Admin /hosts red-badge + resilience columns + Polly telemetry observer. Closes task #164 (the remaining slice of Phase 6.1 Stream E.3 after the earlier publisher + hub PR). Three cooperating pieces wired together so the operator-facing /hosts table actually reflects the live Polly counters that the pipeline builder is producing. DriverResiliencePipelineBuilder gains an optional DriverResilienceStatusTracker ctor param — when non-null, every built pipeline wires Polly's OnRetry/OnOpened/OnClosed strategy-options callbacks into the tracker. OnRetry → tracker.RecordFailure (so ConsecutiveFailures climbs per retry), OnOpened → tracker.RecordBreakerOpen (stamps LastCircuitBreakerOpenUtc), OnClosed → tracker.RecordSuccess (resets the failure counter once the target recovers). Absent tracker = silent, preserving the unit-test constructor path + any deployment that doesn't care about resilience observability. Cancellation stays excluded from the failure count via the existing ShouldHandle predicate. HostStatusService.HostStatusRow extends with four new fields — ConsecutiveFailures, LastCircuitBreakerOpenUtc, CurrentBulkheadDepth, LastRecycleUtc — populated via a second LEFT JOIN onto DriverInstanceResilienceStatuses keyed on (DriverInstanceId, HostName). LEFT JOIN because brand-new hosts haven't been sampled yet; a missing row means zero failures + never-opened breaker, which is the correct default. New FailureFlagThreshold constant (=3, matches plan decision #143's conservative half-of-breaker convention) + IsFlagged predicate so the UI can pre-warn before the breaker actually trips. Hosts.razor paints three new columns between State and Last-transition — Fail# (bold red when flagged), In-flight (bulkhead-depth proxy), Breaker-opened (relative age). Per-row "Flagged" red badge alongside State when IsFlagged is true. Above the first cluster table, a red alert banner summarises the flagged-host count when ≥1 host is flagged, so operators see the problem before scanning rows. Three new tests in DriverResiliencePipelineBuilderTests — Tracker_RecordsFailure_OnEveryRetry verifies ConsecutiveFailures reaches RetryCount after a transient-forever operation, Tracker_StampsBreakerOpen_WhenBreakerTrips verifies LastBreakerOpenUtc is set after threshold failures on a Write pipeline, Tracker_IsolatesCounters_PerHost verifies one dead host does not leak failure counts into a healthy sibling. Full suite — Core.Tests 14/14 resilience-builder tests passing (11 existing + 3 new), Admin.Tests 72/72 passing, Admin project builds 0 errors. SignalR live push of status changes + browser visual review are deliberately left to a follow-up — this PR keeps the structural change minimal (polling refresh already exists in the page's 10s timer; SignalR would be a structural add that touches hub registration + client subscription).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.OtOpcUa.Admin/Components/Pages/Hosts.razor

@@ -56,6 +56,16 @@ else
         </div></div></div>
     </div>
 
+    @if (_rows.Any(HostStatusService.IsFlagged))
+    {
+        var flaggedCount = _rows.Count(HostStatusService.IsFlagged);
+        <div class="alert alert-danger small mb-3">
+            <strong>@flaggedCount host@(flaggedCount == 1 ? "" : "s")</strong>
+            reporting ≥ @HostStatusService.FailureFlagThreshold consecutive failures — circuit breaker
+            may trip soon. Inspect the resilience columns below to locate.
+        </div>
+    }
+
     @foreach (var cluster in _rows.GroupBy(r => r.ClusterId ?? "(unassigned)").OrderBy(g => g.Key))
     {
         <h2 class="h5 mt-4">Cluster: <code>@cluster.Key</code></h2>
@@ -66,6 +76,9 @@ else
                     <th>Driver</th>
                     <th>Host</th>
                     <th>State</th>
+                    <th class="text-end" title="Consecutive failures — resets when a call succeeds or the breaker closes">Fail#</th>
+                    <th class="text-end" title="In-flight capability calls (bulkhead-depth proxy)">In-flight</th>
+                    <th>Breaker opened</th>
                     <th>Last transition</th>
                     <th>Last seen</th>
                     <th>Detail</th>
@@ -84,10 +97,21 @@ else
                         {
                             <span class="badge bg-warning text-dark ms-1">Stale</span>
                         }
+                        @if (HostStatusService.IsFlagged(r))
+                        {
+                            <span class="badge bg-danger ms-1" title="≥ @HostStatusService.FailureFlagThreshold consecutive failures">Flagged</span>
+                        }
+                    </td>
+                    <td class="text-end small @(HostStatusService.IsFlagged(r) ? "text-danger fw-bold" : "")">
+                        @r.ConsecutiveFailures
+                    </td>
+                    <td class="text-end small">@r.CurrentBulkheadDepth</td>
+                    <td class="small">
+                        @(r.LastCircuitBreakerOpenUtc is null ? "—" : FormatAge(r.LastCircuitBreakerOpenUtc.Value))
                     </td>
                     <td class="small">@FormatAge(r.StateChangedUtc)</td>
                     <td class="small @(HostStatusService.IsStale(r) ? "text-warning" : "")">@FormatAge(r.LastSeenUtc)</td>
-                    <td class="text-truncate small" style="max-width: 320px;" title="@r.Detail">@r.Detail</td>
+                    <td class="text-truncate small" style="max-width: 240px;" title="@r.Detail">@r.Detail</td>
                 </tr>
             }
             </tbody>