diff --git a/src/Agent/AutopilotMonitor.DecisionCore.Tests/Scenarios/ClassicScenarioTests.cs b/src/Agent/AutopilotMonitor.DecisionCore.Tests/Scenarios/ClassicScenarioTests.cs
index 17c543d8..9a90ba59 100644
--- a/src/Agent/AutopilotMonitor.DecisionCore.Tests/Scenarios/ClassicScenarioTests.cs
+++ b/src/Agent/AutopilotMonitor.DecisionCore.Tests/Scenarios/ClassicScenarioTests.cs
@@ -106,5 +106,44 @@ namespace AutopilotMonitor.DecisionCore.Tests.Scenarios
             Assert.Equal(r1.FinalStepHash, r2.FinalStepHash);
             Assert.Equal(16, r1.FinalStepHash.Length);
         }
+
+        [Fact]
+        public void LateProvisioningComplete_afterAccountSetup_doesNotCompletePrematurely()
+        {
+            // Plan §6.1 regression guard — reproduces session e259c121-dc13-46d6-8e96-118f1da9845e.
+            // DeviceSetupProvisioningComplete arrives AFTER AccountSetup has started and
+            // DesktopArrived was observed, but BEFORE HelloResolved. The SelfDeploying terminal
+            // handler must NOT complete the session on the Classic path.
+            var result = RunFixture(
+                fixtureFilename: "userdriven-late-provisioning-complete-v1.jsonl",
+                sessionId: "session-anon-0006",
+                tenantId: "tenant-anon-0006");
+
+            Assert.Equal(SessionStage.Completed, result.FinalState.Stage);
+            Assert.Equal(SessionOutcome.EnrollmentComplete, result.FinalState.Outcome);
+            Assert.Equal("Success", result.FinalState.HelloOutcome!.Value);
+            Assert.NotNull(result.FinalState.HelloResolvedUtc);
+            Assert.NotNull(result.FinalState.DesktopArrivedUtc);
+            Assert.NotNull(result.FinalState.AccountSetupEnteredUtc);
+            Assert.Empty(result.FinalState.Deadlines);
+
+            // Completion must come from HelloResolved (AND-gate with prior DesktopArrived),
+            // NOT from DeviceSetupProvisioningComplete.
+            var last = result.Transitions[^1];
+            Assert.Equal("HelloResolved", last.Trigger);
+            Assert.True(last.Taken);
+
+            // The DeviceSetupProvisioningComplete signal is observed as a taken but stage-unchanged
+            // step (informational on Classic path — not a terminal trigger).
+            var provTransition = Assert.Single(
+                result.Transitions,
+                t => t.Trigger == nameof(AutopilotMonitor.DecisionCore.Signals.DecisionSignalKind.DeviceSetupProvisioningComplete));
+            Assert.True(provTransition.Taken);
+            Assert.Equal(SessionStage.EspAccountSetup, provTransition.FromStage);
+            Assert.Equal(SessionStage.EspAccountSetup, provTransition.ToStage);
+
+            // DeviceOnlyDeployment hypothesis must stay Unknown — this is a Classic UserDriven path.
+            Assert.Equal(HypothesisLevel.Unknown, result.FinalState.DeviceOnlyDeployment.Level);
+        }
     }
 }
diff --git a/src/Shared/AutopilotMonitor.DecisionCore/Engine/DecisionEngine.SelfDeploying.cs b/src/Shared/AutopilotMonitor.DecisionCore/Engine/DecisionEngine.SelfDeploying.cs
index 26d17e67..7fe1827a 100644
--- a/src/Shared/AutopilotMonitor.DecisionCore/Engine/DecisionEngine.SelfDeploying.cs
+++ b/src/Shared/AutopilotMonitor.DecisionCore/Engine/DecisionEngine.SelfDeploying.cs
@@ -27,18 +27,43 @@ namespace AutopilotMonitor.DecisionCore.Engine
         /// <summary>
         /// Handle <see cref="DecisionSignalKind.DeviceSetupProvisioningComplete"/>.
         /// <para>
-        /// The canonical SelfDeploying / Device-Only terminal signal. Cancels the
-        /// <see cref="DeadlineNames.DeviceOnlyEspDetection"/> deadline if still armed,
-        /// finalizes the <see cref="DecisionState.DeviceOnlyDeployment"/> hypothesis based
-        /// on whether any user-presence fact was observed, and transitions the session to
-        /// <see cref="SessionStage.Completed"/> with <see cref="SessionOutcome.EnrollmentComplete"/>.
+        /// Terminal only on the SelfDeploying / Device-Only path (no AccountSetup phase ever
+        /// entered). On the Classic UserDriven-v1 path — where <see cref="DecisionState.AccountSetupEnteredUtc"/>
+        /// is already set — this is just the ProvisioningStatusTracker marking DeviceSetupCategory
+        /// resolved; completion on that path requires <see cref="DecisionSignalKind.HelloResolved"/>
+        /// + <see cref="DecisionSignalKind.DesktopArrived"/> (handled by Classic.cs).
+        /// </para>
+        /// <para>
+        /// Guarding on <see cref="DecisionState.AccountSetupEnteredUtc"/> prevents the regression
+        /// observed in session e259c121-dc13-46d6-8e96-118f1da9845e (2026-04-22), where a late
+        /// DeviceSetupProvisioningComplete (payload <c>deviceSetupResolved=unknown</c>) fired while
+        /// Stage was <see cref="SessionStage.EspAccountSetup"/> and <see cref="DecisionState.HelloResolvedUtc"/>
+        /// was still null — terminating the session before Hello even ran.
         /// </para>
         /// </summary>
         private DecisionStep HandleDeviceSetupProvisioningCompleteV1(DecisionState state, DecisionSignal signal)
         {
             var nextStep = state.StepIndex + 1;
 
-            // Determine DeviceOnlyDeployment verdict.
+            // Classic-path guard: AccountSetup already started → this signal is informational only.
+            if (state.AccountSetupEnteredUtc != null)
+            {
+                var passthroughState = state.ToBuilder()
+                    .WithStepIndex(nextStep)
+                    .WithLastAppliedSignalOrdinal(signal.SessionSignalOrdinal)
+                    .Build();
+
+                var passthroughTransition = BuildTakenTransition(
+                    before: state,
+                    signal: signal,
+                    toStage: state.Stage,
+                    nextStepIndex: nextStep,
+                    trigger: nameof(DecisionSignalKind.DeviceSetupProvisioningComplete));
+
+                return new DecisionStep(passthroughState, passthroughTransition, Array.Empty<DecisionEffect>());
+            }
+
+            // SelfDeploying / Device-Only terminal path.
             var hasUserPresence =
                 (state.AadJoinedWithUser != null && state.AadJoinedWithUser.Value) ||
                 state.HelloResolvedUtc != null ||
@@ -62,10 +87,9 @@ namespace AutopilotMonitor.DecisionCore.Engine
                 .ClearDeadlines();
             builder.DeviceOnlyDeployment = updatedHypothesis;
 
-            // Also strengthen EnrollmentType: observing DeviceSetupProvisioningComplete
-            // without preceding AccountSetup strongly implies SelfDeploying-v1.
-            if (state.AccountSetupEnteredUtc == null &&
-                state.EnrollmentType.Level < HypothesisLevel.Strong)
+            // Strengthen EnrollmentType: observing DeviceSetupProvisioningComplete without
+            // preceding AccountSetup strongly implies SelfDeploying-v1.
+            if (state.EnrollmentType.Level < HypothesisLevel.Strong)
             {
                 builder.EnrollmentType = state.EnrollmentType.With(
                     level: HypothesisLevel.Strong,
diff --git a/tests/fixtures/enrollment-sessions/userdriven-late-provisioning-complete-v1.jsonl b/tests/fixtures/enrollment-sessions/userdriven-late-provisioning-complete-v1.jsonl
new file mode 100644
index 00000000..742c344a
--- /dev/null
+++ b/tests/fixtures/enrollment-sessions/userdriven-late-provisioning-complete-v1.jsonl
@@ -0,0 +1,19 @@
+# Scenario: UserDriven-v1 with late spurious DeviceSetupProvisioningComplete after AccountSetup started.
+# Reproduces regression from session e259c121-dc13-46d6-8e96-118f1da9845e (2026-04-22):
+# ProvisioningStatusTracker fired DeviceSetupProvisioningComplete (payload
+# deviceSetupResolved="unknown") AFTER AccountSetup was already in progress and
+# DesktopArrived had been observed — but HelloResolved had NOT yet fired.
+# Before the fix: the reducer completed the session to Stage=Completed unconditionally on
+# DeviceSetupProvisioningComplete, short-circuiting Hello.
+# After the fix: the handler detects AccountSetupEnteredUtc != null and treats the signal as
+# informational only (stage unchanged, no completion effect). Completion happens on the
+# subsequent HelloResolved via the Classic Hello+Desktop AND-gate.
+# Expected terminal: Stage=Completed, Outcome=EnrollmentComplete, HelloOutcome=Success,
+# last trigger = HelloResolved (NOT DeviceSetupProvisioningComplete).
+# Plan: §6.1 regression fixture.
+{"SessionSignalOrdinal":0,"SessionTraceOrdinal":0,"Kind":"SessionStarted","KindSchemaVersion":1,"OccurredAtUtc":"2026-04-22T17:48:00Z","SourceOrigin":"orchestrator","Evidence":{"Kind":"Synthetic","Identifier":"session:userdriven-late-provisioning-complete:started","Summary":"Session start anchor"}}
+{"SessionSignalOrdinal":1,"SessionTraceOrdinal":1,"Kind":"EspPhaseChanged","KindSchemaVersion":1,"OccurredAtUtc":"2026-04-22T17:48:30Z","SourceOrigin":"EspAndHelloTracker","Evidence":{"Kind":"Derived","Identifier":"esp-phase-detector-v1","Summary":"ESP phase=DeviceSetup","DerivationInputs":{"rawValue":"1"}},"Payload":{"phase":"DeviceSetup"}}
+{"SessionSignalOrdinal":2,"SessionTraceOrdinal":2,"Kind":"EspPhaseChanged","KindSchemaVersion":1,"OccurredAtUtc":"2026-04-22T17:51:38Z","SourceOrigin":"EspAndHelloTracker","Evidence":{"Kind":"Derived","Identifier":"esp-phase-detector-v1","Summary":"ESP phase=AccountSetup","DerivationInputs":{"rawValue":"2"}},"Payload":{"phase":"AccountSetup"}}
+{"SessionSignalOrdinal":3,"SessionTraceOrdinal":3,"Kind":"DesktopArrived","KindSchemaVersion":1,"OccurredAtUtc":"2026-04-22T17:51:58Z","SourceOrigin":"DesktopArrivalDetector","Evidence":{"Kind":"Derived","Identifier":"desktop-arrival-detector-v1","Summary":"Explorer.exe running as real user","DerivationInputs":{"user":"user-anon-0006","explorerPid":"4242"}}}
+{"SessionSignalOrdinal":4,"SessionTraceOrdinal":4,"Kind":"DeviceSetupProvisioningComplete","KindSchemaVersion":1,"OccurredAtUtc":"2026-04-22T17:51:59Z","SourceOrigin":"ProvisioningStatusTracker","Evidence":{"Kind":"Derived","Identifier":"provisioning-status-tracker-v1","Summary":"DeviceSetupCategory subcategories succeeded but category unresolved","DerivationInputs":{"deviceSetupResolved":"unknown"}},"Payload":{"deviceSetupResolved":"unknown"}}
+{"SessionSignalOrdinal":5,"SessionTraceOrdinal":5,"Kind":"HelloResolved","KindSchemaVersion":1,"OccurredAtUtc":"2026-04-22T17:53:30Z","SourceOrigin":"EspAndHelloTracker","Evidence":{"Kind":"Raw","Identifier":"hello-event-recordId:77","Summary":"Hello for Business enrolled"},"Payload":{"outcome":"Success"}}