fix(health): route site heartbeats into the aggregator

CentralCommunicationActor.HandleHeartbeat was forwarding each incoming
HeartbeatMessage to Context.Parent, which resolves to the /user
guardian — a non-actor. Every site heartbeat went straight to dead
letters (~1026 per central node per 30 minutes at the default ~2s
interval across three sites).

The aggregator now exposes MarkHeartbeat(siteId, receivedAt) which
bumps LastReportReceivedAt on already-known sites (and clears IsOnline
if it had flipped) without touching LatestReport. Heartbeats from
unregistered sites are dropped — first registration still happens on
the first full report. CentralCommunicationActor calls this in place
of the no-op Tell.

The result: heartbeats now serve their stated health-monitoring
purpose (per CLAUDE.md) by keeping a site marked online between the
30s full reports if a single report is briefly delayed, and the dead
letter noise disappears entirely.

src/ScadaLink.CentralUI/Components/Pages/Design/ApiMethodForm.razor

@@ -28,6 +28,40 @@
                     <label class="form-label">Timeout (seconds)</label>
                     <input type="number" class="form-control" @bind="_timeoutSeconds" min="1" />
                 </div>
+                <div class="mb-3">
+                    <label class="form-label">Approved API Keys</label>
+                    @if (_allKeys.Count == 0)
+                    {
+                        <div class="form-text">
+                            No API keys configured.
+                            <a href="/admin/api-keys">Create one</a> to authorize callers for this method.
+                        </div>
+                    }
+                    else
+                    {
+                        <div class="border rounded p-2" style="max-height: 220px; overflow-y: auto;">
+                            @foreach (var key in _allKeys)
+                            {
+                                var checkboxId = $"approved-key-{key.Id}";
+                                <div class="form-check">
+                                    <input class="form-check-input" type="checkbox" id="@checkboxId"
+                                           checked="@_selectedKeyIds.Contains(key.Id)"
+                                           @onchange="e => ToggleKey(key.Id, (bool)e.Value!)" />
+                                    <label class="form-check-label" for="@checkboxId">
+                                        @key.Name
+                                        @if (!key.IsEnabled)
+                                        {
+                                            <span class="badge bg-secondary ms-1">Disabled</span>
+                                        }
+                                    </label>
+                                </div>
+                            }
+                        </div>
+                        <div class="form-text">
+                            Callers must present a checked key in the <code>X-API-Key</code> header to invoke this method.
+                        </div>
+                    }
+                </div>
                 <div class="mb-3">
                     <label class="form-label">Parameters</label>
                     <SchemaBuilder Mode="object"
@@ -77,9 +111,17 @@
         = Array.Empty<ScadaLink.CentralUI.ScriptAnalysis.DiagnosticMarker>();
 
     private ApiMethod? _existing;
+    private List<ApiKey> _allKeys = new();
+    private HashSet<int> _selectedKeyIds = new();
 
     protected override async Task OnInitializedAsync()
     {
+        try
+        {
+            _allKeys = (await InboundApiRepository.GetAllApiKeysAsync()).ToList();
+        }
+        catch (Exception ex) { _formError = ex.Message; }
+
         if (Id.HasValue)
         {
             try
@@ -92,6 +134,7 @@
                     _timeoutSeconds = _existing.TimeoutSeconds;
                     _params = _existing.ParameterDefinitions;
                     _returns = _existing.ReturnDefinition;
+                    _selectedKeyIds = ParseApprovedKeyIds(_existing.ApprovedApiKeyIds);
                 }
             }
             catch (Exception ex) { _formError = ex.Message; }
@@ -99,6 +142,25 @@
         _loading = false;
     }
 
+    private static HashSet<int> ParseApprovedKeyIds(string? value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+            return new HashSet<int>();
+        return value.Split(',', StringSplitOptions.RemoveEmptyEntries)
+            .Select(s => int.TryParse(s.Trim(), out var id) ? id : -1)
+            .Where(id => id > 0)
+            .ToHashSet();
+    }
+
+    private void ToggleKey(int keyId, bool isChecked)
+    {
+        if (isChecked) _selectedKeyIds.Add(keyId);
+        else _selectedKeyIds.Remove(keyId);
+    }
+
+    private string? SerializeApprovedKeyIds() =>
+        _selectedKeyIds.Count == 0 ? null : string.Join(",", _selectedKeyIds.OrderBy(id => id));
+
     private async Task Save()
     {
         _formError = null;
@@ -110,12 +172,14 @@
 
         try
         {
+            var approvedKeyIds = SerializeApprovedKeyIds();
             if (_existing != null)
             {
                 _existing.Script = _script;
                 _existing.TimeoutSeconds = _timeoutSeconds;
                 _existing.ParameterDefinitions = _params?.Trim();
                 _existing.ReturnDefinition = _returns?.Trim();
+                _existing.ApprovedApiKeyIds = approvedKeyIds;
                 await InboundApiRepository.UpdateApiMethodAsync(_existing);
             }
             else
@@ -124,7 +188,8 @@
                 {
                     TimeoutSeconds = _timeoutSeconds,
                     ParameterDefinitions = _params?.Trim(),
-                    ReturnDefinition = _returns?.Trim()
+                    ReturnDefinition = _returns?.Trim(),
+                    ApprovedApiKeyIds = approvedKeyIds
                 };
                 await InboundApiRepository.AddApiMethodAsync(m);
             }

src/ScadaLink.CentralUI/Components/Pages/Monitoring/ParkedMessages.razor

@@ -3,6 +3,7 @@
 @using ScadaLink.Commons.Entities.Sites
 @using ScadaLink.Commons.Interfaces.Repositories
 @using ScadaLink.Commons.Messages.RemoteQuery
+@using ScadaLink.Commons.Types.Enums
 @using ScadaLink.Communication
 @inject ISiteRepository SiteRepository
 @inject CommunicationService CommunicationService
@@ -10,22 +11,94 @@
 @inject IDialogService Dialog
 
 <div class="container-fluid mt-3">
-    <h4 class="mb-3">Parked Messages</h4>
-
     <ToastNotification @ref="_toast" />
 
-    <div class="row mb-3 g-2 align-items-end">
+    <div class="d-flex align-items-baseline flex-wrap mb-3">
-        <div class="col-md-3">
+        <h4 class="mb-0 me-3">Parked Messages</h4>
-            <label class="form-label small" for="pm-filter-site">Site</label>
+        @if (_messages != null && _messages.Count > 0)
-            <select id="pm-filter-site" class="form-select form-select-sm" aria-label="Site" @bind="_selectedSiteId">
+        {
-                <option value="">Select site...</option>
+            <span class="text-muted small">
+                @_totalCount parked · @DistinctTargets target system@(DistinctTargets == 1 ? "" : "s")
+                @if (OldestMessage != null)
+                {
+                    <span> · oldest @Relative(OldestMessage.LastAttemptTimestamp)</span>
+                }
+                @if (FilteredCount != _messages.Count)
+                {
+                    <span class="ms-2">(showing @FilteredCount of @_messages.Count)</span>
+                }
+            </span>
+        }
+    </div>
+
+    <div class="card mb-3">
+        <div class="card-body py-2">
+            <div class="row g-2 align-items-end">
+                <div class="col-auto">
+                    <label class="form-label small mb-1" for="pm-filter-site">Site</label>
+                    <select id="pm-filter-site" class="form-select form-select-sm" style="min-width: 180px;"
+                            value="@_selectedSiteId" @onchange="OnSiteChanged">
+                        <option value="">Select site…</option>
                         @foreach (var site in _sites)
                         {
                             <option value="@site.SiteIdentifier">@site.Name</option>
                         }
                     </select>
                 </div>
-        <div class="col-md-2">
+                <div class="col-auto">
+                    <label class="form-label small mb-1" for="pm-filter-cat">Category</label>
+                    <select id="pm-filter-cat" class="form-select form-select-sm" style="min-width: 150px;"
+                            @bind="_categoryFilter">
+                        <option value="">All</option>
+                        <option value="ExternalSystem">External system</option>
+                        <option value="Notification">Notification</option>
+                        <option value="CachedDbWrite">DB write</option>
+                    </select>
+                </div>
+                <div class="col-auto">
+                    <label class="form-label small mb-1" for="pm-filter-target">Target</label>
+                    <select id="pm-filter-target" class="form-select form-select-sm" style="min-width: 160px;"
+                            @bind="_targetFilter">
+                        <option value="">Any</option>
+                        @foreach (var t in DistinctTargetsList)
+                        {
+                            <option value="@t">@t</option>
+                        }
+                    </select>
+                </div>
+                <div class="col-auto">
+                    <label class="form-label small mb-1" for="pm-filter-origin">Origin</label>
+                    <select id="pm-filter-origin" class="form-select form-select-sm" style="min-width: 160px;"
+                            @bind="_originFilter">
+                        <option value="">Any</option>
+                        <option value="__none__">(none)</option>
+                        @foreach (var o in DistinctOriginsList)
+                        {
+                            <option value="@o">@o</option>
+                        }
+                    </select>
+                </div>
+                <div class="col-auto">
+                    <label class="form-label small mb-1" for="pm-filter-age">Age</label>
+                    <select id="pm-filter-age" class="form-select form-select-sm" style="min-width: 130px;"
+                            @bind="_ageFilter">
+                        <option value="All">All</option>
+                        <option value="LastHour">Last hour</option>
+                        <option value="LastDay">Last 24h</option>
+                        <option value="LastWeek">Last 7d</option>
+                    </select>
+                </div>
+                <div class="col">
+                    <label class="form-label small mb-1" for="pm-filter-search">Search</label>
+                    <input id="pm-filter-search" type="search" class="form-control form-control-sm"
+                           placeholder="ID, target, method, error…"
+                           @bind="_searchFilter" @bind:event="oninput" />
+                </div>
+                <div class="col-auto">
+                    <button class="btn btn-outline-secondary btn-sm" @onclick="ClearFilters"
+                            disabled="@(!HasActiveFilters)">Clear</button>
+                </div>
+                <div class="col-auto">
                     <button class="btn btn-primary btn-sm" @onclick="Search"
                             disabled="@(string.IsNullOrEmpty(_selectedSiteId) || _searching)">
                         @if (_searching) { <span class="spinner-border spinner-border-sm me-1" role="status"></span> }
@@ -33,163 +106,288 @@
                     </button>
                 </div>
             </div>
+        </div>
+    </div>
+
+    @if (_selectedIds.Count > 0)
+    {
+        <div class="alert alert-secondary py-2 d-flex align-items-center mb-3">
+            <strong class="me-3">@_selectedIds.Count selected</strong>
+            <button class="btn btn-outline-success btn-sm me-2"
+                    @onclick="BulkRetry" disabled="@_bulkInProgress">
+                @if (_bulkInProgress && _bulkAction == "Retry") { <span class="spinner-border spinner-border-sm me-1" role="status"></span> }
+                Retry selected
+            </button>
+            <button class="btn btn-outline-danger btn-sm me-2"
+                    @onclick="BulkDiscard" disabled="@_bulkInProgress">
+                @if (_bulkInProgress && _bulkAction == "Discard") { <span class="spinner-border spinner-border-sm me-1" role="status"></span> }
+                Discard selected
+            </button>
+            <button type="button" class="btn-close ms-auto"
+                    aria-label="Clear selection" @onclick="ClearSelection"></button>
+        </div>
+    }
 
     @if (_errorMessage != null)
     {
         <div class="alert alert-danger">@_errorMessage</div>
     }
 
-    @if (_messages != null)
+    @if (_messages == null)
     {
-        <table class="table table-sm table-striped table-hover">
+        @if (!string.IsNullOrEmpty(_selectedSiteId) && _searching)
-            <thead class="table-dark">
+        {
+            <div class="text-muted small">Loading…</div>
+        }
+    }
+    else if (_messages.Count == 0)
+    {
+        <div class="card">
+            <div class="card-body text-center text-muted py-5">
+                <div class="fs-5 mb-1">No parked messages</div>
+                <div class="small">Nothing has failed enough to give up on at this site.</div>
+            </div>
+        </div>
+    }
+    else
+    {
+        var filtered = FilteredMessages;
+        <div class="table-responsive">
+            <table class="table table-sm table-hover mb-2 align-middle parked-table">
+                <thead class="table-light">
                     <tr>
-                    <th style="width: 1%;"></th>
+                        <th style="width: 36px;">
-                    <th>Message ID</th>
+                            <input class="form-check-input" type="checkbox"
-                    <th>Target System</th>
+                                   checked="@AllFilteredSelected"
-                    <th>Method</th>
+                                   @onchange="ToggleSelectAll"
+                                   aria-label="Select all" />
+                        </th>
+                        <th>Target / Method</th>
+                        <th>Origin</th>
                         <th>Error</th>
-                    <th>Attempts</th>
+                        <th style="width: 110px;">Attempts</th>
-                    <th>Original</th>
+                        <th style="width: 160px;">Last attempt</th>
-                    <th>Last Attempt</th>
-                    <th style="width: 120px;">Actions</th>
                     </tr>
                 </thead>
                 <tbody>
-                @if (_messages.Count == 0)
+                    @if (filtered.Count == 0)
                     {
-                    <tr><td colspan="9" class="text-muted text-center">No parked messages.</td></tr>
+                        <tr><td colspan="6" class="text-muted text-center py-3">No messages match the current filters.</td></tr>
                     }
-                @for (int i = 0; i < _messages.Count; i++)
+                    @foreach (var msg in filtered)
                     {
-                    var idx = i;
+                        var isSelected = _selectedIds.Contains(msg.MessageId);
-                    var msg = _messages[idx];
+                        <tr @key="msg.MessageId"
-                    var idShort = msg.MessageId[..Math.Min(12, msg.MessageId.Length)];
+                            class="parked-row @SeverityClass(msg) @(isSelected ? "table-active" : "")"
-                    var expanded = _expandedRows.Contains(idx);
+                            @onclick="() => OpenDrawer(msg)"
-                    var retryActive = _actionInProgress && _activeMessageId == msg.MessageId && _activeAction == "Retry";
+                            style="cursor: pointer;">
-                    var discardActive = _actionInProgress && _activeMessageId == msg.MessageId && _activeAction == "Discard";
+                            <td @onclick:stopPropagation="true">
-                    <tr>
+                                <input class="form-check-input" type="checkbox"
-                        <td>
+                                       checked="@isSelected"
-                            <button class="btn btn-link btn-sm p-0"
+                                       @onchange="e => ToggleSelect(msg.MessageId, (bool)e.Value!)"
-                                    @onclick="() => ToggleRow(idx)"
+                                       aria-label="@($"Select {msg.MessageId[..Math.Min(8, msg.MessageId.Length)]}")" />
-                                    aria-label="@(expanded ? "Hide error details" : "View error details")">
-                                @(expanded ? "Hide" : "View")
-                            </button>
                             </td>
-                        <td class="small">
-                            <code class="small">@idShort…</code>
-                            <button class="btn btn-link btn-sm p-0 ms-1"
-                                    @onclick="() => CopyAsync(msg.MessageId)"
-                                    title="Copy message ID"
-                                    aria-label="Copy message ID @msg.MessageId">📋</button>
-                        </td>
-                        <td class="small">@msg.TargetSystem</td>
-                        <td class="small">@msg.MethodName</td>
-                        <td class="small text-danger text-truncate" style="max-width: 320px;">@msg.ErrorMessage</td>
-                        <td class="small text-center">@msg.AttemptCount</td>
-                        <td class="small"><TimestampDisplay Value="@msg.OriginalTimestamp" /></td>
-                        <td class="small"><TimestampDisplay Value="@msg.LastAttemptTimestamp" /></td>
                             <td>
-                            <button class="btn btn-outline-success btn-sm py-0 px-1 me-1"
+                                <div class="fw-semibold">@msg.TargetSystem</div>
-                                    @onclick="() => RetryMessage(msg)"
+                                <div class="small text-muted">@msg.MethodName</div>
-                                    disabled="@_actionInProgress"
+                            </td>
-                                    title="Retry message (move back to pending)"
+                            <td>
-                                    aria-label="Retry message @idShort">
+                                @if (!string.IsNullOrEmpty(msg.OriginInstance))
-                                @if (retryActive)
                                 {
-                                    <span class="spinner-border spinner-border-sm me-1" role="status"></span>
+                                    <code class="small">@msg.OriginInstance</code>
                                 }
-                                Retry
+                                else
-                            </button>
-                            <button class="btn btn-outline-danger btn-sm py-0 px-1"
-                                    @onclick="() => DiscardMessage(msg)"
-                                    disabled="@_actionInProgress"
-                                    title="Permanently discard message"
-                                    aria-label="Discard message @idShort">
-                                @if (discardActive)
                                 {
-                                    <span class="spinner-border spinner-border-sm me-1" role="status"></span>
+                                    <span class="text-muted small">—</span>
                                 }
-                                Discard
+                            </td>
-                            </button>
+                            <td>
+                                <div class="text-danger small parked-error-clamp">@msg.ErrorMessage</div>
+                            </td>
+                            <td>
+                                <div class="small font-monospace">
+                                    @msg.AttemptCount<span class="text-muted">/@msg.MaxAttempts</span>
+                                </div>
+                                <div class="progress mt-1" style="height: 3px;">
+                                    <div class="progress-bar @AttemptBarClass(msg)"
+                                         role="progressbar"
+                                         style="width: @AttemptPercent(msg)%;"
+                                         aria-valuenow="@msg.AttemptCount"
+                                         aria-valuemin="0"
+                                         aria-valuemax="@Math.Max(1, msg.MaxAttempts)"></div>
+                                </div>
+                            </td>
+                            <td>
+                                <div class="small" title="@AbsoluteUtc(msg.LastAttemptTimestamp)">
+                                    @Relative(msg.LastAttemptTimestamp)
+                                </div>
                             </td>
                         </tr>
-                    @if (expanded)
-                    {
-                        <tr>
-                            <td colspan="9">
-                                <pre class="small mb-0">@msg.ErrorMessage</pre>
-                            </td>
-                        </tr>
-                    }
                     }
                 </tbody>
             </table>
+        </div>
 
-        @if (_totalCount > 0)
+        @if (_totalCount > _pageSize)
         {
             <div class="d-flex justify-content-between align-items-center">
-                <span class="text-muted small">Page @_pageNumber of @((_totalCount + _pageSize - 1) / _pageSize) (@_totalCount total)</span>
+                <span class="text-muted small">
+                    Page @_pageNumber of @((_totalCount + _pageSize - 1) / _pageSize) · @_totalCount total
+                </span>
                 <div>
-                    <button class="btn btn-outline-secondary btn-sm me-1" @onclick="PrevPage" disabled="@(_pageNumber <= 1)">Previous</button>
+                    <button class="btn btn-outline-secondary btn-sm me-1"
-                    <button class="btn btn-outline-secondary btn-sm" @onclick="NextPage" disabled="@(_messages.Count < _pageSize)">Next</button>
+                            @onclick="PrevPage" disabled="@(_pageNumber <= 1)">Previous</button>
+                    <button class="btn btn-outline-secondary btn-sm"
+                            @onclick="NextPage" disabled="@(_messages.Count < _pageSize)">Next</button>
                 </div>
             </div>
         }
     }
 </div>
 
+@if (_drawerMessage != null)
+{
+    <div class="offcanvas-backdrop fade show" @onclick="CloseDrawer"></div>
+    <div class="offcanvas offcanvas-end show parked-drawer" tabindex="-1" style="visibility: visible;">
+        <div class="offcanvas-header border-bottom">
+            <div>
+                <div class="text-muted small text-uppercase">Parked message</div>
+                <h5 class="offcanvas-title mb-0">@_drawerMessage.TargetSystem</h5>
+                <div class="small text-muted">@_drawerMessage.MethodName</div>
+            </div>
+            <button type="button" class="btn-close" aria-label="Close" @onclick="CloseDrawer"></button>
+        </div>
+        <div class="offcanvas-body small">
+            <dl class="row mb-3">
+                <dt class="col-4 text-muted fw-normal">Message ID</dt>
+                <dd class="col-8 d-flex align-items-center gap-2">
+                    <code class="text-truncate" style="min-width: 0;">@_drawerMessage.MessageId</code>
+                    <button class="btn btn-link btn-sm p-0" title="Copy message ID"
+                            @onclick="() => CopyAsync(_drawerMessage.MessageId)">📋</button>
+                </dd>
+                <dt class="col-4 text-muted fw-normal">Category</dt>
+                <dd class="col-8">@CategoryLabel(_drawerMessage.Category)</dd>
+                <dt class="col-4 text-muted fw-normal">Origin instance</dt>
+                <dd class="col-8">
+                    @if (!string.IsNullOrEmpty(_drawerMessage.OriginInstance))
+                    {
+                        <code>@_drawerMessage.OriginInstance</code>
+                    }
+                    else
+                    {
+                        <span class="text-muted">—</span>
+                    }
+                </dd>
+                <dt class="col-4 text-muted fw-normal">Attempts</dt>
+                <dd class="col-8 font-monospace">@_drawerMessage.AttemptCount / @_drawerMessage.MaxAttempts</dd>
+                <dt class="col-4 text-muted fw-normal">Originally enqueued</dt>
+                <dd class="col-8">
+                    @Relative(_drawerMessage.OriginalTimestamp)
+                    <span class="text-muted">· @AbsoluteUtc(_drawerMessage.OriginalTimestamp)</span>
+                </dd>
+                <dt class="col-4 text-muted fw-normal">Last attempt</dt>
+                <dd class="col-8">
+                    @Relative(_drawerMessage.LastAttemptTimestamp)
+                    <span class="text-muted">· @AbsoluteUtc(_drawerMessage.LastAttemptTimestamp)</span>
+                </dd>
+            </dl>
+
+            <div class="text-muted text-uppercase small fw-semibold mb-1">Error</div>
+            <pre class="bg-light border rounded p-2 small mb-0 parked-error-pre">@_drawerMessage.ErrorMessage</pre>
+        </div>
+        <div class="border-top p-3 d-flex gap-2">
+            <button class="btn btn-outline-success btn-sm flex-grow-1"
+                    @onclick="RetryFromDrawer" disabled="@_actionInProgress">
+                @if (_actionInProgress && _activeAction == "Retry") { <span class="spinner-border spinner-border-sm me-1" role="status"></span> }
+                Retry
+            </button>
+            <button class="btn btn-outline-danger btn-sm flex-grow-1"
+                    @onclick="DiscardFromDrawer" disabled="@_actionInProgress">
+                @if (_actionInProgress && _activeAction == "Discard") { <span class="spinner-border spinner-border-sm me-1" role="status"></span> }
+                Discard
+            </button>
+        </div>
+    </div>
+}
+
+<style>
+    .parked-row { border-left: 3px solid transparent; }
+    .parked-row.sev-danger { border-left-color: var(--bs-danger); }
+    .parked-row.sev-warning { border-left-color: var(--bs-warning); }
+    .parked-row.sev-secondary { border-left-color: var(--bs-secondary-bg-subtle); }
+    .parked-error-clamp {
+        display: -webkit-box;
+        -webkit-line-clamp: 2;
+        -webkit-box-orient: vertical;
+        overflow: hidden;
+        max-width: 520px;
+    }
+    .parked-drawer { width: min(560px, 95vw); }
+    .parked-error-pre { white-space: pre-wrap; word-break: break-word; max-height: 300px; overflow-y: auto; }
+    .parked-table tbody tr { transition: background-color 0.1s ease; }
+</style>
+
 @code {
     private List<Site> _sites = new();
     private string _selectedSiteId = string.Empty;
     private List<ParkedMessageEntry>? _messages;
     private int _totalCount;
     private int _pageNumber = 1;
-    private int _pageSize = 25;
+    private int _pageSize = 50;
     private bool _searching;
     private string? _errorMessage;
 
+    // Filters
+    private string _categoryFilter = string.Empty;
+    private string _targetFilter = string.Empty;
+    private string _originFilter = string.Empty;
+    private string _ageFilter = "All";
+    private string _searchFilter = string.Empty;
+
+    // Selection
+    private readonly HashSet<string> _selectedIds = new();
+    private bool _bulkInProgress;
+    private string? _bulkAction;
+
+    // Per-row action state
     private bool _actionInProgress;
-    private string? _activeMessageId;
     private string? _activeAction;
+
+    // Drawer
+    private ParkedMessageEntry? _drawerMessage;
+
     private ToastNotification _toast = default!;
-    private readonly HashSet<int> _expandedRows = new();
 
     protected override async Task OnInitializedAsync()
     {
         _sites = (await SiteRepository.GetAllSitesAsync()).ToList();
     }
 
+    private async Task OnSiteChanged(ChangeEventArgs e)
+    {
+        _selectedSiteId = e.Value?.ToString() ?? string.Empty;
+        if (!string.IsNullOrEmpty(_selectedSiteId))
+        {
+            await Search();
+        }
+        else
+        {
+            _messages = null;
+            _selectedIds.Clear();
+            _drawerMessage = null;
+        }
+    }
+
     private async Task Search()
     {
         _pageNumber = 1;
-        _expandedRows.Clear();
+        _selectedIds.Clear();
+        _drawerMessage = null;
         await FetchPage();
     }
 
-    private async Task PrevPage() { _pageNumber--; await FetchPage(); }
+    private async Task PrevPage() { _pageNumber--; _selectedIds.Clear(); await FetchPage(); }
-    private async Task NextPage() { _pageNumber++; await FetchPage(); }
+    private async Task NextPage() { _pageNumber++; _selectedIds.Clear(); await FetchPage(); }
-
-    private void ToggleRow(int idx)
-    {
-        if (!_expandedRows.Add(idx))
-        {
-            _expandedRows.Remove(idx);
-        }
-    }
-
-    private async Task CopyAsync(string text)
-    {
-        try
-        {
-            await JS.InvokeVoidAsync("navigator.clipboard.writeText", text);
-            _toast.ShowSuccess("Copied to clipboard.");
-        }
-        catch
-        {
-            _toast.ShowError("Copy failed.");
-        }
-    }
 
     private async Task FetchPage()
     {
@@ -205,12 +403,10 @@
                 Timestamp: DateTimeOffset.UtcNow);
 
             var response = await CommunicationService.QueryParkedMessagesAsync(_selectedSiteId, request);
-
             if (response.Success)
             {
                 _messages = response.Messages.ToList();
                 _totalCount = response.TotalCount;
-                _expandedRows.Clear();
             }
             else
             {
@@ -224,73 +420,302 @@
         _searching = false;
     }
 
-    private async Task RetryMessage(ParkedMessageEntry msg)
+    private void ClearFilters()
     {
-        _actionInProgress = true;
+        _categoryFilter = string.Empty;
-        _activeMessageId = msg.MessageId;
+        _targetFilter = string.Empty;
-        _activeAction = "Retry";
+        _originFilter = string.Empty;
-        try
+        _ageFilter = "All";
+        _searchFilter = string.Empty;
+    }
+
+    private bool HasActiveFilters =>
+        !string.IsNullOrEmpty(_categoryFilter) ||
+        !string.IsNullOrEmpty(_targetFilter) ||
+        !string.IsNullOrEmpty(_originFilter) ||
+        _ageFilter != "All" ||
+        !string.IsNullOrEmpty(_searchFilter);
+
+    private List<ParkedMessageEntry> FilteredMessages
     {
-            var request = new ParkedMessageRetryRequest(
+        get
-                CorrelationId: Guid.NewGuid().ToString("N"),
-                SiteId: _selectedSiteId,
-                MessageId: msg.MessageId,
-                Timestamp: DateTimeOffset.UtcNow);
-            var response = await CommunicationService.RetryParkedMessageAsync(_selectedSiteId, request);
-            if (response.Success)
         {
-                _toast.ShowSuccess($"Message {msg.MessageId[..Math.Min(12, msg.MessageId.Length)]} queued for retry.");
+            if (_messages == null) return new();
-                await FetchPage();
+            IEnumerable<ParkedMessageEntry> q = _messages;
+
+            if (!string.IsNullOrEmpty(_categoryFilter) &&
+                Enum.TryParse<StoreAndForwardCategory>(_categoryFilter, out var cat))
+                q = q.Where(m => m.Category == cat);
+
+            if (!string.IsNullOrEmpty(_targetFilter))
+                q = q.Where(m => m.TargetSystem == _targetFilter);
+
+            if (_originFilter == "__none__")
+                q = q.Where(m => string.IsNullOrEmpty(m.OriginInstance));
+            else if (!string.IsNullOrEmpty(_originFilter))
+                q = q.Where(m => m.OriginInstance == _originFilter);
+
+            if (_ageFilter != "All")
+            {
+                var cutoff = _ageFilter switch
+                {
+                    "LastHour" => DateTimeOffset.UtcNow.AddHours(-1),
+                    "LastDay" => DateTimeOffset.UtcNow.AddDays(-1),
+                    "LastWeek" => DateTimeOffset.UtcNow.AddDays(-7),
+                    _ => DateTimeOffset.MinValue
+                };
+                q = q.Where(m => m.LastAttemptTimestamp >= cutoff);
+            }
+
+            if (!string.IsNullOrEmpty(_searchFilter))
+            {
+                var s = _searchFilter.Trim();
+                q = q.Where(m =>
+                    m.MessageId.Contains(s, StringComparison.OrdinalIgnoreCase) ||
+                    m.TargetSystem.Contains(s, StringComparison.OrdinalIgnoreCase) ||
+                    m.MethodName.Contains(s, StringComparison.OrdinalIgnoreCase) ||
+                    m.ErrorMessage.Contains(s, StringComparison.OrdinalIgnoreCase) ||
+                    (m.OriginInstance ?? string.Empty).Contains(s, StringComparison.OrdinalIgnoreCase));
+            }
+
+            return q.ToList();
+        }
+    }
+
+    private int FilteredCount => FilteredMessages.Count;
+    private int DistinctTargets => _messages?.Select(m => m.TargetSystem).Distinct().Count() ?? 0;
+
+    private IEnumerable<string> DistinctTargetsList =>
+        _messages?.Select(m => m.TargetSystem).Distinct().OrderBy(s => s).ToList()
+            ?? (IEnumerable<string>)Array.Empty<string>();
+
+    private IEnumerable<string> DistinctOriginsList =>
+        _messages?.Where(m => !string.IsNullOrEmpty(m.OriginInstance))
+            .Select(m => m.OriginInstance!).Distinct().OrderBy(s => s).ToList()
+            ?? (IEnumerable<string>)Array.Empty<string>();
+
+    private ParkedMessageEntry? OldestMessage =>
+        _messages?.OrderBy(m => m.LastAttemptTimestamp).FirstOrDefault();
+
+    // ── Selection ──
+
+    private bool AllFilteredSelected
+    {
+        get
+        {
+            var filtered = FilteredMessages;
+            return filtered.Count > 0 && filtered.All(m => _selectedIds.Contains(m.MessageId));
+        }
+    }
+
+    private void ToggleSelect(string id, bool isChecked)
+    {
+        if (isChecked) _selectedIds.Add(id);
+        else _selectedIds.Remove(id);
+    }
+
+    private void ToggleSelectAll(ChangeEventArgs e)
+    {
+        var on = (bool)e.Value!;
+        var filtered = FilteredMessages;
+        if (on)
+        {
+            foreach (var m in filtered) _selectedIds.Add(m.MessageId);
         }
         else
         {
-                _toast.ShowError(response.ErrorMessage ?? "Retry failed.");
+            foreach (var m in filtered) _selectedIds.Remove(m.MessageId);
         }
     }
-        catch (Exception ex)
-        {
-            _toast.ShowError($"Retry failed: {ex.Message}");
-        }
-        _activeMessageId = null;
-        _activeAction = null;
-        _actionInProgress = false;
-    }
 
-    private async Task DiscardMessage(ParkedMessageEntry msg)
+    private void ClearSelection() => _selectedIds.Clear();
+
+    // ── Drawer ──
+
+    private void OpenDrawer(ParkedMessageEntry msg) => _drawerMessage = msg;
+    private void CloseDrawer() => _drawerMessage = null;
+
+    private async Task RetryFromDrawer()
     {
+        if (_drawerMessage == null) return;
+        var msg = _drawerMessage;
+        await RetrySingle(msg);
+        CloseDrawer();
+    }
+
+    private async Task DiscardFromDrawer()
+    {
+        if (_drawerMessage == null) return;
+        var msg = _drawerMessage;
+        var ok = await DiscardSingle(msg);
+        if (ok) CloseDrawer();
+    }
+
+    // ── Bulk ──
+
+    private async Task BulkRetry()
+    {
+        var ids = _selectedIds.ToList();
+        if (ids.Count == 0) return;
+
         var confirmed = await Dialog.ConfirmAsync(
-            "Discard Parked Message",
+            "Retry parked messages",
-            $"Permanently discard message {msg.MessageId[..Math.Min(12, msg.MessageId.Length)]}? This cannot be undone.",
+            $"Move {ids.Count} message{(ids.Count == 1 ? "" : "s")} back to the pending queue?");
+        if (!confirmed) return;
+
+        _bulkInProgress = true;
+        _bulkAction = "Retry";
+        int success = 0, failed = 0;
+        foreach (var id in ids)
+        {
+            try
+            {
+                var req = new ParkedMessageRetryRequest(Guid.NewGuid().ToString("N"), _selectedSiteId, id, DateTimeOffset.UtcNow);
+                var resp = await CommunicationService.RetryParkedMessageAsync(_selectedSiteId, req);
+                if (resp.Success) success++; else failed++;
+            }
+            catch { failed++; }
+        }
+        _toast.ShowSuccess($"{success} queued for retry" + (failed > 0 ? $", {failed} failed" : "."));
+        _selectedIds.Clear();
+        _bulkInProgress = false;
+        _bulkAction = null;
+        await FetchPage();
+    }
+
+    private async Task BulkDiscard()
+    {
+        var ids = _selectedIds.ToList();
+        if (ids.Count == 0) return;
+
+        var confirmed = await Dialog.ConfirmAsync(
+            "Discard parked messages",
+            $"Permanently discard {ids.Count} message{(ids.Count == 1 ? "" : "s")}? This cannot be undone.",
             danger: true);
         if (!confirmed) return;
 
-        _actionInProgress = true;
+        _bulkInProgress = true;
-        _activeMessageId = msg.MessageId;
+        _bulkAction = "Discard";
-        _activeAction = "Discard";
+        int success = 0, failed = 0;
+        foreach (var id in ids)
+        {
             try
             {
-            var request = new ParkedMessageDiscardRequest(
+                var req = new ParkedMessageDiscardRequest(Guid.NewGuid().ToString("N"), _selectedSiteId, id, DateTimeOffset.UtcNow);
-                CorrelationId: Guid.NewGuid().ToString("N"),
+                var resp = await CommunicationService.DiscardParkedMessageAsync(_selectedSiteId, req);
-                SiteId: _selectedSiteId,
+                if (resp.Success) success++; else failed++;
-                MessageId: msg.MessageId,
+            }
-                Timestamp: DateTimeOffset.UtcNow);
+            catch { failed++; }
-            var response = await CommunicationService.DiscardParkedMessageAsync(_selectedSiteId, request);
+        }
-            if (response.Success)
+        _toast.ShowSuccess($"{success} discarded" + (failed > 0 ? $", {failed} failed" : "."));
-            {
+        _selectedIds.Clear();
-                _toast.ShowSuccess($"Message {msg.MessageId[..Math.Min(12, msg.MessageId.Length)]} discarded.");
+        _bulkInProgress = false;
+        _bulkAction = null;
         await FetchPage();
     }
-            else
+
+    // ── Single actions ──
+
+    private async Task RetrySingle(ParkedMessageEntry msg)
     {
-                _toast.ShowError(response.ErrorMessage ?? "Discard failed.");
+        _actionInProgress = true;
-            }
+        _activeAction = "Retry";
-        }
+        try
-        catch (Exception ex)
         {
-            _toast.ShowError($"Discard failed: {ex.Message}");
+            var req = new ParkedMessageRetryRequest(Guid.NewGuid().ToString("N"), _selectedSiteId, msg.MessageId, DateTimeOffset.UtcNow);
+            var resp = await CommunicationService.RetryParkedMessageAsync(_selectedSiteId, req);
+            if (resp.Success)
+            {
+                _toast.ShowSuccess($"Message {ShortId(msg.MessageId)} queued for retry.");
+                await FetchPage();
             }
-        _activeMessageId = null;
+            else _toast.ShowError(resp.ErrorMessage ?? "Retry failed.");
-        _activeAction = null;
+        }
+        catch (Exception ex) { _toast.ShowError($"Retry failed: {ex.Message}"); }
         _actionInProgress = false;
+        _activeAction = null;
     }
+
+    private async Task<bool> DiscardSingle(ParkedMessageEntry msg)
+    {
+        var confirmed = await Dialog.ConfirmAsync(
+            "Discard parked message",
+            $"Permanently discard message {ShortId(msg.MessageId)}? This cannot be undone.",
+            danger: true);
+        if (!confirmed) return false;
+
+        _actionInProgress = true;
+        _activeAction = "Discard";
+        bool ok = false;
+        try
+        {
+            var req = new ParkedMessageDiscardRequest(Guid.NewGuid().ToString("N"), _selectedSiteId, msg.MessageId, DateTimeOffset.UtcNow);
+            var resp = await CommunicationService.DiscardParkedMessageAsync(_selectedSiteId, req);
+            if (resp.Success)
+            {
+                _toast.ShowSuccess($"Message {ShortId(msg.MessageId)} discarded.");
+                ok = true;
+                await FetchPage();
+            }
+            else _toast.ShowError(resp.ErrorMessage ?? "Discard failed.");
+        }
+        catch (Exception ex) { _toast.ShowError($"Discard failed: {ex.Message}"); }
+        _actionInProgress = false;
+        _activeAction = null;
+        return ok;
+    }
+
+    private async Task CopyAsync(string text)
+    {
+        try
+        {
+            await JS.InvokeVoidAsync("navigator.clipboard.writeText", text);
+            _toast.ShowSuccess("Copied to clipboard.");
+        }
+        catch { _toast.ShowError("Copy failed."); }
+    }
+
+    // ── Helpers ──
+
+    private static string ShortId(string id) => id[..Math.Min(12, id.Length)];
+
+    private static string Relative(DateTimeOffset t)
+    {
+        var diff = DateTimeOffset.UtcNow - t;
+        if (diff.TotalSeconds < 0) return "just now";
+        if (diff.TotalSeconds < 60) return "just now";
+        if (diff.TotalMinutes < 60) return $"{(int)diff.TotalMinutes}m ago";
+        if (diff.TotalHours < 24) return $"{(int)diff.TotalHours}h ago";
+        if (diff.TotalDays < 30) return $"{(int)diff.TotalDays}d ago";
+        return t.UtcDateTime.ToString("yyyy-MM-dd");
+    }
+
+    private static string AbsoluteUtc(DateTimeOffset t) =>
+        $"{t.UtcDateTime:yyyy-MM-dd HH:mm:ss} UTC";
+
+    private static string SeverityClass(ParkedMessageEntry msg)
+    {
+        var exhausted = msg.MaxAttempts > 0 && msg.AttemptCount >= msg.MaxAttempts;
+        if (!exhausted) return "sev-secondary";
+        var age = DateTimeOffset.UtcNow - msg.LastAttemptTimestamp;
+        return age < TimeSpan.FromHours(1) ? "sev-danger" : "sev-warning";
+    }
+
+    private static int AttemptPercent(ParkedMessageEntry msg)
+    {
+        if (msg.MaxAttempts <= 0) return 100;
+        var pct = (int)Math.Round(msg.AttemptCount * 100.0 / msg.MaxAttempts);
+        return Math.Clamp(pct, 0, 100);
+    }
+
+    private static string AttemptBarClass(ParkedMessageEntry msg) =>
+        msg.AttemptCount >= msg.MaxAttempts ? "bg-danger" : "bg-warning";
+
+    private static string CategoryLabel(StoreAndForwardCategory c) => c switch
+    {
+        StoreAndForwardCategory.ExternalSystem => "External system",
+        StoreAndForwardCategory.Notification => "Notification",
+        StoreAndForwardCategory.CachedDbWrite => "Cached DB write",
+        _ => c.ToString()
+    };
 }

src/ScadaLink.Commons/Messages/RemoteQuery/ParkedMessageQueryResponse.cs

@@ -1,3 +1,5 @@
+using ScadaLink.Commons.Types.Enums;
+
 namespace ScadaLink.Commons.Messages.RemoteQuery;
 
 /// <summary>
@@ -10,7 +12,10 @@ public record ParkedMessageEntry(
     string ErrorMessage,
     int AttemptCount,
     DateTimeOffset OriginalTimestamp,
-    DateTimeOffset LastAttemptTimestamp);
+    DateTimeOffset LastAttemptTimestamp,
+    int MaxAttempts = 0,
+    StoreAndForwardCategory Category = StoreAndForwardCategory.ExternalSystem,
+    string? OriginInstance = null);
 
 public record ParkedMessageQueryResponse(
     string CorrelationId,

src/ScadaLink.Communication/Actors/CentralCommunicationActor.cs

@@ -100,8 +100,8 @@ public class CentralCommunicationActor : ReceiveActor
 
     private void HandleHeartbeat(HeartbeatMessage heartbeat)
     {
-        // Forward heartbeat to parent for any interested central actors
+        var aggregator = _serviceProvider.GetService<ICentralHealthAggregator>();
-        Context.Parent.Tell(heartbeat);
+        aggregator?.MarkHeartbeat(heartbeat.SiteId, heartbeat.Timestamp);
     }
 
     /// <summary>

src/ScadaLink.Communication/Actors/SiteCommunicationActor.cs

@@ -136,6 +136,28 @@ public class SiteCommunicationActor : ReceiveActor, IWithTimers
             }
         });
 
+        Receive<ParkedMessageRetryRequest>(msg =>
+        {
+            if (_parkedMessageHandler != null)
+                _parkedMessageHandler.Forward(msg);
+            else
+            {
+                Sender.Tell(new ParkedMessageRetryResponse(
+                    msg.CorrelationId, false, "Parked message handler not available"));
+            }
+        });
+
+        Receive<ParkedMessageDiscardRequest>(msg =>
+        {
+            if (_parkedMessageHandler != null)
+                _parkedMessageHandler.Forward(msg);
+            else
+            {
+                Sender.Tell(new ParkedMessageDiscardResponse(
+                    msg.CorrelationId, false, "Parked message handler not available"));
+            }
+        });
+
         // Internal: send heartbeat tick
         Receive<SendHeartbeat>(_ => SendHeartbeatToCentral());
 

src/ScadaLink.HealthMonitoring/CentralHealthAggregator.cs

@@ -76,6 +76,26 @@ public class CentralHealthAggregator : BackgroundService, ICentralHealthAggregat
             });
     }
 
+    /// <summary>
+    /// Bumps the last-seen timestamp for a site already known via a prior
+    /// SiteHealthReport. Heartbeats from sites we have not yet received a
+    /// full report from are ignored — registration only happens on report.
+    /// </summary>
+    public void MarkHeartbeat(string siteId, DateTimeOffset receivedAt)
+    {
+        if (!_siteStates.TryGetValue(siteId, out var state))
+            return;
+
+        if (receivedAt > state.LastReportReceivedAt)
+            state.LastReportReceivedAt = receivedAt;
+
+        if (!state.IsOnline)
+        {
+            state.IsOnline = true;
+            _logger.LogInformation("Site {SiteId} is back online (heartbeat)", siteId);
+        }
+    }
+
     /// <summary>
     /// Get the current health state for all known sites.
     /// </summary>

src/ScadaLink.HealthMonitoring/ICentralHealthAggregator.cs

@@ -9,6 +9,15 @@ namespace ScadaLink.HealthMonitoring;
 public interface ICentralHealthAggregator
 {
     void ProcessReport(SiteHealthReport report);
+
+    /// <summary>
+    /// Bumps the last-seen timestamp for a site already known via a prior
+    /// SiteHealthReport. Used to keep a site marked online between full
+    /// 30s reports when ~2s heartbeats are arriving — protects against the
+    /// 60s offline threshold firing on a transiently delayed report.
+    /// </summary>
+    void MarkHeartbeat(string siteId, DateTimeOffset receivedAt);
+
     IReadOnlyDictionary<string, SiteHealthState> GetAllSiteStates();
     SiteHealthState? GetSiteState(string siteId);
 }

src/ScadaLink.Host/Actors/AkkaHostedService.cs

@@ -316,6 +316,21 @@ akka {{
             siteCommActor.Tell(new RegisterLocalHandler(LocalHandlerType.EventLog, eventLogHandler));
         }
 
+        // Parked message handler — bridges Akka to StoreAndForwardService
+        var storeAndForwardService = _serviceProvider.GetService<StoreAndForwardService>();
+        if (storeAndForwardService != null)
+        {
+            // Initialize SQLite schema and start the retry timer. Must complete before
+            // any actor or HTTP handler touches the service.
+            storeAndForwardService.StartAsync().GetAwaiter().GetResult();
+
+            var parkedMessageHandler = _actorSystem.ActorOf(
+                Props.Create(() => new ParkedMessageHandlerActor(
+                    storeAndForwardService, _nodeOptions.SiteId!)),
+                "parked-message-handler");
+            siteCommActor.Tell(new RegisterLocalHandler(LocalHandlerType.ParkedMessages, parkedMessageHandler));
+        }
+
         // Register SiteCommunicationActor with ClusterClientReceptionist so central ClusterClients can reach it
         ClusterClientReceptionist.Get(_actorSystem).RegisterService(siteCommActor);
 

src/ScadaLink.StoreAndForward/ParkedMessageHandlerActor.cs

@@ -0,0 +1,122 @@
+using System.Text.Json;
+using Akka.Actor;
+using Akka.Event;
+using ScadaLink.Commons.Messages.RemoteQuery;
+
+namespace ScadaLink.StoreAndForward;
+
+/// <summary>
+/// Akka actor bridge for <see cref="StoreAndForwardService"/> parked-message operations.
+/// Receives Query/Retry/Discard requests from the SiteCommunicationActor and replies
+/// with the matching response records.
+/// </summary>
+public class ParkedMessageHandlerActor : ReceiveActor
+{
+    private readonly ILoggingAdapter _log = Context.GetLogger();
+    private readonly StoreAndForwardService _service;
+    private readonly string _siteId;
+
+    public ParkedMessageHandlerActor(StoreAndForwardService service, string siteId)
+    {
+        _service = service;
+        _siteId = siteId;
+
+        Receive<ParkedMessageQueryRequest>(HandleQuery);
+        Receive<ParkedMessageRetryRequest>(HandleRetry);
+        Receive<ParkedMessageDiscardRequest>(HandleDiscard);
+    }
+
+    private void HandleQuery(ParkedMessageQueryRequest msg)
+    {
+        var sender = Sender;
+        var siteId = _siteId;
+
+        _service.GetParkedMessagesAsync(category: null, msg.PageNumber, msg.PageSize)
+            .ContinueWith(t =>
+            {
+                if (t.IsCompletedSuccessfully)
+                {
+                    var entries = t.Result.Messages
+                        .Select(m => new ParkedMessageEntry(
+                            MessageId: m.Id,
+                            TargetSystem: m.Target,
+                            MethodName: ExtractMethodName(m.PayloadJson, m.Category),
+                            ErrorMessage: m.LastError ?? string.Empty,
+                            AttemptCount: m.RetryCount,
+                            OriginalTimestamp: m.CreatedAt,
+                            LastAttemptTimestamp: m.LastAttemptAt ?? m.CreatedAt,
+                            MaxAttempts: m.MaxRetries,
+                            Category: m.Category,
+                            OriginInstance: m.OriginInstanceName))
+                        .ToList();
+
+                    return new ParkedMessageQueryResponse(
+                        msg.CorrelationId, siteId, entries, t.Result.TotalCount,
+                        msg.PageNumber, msg.PageSize, true, null, DateTimeOffset.UtcNow);
+                }
+
+                return new ParkedMessageQueryResponse(
+                    msg.CorrelationId, siteId, [], 0, msg.PageNumber, msg.PageSize,
+                    false, t.Exception?.GetBaseException().Message, DateTimeOffset.UtcNow);
+            }).PipeTo(sender);
+    }
+
+    private void HandleRetry(ParkedMessageRetryRequest msg)
+    {
+        var sender = Sender;
+
+        _service.RetryParkedMessageAsync(msg.MessageId)
+            .ContinueWith(t =>
+            {
+                if (t.IsCompletedSuccessfully)
+                {
+                    return new ParkedMessageRetryResponse(
+                        msg.CorrelationId, t.Result,
+                        t.Result ? null : "Message not found or no longer parked.");
+                }
+
+                return new ParkedMessageRetryResponse(
+                    msg.CorrelationId, false, t.Exception?.GetBaseException().Message);
+            }).PipeTo(sender);
+    }
+
+    private void HandleDiscard(ParkedMessageDiscardRequest msg)
+    {
+        var sender = Sender;
+
+        _service.DiscardParkedMessageAsync(msg.MessageId)
+            .ContinueWith(t =>
+            {
+                if (t.IsCompletedSuccessfully)
+                {
+                    return new ParkedMessageDiscardResponse(
+                        msg.CorrelationId, t.Result,
+                        t.Result ? null : "Message not found or no longer parked.");
+                }
+
+                return new ParkedMessageDiscardResponse(
+                    msg.CorrelationId, false, t.Exception?.GetBaseException().Message);
+            }).PipeTo(sender);
+    }
+
+    private static string ExtractMethodName(string payloadJson, Commons.Types.Enums.StoreAndForwardCategory category)
+    {
+        if (string.IsNullOrEmpty(payloadJson))
+            return category.ToString();
+
+        try
+        {
+            using var doc = JsonDocument.Parse(payloadJson);
+            var root = doc.RootElement;
+            if (root.TryGetProperty("MethodName", out var method) && method.ValueKind == JsonValueKind.String)
+                return method.GetString() ?? category.ToString();
+            if (root.TryGetProperty("Subject", out var subject) && subject.ValueKind == JsonValueKind.String)
+                return subject.GetString() ?? category.ToString();
+        }
+        catch (JsonException)
+        {
+        }
+
+        return category.ToString();
+    }
+}

src/ScadaLink.StoreAndForward/ScadaLink.StoreAndForward.csproj

@@ -8,6 +8,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Akka" Version="1.5.62" />
     <PackageReference Include="Microsoft.Data.Sqlite" Version="10.0.7" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.7" />
     <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.7" />

tests/ScadaLink.Communication.Tests/CentralCommunicationActorTests.cs

@@ -11,6 +11,7 @@ using ScadaLink.Commons.Messages.Deployment;
 using ScadaLink.Commons.Messages.DebugView;
 using ScadaLink.Commons.Messages.Health;
 using ScadaLink.Communication.Actors;
+using ScadaLink.HealthMonitoring;
 using Akka.TestKit;
 
 namespace ScadaLink.Communication.Tests;
@@ -140,25 +141,27 @@ public class CentralCommunicationActorTests : TestKit
     }
 
     [Fact]
-    public void Heartbeat_ForwardedToParent()
+    public void Heartbeat_BumpsAggregatorTimestamp()
     {
         var mockRepo = Substitute.For<ISiteRepository>();
         mockRepo.GetAllSitesAsync(Arg.Any<CancellationToken>())
             .Returns(new List<Site>());
 
+        var aggregator = Substitute.For<ICentralHealthAggregator>();
+
         var services = new ServiceCollection();
         services.AddScoped(_ => mockRepo);
+        services.AddSingleton(aggregator);
         var sp = services.BuildServiceProvider();
 
         var siteClientFactory = Substitute.For<ISiteClientFactory>();
-        var parentProbe = CreateTestProbe();
+        var centralActor = Sys.ActorOf(
-        var centralActor = parentProbe.ChildActorOf(
             Props.Create(() => new CentralCommunicationActor(sp, siteClientFactory)));
 
-        var heartbeat = new HeartbeatMessage("site1", "host1", true, DateTimeOffset.UtcNow);
+        var timestamp = DateTimeOffset.UtcNow;
-        centralActor.Tell(heartbeat);
+        centralActor.Tell(new HeartbeatMessage("site1", "host1", true, timestamp));
 
-        parentProbe.ExpectMsg<HeartbeatMessage>(msg => msg.SiteId == "site1");
+        AwaitAssert(() => aggregator.Received(1).MarkHeartbeat("site1", timestamp));
     }
 
     [Fact]

tests/ScadaLink.Communication.Tests/ScadaLink.Communication.Tests.csproj

@@ -25,6 +25,7 @@
   <ItemGroup>
     <ProjectReference Include="../../src/ScadaLink.Communication/ScadaLink.Communication.csproj" />
     <ProjectReference Include="../../src/ScadaLink.Commons/ScadaLink.Commons.csproj" />
+    <ProjectReference Include="../../src/ScadaLink.HealthMonitoring/ScadaLink.HealthMonitoring.csproj" />
   </ItemGroup>
 
 </Project>