Close all four stability-review 2026-04-13 findings so a failed runtime probe subscription can no longer leave a phantom entry that Tick() flips to Stopped and fans out false BadOutOfService quality across a host's subtree, a silently-failed dashboard bind no longer lets the service advertise a successful start while an operator-visible endpoint is dead, the seven sync-over-async sites in LmxNodeManager (rebuild probe sync, Read, Write, four HistoryRead overrides) can no longer park the OPC UA stack thread indefinitely on a hung backend, and alarm auto-subscribe + transferred-subscription restore no longer race shutdown as untracked fire-and-forget tasks.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/ZB.MOM.WW.LmxOpcUa.Tests/Status/StatusWebServerTests.cs

@@ -96,6 +96,26 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Status
             response.StatusCode.ShouldBe(HttpStatusCode.MethodNotAllowed);
         }
 
+        /// <summary>
+        ///     Confirms that Start() returns false and logs a failure when the target port is
+        ///     already bound by another listener. Regression guard for the stability-review 2026-04-13
+        ///     Finding 2: OpcUaService now surfaces this return value into DashboardStartFailed.
+        /// </summary>
+        [Fact]
+        public void Start_WhenPortInUse_ReturnsFalse()
+        {
+            var port = new Random().Next(19000, 19500);
+            using var blocker = new HttpListener();
+            blocker.Prefixes.Add($"http://localhost:{port}/");
+            blocker.Start();
+
+            var reportService = new StatusReportService(new HealthCheckService(), 10);
+            reportService.SetComponents(new FakeMxAccessClient(), null, null, null);
+            using var contested = new StatusWebServer(reportService, port);
+
+            contested.Start().ShouldBeFalse();
+        }
+
         /// <summary>
         ///     Confirms that cache-control headers disable caching for dashboard responses.
         /// </summary>