.Parameters = new Dictionary<string, string> { ["emitOnlyIfExists"] = "true" };
+
+            _executor.UpdateRules(new List<GatherRule> { rule });
+            Assert.True(_executor.WaitForStartupRules(30));
+            Thread.Sleep(300);
+            Assert.Equal(0, EventCount); // zero noise while the key is absent
+
+            // When the key appears (simulated via the state machine), the result emits as first.
+            Assert.True(_executor.ShouldEmitOnChange(rule, Result(("exists", true), ("Version", "1"))));
+        }
+    }
+}
diff --git a/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Gather/GatherRuleExecutorPhaseScopeTests.cs b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Gather/GatherRuleExecutorPhaseScopeTests.cs
new file mode 100644
index 00000000..ab96ac22
--- /dev/null
+++ b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Gather/GatherRuleExecutorPhaseScopeTests.cs
@@ -0,0 +1,326 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+using AutopilotMonitor.Agent.V2.Core.Logging;
+using AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather;
+using AutopilotMonitor.Agent.V2.Core.Tests.Harness;
+using AutopilotMonitor.Shared.Models;
+using Xunit;
+
+namespace AutopilotMonitor.Agent.V2.Core.Tests.Monitoring.Gather
+{
+    /// <summary>
+    /// Phase scoping on <see cref="GatherRuleExecutor"/> (ActivePhases / ActiveFromPhase):
+    /// the scope matrix is asserted synchronously via the internal <c>IsRuleInScope</c>
+    /// (no timer races); the trigger-path wiring (deferred startup, phase_change / on_event
+    /// gating) is asserted through the public API with positive event waits.
+    /// Rules use the absent-registry-path pattern from
+    /// <see cref="RegistryCollectorEmitOnlyIfExistsTests"/> so no real system state is touched.
+    /// </summary>
+    [Collection("SerialThreading")] // deferred startup rules execute on the shared ThreadPool
+    public sealed class GatherRuleExecutorPhaseScopeTests : IDisposable
+    {
+        private readonly TempDirectory _tmp = new TempDirectory();
+        private readonly List<EnrollmentEvent> _events = new List<EnrollmentEvent>();
+        private readonly object _eventsGate = new object();
+        private readonly GatherRuleExecutor _executor;
+
+        private const string AbsentPath =
+            "HKLM\\SOFTWARE\\AutopilotMonitorTests\\DefinitelyAbsent_5b1c8d2e-0000-0000-0000-000000000000";
+
+        public GatherRuleExecutorPhaseScopeTests()
+        {
+            var logger = new AgentLogger(_tmp.Path, AgentLogLevel.Info);
+            _executor = new GatherRuleExecutor(
+                "sess", "tenant",
+                evt => { lock (_eventsGate) _events.Add(evt); },
+                logger)
+            {
+                // Bypass the registry allowlist guard for the synthetic test path.
+                UnrestrictedMode = true
+            };
+        }
+
+        public void Dispose()
+        {
+            _executor.Dispose();
+            _tmp.Dispose();
+        }
+
+        private int EventCount { get { lock (_eventsGate) return _events.Count; } }
+
+        private bool WaitForEventCount(int count, int timeoutMs = 10000)
+        {
+            var sw = Stopwatch.StartNew();
+            while (sw.ElapsedMilliseconds < timeoutMs)
+            {
+                if (EventCount >= count) return true;
+                Thread.Sleep(25);
+            }
+            return EventCount >= count;
+        }
+
+        /// <summary>Interval rule with a 1h period — the timer never ticks within a test run,
+        /// so these rules exist purely for synchronous scope-matrix assertions.</summary>
+        private static GatherRule ScopeProbeRule(string id, List<string> activePhases = null, string fromPhase = null)
+            => new GatherRule
+            {
+                RuleId = id,
+                Title = id,
+                CollectorType = "registry",
+                Target = AbsentPath,
+                Trigger = "interval",
+                IntervalSeconds = 3600,
+                OutputEventType = "gather_test",
+                Enabled = true,
+                ActivePhases = activePhases,
+                ActiveFromPhase = fromPhase,
+            };
+
+        private static GatherRule StartupRule(string id, List<string> activePhases = null, string fromPhase = null)
+            => new GatherRule
+            {
+                RuleId = id,
+                Title = id,
+                CollectorType = "registry",
+                Target = AbsentPath,
+                Trigger = "startup",
+                OutputEventType = "gather_test",
+                Enabled = true,
+                ActivePhases = activePhases,
+                ActiveFromPhase = fromPhase,
+            };
+
+        // ── Scope matrix (synchronous) ─────────────────────────────────────
+
+        [Fact]
+        public void UnscopedRule_IsInScope_EvenBeforeAnyPhaseSignal()
+        {
+            var rule = ScopeProbeRule("GATHER-SCOPE-000");
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            Assert.True(_executor.IsRuleInScope(rule));
+        }
+
+        [Fact]
+        public void ActivePhases_InactiveBeforeFirstPhaseSignal()
+        {
+            var rule = ScopeProbeRule("GATHER-SCOPE-001", activePhases: new List<string> { "AccountSetup" });
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            Assert.False(_executor.IsRuleInScope(rule));
+        }
+
+        [Fact]
+        public void ActivePhases_ActiveDuringListedPhase_InactiveAfterLeaving()
+        {
+            var rule = ScopeProbeRule("GATHER-SCOPE-002", activePhases: new List<string> { "AccountSetup" });
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            _executor.OnPhaseChanged(EnrollmentPhase.DeviceSetup);
+            Assert.False(_executor.IsRuleInScope(rule));
+
+            _executor.OnPhaseChanged(EnrollmentPhase.AccountSetup);
+            Assert.True(_executor.IsRuleInScope(rule));
+
+            _executor.OnPhaseChanged(EnrollmentPhase.AppsUser);
+            Assert.False(_executor.IsRuleInScope(rule));
+        }
+
+        [Fact]
+        public void ActivePhases_MatchIsCaseInsensitive()
+        {
+            var rule = ScopeProbeRule("GATHER-SCOPE-003", activePhases: new List<string> { "accountsetup" });
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            _executor.OnPhaseChanged(EnrollmentPhase.AccountSetup);
+            Assert.True(_executor.IsRuleInScope(rule));
+        }
+
+        [Fact]
+        public void FromPhase_LatchesAtThreshold_AndStaysSticky_IncludingThroughFailed()
+        {
+            var rule = ScopeProbeRule("GATHER-SCOPE-010", fromPhase: "AccountSetup");
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            _executor.OnPhaseChanged(EnrollmentPhase.DeviceSetup);
+            Assert.False(_executor.IsRuleInScope(rule)); // threshold not reached
+
+            _executor.OnPhaseChanged(EnrollmentPhase.AccountSetup);
+            Assert.True(_executor.IsRuleInScope(rule)); // latched
+
+            _executor.OnPhaseChanged(EnrollmentPhase.Failed);
+            Assert.True(_executor.IsRuleInScope(rule)); // sticky through Failed
+        }
+
+        [Fact]
+        public void FromPhase_NoSpuriousActivationViaFailed()
+        {
+            // Failed=99 would ordinal-satisfy every threshold — it must never latch.
+            var rule = ScopeProbeRule("GATHER-SCOPE-011", fromPhase: "AccountSetup");
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            _executor.OnPhaseChanged(EnrollmentPhase.Failed);
+            Assert.False(_executor.IsRuleInScope(rule));
+        }
+
+        [Fact]
+        public void FromPhase_LatchesWhenThresholdIsSkippedOver()
+        {
+            // The session may never report the exact threshold phase — a later phase latches too.
+            var rule = ScopeProbeRule("GATHER-SCOPE-012", fromPhase: "AccountSetup");
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            _executor.OnPhaseChanged(EnrollmentPhase.FinalizingSetup);
+            Assert.True(_executor.IsRuleInScope(rule));
+        }
+
+        [Fact]
+        public void FromPhase_RuleDeliveredByRefreshAfterPhaseReached_LatchesImmediately()
+        {
+            _executor.UpdateRules(new List<GatherRule>());
+            _executor.OnPhaseChanged(EnrollmentPhase.AccountSetup);
+
+            // Config refresh delivers a new from-phase rule whose threshold already passed.
+            var rule = ScopeProbeRule("GATHER-SCOPE-013", fromPhase: "DeviceSetup");
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            Assert.True(_executor.IsRuleInScope(rule));
+        }
+
+        [Fact]
+        public void BothFieldsSet_ActivePhasesWins()
+        {
+            // Backend validation rejects this shape; the agent defensively prefers ActivePhases.
+            var rule = ScopeProbeRule("GATHER-SCOPE-020",
+                activePhases: new List<string> { "DeviceSetup" }, fromPhase: "Start");
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            _executor.OnPhaseChanged(EnrollmentPhase.AccountSetup);
+            Assert.False(_executor.IsRuleInScope(rule)); // FromPhase(Start) would say yes — list wins
+
+            _executor.OnPhaseChanged(EnrollmentPhase.DeviceSetup);
+            Assert.True(_executor.IsRuleInScope(rule));
+        }
+
+        [Fact]
+        public void IgnorePhaseScope_BypassesScope_WithoutPhaseContext()
+        {
+            _executor.IgnorePhaseScope = true;
+            var during = ScopeProbeRule("GATHER-SCOPE-030", activePhases: new List<string> { "AccountSetup" });
+            var from = ScopeProbeRule("GATHER-SCOPE-031", fromPhase: "Complete");
+            _executor.UpdateRules(new List<GatherRule> { during, from });
+
+            Assert.True(_executor.IsRuleInScope(during));
+            Assert.True(_executor.IsRuleInScope(from));
+        }
+
+        // ── Trigger-path wiring (async, positive waits) ────────────────────
+
+        [Fact]
+        public void UnscopedStartupRule_RunsImmediately()
+        {
+            _executor.UpdateRules(new List<GatherRule> { StartupRule("GATHER-START-000") });
+
+            Assert.True(_executor.WaitForStartupRules(30));
+            Assert.True(WaitForEventCount(1));
+        }
+
+        [Fact]
+        public void ScopedStartupRule_IsDeferred_ThenFiresExactlyOnce_WhenScopeActivates()
+        {
+            _executor.UpdateRules(new List<GatherRule>
+            {
+                StartupRule("GATHER-START-001", fromPhase: "AccountSetup")
+            });
+
+            // Not in scope at UpdateRules: nothing queued, latch trivially satisfied.
+            Assert.True(_executor.WaitForStartupRules(30));
+            Assert.Equal(0, EventCount);
+
+            _executor.OnPhaseChanged(EnrollmentPhase.DeviceSetup);
+            Assert.Equal(0, EventCount);
+
+            _executor.OnPhaseChanged(EnrollmentPhase.AccountSetup);
+            Assert.True(WaitForEventCount(1), "deferred startup rule should fire when its scope activates");
+
+            // Later phase changes must not re-fire it (dedup via _startupRulesExecuted).
+            _executor.OnPhaseChanged(EnrollmentPhase.AppsUser);
+            _executor.OnPhaseChanged(EnrollmentPhase.FinalizingSetup);
+            Thread.Sleep(300);
+            Assert.Equal(1, EventCount);
+        }
+
+        [Fact]
+        public void PhaseChangeRule_OutOfScopePhase_DoesNotFire_InScopePhaseFires()
+        {
+            // TriggerPhase empty = fires on every phase change; scope narrows it to AccountSetup.
+            var rule = new GatherRule
+            {
+                RuleId = "GATHER-PC-001",
+                Title = "pc",
+                CollectorType = "registry",
+                Target = AbsentPath,
+                Trigger = "phase_change",
+                TriggerPhase = "",
+                OutputEventType = "gather_test",
+                Enabled = true,
+                ActivePhases = new List<string> { "AccountSetup" },
+            };
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            _executor.OnPhaseChanged(EnrollmentPhase.DeviceSetup);
+            Thread.Sleep(300);
+            Assert.Equal(0, EventCount);
+
+            _executor.OnPhaseChanged(EnrollmentPhase.AccountSetup);
+            Assert.True(WaitForEventCount(1));
+
+            // Same phase again: the (rule, phase) dedup slot is now consumed.
+            _executor.OnPhaseChanged(EnrollmentPhase.AccountSetup);
+            Thread.Sleep(300);
+            Assert.Equal(1, EventCount);
+        }
+
+        [Fact]
+        public void OnEventRule_GatedByScope()
+        {
+            var rule = new GatherRule
+            {
+                RuleId = "GATHER-OE-001",
+                Title = "oe",
+                CollectorType = "registry",
+                Target = AbsentPath,
+                Trigger = "on_event",
+                TriggerEventType = "app_install_failed",
+                OutputEventType = "gather_test",
+                Enabled = true,
+                ActivePhases = new List<string> { "AccountSetup" },
+            };
+            _executor.UpdateRules(new List<GatherRule> { rule });
+
+            _executor.OnEvent("app_install_failed"); // no phase signal yet → out of scope
+            Thread.Sleep(300);
+            Assert.Equal(0, EventCount);
+
+            _executor.OnPhaseChanged(EnrollmentPhase.AccountSetup);
+            _executor.OnEvent("app_install_failed");
+            Assert.True(WaitForEventCount(1));
+        }
+
+        [Fact]
+        public void IgnorePhaseScope_ScopedStartupRule_RunsImmediately()
+        {
+            // The --run-gather-rules diagnostic path: scoped rules must execute unconditionally.
+            _executor.IgnorePhaseScope = true;
+            _executor.UpdateRules(new List<GatherRule>
+            {
+                StartupRule("GATHER-START-002", activePhases: new List<string> { "AccountSetup" })
+            });
+
+            Assert.True(_executor.WaitForStartupRules(30));
+            Assert.True(WaitForEventCount(1));
+        }
+    }
+}
diff --git a/src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Telemetry/Gather/GatherRuleExecutor.cs b/src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Telemetry/Gather/GatherRuleExecutor.cs
index 0ff8c842..29f157de 100644
--- a/src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Telemetry/Gather/GatherRuleExecutor.cs
+++ b/src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Telemetry/Gather/GatherRuleExecutor.cs
@@ -1,6 +1,9 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
 using System.Threading;
 using AutopilotMonitor.Agent.V2.Core.Logging;
 using AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather.Collectors;
@@ -28,6 +31,25 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather
         private readonly HashSet<string> _phaseRulesExecuted = new HashSet<string>();
         private CountdownEvent _startupRulesLatch;   // non-null only while startup rules are pending
 
+        // Phase-scope + emit-mode state (ActivePhases / ActiveFromPhase / EmitMode on GatherRule).
+        // Guarded by _scopeLock; collector work always runs outside the lock. The state deliberately
+        // survives UpdateRules config refreshes — an agent restart causes at most one re-emit per
+        // on_change rule (acceptable under the per-enrollment lifecycle).
+        private readonly object _scopeLock = new object();
+        private EnrollmentPhase _currentPhase = EnrollmentPhase.Unknown;
+        private readonly HashSet<string> _fromPhaseLatched = new HashSet<string>();
+        private readonly Dictionary<string, string> _lastEmittedHash = new Dictionary<string, string>();
+        private readonly Dictionary<string, (int Count, DateTime SinceUtc)> _suppressed =
+            new Dictionary<string, (int Count, DateTime SinceUtc)>();
+        private readonly HashSet<string> _scopeBypassLogged = new HashSet<string>();
+
+        /// <summary>
+        /// When true, phase scoping (ActivePhases / ActiveFromPhase) is bypassed and scoped rules
+        /// execute unconditionally. Used by the standalone <c>--run-gather-rules</c> diagnostic
+        /// mode, which has no enrollment phase context. EmitMode is unaffected.
+        /// </summary>
+        public bool IgnorePhaseScope { get; set; }
+
         /// <summary>
         /// When true, guardrails are relaxed: all registry, WMI, and command targets are allowed.
         /// File paths allow everything except C:\Users. Set from tenant configuration.
@@ -89,10 +111,27 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather
 
             _activeRules = rules.Where(r => r.Enabled).ToList();
 
-            // Execute startup rules — track completion via CountdownEvent so callers can wait
-            var pendingStartup = _activeRules
-                .Where(r => r.Trigger == "startup" && !_startupRulesExecuted.Contains(r.RuleId))
-                .ToList();
+            // Execute startup rules — track completion via CountdownEvent so callers can wait.
+            // Scoped startup rules that are not yet in scope are deferred: they run once from
+            // OnPhaseChanged when their scope activates (same _startupRulesExecuted dedup — a
+            // rule runs either here or there, never both). Unscoped rules behave as before.
+            List<GatherRule> pendingStartup;
+            lock (_scopeLock)
+            {
+                // A config refresh may deliver new from-phase rules after their phase was
+                // already reached — evaluate latches against the current phase first.
+                EvaluateFromPhaseLatchesLocked();
+
+                pendingStartup = _activeRules
+                    .Where(r => r.Trigger == "startup" && !_startupRulesExecuted.Contains(r.RuleId))
+                    .Where(r => IsRuleInScopeLocked(r))
+                    .ToList();
+
+                foreach (var rule in pendingStartup)
+                {
+                    _startupRulesExecuted.Add(rule.RuleId);
+                }
+            }
 
             if (pendingStartup.Count > 0)
             {
@@ -101,7 +140,6 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather
 
                 foreach (var rule in pendingStartup)
                 {
-                    _startupRulesExecuted.Add(rule.RuleId);
                     ThreadPool.QueueUserWorkItem(_ =>
                     {
                         try   { ExecuteRule(rule); }
@@ -110,18 +148,26 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather
                 }
             }
 
-            // Set up interval timers
+            // Set up interval timers. Timers for scoped rules keep running while out of scope —
+            // the tick gate makes an out-of-scope tick a free no-op, avoiding start/stop
+            // lifecycle races on phase transitions.
             foreach (var rule in _activeRules.Where(r => r.Trigger == "interval" && r.IntervalSeconds.HasValue))
             {
-                var interval = TimeSpan.FromSeconds(rule.IntervalSeconds.Value);
+                var intervalRule = rule;
+                var interval = TimeSpan.FromSeconds(intervalRule.IntervalSeconds.Value);
                 var timer = new Timer(
-                    _ => ExecuteRule(rule),
+                    _ =>
+                    {
+                        if (!IsRuleInScope(intervalRule))
+                            return;
+                        ExecuteRule(intervalRule);
+                    },
                     null,
                     interval, // Initial delay = one interval
                     interval
                 );
-                _intervalTimers[rule.RuleId] = timer;
-                _logger.Info($"  Interval rule {rule.RuleId} scheduled every {rule.IntervalSeconds}s");
+                _intervalTimers[intervalRule.RuleId] = timer;
+                _logger.Info($"  Interval rule {intervalRule.RuleId} scheduled every {intervalRule.IntervalSeconds}s");
             }
 
             _logger.Info($"GatherRuleExecutor: {_activeRules.Count(r => r.Trigger == "startup")} startup, " +
@@ -135,11 +181,43 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather
         {
             var phaseName = newPhase.ToString();
 
+            // Update the phase + from-phase latches FIRST so deferred startup activation and
+            // the phase_change rules below all evaluate against the NEW phase.
+            List<GatherRule> deferredStartup;
+            lock (_scopeLock)
+            {
+                _currentPhase = newPhase;
+                EvaluateFromPhaseLatchesLocked();
+
+                deferredStartup = _activeRules
+                    .Where(r => r.Trigger == "startup" && HasPhaseScope(r)
+                                && !_startupRulesExecuted.Contains(r.RuleId)
+                                && IsRuleInScopeLocked(r))
+                    .ToList();
+
+                foreach (var rule in deferredStartup)
+                {
+                    _startupRulesExecuted.Add(rule.RuleId);
+                }
+            }
+
+            foreach (var rule in deferredStartup)
+            {
+                var deferredRule = rule;
+                _logger.Info($"Phase {phaseName} activated deferred startup rule {deferredRule.RuleId}");
+                ThreadPool.QueueUserWorkItem(_ => ExecuteRule(deferredRule));
+            }
+
             foreach (var rule in _activeRules.Where(r => r.Trigger == "phase_change"))
             {
                 if (string.IsNullOrEmpty(rule.TriggerPhase) ||
                     string.Equals(rule.TriggerPhase, phaseName, StringComparison.OrdinalIgnoreCase))
                 {
+                    // Scope gate BEFORE the dedup add — an out-of-scope pass must not consume
+                    // the once-per-(rule, phase) execution slot.
+                    if (!IsRuleInScope(rule))
+                        continue;
+
                     // Deduplicate: only fire once per (ruleId, phase) combination
                     var deduplicationKey = $"{rule.RuleId}|{phaseName}";
                     if (!_phaseRulesExecuted.Add(deduplicationKey))
@@ -163,6 +241,9 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather
             {
                 if (string.Equals(rule.TriggerEventType, eventType, StringComparison.OrdinalIgnoreCase))
                 {
+                    if (!IsRuleInScope(rule))
+                        continue;
+
                     _logger.Info($"Event triggered rule {rule.RuleId} (event: {eventType})");
                     ThreadPool.QueueUserWorkItem(_ => ExecuteRule(rule));
                 }
@@ -192,6 +273,14 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather
 
                 if (result.Count > 0)
                 {
+                    // EmitMode "on_change": hash the raw collector result (before ruleId/title
+                    // injection) and only emit when it differs from the last emitted one. An
+                    // empty result never reaches this point, so an emitOnlyIfExists miss neither
+                    // emits nor updates the hash — composing to "one event on appearance, then
+                    // only on change".
+                    if (IsOnChangeMode(rule) && !ShouldEmitOnChange(rule, result))
+                        return;
+
                     result["ruleId"] = rule.RuleId;
                     result["ruleTitle"] = rule.Title;
 
@@ -229,6 +318,199 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather
             }
         }
 
+        // ===== Phase scope (ActivePhases / ActiveFromPhase) =====
+
+        private static bool HasPhaseScope(GatherRule rule)
+        {
+            return (rule.ActivePhases != null && rule.ActivePhases.Count > 0)
+                || !string.IsNullOrEmpty(rule.ActiveFromPhase);
+        }
+
+        // Internal so the scope matrix is testable synchronously (no timer/ThreadPool races).
+        internal bool IsRuleInScope(GatherRule rule)
+        {
+            lock (_scopeLock)
+            {
+                return IsRuleInScopeLocked(rule);
+            }
+        }
+
+        private bool IsRuleInScopeLocked(GatherRule rule)
+        {
+            if (!HasPhaseScope(rule))
+                return true; // unscoped — legacy behavior
+
+            if (IgnorePhaseScope)
+            {
+                if (_scopeBypassLogged.Add(rule.RuleId))
+                    _logger.Info($"Gather rule {rule.RuleId}: phase scope ignored (diagnostic mode)");
+                return true;
+            }
+
+            // Both fields set is rejected by backend validation; defensively prefer ActivePhases.
+            if (rule.ActivePhases != null && rule.ActivePhases.Count > 0)
+            {
+                // No phase signal yet (or scope tokens that never match, e.g. "Unknown"):
+                // scoped rules stay inactive.
+                if (_currentPhase == EnrollmentPhase.Unknown)
+                    return false;
+
+                var phaseName = _currentPhase.ToString();
+                foreach (var phase in rule.ActivePhases)
+                {
+                    if (string.Equals(phase, phaseName, StringComparison.OrdinalIgnoreCase))
+                        return true;
+                }
+                return false;
+            }
+
+            return _fromPhaseLatched.Contains(rule.RuleId);
+        }
+
+        /// <summary>
+        /// Latches every from-phase rule whose threshold the current phase has reached.
+        /// Never latches on Unknown/Failed (Failed=99 would ordinal-satisfy every threshold);
+        /// once latched a rule stays active for the session — including through Failed.
+        /// Caller must hold <see cref="_scopeLock"/>.
+        /// </summary>
+        private void EvaluateFromPhaseLatchesLocked()
+        {
+            if (_currentPhase == EnrollmentPhase.Unknown || _currentPhase == EnrollmentPhase.Failed)
+                return;
+
+            foreach (var rule in _activeRules)
+            {
+                if (string.IsNullOrEmpty(rule.ActiveFromPhase)) continue;
+                if (rule.ActivePhases != null && rule.ActivePhases.Count > 0) continue; // ActivePhases wins
+                if (_fromPhaseLatched.Contains(rule.RuleId)) continue;
+
+                if (Enum.TryParse<EnrollmentPhase>(rule.ActiveFromPhase, ignoreCase: true, out var fromPhase)
+                    && fromPhase != EnrollmentPhase.Unknown
+                    && fromPhase != EnrollmentPhase.Failed
+                    && (int)_currentPhase >= (int)fromPhase)
+                {
+                    _fromPhaseLatched.Add(rule.RuleId);
+                    _logger.Info($"Gather rule {rule.RuleId}: from-phase scope latched at {_currentPhase} (activeFromPhase={rule.ActiveFromPhase})");
+                }
+            }
+        }
+
+        // ===== Emit mode (on_change) =====
+
+        private static bool IsOnChangeMode(GatherRule rule)
+        {
+            return string.Equals(rule.EmitMode, "on_change", StringComparison.OrdinalIgnoreCase);
+        }
+
+        /// <summary>
+        /// on_change decision for a non-empty collector result: true = emit (first result for the
+        /// rule, or the result changed), false = suppress. Hashes the result BEFORE ruleId/title
+        /// injection. On emit after a suppression streak, injects <c>suppressedPolls</c> and
+        /// <c>suppressedSinceUtc</c> into the result so the gap is observable.
+        /// Internal so the state machine is testable synchronously (no timer/ThreadPool races).
+        /// </summary>
+        internal bool ShouldEmitOnChange(GatherRule rule, Dictionary<string, object> result)
+        {
+            var hash = ComputeCanonicalHash(result);
+            bool emit;
+            lock (_scopeLock)
+            {
+                string lastHash;
+                if (_lastEmittedHash.TryGetValue(rule.RuleId, out lastHash) && lastHash == hash)
+                {
+                    (int Count, DateTime SinceUtc) streak;
+                    _suppressed[rule.RuleId] = _suppressed.TryGetValue(rule.RuleId, out streak)
+                        ? (streak.Count + 1, streak.SinceUtc)
+                        : (1, DateTime.UtcNow);
+                    emit = false;
+                }
+                else
+                {
+                    _lastEmittedHash[rule.RuleId] = hash;
+                    (int Count, DateTime SinceUtc) streak;
+                    if (_suppressed.TryGetValue(rule.RuleId, out streak) && streak.Count > 0)
+                    {
+                        result["suppressedPolls"] = streak.Count;
+                        result["suppressedSinceUtc"] = streak.SinceUtc.ToString("o", CultureInfo.InvariantCulture);
+                    }
+                    _suppressed.Remove(rule.RuleId);
+                    emit = true;
+                }
+            }
+
+            if (!emit)
+                _logger.Debug($"Gather rule {rule.RuleId}: result unchanged, emit suppressed (on_change)");
+            return emit;
+        }
+
+        /// <summary>
+        /// Canonical hash of a collector result: keys ordinal-sorted at every dictionary level,
+        /// values rendered with invariant formatting, then SHA-256. Internal for direct test
+        /// coverage of the canonicalization.
+        /// </summary>
+        internal static string ComputeCanonicalHash(Dictionary<string, object> result)
+        {
+            var sb = new StringBuilder();
+            AppendCanonicalValue(sb, result);
+            using (var sha = SHA256.Create())
+            {
+                var hashBytes = sha.ComputeHash(Encoding.UTF8.GetBytes(sb.ToString()));
+                return Convert.ToBase64String(hashBytes);
+            }
+        }
+
+        private static void AppendCanonicalValue(StringBuilder sb, object value)
+        {
+            if (value == null)
+            {
+                sb.Append("<null>");
+                return;
+            }
+
+            // string first — it is IEnumerable and must not be treated as a sequence
+            if (value is string str)
+            {
+                sb.Append('"').Append(str).Append('"');
+                return;
+            }
+
+            if (value is System.Collections.IDictionary dict)
+            {
+                sb.Append('{');
+                var keys = dict.Keys.Cast<object>()
+                    .Select(k => k?.ToString() ?? string.Empty)
+                    .OrderBy(k => k, StringComparer.Ordinal);
+                foreach (var key in keys)
+                {
+                    sb.Append(key).Append('=');
+                    AppendCanonicalValue(sb, dict[key]);
+                    sb.Append(';');
+                }
+                sb.Append('}');
+                return;
+            }
+
+            if (value is System.Collections.IEnumerable sequence)
+            {
+                sb.Append('[');
+                foreach (var item in sequence)
+                {
+                    AppendCanonicalValue(sb, item);
+                    sb.Append(';');
+                }
+                sb.Append(']');
+                return;
+            }
+
+            if (value is IFormattable formattable)
+            {
+                sb.Append(formattable.ToString(null, CultureInfo.InvariantCulture));
+                return;
+            }
+
+            sb.Append(value);
+        }
+
         private EventSeverity ParseSeverity(string severity)
         {
             return GatherRuleContext.ParseSeverity(severity);
@@ -245,7 +527,8 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Telemetry.Gather
 
         /// <summary>
         /// Blocks until all startup rules that were queued by the most recent <see cref="UpdateRules"/>
-        /// call have finished executing, or the timeout elapses.
+        /// call have finished executing, or the timeout elapses. Deferred scoped startup rules
+        /// (waiting for their phase scope) are not part of the latch.
         /// Returns true if all rules completed within the timeout; false if timed out.
         /// </summary>
         public bool WaitForStartupRules(int timeoutSeconds = 120)
diff --git a/src/Agent/AutopilotMonitor.Agent.V2/Program.GatherRulesMode.cs b/src/Agent/AutopilotMonitor.Agent.V2/Program.GatherRulesMode.cs
index 14b4a082..b9ec9093 100644
--- a/src/Agent/AutopilotMonitor.Agent.V2/Program.GatherRulesMode.cs
+++ b/src/Agent/AutopilotMonitor.Agent.V2/Program.GatherRulesMode.cs
@@ -224,6 +224,11 @@ namespace AutopilotMonitor.Agent.V2
                     // Step 4 — run the executor and wait.
                     using (var executor = new GatherRuleExecutor(sessionId, tenantId, emitEvent, logger, config.ImeLogPathOverride))
                     {
+                        // Diagnostic mode has no enrollment phase context — scoped rules
+                        // (activePhases / activeFromPhase) execute unconditionally here.
+                        executor.IgnorePhaseScope = true;
+                        logger.Info("--run-gather-rules: phase scoping bypassed (no phase context in diagnostic mode).");
+
                         executor.UpdateRules(rules);
 
                         if (consoleMode) Console.WriteLine($"Running {startupRules.Count} rule(s)...");