diff --git a/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Telemetry/Events/EventTimelineEmitterDecisionStateEnrichmentTests.cs b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Telemetry/Events/EventTimelineEmitterDecisionStateEnrichmentTests.cs
new file mode 100644
index 00000000..29253a4b
--- /dev/null
+++ b/src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Telemetry/Events/EventTimelineEmitterDecisionStateEnrichmentTests.cs
@@ -0,0 +1,238 @@
+using System;
+using System.Collections.Generic;
+using AutopilotMonitor.Agent.V2.Core.Telemetry.Events;
+using AutopilotMonitor.Agent.V2.Core.Tests.Harness;
+using AutopilotMonitor.DecisionCore.Engine;
+using AutopilotMonitor.DecisionCore.State;
+using AutopilotMonitor.Shared.Models;
+using Newtonsoft.Json.Linq;
+using SharedConstants = AutopilotMonitor.Shared.Constants;
+using Xunit;
+
+namespace AutopilotMonitor.Agent.V2.Core.Tests.Telemetry.Events
+{
+ ///
+ /// Tests for the decisionState-snapshot enrichment in
+ /// (Plan §A — Edge-Triggered State
+ /// Snapshots, 2026-05-03). The enrichment runs after ResolveData so it
+ /// works for both event paths (parameter-rebuilt Data and typedPayload-merged
+ /// Data) and never clobbers existing event-specific fields.
+ ///
+ public sealed class EventTimelineEmitterDecisionStateEnrichmentTests
+ {
+ private static readonly DateTime At = new DateTime(2026, 5, 1, 13, 45, 32, DateTimeKind.Utc);
+
+ private sealed class Rig : IDisposable
+ {
+ public TempDirectory Tmp { get; } = new TempDirectory();
+ public FakeTelemetryTransport Transport { get; } = new FakeTelemetryTransport();
+ public EventSequenceCounter Counter { get; }
+ public TelemetryEventEmitter Inner { get; }
+ public EventTimelineEmitter Sut { get; }
+
+ public Rig()
+ {
+ Counter = new EventSequenceCounter(new EventSequencePersistence(Tmp.File("seq.json")));
+ Inner = new TelemetryEventEmitter(Transport, Counter, "S1", "T1");
+ Sut = new EventTimelineEmitter(Inner);
+ }
+
+ public JObject EmittedData() =>
+ (JObject)JObject.Parse(Transport.Enqueued[0].PayloadJson)["Data"]!;
+
+ public void Dispose() => Tmp.Dispose();
+ }
+
+ private static DecisionState State() => DecisionState.CreateInitial("S1", "T1");
+
+ // ============================================================================
+ // Full-coverage: every anchor event-type gets decisionState enrichment
+ // ============================================================================
+
+ public static IEnumerable AllAnchorEventTypes => new[]
+ {
+ new object[] { SharedConstants.EventTypes.AgentStarted },
+ new object[] { SharedConstants.EventTypes.EspPhaseChanged },
+ new object[] { SharedConstants.EventTypes.NetworkStateChange },
+ new object[] { SharedConstants.EventTypes.DesktopArrived },
+ new object[] { SharedConstants.EventTypes.AadPlaceholderUserDetected },
+ new object[] { SharedConstants.EventTypes.AadUserJoinedLate },
+ new object[] { SharedConstants.EventTypes.UserAadSignInComplete },
+ new object[] { SharedConstants.EventTypes.HybridLoginPending },
+ new object[] { SharedConstants.EventTypes.AgentShuttingDown },
+ new object[] { SharedConstants.EventTypes.SystemRebootDetected },
+ new object[] { SharedConstants.EventTypes.PerformanceCollectorStopped },
+ new object[] { SharedConstants.EventTypes.AgentMetricsCollectorStopped },
+ new object[] { SharedConstants.EventTypes.PriorRunDiedWithState },
+ };
+
+ [Theory]
+ [MemberData(nameof(AllAnchorEventTypes))]
+ public void Anchor_event_gets_decisionState_added_to_Data(string anchorEventType)
+ {
+ using var r = new Rig();
+ var parameters = new Dictionary { ["eventType"] = anchorEventType };
+
+ r.Sut.Emit(parameters, State(), At);
+
+ var data = r.EmittedData();
+ Assert.NotNull(data["decisionState"]);
+ // schemaVersion proves we wrote the actual builder output, not just any key
+ Assert.Equal(
+ DecisionStateSnapshotBuilder.SchemaVersion,
+ (string?)data["decisionState"]!["schemaVersion"]);
+ }
+
+ // ============================================================================
+ // Parameter-based path — existing Data fields preserved
+ // ============================================================================
+
+ [Fact]
+ public void Anchor_with_parameter_data_preserves_event_specific_fields()
+ {
+ using var r = new Rig();
+ // esp_phase_changed historically carries reason + custom keys via parameters
+ // (not typedPayload). Verify those parameters survive into the wire Data
+ // alongside the new decisionState.
+ var parameters = new Dictionary
+ {
+ ["eventType"] = SharedConstants.EventTypes.EspPhaseChanged,
+ ["reason"] = "IME-ESP-PHASE",
+ ["espPhase"] = "AccountSetup",
+ };
+
+ r.Sut.Emit(parameters, State(), At);
+
+ var data = r.EmittedData();
+ // Original parameter fields stay intact.
+ Assert.Equal("IME-ESP-PHASE", (string?)data["reason"]);
+ Assert.Equal("AccountSetup", (string?)data["espPhase"]);
+ // Plus enrichment.
+ Assert.NotNull(data["decisionState"]);
+ }
+
+ // ============================================================================
+ // typedPayload-based path — existing Data fields preserved
+ // ============================================================================
+
+ [Fact]
+ public void Anchor_with_typedPayload_dict_preserves_existing_fields()
+ {
+ using var r = new Rig();
+ // network_state_change is the canonical typedPayload-bearing anchor — it
+ // flows via InformationalEventPost.Emit(EnrollmentEvent) which routes
+ // EnrollmentEvent.Data through typedPayload. Verify the original payload
+ // survives the enrichment.
+ var parameters = new Dictionary
+ {
+ ["eventType"] = SharedConstants.EventTypes.NetworkStateChange,
+ };
+ var typedPayload = new Dictionary
+ {
+ ["from"] = "WiFi 'GBM_Wireless'",
+ ["to"] = "WiFi 'GBM_Guests'",
+ ["transition"] = "wifi_change",
+ };
+
+ r.Sut.Emit(parameters, State(), At, typedPayload);
+
+ var data = r.EmittedData();
+ Assert.Equal("WiFi 'GBM_Wireless'", (string?)data["from"]);
+ Assert.Equal("WiFi 'GBM_Guests'", (string?)data["to"]);
+ Assert.Equal("wifi_change", (string?)data["transition"]);
+ Assert.NotNull(data["decisionState"]);
+ }
+
+ // ============================================================================
+ // Non-anchor — no enrichment
+ // ============================================================================
+
+ [Theory]
+ [InlineData("enrollment_complete")] // already carries DecisionAuditTrail
+ [InlineData("enrollment_failed")] // already carries DecisionAuditTrail
+ [InlineData("app_install_completed")] // hochfrequent, intentionally excluded
+ [InlineData("performance_snapshot")] // hochfrequent, intentionally excluded
+ [InlineData("download_progress")] // hochfrequent, intentionally excluded
+ public void Non_anchor_event_does_NOT_get_decisionState(string nonAnchorEventType)
+ {
+ using var r = new Rig();
+ var parameters = new Dictionary
+ {
+ ["eventType"] = nonAnchorEventType,
+ ["reason"] = "test",
+ };
+
+ r.Sut.Emit(parameters, State(), At);
+
+ var data = r.EmittedData();
+ Assert.Null(data["decisionState"]);
+ }
+
+ // ============================================================================
+ // Idempotence — pre-existing decisionState in typedPayload is not clobbered
+ // ============================================================================
+
+ [Fact]
+ public void Anchor_with_decisionState_already_in_typedPayload_is_NOT_clobbered()
+ {
+ using var r = new Rig();
+ // Defensive contract: if for some reason an upstream caller already put a
+ // "decisionState" key in the typedPayload, the emitter must not overwrite
+ // it. This shouldn't occur in production (only the emitter writes that
+ // key) but documents the merge invariant.
+ var parameters = new Dictionary
+ {
+ ["eventType"] = SharedConstants.EventTypes.AgentStarted,
+ };
+ var prebuilt = new Dictionary
+ {
+ ["sentinel"] = "prebuilt-snapshot",
+ };
+ var typedPayload = new Dictionary
+ {
+ ["decisionState"] = prebuilt,
+ ["original"] = "value",
+ };
+
+ r.Sut.Emit(parameters, State(), At, typedPayload);
+
+ var data = r.EmittedData();
+ // The prebuilt sentinel survives — emitter respected the existing key.
+ Assert.Equal("prebuilt-snapshot", (string?)data["decisionState"]!["sentinel"]);
+ // Original sibling field also survives.
+ Assert.Equal("value", (string?)data["original"]);
+ }
+
+ // ============================================================================
+ // decisionState shape sanity — reads through to the actual builder output
+ // ============================================================================
+
+ [Fact]
+ public void Anchor_decisionState_carries_top_level_allowlist_keys()
+ {
+ using var r = new Rig();
+ var parameters = new Dictionary
+ {
+ ["eventType"] = SharedConstants.EventTypes.DesktopArrived,
+ };
+
+ r.Sut.Emit(parameters, State(), At);
+
+ var data = r.EmittedData();
+ var snap = (JObject)data["decisionState"]!;
+ // Spot-check the top-level allowlist contract — full coverage lives in
+ // DecisionStateSnapshotBuilderTests.
+ Assert.NotNull(snap["schemaVersion"]);
+ Assert.NotNull(snap["stepIndex"]);
+ Assert.NotNull(snap["lastAppliedSignalOrdinal"]);
+ Assert.NotNull(snap["stage"]);
+ Assert.NotNull(snap["facts"]);
+ Assert.NotNull(snap["scenario"]);
+ Assert.NotNull(snap["activeDeadlines"]);
+ // Outcome is null on a fresh state — must be present as JSON null,
+ // not missing (consumer differentiates "no outcome" from "missing field").
+ Assert.True(snap.ContainsKey("outcome"));
+ Assert.Equal(JTokenType.Null, snap["outcome"]!.Type);
+ }
+ }
+}
diff --git a/src/Agent/AutopilotMonitor.Agent.V2.Core/Telemetry/Events/EventTimelineEmitter.cs b/src/Agent/AutopilotMonitor.Agent.V2.Core/Telemetry/Events/EventTimelineEmitter.cs
index 94103096..75819481 100644
--- a/src/Agent/AutopilotMonitor.Agent.V2.Core/Telemetry/Events/EventTimelineEmitter.cs
+++ b/src/Agent/AutopilotMonitor.Agent.V2.Core/Telemetry/Events/EventTimelineEmitter.cs
@@ -2,6 +2,7 @@
using System;
using System.Collections.Generic;
using AutopilotMonitor.Agent.V2.Core.Orchestration;
+using AutopilotMonitor.DecisionCore.Engine;
using AutopilotMonitor.DecisionCore.State;
using AutopilotMonitor.Shared.Models;
@@ -101,6 +102,21 @@ namespace AutopilotMonitor.Agent.V2.Core.Telemetry.Events
nameof(parameters));
}
+ var data = ResolveData(parameters, typedPayload);
+
+ // Plan A — Edge-Triggered State Snapshots (2026-05-03): for events on the
+ // lifecycle-anchor allowlist, attach the current DecisionState snapshot under
+ // data["decisionState"] for post-mortem diagnosis without client-side logs.
+ // Mutation is safe: ResolveData always returns a fresh Dictionary instance
+ // (both the typedPayload-as-dict copy path and the parameter-rebuild path
+ // construct new dicts). The defensive ContainsKey-check prevents clobbering
+ // a snapshot already in the typedPayload — should never occur in practice
+ // but documents the merge contract.
+ if (LifecycleAnchorEventTypes.Contains(eventType) && !data.ContainsKey("decisionState"))
+ {
+ data["decisionState"] = DecisionStateSnapshotBuilder.Build(currentState);
+ }
+
var evt = new EnrollmentEvent
{
SessionId = currentState.SessionId,
@@ -112,7 +128,7 @@ namespace AutopilotMonitor.Agent.V2.Core.Telemetry.Events
Message = BuildMessage(eventType, parameters),
Timestamp = DateTime.SpecifyKind(occurredAtUtc, DateTimeKind.Utc),
ImmediateUpload = ParseImmediateUpload(parameters),
- Data = ResolveData(parameters, typedPayload),
+ Data = data,
// Codex follow-up #3 forward-link: every EmitEventTimelineEntry effect runs
// as part of a reducer step, so currentState.StepIndex == the emitting
diff --git a/src/Agent/AutopilotMonitor.Agent.V2/buildcounter.txt b/src/Agent/AutopilotMonitor.Agent.V2/buildcounter.txt
index 4970e693..2d78492f 100644
--- a/src/Agent/AutopilotMonitor.Agent.V2/buildcounter.txt
+++ b/src/Agent/AutopilotMonitor.Agent.V2/buildcounter.txt
@@ -1 +1 @@
-544
+547