fix(agent,web): a script run duration is judged from both lines' provenance; an offset-error span is omitted, never shown (D-273)

A platform script that ran 10 s was shown as "1h 00m" (session 4377911b): its
start line was self-anchored (+120 min) while its result line, re-read after an
overwrite rewind and therefore never fresh, fell back to the agent's cached zone
(+60 min), was rejected as ahead of the clock, and the duration was taken from
the raw pair. The same shape fired script_timeout_suspected daily in one tenant
on 2-9 s scripts read as 17 h. Fleet 2026-09-20..23: about 1 % of script
durations, 28 of 28 inflated ones carrying derivedTimestamp.

Agent: ScriptExecutionState binds the provenance of its start, result and exit
lines (CmTraceLineProvenance, persisted); EmitScriptCompleted judges the pair -
verified (both measured, or both assumed with the same offset from the same
file), unverified, or suppressed with durationSuppressedReason
(rejected-endpoint | offset-grid, CmTraceOffsetCalibrator.IsOnOffsetGrid) - and
always emits durationProvenance plus startSourceOffset*. A held completion's
sourceOffset* tags now describe its own result line; script_timeout_suspected
only judges a measurable duration; the emitted-run marker is capped at the
clock so a future-shifted result no longer swallows the next run's start.

Web: the reducer applies the same rule to stored events from older agents,
pairing a final with the latest script_started of its policy, and the panel
shows "n/a" with the explanation where the run time would be.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Ime/CmTraceOffsetCalibratorTests.cs

@@ -186,5 +186,20 @@ namespace AutopilotMonitor.Agent.V2.Core.Tests.Monitoring.Ime
             DateTime resolved;
             Assert.False(sut.TryResolveUtc(Source, UtcNow, out resolved));
         }
+
+        [Theory]
+        [InlineData(3610.39, true, 4)]     // session 4377911b: +1 h on a 10 s script
+        [InlineData(61203.0, true, 68)]    // 17 h on a 3 s script
+        [InlineData(7205.66, true, 8)]     // session cbaed57b: +2 h
+        [InlineData(-3596.0, true, 4)]     // the same error on the start end
+        [InlineData(26.4, false, 0)]       // a run time below one grid step
+        [InlineData(1030.0, false, 1)]     // 17 min 10 s: residual past the tolerance
+        [InlineData(900.0, true, 1)]       // exactly one step — a genuine 15-minute run reads the same, the caller needs mixed provenance too
+        public void A_grid_sized_span_is_the_signature_of_an_offset_error(double seconds, bool onGrid, int expectedSteps)
+        {
+            int steps;
+            Assert.Equal(onGrid, CmTraceOffsetCalibrator.IsOnOffsetGrid(TimeSpan.FromSeconds(seconds), out steps));
+            if (onGrid) Assert.Equal(expectedSteps, steps);
+        }
     }
 }

src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Ime/ImeLogTrackerResultHoldTests.cs

@@ -304,5 +304,29 @@ namespace AutopilotMonitor.Agent.V2.Core.Tests.Monitoring.Ime
             tracker.HandlePlatformScriptStarted("policyZ");
             Assert.Single(started);
         }
+
+        [Fact]
+        public void Emitted_marker_is_capped_at_the_clock_so_the_next_run_still_opens_a_slot()
+        {
+            // Session 4377911b: the result line was re-read after an overwrite rewind and resolved
+            // in the reader's zone, one hour ahead of the clock. Stored uncapped, that stamp made
+            // the genuine second run's start line read as a late line of the first run and its
+            // result a duplicate.
+            using var h = new Harness();
+            h.Start("d94468af", T0.AddSeconds(-10));
+            h.Result("d94468af", T0.AddHours(1));
+            h.Exit("d94468af", T0.AddSeconds(-1));
+            h.Flush();
+            Assert.Single(h.Completed);
+
+            // The second run, two minutes later on the clock — still "before" the uncapped stamp.
+            h.Now = T0.AddMinutes(2);
+            h.Start("d94468af", h.Now.AddSeconds(-5));
+            h.Result("d94468af", h.Now.AddSeconds(-1));
+            h.Exit("d94468af", h.Now.AddSeconds(-2));
+            h.Flush();
+
+            Assert.Equal(2, h.Completed.Count);
+        }
     }
 }

src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Monitoring/Ime/ImeLogTrackerScriptStatePersistenceTests.cs

@@ -154,5 +154,45 @@ namespace AutopilotMonitor.Agent.V2.Core.Tests.Monitoring.Ime
             Assert.False(tracker2.TryClaimScriptTimeoutSuspected("policyF")); // cross-restart dedup
             Assert.True(tracker2.TryClaimScriptTimeoutSuspected("policyG"));  // other policies unaffected
         }
+
+        [Fact]
+        public void Line_provenance_of_a_pending_script_survives_restart()
+        {
+            using var tmp = new TempDirectory();
+            var observedAt = new DateTime(2026, 9, 17, 13, 20, 7, DateTimeKind.Utc);
+            var start = new CmTraceLineProvenance
+            {
+                SourceLocalTs = new DateTime(2026, 9, 17, 15, 19, 57, DateTimeKind.Unspecified),
+                Origin = CmTraceOffsetOrigin.LineAnchored,
+                OffsetMinutes = 120,
+                MeasuredWriterOffsetMinutes = 120,
+                SourceFileName = "IntuneManagementExtension.log",
+            };
+            var exit = new CmTraceLineProvenance
+            {
+                SourceLocalTs = new DateTime(2026, 9, 17, 15, 20, 7, DateTimeKind.Unspecified),
+                Origin = CmTraceOffsetOrigin.None,
+                OffsetMinutes = 60,
+                SourceFileName = "AgentExecutor.log",
+            };
+
+            var tracker1 = BuildTracker(tmp, out _);
+            tracker1.SeedPendingPlatformScriptForTesting("policyH", exitCode: 0, exitObservedAtUtc: observedAt,
+                startedAtUtc: observedAt.AddSeconds(-10), startedAtProvenance: start, exitProvenance: exit);
+            tracker1.SaveStateForTest();
+
+            var tracker2 = BuildTracker(tmp, out var emitted2);
+            tracker2.LoadStateForTest();
+            tracker2.FlushPendingPlatformScriptResults(observedAt.AddSeconds(20));
+
+            var script = Assert.Single(emitted2);
+            Assert.Equal(CmTraceOffsetOrigin.LineAnchored, script.StartedAtProvenance.Origin);
+            Assert.Equal(120, script.StartedAtProvenance.OffsetMinutes);
+            Assert.Equal(start.SourceLocalTs, script.StartedAtProvenance.SourceLocalTs);
+            Assert.Equal(DateTimeKind.Unspecified, script.StartedAtProvenance.SourceLocalTs!.Value.Kind); // no zone was ever attached
+            Assert.Equal("AgentExecutor.log", script.ExitProvenance.SourceFileName);
+            Assert.Equal(60, script.ExitProvenance.OffsetMinutes);
+            Assert.Null(script.ResultProvenance);
+        }
     }
 }

src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/SignalAdapters/ImeLogTrackerAdapterDurationProvenanceTests.cs

@@ -0,0 +1,292 @@
+using System;
+using AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime;
+using AutopilotMonitor.Agent.V2.Core.SignalAdapters;
+using AutopilotMonitor.Agent.V2.Core.Tests.Harness;
+using SharedEventTypes = AutopilotMonitor.Shared.Constants.EventTypes;
+using Xunit;
+
+namespace AutopilotMonitor.Agent.V2.Core.Tests.SignalAdapters
+{
+    /// <summary>
+    /// A script run duration is the span between two CMTrace lines, each resolved on its own zone
+    /// belief. When the beliefs differ the span is a whole number of offset-grid steps plus the run
+    /// time, not the run time: session 4377911b read a 10 s script as 3610 s (start line-anchored
+    /// +120, result re-read after an overwrite rewind in the reader's zone +60 and rejected as
+    /// ahead of the clock), a fleet tenant read 2–9 s scripts as 17 h every day. The adapter judges
+    /// the pair from the provenance bound to each line and omits the span rather than lie.
+    /// </summary>
+    public sealed class ImeLogTrackerAdapterDurationProvenanceTests
+    {
+        private const string ServiceLog = "IntuneManagementExtension.log";
+        private const string ExecutorLog = "AgentExecutor.log";
+
+        private static CmTraceLineProvenance Line(
+            DateTime resolvedUtc, int offsetMinutes, CmTraceOffsetOrigin origin,
+            string file = ServiceLog, string? anchor = null, int? measured = null) =>
+            new CmTraceLineProvenance
+            {
+                // The writer's local time is the resolved value with the applied offset put back.
+                SourceLocalTs = DateTime.SpecifyKind(resolvedUtc.AddMinutes(offsetMinutes), DateTimeKind.Unspecified),
+                Origin = origin,
+                OffsetMinutes = offsetMinutes,
+                EraAnchorKind = anchor,
+                MeasuredWriterOffsetMinutes = measured,
+                SourceFileName = file,
+            };
+
+        private static ScriptExecutionState Platform(string policyId, DateTime startedAtUtc, CmTraceLineProvenance start,
+            DateTime? resultObservedAtUtc = null, CmTraceLineProvenance? result = null, string outcome = "Success", int exitCode = 0) =>
+            new ScriptExecutionState
+            {
+                PolicyId = policyId,
+                ScriptType = "platform",
+                ExitCode = exitCode,
+                Result = outcome,
+                ResultSource = "ime_policy_result",
+                StartedAtUtc = startedAtUtc,
+                StartedAtProvenance = start,
+                ResultObservedAtUtc = resultObservedAtUtc,
+                ResultProvenance = result,
+            };
+
+        [Fact]
+        public void Rejected_result_line_against_a_line_anchored_start_omits_the_span()
+        {
+            // Session 4377911b, script d94468af: start 15:19:57.005 local, self-anchored (+120);
+            // result 15:20:07.391 local, re-read after a rewind and resolved in the reader's
+            // zone (+60) → 14:20:07Z, one hour ahead of the clock. The raw pair reads 3610 s.
+            var clockNow = new DateTime(2026, 9, 17, 13, 20, 7, 437, DateTimeKind.Utc);
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var startUtc = new DateTime(2026, 9, 17, 13, 19, 57, 5, DateTimeKind.Utc);
+            var resultRaw = new DateTime(2026, 9, 17, 14, 20, 7, 391, DateTimeKind.Utc);
+
+            adapter.TriggerScriptCompletedFromTest(Platform("d94468af",
+                startUtc, Line(startUtc, 120, CmTraceOffsetOrigin.LineAnchored, measured: 120),
+                resultRaw, Line(resultRaw, 60, CmTraceOffsetOrigin.None, measured: 120)));
+
+            var info = f.InfoEvent(SharedEventTypes.ScriptCompleted);
+            Assert.Equal(clockNow, info.OccurredAtUtc);                              // stamp: clamped to the clock
+            Assert.Equal("true", info.Payload!["derivedTimestamp"]);
+            Assert.Equal(resultRaw.ToString("o"), info.Payload["rejectedSourceTimestamp"]);
+            Assert.False(info.Payload.ContainsKey("durationSeconds"));
+            Assert.False(info.Payload.ContainsKey("durationBasis"));
+            Assert.Equal("rejected-endpoint", info.Payload["durationSuppressedReason"]);
+            Assert.Equal("unverified", info.Payload["durationProvenance"]);
+            // The end line's own provenance and the start line's, side by side.
+            Assert.Equal("reader-zone-fallback", info.Payload["sourceOffsetOrigin"]);
+            Assert.Equal("60", info.Payload["sourceOffsetMinutes"]);
+            Assert.Equal("120", info.Payload["measuredWriterOffsetMinutes"]);
+            Assert.Equal("2026-09-17T15:20:07.3910000", info.Payload["sourceLocalTs"]);
+            Assert.Equal("line-anchored", info.Payload["startSourceOffsetOrigin"]);
+            Assert.Equal("120", info.Payload["startSourceOffsetMinutes"]);
+        }
+
+        [Fact]
+        public void Rejected_era_anchored_result_of_a_failed_script_omits_the_span_and_the_timeout_verdict()
+        {
+            // Fleet shape (script_failed, daily in one tenant): result era-anchored at −420 (the
+            // OOBE default zone's era) on a line written under +600 → 17 h ahead of the clock;
+            // the 61203 s "run" of a 3 s script fired script_timeout_suspected every day.
+            var clockNow = new DateTime(2026, 9, 21, 1, 30, 13, DateTimeKind.Utc);
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var startUtc = clockNow.AddSeconds(-8);
+            var resultRaw = clockNow.AddSeconds(-5).AddHours(17);
+
+            adapter.TriggerScriptCompletedFromTest(Platform("88d406eb",
+                startUtc, Line(startUtc, 600, CmTraceOffsetOrigin.LineAnchored),
+                resultRaw, Line(resultRaw, -420, CmTraceOffsetOrigin.EraAnchored, anchor: "bootstrap-policy-result", measured: 600),
+                outcome: "Failed"));
+
+            var failed = f.InfoEvent(SharedEventTypes.ScriptFailed);
+            Assert.Equal("rejected-endpoint", failed.Payload!["durationSuppressedReason"]);
+            Assert.False(failed.Payload.ContainsKey("durationSeconds"));
+            Assert.Equal("era-anchored", failed.Payload["sourceOffsetOrigin"]);
+            Assert.Equal("bootstrap-policy-result", failed.Payload["sourceOffsetAnchor"]);
+            Assert.Empty(f.InfoEvents(SharedEventTypes.ScriptTimeoutSuspected));
+        }
+
+        [Fact]
+        public void Mixed_pair_on_the_offset_grid_omits_the_span_even_when_nothing_was_rejected()
+        {
+            // Session cbaed57b: start from AgentExecutor.log in the reader's zone (+120, two
+            // hours too early), result era-anchored at 0 in the service log → 7205 s.
+            var clockNow = new DateTime(2026, 9, 11, 8, 48, 25, DateTimeKind.Utc);
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var resultUtc = clockNow.AddSeconds(-1);
+            var startUtc = resultUtc.AddSeconds(-7205);
+
+            adapter.TriggerScriptCompletedFromTest(Platform("846cea22",
+                startUtc, Line(startUtc, 120, CmTraceOffsetOrigin.None, file: ExecutorLog),
+                resultUtc, Line(resultUtc, 0, CmTraceOffsetOrigin.EraAnchored, anchor: "bootstrap-policy-result")));
+
+            var info = f.InfoEvent(SharedEventTypes.ScriptCompleted);
+            Assert.False(info.Payload!.ContainsKey("derivedTimestamp"));
+            Assert.False(info.Payload.ContainsKey("durationSeconds"));
+            Assert.Equal("offset-grid", info.Payload["durationSuppressedReason"]);
+            Assert.Equal("unverified", info.Payload["durationProvenance"]);
+        }
+
+        [Fact]
+        public void Mixed_pair_off_the_grid_keeps_the_span_as_unverified()
+        {
+            var clockNow = ImeLogTrackerAdapterFixture.DefaultClockStart;
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var resultUtc = clockNow.AddSeconds(-1);
+            var startUtc = resultUtc.AddSeconds(-26);
+
+            adapter.TriggerScriptCompletedFromTest(Platform("f6f67f79",
+                startUtc, Line(startUtc, 120, CmTraceOffsetOrigin.LineAnchored),
+                resultUtc, Line(resultUtc, 120, CmTraceOffsetOrigin.None)));
+
+            var info = f.InfoEvent(SharedEventTypes.ScriptCompleted);
+            Assert.Equal("26.00", info.Payload!["durationSeconds"]);
+            Assert.Equal("script_runtime", info.Payload["durationBasis"]);
+            Assert.Equal("unverified", info.Payload["durationProvenance"]);
+            Assert.False(info.Payload.ContainsKey("durationSuppressedReason"));
+        }
+
+        [Fact]
+        public void Two_line_anchored_ends_on_the_grid_are_a_verified_fifteen_minute_run()
+        {
+            var clockNow = ImeLogTrackerAdapterFixture.DefaultClockStart;
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var resultUtc = clockNow.AddSeconds(-1);
+            var startUtc = resultUtc.AddSeconds(-900);
+
+            adapter.TriggerScriptCompletedFromTest(Platform("11111111",
+                startUtc, Line(startUtc, 120, CmTraceOffsetOrigin.LineAnchored),
+                resultUtc, Line(resultUtc, 120, CmTraceOffsetOrigin.LineAnchored)));
+
+            var info = f.InfoEvent(SharedEventTypes.ScriptCompleted);
+            Assert.Equal("900.00", info.Payload!["durationSeconds"]);
+            Assert.Equal("verified", info.Payload["durationProvenance"]);
+        }
+
+        [Fact]
+        public void Two_fallback_ends_from_the_same_file_share_their_error_and_stay_measurable()
+        {
+            var clockNow = ImeLogTrackerAdapterFixture.DefaultClockStart;
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var resultUtc = clockNow.AddSeconds(-1);
+            var startUtc = resultUtc.AddSeconds(-900);
+
+            adapter.TriggerScriptCompletedFromTest(Platform("22222222",
+                startUtc, Line(startUtc, 60, CmTraceOffsetOrigin.None),
+                resultUtc, Line(resultUtc, 60, CmTraceOffsetOrigin.None)));
+
+            var info = f.InfoEvent(SharedEventTypes.ScriptCompleted);
+            Assert.Equal("900.00", info.Payload!["durationSeconds"]);
+            Assert.Equal("verified", info.Payload["durationProvenance"]);
+        }
+
+        [Fact]
+        public void Two_fallback_ends_from_different_files_are_different_writers()
+        {
+            // Same reader zone applied to both, but the executor child process and the service
+            // can hold different beliefs (cbaed57b) — a grid-sized span is not trusted.
+            var clockNow = ImeLogTrackerAdapterFixture.DefaultClockStart;
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var resultUtc = clockNow.AddSeconds(-1);
+            var startUtc = resultUtc.AddSeconds(-900);
+
+            adapter.TriggerScriptCompletedFromTest(Platform("33333333",
+                startUtc, Line(startUtc, 60, CmTraceOffsetOrigin.None, file: ExecutorLog),
+                resultUtc, Line(resultUtc, 60, CmTraceOffsetOrigin.None)));
+
+            var info = f.InfoEvent(SharedEventTypes.ScriptCompleted);
+            Assert.False(info.Payload!.ContainsKey("durationSeconds"));
+            Assert.Equal("offset-grid", info.Payload["durationSuppressedReason"]);
+        }
+
+        [Fact]
+        public void Without_provenance_the_pair_is_taken_as_before()
+        {
+            // States from before the field (persisted by an older agent) and synthetic events:
+            // no snapshot on either end, the 30-minute Failed run still reads as a timeout.
+            var clockNow = ImeLogTrackerAdapterFixture.DefaultClockStart;
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            f.Tracker.LastMatchedLogTimestamp = clockNow.AddSeconds(-1);
+            adapter.TriggerScriptCompletedFromTest(new ScriptExecutionState
+            {
+                PolicyId = "44444444",
+                ScriptType = "platform",
+                ExitCode = 0,
+                Result = "Failed",
+                StartedAtUtc = clockNow.AddSeconds(-1801),
+            });
+
+            var failed = f.InfoEvent(SharedEventTypes.ScriptFailed);
+            Assert.Equal("1800.00", failed.Payload!["durationSeconds"]);
+            Assert.False(failed.Payload.ContainsKey("durationProvenance"));
+            Assert.False(failed.Payload.ContainsKey("durationSuppressedReason"));
+            Assert.Single(f.InfoEvents(SharedEventTypes.ScriptTimeoutSuspected));
+        }
+
+        [Fact]
+        public void Negative_grid_sized_span_from_a_future_shifted_start_is_named_not_dropped_silently()
+        {
+            var clockNow = ImeLogTrackerAdapterFixture.DefaultClockStart;
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var resultUtc = clockNow.AddSeconds(-1);
+            var startUtc = resultUtc.AddSeconds(3595); // resolved one hour ahead of its real instant
+
+            adapter.TriggerScriptCompletedFromTest(Platform("55555555",
+                startUtc, Line(startUtc, 60, CmTraceOffsetOrigin.None),
+                resultUtc, Line(resultUtc, 120, CmTraceOffsetOrigin.LineAnchored)));
+
+            var info = f.InfoEvent(SharedEventTypes.ScriptCompleted);
+            Assert.False(info.Payload!.ContainsKey("durationSeconds"));
+            Assert.Equal("offset-grid", info.Payload["durationSuppressedReason"]);
+        }
+
+        [Fact]
+        public void Health_script_cycle_is_judged_the_same_way()
+        {
+            // HS-SCRIPT-START self-anchored, HS-NEW-RESULT re-read in the reader's zone and
+            // rejected: the cycle duration is omitted, the compliance verdict stays.
+            var clockNow = ImeLogTrackerAdapterFixture.DefaultClockStart;
+            using var f = new ImeLogTrackerAdapterFixture(clockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var startUtc = clockNow.AddSeconds(-40);
+            var resultRaw = clockNow.AddSeconds(-2).AddHours(1);
+
+            adapter.TriggerScriptCompletedFromTest(new ScriptExecutionState
+            {
+                PolicyId = "66666666",
+                ScriptType = "remediation",
+                ScriptPart = "detection",
+                ExitCode = 0,
+                ComplianceResult = "True",
+                StartedAtUtc = startUtc,
+                StartedAtProvenance = Line(startUtc, 120, CmTraceOffsetOrigin.LineAnchored),
+                ResultObservedAtUtc = resultRaw,
+                ResultProvenance = Line(resultRaw, 60, CmTraceOffsetOrigin.None),
+                DurationBasis = "cycle_including_reporting_latency",
+            });
+
+            var info = f.InfoEvent(SharedEventTypes.ScriptCompleted);
+            Assert.Equal("True", info.Payload!["complianceResult"]);
+            Assert.False(info.Payload.ContainsKey("durationSeconds"));
+            Assert.Equal("rejected-endpoint", info.Payload["durationSuppressedReason"]);
+        }
+    }
+}

src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/SignalAdapters/ImeLogTrackerAdapterResultHoldTests.cs

@@ -1,4 +1,5 @@
 using System;
+using AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime;
 using AutopilotMonitor.Agent.V2.Core.SignalAdapters;
 using AutopilotMonitor.Agent.V2.Core.Tests.Harness;
 using SharedEventTypes = AutopilotMonitor.Shared.Constants.EventTypes;
@@ -45,5 +46,46 @@ namespace AutopilotMonitor.Agent.V2.Core.Tests.SignalAdapters
             Assert.Equal("ime_policy_result", info.Payload["resultSource"]);
             Assert.Equal("92.00", info.Payload["durationSeconds"]);
         }
+
+        [Fact]
+        public void Held_completion_carries_the_provenance_of_its_result_line()
+        {
+            using var f = new ImeLogTrackerAdapterFixture(ClockNow);
+            using var adapter = new ImeLogTrackerAdapter(f.Tracker, f.Ingress, f.Clock);
+
+            var startTs = ClockNow.AddSeconds(-95);
+            var resultTs = ClockNow.AddSeconds(-3);
+
+            // Start and result lines both self-anchored (+120).
+            f.Tracker.LastMatchedLogTimestamp = startTs;
+            f.Tracker.LastMatchedSourceLocalTimestamp = DateTime.SpecifyKind(startTs.AddMinutes(120), DateTimeKind.Unspecified);
+            f.Tracker.LastMatchedSourceOffsetOrigin = CmTraceOffsetOrigin.LineAnchored;
+            f.Tracker.LastMatchedSourceOffsetMinutes = 120;
+            f.Tracker.HandlePlatformScriptStarted("376ee51a");
+
+            f.Tracker.LastMatchedLogTimestamp = resultTs;
+            f.Tracker.LastMatchedSourceLocalTimestamp = DateTime.SpecifyKind(resultTs.AddMinutes(120), DateTimeKind.Unspecified);
+            f.Tracker.LastMatchedPatternId = "PS-SCRIPT-RESULT";
+            f.Tracker.CompletePlatformScriptFromImeResultForTesting("376ee51a", "Success", resultTs);
+
+            // By the time the held completion is emitted, the last matched line is an unrelated
+            // one resolved in the reader's zone.
+            f.Tracker.LastMatchedLogTimestamp = ClockNow.AddSeconds(-1);
+            f.Tracker.LastMatchedSourceLocalTimestamp = DateTime.SpecifyKind(ClockNow.AddSeconds(-1).AddMinutes(60), DateTimeKind.Unspecified);
+            f.Tracker.LastMatchedSourceOffsetOrigin = CmTraceOffsetOrigin.None;
+            f.Tracker.LastMatchedSourceOffsetMinutes = 60;
+            f.Tracker.LastMatchedPatternId = "IME-DOWNLOADING";
+            f.Tracker.RecordPlatformScriptExitCodeForTesting("376ee51a", 0, resultTs.AddMilliseconds(-8));
+            f.Tracker.FlushPendingPlatformScriptResults(f.Clock.UtcNow);
+
+            var info = f.InfoEvent(SharedEventTypes.ScriptCompleted);
+            Assert.Equal("line-anchored", info.Payload!["sourceOffsetOrigin"]);
+            Assert.Equal("120", info.Payload["sourceOffsetMinutes"]);
+            Assert.Equal(resultTs.AddMinutes(120).ToString("yyyy-MM-ddTHH:mm:ss.fffffff"), info.Payload["sourceLocalTs"]);
+            Assert.Equal("line-anchored", info.Payload["startSourceOffsetOrigin"]);
+            Assert.Equal("120", info.Payload["startSourceOffsetMinutes"]);
+            Assert.Equal("92.00", info.Payload["durationSeconds"]);
+            Assert.Equal("verified", info.Payload["durationProvenance"]);
+        }
     }
 }

src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Enrollment/Ime/CmTraceLineProvenance.cs

@@ -0,0 +1,57 @@
+using System;
+
+namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
+{
+    /// <summary>
+    /// How ONE CMTrace line's UTC value was arrived at, captured at the line itself.
+    /// <para>
+    /// The tracker exposes the provenance of the line it matched last. A consumer that acts later —
+    /// a platform-script result held for its executor end block, a run duration spanning a start
+    /// line and a result line — must describe ITS line, not whichever line happened to be matched
+    /// last, so the snapshot travels on <see cref="ScriptExecutionState"/> (persisted as a plain
+    /// DTO; null on state files written before it existed).
+    /// </para>
+    /// </summary>
+    public sealed class CmTraceLineProvenance
+    {
+        /// <summary>
+        /// The line's local time exactly as the writer wrote it (Kind Unspecified, no zone). Null
+        /// when the value did not come from a CMTrace line at all (clock fallback).
+        /// </summary>
+        public DateTime? SourceLocalTs { get; set; }
+
+        /// <summary>How the offset applied to <see cref="SourceLocalTs"/> was obtained.</summary>
+        public CmTraceOffsetOrigin Origin { get; set; }
+
+        /// <summary>The offset that was applied, in minutes (local = UTC + offset).</summary>
+        public int? OffsetMinutes { get; set; }
+
+        /// <summary>For <see cref="CmTraceOffsetOrigin.EraAnchored"/>: which anchor established the era's offset.</summary>
+        public string EraAnchorKind { get; set; }
+
+        /// <summary>What the calibrator measured for the source file — observational, never applied.</summary>
+        public int? MeasuredWriterOffsetMinutes { get; set; }
+
+        /// <summary>Name of the log file the line was read from — the closest thing to a writer identity the tracker has.</summary>
+        public string SourceFileName { get; set; }
+
+        /// <summary>
+        /// True when the applied offset was ASSUMED for this line rather than declared by the
+        /// writer or measured against the agent clock: the reader's own zone (fallback), a writer
+        /// era's anchor, or the retired per-file calibration. A clock-derived value (no source
+        /// timestamp) sits on the true UTC axis and is not an assumption.
+        /// </summary>
+        public bool IsAssumed()
+        {
+            if (!SourceLocalTs.HasValue) return false;
+            switch (Origin)
+            {
+                case CmTraceOffsetOrigin.Bias:
+                case CmTraceOffsetOrigin.LineAnchored:
+                    return false;
+                default:
+                    return true;
+            }
+        }
+    }
+}

src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Enrollment/Ime/CmTraceOffsetCalibrator.cs

@@ -159,6 +159,23 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
             return true;
         }
 
+        /// <summary>
+        /// Whether a span between two resolved lines is the signature of a wrong offset on one
+        /// of them rather than of elapsed time: a zone error is always a whole number of grid
+        /// steps, so a span within <see cref="MaxGridResidual"/> of k × <see cref="OffsetGrid"/>
+        /// (k ≥ 1) reads as an offset error plus a run time of seconds. Sign is ignored — a wrong
+        /// offset on the START end produces the same magnitude with the opposite sign.
+        /// </summary>
+        internal static bool IsOnOffsetGrid(TimeSpan span, out int gridSteps)
+        {
+            var magnitude = span.Duration();
+            gridSteps = (int)Math.Round(magnitude.TotalMinutes / OffsetGrid.TotalMinutes, MidpointRounding.AwayFromZero);
+            if (gridSteps < 1) return false;
+
+            var nearest = TimeSpan.FromMinutes(gridSteps * OffsetGrid.TotalMinutes);
+            return (magnitude - nearest).Duration() <= MaxGridResidual;
+        }
+
         public bool TryCalibrate(string sourceKey, DateTime localTimestamp, DateTime agentUtcNow)
         {
             if (string.IsNullOrEmpty(sourceKey)) return false;

src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Enrollment/Ime/ImeLogTracker.Handlers.cs

@@ -252,8 +252,8 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
                 // duration when the consolidated [HS] new result line arrives (the slot above is
                 // cleared by the early-signal HS-COMPLIANCE handler, so timing lives in its own
                 // map). Prefer the source CMTrace timestamp; latest start wins on a policy re-run.
-                var startedAtUtc = LastMatchedLogTimestamp ?? DateTime.UtcNow;
-                _healthScriptStartTimes[id] = startedAtUtc;
+                var startedAtUtc = LastMatchedLogTimestamp ?? UtcNowProvider();
+                _healthScriptStartTimes[id] = (startedAtUtc, CaptureLastMatchedProvenance());
                 _logger.Info($"ImeLogTracker: health script started: {id}");
 
                 // A replayed line of a previous enrollment bypasses the recurrence gate: the
@@ -281,6 +281,7 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
         internal void HandlePlatformScriptStarted(string id, string source = null)
         {
             var currentStartTs = LastMatchedLogTimestamp ?? UtcNowProvider();
+            var currentStartProvenance = CaptureLastMatchedProvenance();
 
             // A start line older than the result this policy already emitted is the late start
             // line of THAT run: its AgentExecutor block surfaced after the IME result — the two
@@ -323,6 +324,7 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
                     // The slot was opened by its result while the start block was still hidden;
                     // the recovered start line dates the run.
                     pendingSlot.StartedAtUtc = currentStartTs;
+                    pendingSlot.StartedAtProvenance = currentStartProvenance;
                     _stateDirty = true;
                 }
             }
@@ -343,6 +345,7 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
                     // Set only at slot creation: the start line fires twice (agentexecutor + ime
                     // source) but the earliest wins.
                     StartedAtUtc = currentStartTs,
+                    StartedAtProvenance = currentStartProvenance,
                 };
                 // Live "running" indicator — same signal health scripts emit. Gated on slot
                 // creation so the duplicate start line (agentexecutor + ime source) doesn't
@@ -433,7 +436,7 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
 
             var script = GetCurrentScriptForLineUpdate(parameters, out var ownerPolicyId);
             if (script != null)
-                ApplyExitCode(script, exitCode, LastMatchedLogTimestamp ?? UtcNowProvider());
+                ApplyExitCode(script, exitCode, LastMatchedLogTimestamp ?? UtcNowProvider(), CaptureLastMatchedProvenance());
             else if (ownerPolicyId != null)
                 _logger.Debug($"ImeLogTracker: exit code {exitCode} belongs to platform script {ownerPolicyId}, whose completion was already emitted — dropped");
             // An exit code means the executor just wrote its end block and IME is about to
@@ -442,15 +445,19 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
             RequestOverwriteCheck();
         }
 
-        private void ApplyExitCode(ScriptExecutionState script, int exitCode, DateTime observedAtUtc)
+        private void ApplyExitCode(ScriptExecutionState script, int exitCode, DateTime observedAtUtc, CmTraceLineProvenance exitProvenance)
         {
             script.ExitCode = exitCode;
             // Stamp when we learned the script's exit code so the deadline-based fallback
             // (FlushPendingPlatformScriptResults) can fire if IME never logs its authoritative
             // PS-SCRIPT-RESULT line in time. Prefer the source CMTrace timestamp (already
-            // UTC-normalized by the parser) so replayed log content is dated correctly.
+            // UTC-normalized by the parser) so replayed log content is dated correctly. The
+            // line's provenance rides along: the fallback emit is bound to this line.
             if (string.Equals(script.ScriptType, "platform", StringComparison.OrdinalIgnoreCase))
+            {
                 script.ExitObservedAtUtc = observedAtUtc;
+                script.ExitProvenance = exitProvenance;
+            }
             _logger.Debug($"ImeLogTracker: script exit code {exitCode} for {script.PolicyId}");
         }
 
@@ -500,7 +507,7 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
 
             if (string.IsNullOrEmpty(id)) return;
 
-            CompletePlatformScriptFromImeResult(id, result, LastMatchedLogTimestamp, LastMatchedPatternId);
+            CompletePlatformScriptFromImeResult(id, result, LastMatchedLogTimestamp, LastMatchedPatternId, CaptureLastMatchedProvenance());
         }
 
         /// <summary>
@@ -514,7 +521,7 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
         /// line reopened the slot, produced a fallback duplicate (session e7f3c910).
         /// <see cref="FlushPendingPlatformScriptResults"/> emits the held completion.
         /// </summary>
-        internal void CompletePlatformScriptFromImeResult(string policyId, string result, DateTime? resultLineTimestampUtc, string patternId)
+        internal void CompletePlatformScriptFromImeResult(string policyId, string result, DateTime? resultLineTimestampUtc, string patternId, CmTraceLineProvenance resultProvenance)
         {
             // Dedup: the deadline-based fallback (FlushPendingPlatformScriptResults) may already have
             // emitted this script from its AgentExecutor exit code because IME's authoritative
@@ -559,6 +566,7 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
             script.Result = result;
             script.ResultSource = "ime_policy_result";
             script.ResultObservedAtUtc = resultLineTimestampUtc ?? UtcNowProvider();
+            script.ResultProvenance = resultProvenance;
             script.ResultPatternId = patternId;
             _stateDirty = true;
 
@@ -584,7 +592,14 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
         {
             _logger.Info($"ImeLogTracker: platform script completed: {script.PolicyId}, result={script.Result}, exit={script.ExitCode}{(note != null ? $" ({note})" : string.Empty)}");
             EmitScriptEvent(script);
-            _platformScriptResultEmitted[script.PolicyId] = script.ResultObservedAtUtc ?? script.ExitObservedAtUtc ?? UtcNowProvider();
+            // The run's source stamp, capped at the clock: a result line cannot be read before it
+            // was written, so a stamp ahead of the clock is a wrong zone assumption on that line
+            // (a rewound result resolved in the reader's zone, session 4377911b: +1 h). Left
+            // uncapped, the marker made the genuine NEXT run's start line read as a late line of
+            // this run and its result a duplicate.
+            var runStamp = script.ResultObservedAtUtc ?? script.ExitObservedAtUtc ?? UtcNowProvider();
+            var nowUtc = UtcNowProvider();
+            _platformScriptResultEmitted[script.PolicyId] = runStamp > nowUtc ? nowUtc : runStamp;
             _pendingPlatformScripts.Remove(script.PolicyId);
             _stateDirty = true;
         }
@@ -681,7 +696,8 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
 
         /// <summary>Test seam: inject a pending platform script as if AgentExecutor.log had reported
         /// its start + exit code, without an IME PS-SCRIPT-RESULT line.</summary>
-        internal void SeedPendingPlatformScriptForTesting(string policyId, int? exitCode, DateTime? exitObservedAtUtc, string stdout = null, DateTime? startedAtUtc = null)
+        internal void SeedPendingPlatformScriptForTesting(string policyId, int? exitCode, DateTime? exitObservedAtUtc, string stdout = null, DateTime? startedAtUtc = null,
+            CmTraceLineProvenance startedAtProvenance = null, CmTraceLineProvenance exitProvenance = null)
         {
             // Mirrors a fresh execution start: a new run clears any prior emitted-marker (see
             // HandleScriptStarted) so re-runs of the same policy within one lifetime emit again.
@@ -694,6 +710,8 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
                 ExitObservedAtUtc = exitObservedAtUtc,
                 Stdout = stdout,
                 StartedAtUtc = startedAtUtc,
+                StartedAtProvenance = startedAtProvenance,
+                ExitProvenance = exitProvenance,
             };
             NextTestEntry();
             RecordInvocationMarker(policyId, isClose: false);
@@ -703,18 +721,18 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
         /// (the production handler minus regex extraction). <paramref name="resultLineTimestampUtc"/>
         /// stands in for the CMTrace timestamp of the PS-SCRIPT-RESULT line (production reads it
         /// via <see cref="LastMatchedLogTimestamp"/>, the fallback here).</summary>
-        internal void CompletePlatformScriptFromImeResultForTesting(string policyId, string result, DateTime? resultLineTimestampUtc = null)
+        internal void CompletePlatformScriptFromImeResultForTesting(string policyId, string result, DateTime? resultLineTimestampUtc = null, CmTraceLineProvenance resultProvenance = null)
         {
             if (string.IsNullOrEmpty(policyId)) return;
-            CompletePlatformScriptFromImeResult(policyId, result, resultLineTimestampUtc ?? LastMatchedLogTimestamp, "PS-SCRIPT-RESULT");
+            CompletePlatformScriptFromImeResult(policyId, result, resultLineTimestampUtc ?? LastMatchedLogTimestamp, "PS-SCRIPT-RESULT", resultProvenance ?? CaptureLastMatchedProvenance());
         }
 
         /// <summary>Test seam: the AgentExecutor exit-code line of a pending platform script (the
         /// production handler minus regex extraction and positional ownership).</summary>
-        internal void RecordPlatformScriptExitCodeForTesting(string policyId, int exitCode, DateTime observedAtUtc)
+        internal void RecordPlatformScriptExitCodeForTesting(string policyId, int exitCode, DateTime observedAtUtc, CmTraceLineProvenance exitProvenance = null)
         {
             if (_pendingPlatformScripts.TryGetValue(policyId, out var script))
-                ApplyExitCode(script, exitCode, observedAtUtc);
+                ApplyExitCode(script, exitCode, observedAtUtc, exitProvenance);
         }
 
         /// <summary>
@@ -790,8 +808,14 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
                 // HS-NEW-RESULT path whose end stamp includes IME's batched reporting latency.
                 // Peek only: HS-NEW-RESULT still consumes + removes the entry for cycle timing.
                 StartedAtUtc = _healthScriptStartTimes.TryGetValue(id, out var earlyStart)
-                    ? earlyStart
+                    ? earlyStart.Utc
                     : (DateTime?)null,
+                StartedAtProvenance = _healthScriptStartTimes.TryGetValue(id, out var earlyStartProvenance)
+                    ? earlyStartProvenance.Provenance
+                    : null,
+                // The HS-COMPLIANCE line is the end of this phase; emitted synchronously, so the
+                // last matched line is it.
+                ResultProvenance = CaptureLastMatchedProvenance(),
                 DurationBasis = "script_runtime",
             };
 
@@ -860,10 +884,10 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
         /// HS-SCRIPT-START line had been observed, so a subsequent
         /// <see cref="HandleHealthScriptResultJson"/> surfaces a run duration without driving the
         /// full regex pipeline.</summary>
-        internal void SeedHealthScriptStartForTesting(string policyId, DateTime startedAtUtc)
+        internal void SeedHealthScriptStartForTesting(string policyId, DateTime startedAtUtc, CmTraceLineProvenance provenance = null)
         {
             if (string.IsNullOrEmpty(policyId)) return;
-            _healthScriptStartTimes[policyId] = startedAtUtc;
+            _healthScriptStartTimes[policyId] = (startedAtUtc, provenance);
         }
 
         private void HandleHealthScriptResult(Match match, Dictionary<string, string> parameters)
@@ -920,10 +944,12 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
             // emitted phase events — the remediation analog of platform-script timing. Consumed +
             // removed so a later re-run of the same policy re-times from its own start. Null when
             // the start line was never seen in the agent's window (e.g. a replayed result).
-            DateTime? cycleStartedAtUtc = _healthScriptStartTimes.TryGetValue(policyId, out var hsStart)
-                ? hsStart
-                : (DateTime?)null;
+            var hasCycleStart = _healthScriptStartTimes.TryGetValue(policyId, out var hsStart);
+            DateTime? cycleStartedAtUtc = hasCycleStart ? hsStart.Utc : (DateTime?)null;
+            var cycleStartProvenance = hasCycleStart ? hsStart.Provenance : null;
             _healthScriptStartTimes.Remove(policyId);
+            // Every phase ends on this HS-NEW-RESULT line.
+            var resultProvenance = CaptureLastMatchedProvenance();
 
             // Common metadata — applied to every emitted phase event.
             var remediationStatus = TryGetInt(root, "RemediationStatus");
@@ -963,7 +989,9 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
                 targetType: targetType,
                 errorCode: errorCode,
                 errorDetails: errorDetails,
-                startedAtUtc: cycleStartedAtUtc);
+                startedAtUtc: cycleStartedAtUtc,
+                startedAtProvenance: cycleStartProvenance,
+                resultProvenance: resultProvenance);
             // complianceResult mirrors the legacy HS-COMPLIANCE event semantics: True when the
             // pre-detection script reported compliant (exit 0), False otherwise.
             detection.ComplianceResult = firstDetectExit == 0 ? "True" : (firstDetectExit.HasValue ? "False" : null);
@@ -987,7 +1015,9 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
                     targetType: targetType,
                     errorCode: errorCode,
                     errorDetails: errorDetails,
-                    startedAtUtc: cycleStartedAtUtc);
+                    startedAtUtc: cycleStartedAtUtc,
+                startedAtProvenance: cycleStartProvenance,
+                resultProvenance: resultProvenance);
                 // No complianceResult on the remediation phase — there is nothing to be compliant about.
                 EmitScriptEvent(remediation);
             }
@@ -1009,7 +1039,9 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
                     targetType: targetType,
                     errorCode: errorCode,
                     errorDetails: errorDetails,
-                    startedAtUtc: cycleStartedAtUtc);
+                    startedAtUtc: cycleStartedAtUtc,
+                startedAtProvenance: cycleStartProvenance,
+                resultProvenance: resultProvenance);
                 postDetection.ComplianceResult = lastDetectExit == 0 ? "True" : (lastDetectExit.HasValue ? "False" : null);
                 EmitScriptEvent(postDetection);
             }
@@ -1032,7 +1064,9 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
             int? targetType,
             int? errorCode,
             string errorDetails,
-            DateTime? startedAtUtc) =>
+            DateTime? startedAtUtc,
+            CmTraceLineProvenance startedAtProvenance,
+            CmTraceLineProvenance resultProvenance) =>
             new ScriptExecutionState
             {
                 PolicyId = policyId,
@@ -1049,6 +1083,8 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
                 // Cycle start (HS-SCRIPT-START). Every phase carries the same cycle start so the
                 // adapter computes the total run duration; the Web surfaces it once at card level.
                 StartedAtUtc = startedAtUtc,
+                StartedAtProvenance = startedAtProvenance,
+                ResultProvenance = resultProvenance,
                 // End stamp is the HS-NEW-RESULT line — written only after IME's batched report
                 // to the service, so this duration overstates the actual script execution time.
                 DurationBasis = "cycle_including_reporting_latency"

src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Enrollment/Ime/ImeLogTracker.LogProcessing.cs

@@ -505,6 +505,21 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
             "imetokenfailure",
         };
 
+        /// <summary>
+        /// Snapshot of the last matched line's provenance, for a consumer that acts later than
+        /// the match (a held platform-script result, a run duration across two lines) and must
+        /// describe THAT line rather than whichever line is matched by then.
+        /// </summary>
+        internal CmTraceLineProvenance CaptureLastMatchedProvenance() => new CmTraceLineProvenance
+        {
+            SourceLocalTs = LastMatchedSourceLocalTimestamp,
+            Origin = LastMatchedSourceOffsetOrigin,
+            OffsetMinutes = LastMatchedSourceOffsetMinutes,
+            EraAnchorKind = LastMatchedEraAnchorKind,
+            MeasuredWriterOffsetMinutes = LastMatchedMeasuredWriterOffsetMinutes,
+            SourceFileName = _currentSourceFileName,
+        };
+
         private void HandlePatternMatch(CompiledPattern pattern, Match match, string message, CmTraceLogEntry entry)
         {
             LastMatchedPatternId = pattern.PatternId;

src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Enrollment/Ime/ImeLogTracker.cs

@@ -205,8 +205,10 @@ namespace AutopilotMonitor.Agent.V2.Core.Monitoring.Enrollment.Ime
         // the remediation-script analog of the platform-script StartedAtUtc timing. Kept in a
         // dedicated map (not on _pendingHealthScript) because the early-signal HS-COMPLIANCE
         // handler clears that slot before HS-NEW-RESULT arrives. Consumed + removed on result emit.
-        private readonly Dictionary<string, DateTime> _healthScriptStartTimes =
-            new Dictionary<string, DateTime>(StringComparer.OrdinalIgnoreCase);
+        // The start line's provenance rides along so the adapter can tell whether start and result
+        // were resolved on the same zone assumption before it subtracts them.
+        private readonly Dictionary<string, (DateTime Utc, CmTraceLineProvenance Provenance)> _healthScriptStartTimes =
+            new Dictionary<string, (DateTime Utc, CmTraceLineProvenance Provenance)>(StringComparer.OrdinalIgnoreCase);
 
         // Restart-safe dedup for the adapter's one-shot script_timeout_suspected Warning.
         // Owned by the tracker (not the adapter) solely so it rides the persisted state file —

src/Agent/AutopilotMonitor.Agent.V2.Core/Monitoring/Enrollment/Ime/ScriptExecutionState.cs

@@ -29,6 +29,15 @@ public class ScriptExecutionState
     /// </summary>
     public System.DateTime? StartedAtUtc { get; set; }
 
+    /// <summary>
+    /// Provenance of <see cref="StartedAtUtc"/>: how the start line's offset was obtained. Paired
+    /// with <see cref="ResultProvenance"/> / <see cref="ExitProvenance"/> by the adapter to decide
+    /// whether a run duration is measurable — two lines resolved on different zone assumptions
+    /// differ by whole offset-grid steps, not by run time (session 4377911b: a 10 s script read
+    /// as 3610 s). Null when the start was never observed or on state files from before the field.
+    /// </summary>
+    public CmTraceLineProvenance StartedAtProvenance { get; set; }
+
     /// <summary>"detection", "remediation", or "post-detection" (remediation scripts only).</summary>
     public string ScriptPart { get; set; }
 
@@ -66,6 +75,9 @@ public class ScriptExecutionState
     /// </summary>
     public System.DateTime? ExitObservedAtUtc { get; set; }
 
+    /// <summary>Provenance of the exit-code line behind <see cref="ExitObservedAtUtc"/> (the fallback emit's end).</summary>
+    public CmTraceLineProvenance ExitProvenance { get; set; }
+
     /// <summary>
     /// Source (CMTrace) timestamp of the IME <c>PS-SCRIPT-RESULT</c> line that delivered
     /// <see cref="Result"/> (platform scripts, <c>ime_policy_result</c> only). The emitted event is
@@ -76,6 +88,14 @@ public class ScriptExecutionState
     /// </summary>
     public System.DateTime? ResultObservedAtUtc { get; set; }
 
+    /// <summary>
+    /// Provenance of the line that delivered <see cref="Result"/> — bound here for the same reason
+    /// as <see cref="ResultObservedAtUtc"/>: a held completion is emitted passes later, when the
+    /// tracker's "last matched" provenance describes an unrelated line. For health scripts the
+    /// result line of the phase (HS-COMPLIANCE early signal or HS-NEW-RESULT).
+    /// </summary>
+    public CmTraceLineProvenance ResultProvenance { get; set; }
+
     /// <summary>Pattern id of the line that delivered <see cref="Result"/> (surfaced as <c>patternId</c> on the event).</summary>
     public string ResultPatternId { get; set; }
 

src/Agent/AutopilotMonitor.Agent.V2.Core/SignalAdapters/ImeLogTrackerAdapter.cs

@@ -461,31 +461,35 @@ namespace AutopilotMonitor.Agent.V2.Core.SignalAdapters
         /// no second clock frame, so there is nothing to record.
         /// </para>
         /// </summary>
-        private void TagDerivedTimestamp(IDictionary<string, string> data, bool derivedFromClock, DateTime? rawSourceTs)
+        private void TagDerivedTimestamp(IDictionary<string, string> data, bool derivedFromClock, DateTime? rawSourceTs, CmTraceLineProvenance? lineProvenance = null)
         {
             var culture = System.Globalization.CultureInfo.InvariantCulture;
 
-            var sourceLocal = _tracker.LastMatchedSourceLocalTimestamp;
+            // The line the event is bound to. Callers that emit later than the match (a held
+            // platform-script result) pass the snapshot taken at their line; everyone else is
+            // emitting while its line is still the last matched one.
+            var line = lineProvenance ?? _tracker.CaptureLastMatchedProvenance();
+            var sourceLocal = line.SourceLocalTs;
             if (sourceLocal.HasValue)
             {
                 // No zone suffix: the value genuinely carries none, and formatting one in would
                 // re-introduce the very assumption this whole change removes.
                 data["sourceLocalTs"] = sourceLocal.Value.ToString("yyyy-MM-ddTHH:mm:ss.fffffff", culture);
-                data["sourceOffsetOrigin"] = OriginTag(_tracker.LastMatchedSourceOffsetOrigin);
+                data["sourceOffsetOrigin"] = OriginTag(line.Origin);
 
-                var offsetMinutes = _tracker.LastMatchedSourceOffsetMinutes;
+                var offsetMinutes = line.OffsetMinutes;
                 if (offsetMinutes.HasValue)
                     data["sourceOffsetMinutes"] = offsetMinutes.Value.ToString(culture);
 
                 // Which era anchor the offset came from — forensics for the era-anchored origin.
-                var anchorKind = _tracker.LastMatchedEraAnchorKind;
+                var anchorKind = line.EraAnchorKind;
                 if (!string.IsNullOrEmpty(anchorKind))
                     data["sourceOffsetAnchor"] = anchorKind;
 
                 // Observational only — what the calibrator measured, which since the 2026-08-20
                 // revert is deliberately NOT what was applied. Kept separate so the two can never
                 // be read as the same thing.
-                var measured = _tracker.LastMatchedMeasuredWriterOffsetMinutes;
+                var measured = line.MeasuredWriterOffsetMinutes;
                 if (measured.HasValue)
                     data["measuredWriterOffsetMinutes"] = measured.Value.ToString(culture);
             }
@@ -1293,7 +1297,11 @@ namespace AutopilotMonitor.Agent.V2.Core.SignalAdapters
             if (SuppressIfHistoricReplay(derivedFromClock, rawSourceTs, eventType, script.PolicyId))
                 return;
 
-            TagDerivedTimestamp(data, derivedFromClock, rawSourceTs);
+            // The line that delivered the result is bound on the state (D-247), so a completion
+            // emitted passes later still describes ITS line. Null (states from before the field,
+            // synthetic tests) falls back to the tracker's last matched line as before.
+            var endProvenance = isFallback ? script.ExitProvenance : script.ResultProvenance;
+            TagDerivedTimestamp(data, derivedFromClock, rawSourceTs, endProvenance);
 
             // Per-script run duration (start line → this completion). Surfaced on every
             // script completion so the UI can flag slow / inefficient scripts, not just timed-out
@@ -1301,11 +1309,13 @@ namespace AutopilotMonitor.Agent.V2.Core.SignalAdapters
             // against clock skew between the (possibly clock-derived) completion stamp and start.
             //
             // When the completion timestamp was clock-derived because the source line's timestamp
-            // was rejected (future-skew CMTrace clock jump — the stale case never reaches here),
-            // `now` lives on the clock's timeline while StartedAtUtc was captured RAW from the
-            // source log. Mixing the two produced absurd durations (session eaf3d8c4: 170 h), so
-            // the duration uses the raw source pair — both ends on the same timeline, the
-            // difference is the true runtime. The event stamp stays `now` (timeline position).
+            // was rejected (future-skew — the stale case never reaches here), `now` lives on the
+            // clock's timeline while StartedAtUtc was captured RAW from the source log. Mixing the
+            // two produced absurd durations (session eaf3d8c4: 170 h), so the span is taken from
+            // the raw source pair. That pair is a run time only when both lines were resolved on
+            // the same zone belief — JudgeDurationPair decides, from the provenance bound to each
+            // line, whether the span is verified, unverified, or an offset error to omit (session
+            // 4377911b: a 10 s script read as 3610 s). The event stamp stays `now`.
             //
             // L19 (delta review 2026-07-02): the same field name carries two different semantics —
             // start→own-end-signal (≈ script runtime) vs HS-SCRIPT-START→HS-NEW-RESULT (the whole
@@ -1317,15 +1327,26 @@ namespace AutopilotMonitor.Agent.V2.Core.SignalAdapters
             var completionForDuration = derivedFromClock && rawSourceTs.HasValue
                 ? NormalizeUtc(rawSourceTs.Value)
                 : now;
+            TimeSpan? measurableDuration = null;
             if (script.StartedAtUtc.HasValue)
             {
-                var durationSeconds = (completionForDuration - script.StartedAtUtc.Value).TotalSeconds;
+                var span = completionForDuration - script.StartedAtUtc.Value;
+                var verdict = JudgeDurationPair(script.StartedAtProvenance, endProvenance,
+                    endStampRejected: derivedFromClock && rawSourceTs.HasValue, span, out var suppressedReason);
+                if (verdict != DurationPairVerdict.Unknown)
+                    data["durationProvenance"] = verdict == DurationPairVerdict.Verified ? "verified" : "unverified";
+
+                if (verdict == DurationPairVerdict.Suppressed)
+                {
+                    data["durationSuppressedReason"] = suppressedReason!;
+                }
                 // Plausibility backstop: IME's script execution timeout is ~30 min; anything above
                 // 24 h is a cross-run artifact (e.g. a stale pending start slot from a previous
                 // enrollment paired with a fresh completion) — omit rather than lie.
-                if (durationSeconds >= 0 && durationSeconds <= StaleSourceThreshold.TotalSeconds)
+                else if (span >= TimeSpan.Zero && span <= StaleSourceThreshold)
                 {
-                    data["durationSeconds"] = durationSeconds.ToString("F2", culture);
+                    measurableDuration = span;
+                    data["durationSeconds"] = span.TotalSeconds.ToString("F2", culture);
                     data["durationBasis"] = script.DurationBasis
                         ?? (IsRemediation(script.ScriptType)
                             ? "cycle_including_reporting_latency"
@@ -1333,6 +1354,18 @@ namespace AutopilotMonitor.Agent.V2.Core.SignalAdapters
                 }
             }
 
+            // The start line's provenance, next to the end line's (sourceOffset*), so the pair can
+            // be judged downstream as well.
+            var startProvenance = script.StartedAtProvenance;
+            if (startProvenance != null && startProvenance.SourceLocalTs.HasValue)
+            {
+                data["startSourceOffsetOrigin"] = OriginTag(startProvenance.Origin);
+                if (startProvenance.OffsetMinutes.HasValue)
+                    data["startSourceOffsetMinutes"] = startProvenance.OffsetMinutes.Value.ToString(culture);
+                if (!string.IsNullOrEmpty(startProvenance.EraAnchorKind))
+                    data["startSourceOffsetAnchor"] = startProvenance.EraAnchorKind;
+            }
+
             var label = IsRemediation(script.ScriptType) ? "Remediation script" : "Platform script";
             var shortId = script.PolicyId.Length >= 8 ? script.PolicyId.Substring(0, 8) : script.PolicyId;
             string messageCore;
@@ -1375,7 +1408,51 @@ namespace AutopilotMonitor.Agent.V2.Core.SignalAdapters
                 $"ImeAdapter: script completed policyId={shortId} type={script.ScriptType ?? "?"} result={script.Result ?? "?"} exit={(script.ExitCode.HasValue ? script.ExitCode.Value.ToString() : "n/a")}");
 
             MaybeEmitBootstrapDetected(script, now);
-            MaybeEmitScriptTimeoutSuspected(script, now, completionForDuration);
+            MaybeEmitScriptTimeoutSuspected(script, now, measurableDuration);
+        }
+
+        internal enum DurationPairVerdict { Unknown, Verified, Unverified, Suppressed }
+
+        /// <summary>
+        /// Whether the span between a start line and an end line measures elapsed time.
+        /// <para>
+        /// Each CMTrace line is resolved on its own zone belief: declared or measured (bias,
+        /// line-anchored, or the clock itself) — or ASSUMED (the reader's zone, a writer era's
+        /// anchor). Two measured ends sit on the true UTC axis; two assumed ends resolved with the
+        /// same offset from the same file share their error, which cancels (D-191). Any other pair
+        /// is unverified, and its span is omitted when the end stamp was rejected as ahead of the
+        /// clock — its assumption is proven wrong and the raw pair inherits the error (session
+        /// 4377911b: a 10 s script read as 3610 s) — or when the span sits on the 15-minute offset
+        /// grid, the signature of a wrong assumption on either end (session cbaed57b: 7200 s). A
+        /// missing snapshot (state files from before the field, synthetic tests) leaves the rule
+        /// off and the pair treated as before.
+        /// </para>
+        /// </summary>
+        internal static DurationPairVerdict JudgeDurationPair(
+            CmTraceLineProvenance? start, CmTraceLineProvenance? end, bool endStampRejected, TimeSpan span, out string? suppressedReason)
+        {
+            suppressedReason = null;
+            if (start == null || end == null) return DurationPairVerdict.Unknown;
+
+            var startAssumed = start.IsAssumed();
+            var endAssumed = end.IsAssumed();
+            var sameTimeline = (!startAssumed && !endAssumed)
+                || (startAssumed && endAssumed
+                    && start.OffsetMinutes == end.OffsetMinutes
+                    && string.Equals(start.SourceFileName, end.SourceFileName, StringComparison.OrdinalIgnoreCase));
+            if (sameTimeline) return DurationPairVerdict.Verified;
+
+            if (endStampRejected)
+            {
+                suppressedReason = "rejected-endpoint";
+                return DurationPairVerdict.Suppressed;
+            }
+            if (CmTraceOffsetCalibrator.IsOnOffsetGrid(span, out _))
+            {
+                suppressedReason = "offset-grid";
+                return DurationPairVerdict.Suppressed;
+            }
+            return DurationPairVerdict.Unverified;
         }
 
         /// <summary>
@@ -1387,19 +1464,19 @@ namespace AutopilotMonitor.Agent.V2.Core.SignalAdapters
         /// late start / pre-failed ESP. Advisory only: no state mutation, the underlying
         /// <c>script_failed</c> is still emitted separately. Health (remediation) scripts are
         /// excluded — they re-run on their own cadence and have a different timeout regime.
-        /// <paramref name="durationEndUtc"/> is the timeline-consistent completion for duration
-        /// math (raw source ts on rejected-timestamp emissions); <paramref name="occurredAtUtc"/>
-        /// stamps the emitted event.
+        /// <paramref name="measurableDuration"/> is the run duration the completion event carries —
+        /// null when it was omitted (no start line, implausible span, or a start/end pair resolved
+        /// on different zone assumptions: the fleet's daily 17 h "timeouts" of 2–9 s scripts were
+        /// offset errors); <paramref name="occurredAtUtc"/> stamps the emitted event.
         /// </summary>
-        private void MaybeEmitScriptTimeoutSuspected(ScriptExecutionState script, DateTime occurredAtUtc, DateTime durationEndUtc)
+        private void MaybeEmitScriptTimeoutSuspected(ScriptExecutionState script, DateTime occurredAtUtc, TimeSpan? measurableDuration)
         {
             if (IsRemediation(script.ScriptType)) return;                 // platform scripts only
-            if (!script.StartedAtUtc.HasValue) return;                    // no start ⇒ no duration
+            if (!measurableDuration.HasValue) return;                     // no measurable duration ⇒ no verdict
             if (!string.Equals(script.Result, "Failed", StringComparison.OrdinalIgnoreCase)) return;
 
-            var duration = durationEndUtc - script.StartedAtUtc.Value;
+            var duration = measurableDuration.Value;
             if (duration < ScriptTimeoutSuspectedThreshold) return;
-            if (duration > StaleSourceThreshold) return;                  // implausible — cross-run artifact, not a hung script
 
             if (!_tracker.TryClaimScriptTimeoutSuspected(script.PolicyId)) return; // restart-safe dedup per policyId (persisted tracker state)
 

src/Web/autopilot-monitor-web/components/ScriptExecutions.tsx

@@ -25,6 +25,11 @@ import { getErrorCodeEntry, formatErrorCode, errorCodeTooltip } from "@/utils/er
 import { userPhaseSplitIndex, type UserPhaseBoundary } from "@/lib/userPhaseBoundary";
 import PhaseDivider from "@/components/PhaseDivider";
 
+// Shown where the run time would be when the agent (or the reducer, for older events) withheld
+// it: the start and end log lines were resolved on different timezone assumptions, so their
+// span is hours of offset error rather than run time (a 10 s script once read "1h 00m").
+const DURATION_SUPPRESSED_TITLE = "Run time not measurable: the start and end log lines were resolved on different timezone assumptions, so their span would be offset error, not run time";
+
 interface ScriptExecutionsProps {
   events: ScriptInputEvent[];
   showScriptOutput?: boolean;
@@ -531,6 +536,9 @@ function ScriptItemRow({ item, showScriptOutput, latestBootstrapVersion, nested,
               {durationLabel}
             </span>
           )}
+          {!durationLabel && !nested && item.state !== "Running" && item.durationSuppressedReason && (
+            <span className="font-mono text-gray-400" title={DURATION_SUPPRESSED_TITLE}>n/a</span>
+          )}
           {item.state !== "Running" && (
             <button
               onClick={() => setShowDetails(!showDetails)}
@@ -557,6 +565,9 @@ function ScriptItemRow({ item, showScriptOutput, latestBootstrapVersion, nested,
             {!nested && item.targetType != null && <span><span className="font-medium text-gray-700">Target:</span> {item.targetType === 2 ? "Device" : "User"}</span>}
             {item.exitCode != null && <span><span className="font-medium text-gray-700">Exit Code:</span> <span className="font-mono">{item.exitCode}</span></span>}
             {detailDurationLabel && <span><span className="font-medium text-gray-700">Duration:</span> <span className={`font-mono ${isSlowDuration ? "text-amber-600" : ""}`}>{detailDurationLabel}</span></span>}
+            {!detailDurationLabel && item.durationSuppressedReason && (
+              <span title={DURATION_SUPPRESSED_TITLE}><span className="font-medium text-gray-700">Duration:</span> <span className="font-mono text-gray-400">n/a</span></span>
+            )}
             {reportedAfterLabel && (
               <span title="Time from script start until IME reported the result to the Intune service — includes IME's batched reporting delay, so it is longer than the script actually ran">
                 <span className="font-medium text-gray-700">Reported after:</span> <span className="font-mono">{reportedAfterLabel}</span>

src/Web/autopilot-monitor-web/lib/__tests__/scriptExecutions.test.ts

@@ -7,6 +7,7 @@ import {
   groupScriptItems,
   isDetectOnlyRow,
   isNonCompliantReport,
+  isOnOffsetGrid,
   mapRemediationStatus,
   partitionHistoricScriptEvents,
   reduceScriptEvents,
@@ -1069,3 +1070,134 @@ describe("applyObservationEnd", () => {
     expect(ended.headerLabel).toBe("Incomplete");
   });
 });
+
+describe("reduceScriptEvents — duration provenance (offset error is not run time)", () => {
+  const start = (data: Record<string, unknown>, at = 0): ScriptInputEvent =>
+    finalEvent({ eventType: "script_started", ts: at, data: { policyId: "p1", scriptType: "platform", ...data } });
+  const final = (data: Record<string, unknown>, at = 10): ScriptInputEvent =>
+    finalEvent({ ts: at, data: { policyId: "p1", scriptType: "platform", exitCode: "0", result: "Success", ...data } });
+
+  it("drops a duration whose end line was rejected while the start line was measured (session 4377911b)", () => {
+    // Start self-anchored (+120), result re-read after a rewind in the reader's zone (+60) and
+    // rejected as one hour ahead of the clock: the stored 3610 s is offset error plus 10 s.
+    const items = reduceScriptEvents([
+      start({ sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" }),
+      final({
+        durationSeconds: "3610.39", durationBasis: "script_runtime",
+        sourceOffsetOrigin: "reader-zone-fallback", sourceOffsetMinutes: "60",
+        derivedTimestamp: "true", rejectedSourceTimestamp: "2026-09-17T14:20:07.3915051Z",
+      }),
+    ]);
+    expect(items).toHaveLength(1);
+    expect(items[0].durationSeconds).toBeUndefined();
+    expect(items[0].durationSuppressedReason).toBe("rejected-endpoint");
+  });
+
+  it("carries the agent's own verdict and never re-judges a pair the agent judged", () => {
+    const suppressed = reduceScriptEvents([
+      start({ sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" }),
+      final({ durationSuppressedReason: "offset-grid", durationProvenance: "unverified" }),
+    ]);
+    expect(suppressed[0].durationSeconds).toBeUndefined();
+    expect(suppressed[0].durationSuppressedReason).toBe("offset-grid");
+
+    const unverified = reduceScriptEvents([
+      start({ sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" }),
+      final({
+        durationSeconds: "3610.00", durationBasis: "script_runtime", durationProvenance: "unverified",
+        sourceOffsetOrigin: "reader-zone-fallback", sourceOffsetMinutes: "60", derivedTimestamp: "true",
+      }),
+    ]);
+    expect(unverified[0].durationSeconds).toBe(3610);
+    expect(unverified[0].durationSuppressedReason).toBeUndefined();
+  });
+
+  it("drops a mixed pair on the offset grid even when nothing was rejected (session cbaed57b)", () => {
+    const items = reduceScriptEvents([
+      start({ sourceOffsetOrigin: "reader-zone-fallback", sourceOffsetMinutes: "120" }),
+      final({
+        durationSeconds: "7205.66", durationBasis: "script_runtime",
+        sourceOffsetOrigin: "era-anchored", sourceOffsetMinutes: "0",
+      }, 7206),
+    ]);
+    expect(items[0].durationSeconds).toBeUndefined();
+    expect(items[0].durationSuppressedReason).toBe("offset-grid");
+  });
+
+  it("keeps a mixed pair off the grid, and any pair on one timeline", () => {
+    const offGrid = reduceScriptEvents([
+      start({ sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" }),
+      final({ durationSeconds: "26.40", durationBasis: "script_runtime", sourceOffsetOrigin: "reader-zone-fallback", sourceOffsetMinutes: "120" }, 27),
+    ]);
+    expect(offGrid[0].durationSeconds).toBe(26.4);
+    expect(offGrid[0].durationSuppressedReason).toBeUndefined();
+
+    const bothMeasured = reduceScriptEvents([
+      start({ sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" }),
+      final({ durationSeconds: "900.00", durationBasis: "script_runtime", sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" }, 900),
+    ]);
+    expect(bothMeasured[0].durationSeconds).toBe(900);
+
+    const bothAssumedSameOffset = reduceScriptEvents([
+      start({ sourceOffsetOrigin: "reader-zone-fallback", sourceOffsetMinutes: "60" }),
+      final({ durationSeconds: "900.00", durationBasis: "script_runtime", sourceOffsetOrigin: "reader-zone-fallback", sourceOffsetMinutes: "60" }, 900),
+    ]);
+    expect(bothAssumedSameOffset[0].durationSeconds).toBe(900);
+  });
+
+  it("leaves events without provenance, or without a start line, as they were", () => {
+    const noProvenance = reduceScriptEvents([
+      start({}),
+      final({ durationSeconds: "3610.00", durationBasis: "script_runtime", derivedTimestamp: "true" }),
+    ]);
+    expect(noProvenance[0].durationSeconds).toBe(3610);
+
+    const noStart = reduceScriptEvents([
+      final({ durationSeconds: "3610.00", durationBasis: "script_runtime", sourceOffsetOrigin: "reader-zone-fallback", derivedTimestamp: "true" }),
+    ]);
+    expect(noStart[0].durationSeconds).toBe(3610);
+  });
+
+  it("pairs a final with the latest start at or before it", () => {
+    // Run 1 (measured start, rejected end) and run 2 (both measured) of the same policy.
+    const items = reduceScriptEvents([
+      start({ sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" }, 0),
+      final({ durationSeconds: "3610.00", durationBasis: "script_runtime", sourceOffsetOrigin: "reader-zone-fallback", sourceOffsetMinutes: "60", derivedTimestamp: "true", exitCode: "1" }, 10),
+      start({ sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" }, 100),
+      final({ durationSeconds: "8.57", durationBasis: "script_runtime", sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" }, 109),
+    ]);
+    // Same key → the more complete entry wins; the second run's verified duration is kept.
+    expect(items).toHaveLength(1);
+    expect(items[0].durationSeconds).toBe(8.57);
+    expect(items[0].durationSuppressedReason).toBeUndefined();
+  });
+
+  it("withholds the cycle value of a remediation phase quietly (no note where no run time is shown)", () => {
+    const items = reduceScriptEvents([
+      finalEvent({ eventType: "script_started", ts: 0, data: { policyId: "h1", scriptType: "remediation", sourceOffsetOrigin: "line-anchored", sourceOffsetMinutes: "120" } }),
+      finalEvent({ ts: 40, data: {
+        policyId: "h1", scriptType: "remediation", scriptPart: "detection", exitCode: "0",
+        durationSeconds: "3640.00", durationBasis: "cycle_including_reporting_latency",
+        sourceOffsetOrigin: "reader-zone-fallback", sourceOffsetMinutes: "60", derivedTimestamp: "true",
+      } }),
+    ]);
+    expect(items[0].reportedAfterSeconds).toBeUndefined();
+    expect(items[0].durationSeconds).toBeUndefined();
+    expect(items[0].durationSuppressedReason).toBeUndefined();
+  });
+});
+
+describe("isOnOffsetGrid", () => {
+  it("recognises whole offset-grid steps plus seconds of run time, in either direction", () => {
+    expect(isOnOffsetGrid(3610.39)).toBe(true);   // +1 h on a 10 s script
+    expect(isOnOffsetGrid(61203)).toBe(true);     // 17 h on a 3 s script
+    expect(isOnOffsetGrid(7205.66)).toBe(true);   // +2 h
+    expect(isOnOffsetGrid(-3596)).toBe(true);     // the same error on the start end
+    expect(isOnOffsetGrid(900)).toBe(true);       // one step — the caller needs mixed provenance too
+  });
+  it("rejects spans below one step or off the grid", () => {
+    expect(isOnOffsetGrid(26.4)).toBe(false);
+    expect(isOnOffsetGrid(1030)).toBe(false);     // 17 min 10 s
+    expect(isOnOffsetGrid(0)).toBe(false);
+  });
+});

src/Web/autopilot-monitor-web/lib/scriptExecutions.ts

@@ -28,6 +28,14 @@ interface ScriptEventData {
   compliance_result?: string;
   errorDetails?: string;
   error_details?: string;
+  /** Why the agent withheld the run duration ("rejected-endpoint" | "offset-grid"); agents from 2026-09 on. */
+  durationSuppressedReason?: string;
+  /** "verified" | "unverified": the agent judged the start/end pair itself; agents from 2026-09 on. */
+  durationProvenance?: string;
+  /** Timestamp provenance of the event's own log line (see lib/timeProvenance.ts). */
+  sourceOffsetOrigin?: string;
+  /** "true" when the line's own timestamp was rejected and the event was stamped from the clock. */
+  derivedTimestamp?: string | boolean;
 }
 
 export interface ScriptItem {
@@ -61,6 +69,14 @@ export interface ScriptItem {
    * "Reported after Xm" in the details panel, never as the run duration.
    */
   reportedAfterSeconds?: number;
+  /**
+   * Set when the run duration was withheld because the start and end log lines were resolved
+   * on different timezone assumptions — the span is then whole hours of offset error, not run
+   * time (a 10 s script read "1h 00m"). From the agent's own verdict, or from the same rule
+   * applied here to events stored before the agent carried it. Rendered as "n/a" with an
+   * explanation where the duration would be.
+   */
+  durationSuppressedReason?: string;
   state: "Running" | "Success" | "Failed";
   timestamp: string;
   bootstrapVersion?: string | null;
@@ -269,6 +285,69 @@ export function isNonCompliantReport(item: Pick<ScriptItem, "scriptType" | "scri
     && item.complianceResult === "False";
 }
 
+// Every real UTC offset is a whole number of 15-minute steps, so a span within two minutes of
+// k × 15 min (k ≥ 1) is the signature of a wrong offset on one endpoint plus seconds of run
+// time — the agent's CmTraceOffsetCalibrator.IsOnOffsetGrid, mirrored for stored events.
+const OFFSET_GRID_SECONDS = 15 * 60;
+const MAX_GRID_RESIDUAL_SECONDS = 2 * 60;
+
+/** Timestamp origins where the offset was assumed rather than declared by the writer or measured. */
+const ASSUMED_ORIGINS: ReadonlySet<string> = new Set(["reader-zone-fallback", "era-anchored", "calibrated"]);
+
+export function isOnOffsetGrid(seconds: number): boolean {
+  const magnitude = Math.abs(seconds);
+  const steps = Math.round(magnitude / OFFSET_GRID_SECONDS);
+  if (steps < 1) return false;
+  return Math.abs(magnitude - steps * OFFSET_GRID_SECONDS) <= MAX_GRID_RESIDUAL_SECONDS;
+}
+
+/**
+ * Why a final's run duration must not be shown, or null when it may. The agent's own verdict
+ * wins (durationSuppressedReason / durationProvenance). For events from agents without it the
+ * rule is applied here to the paired start line: a pair is on one timeline when both lines were
+ * measured (line-anchored, bias) or both assumed with the same applied offset; any other pair
+ * is dropped when the end line's own timestamp was rejected (its assumption is proven wrong and
+ * the stored duration inherits the error) or when the span sits on the offset grid. Provenance
+ * missing on either line (agents before 2026-08-20) leaves the value as it was.
+ */
+export function judgeDurationPair(
+  start: ScriptEventData | undefined,
+  final: ScriptEventData,
+  durationSeconds: number | undefined
+): string | null {
+  if (typeof final.durationSuppressedReason === "string" && final.durationSuppressedReason.length > 0) {
+    return final.durationSuppressedReason;
+  }
+  if (typeof final.durationProvenance === "string") return null;
+  if (durationSeconds == null || !start) return null;
+
+  const startOrigin = typeof start.sourceOffsetOrigin === "string" ? start.sourceOffsetOrigin : undefined;
+  const endOrigin = typeof final.sourceOffsetOrigin === "string" ? final.sourceOffsetOrigin : undefined;
+  if (!startOrigin || !endOrigin) return null;
+
+  const startAssumed = ASSUMED_ORIGINS.has(startOrigin);
+  const endAssumed = ASSUMED_ORIGINS.has(endOrigin);
+  const sameTimeline = (!startAssumed && !endAssumed)
+    || (startAssumed && endAssumed && toNumber(start.sourceOffsetMinutes) === toNumber(final.sourceOffsetMinutes));
+  if (sameTimeline) return null;
+
+  const endRejected = final.derivedTimestamp === "true" || final.derivedTimestamp === true;
+  if (endRejected) return "rejected-endpoint";
+  return isOnOffsetGrid(durationSeconds) ? "offset-grid" : null;
+}
+
+/** The latest start at or before `finalTimestamp` among a policy's starts (timestamp order). */
+function findPairedStart(starts: ScriptInputEvent[] | undefined, finalTimestamp: string): ScriptInputEvent | undefined {
+  if (!starts || starts.length === 0) return undefined;
+  const finalMs = new Date(finalTimestamp).getTime();
+  let paired: ScriptInputEvent | undefined;
+  for (const start of starts) {
+    if (new Date(start.timestamp).getTime() > finalMs) break;
+    paired = start;
+  }
+  return paired;
+}
+
 /**
  * 2-pass reducer:
  *   1. Sort events by timestamp; collect every script_completed / script_failed final.
@@ -296,6 +375,20 @@ export function reduceScriptEvents(events: ScriptInputEvent[]): ScriptItem[] {
   const finalsByKey = new Map<string, ScriptItem>();
   const policyIdsWithFinal = new Set<string>();
 
+  // script_started events per (policyId, scriptType) in timestamp order — the start line a
+  // final is paired with when its run duration is judged (see judgeDurationPair).
+  const startsByPolicy = new Map<string, ScriptInputEvent[]>();
+  for (const evt of sorted) {
+    if (evt.eventType !== "script_started") continue;
+    const d = evt.data as ScriptEventData | undefined;
+    const startPolicyId = d?.policyId ?? d?.policy_id;
+    if (!startPolicyId) continue;
+    const policyKey = `${startPolicyId}-${d?.scriptType ?? d?.script_type ?? "platform"}`;
+    const list = startsByPolicy.get(policyKey);
+    if (list) list.push(evt);
+    else startsByPolicy.set(policyKey, [evt]);
+  }
+
   for (let idx = 0; idx < sorted.length; idx++) {
     const evt = sorted[idx];
     if (evt.eventType !== "script_completed" && evt.eventType !== "script_failed") continue;
@@ -331,8 +424,13 @@ export function reduceScriptEvents(events: ScriptInputEvent[]): ScriptItem[] {
     const isCycleBasis = typeof rawBasis === "string"
       ? rawBasis === "cycle_including_reporting_latency"
       : scriptType === "remediation";
-    const durationSeconds = isCycleBasis ? undefined : rawDuration;
-    const reportedAfterSeconds = isCycleBasis ? rawDuration : undefined;
+    // A span across two lines resolved on different timezone assumptions is offset error, not
+    // run time — the agent's verdict when it carries one, else the same rule applied to the
+    // paired start line (session 4377911b: 10 s scripts stored as 3610 s).
+    const pairedStart = policyId ? findPairedStart(startsByPolicy.get(`${policyId}-${scriptType}`), evt.timestamp) : undefined;
+    const suppressedReason = judgeDurationPair(pairedStart?.data as ScriptEventData | undefined, d, rawDuration);
+    const durationSeconds = isCycleBasis || suppressedReason ? undefined : rawDuration;
+    const reportedAfterSeconds = !isCycleBasis || suppressedReason ? undefined : rawDuration;
 
     const remediationStatus = toNumber(d.remediationStatus ?? d.remediation_status);
     const targetType = toNumber(d.targetType ?? d.target_type);
@@ -372,6 +470,8 @@ export function reduceScriptEvents(events: ScriptInputEvent[]): ScriptItem[] {
       stderr,
       durationSeconds,
       reportedAfterSeconds,
+      // The note replaces the run duration only; a withheld cycle value is a detail nobody misses.
+      durationSuppressedReason: suppressedReason && !isCycleBasis ? suppressedReason : undefined,
       state: isFailureSignal ? "Failed" : "Success",
       timestamp: evt.timestamp,
       bootstrapVersion: scriptType === "platform" ? extractBootstrapVersion(stdout) : null,
@@ -389,6 +489,8 @@ export function reduceScriptEvents(events: ScriptInputEvent[]): ScriptItem[] {
       const loser = winner === candidate ? existing : candidate;
       winner.durationSeconds ??= loser.durationSeconds;
       winner.reportedAfterSeconds ??= loser.reportedAfterSeconds;
+      if (winner.durationSeconds != null) winner.durationSuppressedReason = undefined;
+      else winner.durationSuppressedReason ??= loser.durationSuppressedReason;
       finalsByKey.set(key, winner);
     }
   }