refactor(auditlog): rename audit correlation field, add cross-helper tests

Outbound API audit rows now carry the request arguments and response body
(sync ApiCall + cached immediate-completion path); the emitter previously
hard-coded both summary fields to null.

src/ScadaLink.CentralUI/Components/Audit/AuditFilterBar.razor

@@ -6,78 +6,58 @@
 
 <div class="card mb-3" data-test="audit-filter-bar">
     <div class="card-body py-2">
-        @* Channel chip multi-select. *@
-        <div class="mb-2" data-test="filter-channel">
-            <label class="form-label small mb-1">Channel</label>
-            <div>
-                @foreach (var channel in Enum.GetValues<AuditChannel>())
+        @* All filters sit in one wrapped row. Kind / Status / Site use compact
+           MultiSelectDropdown controls; Channel is a single-select because the
+           Kind options narrow to the chosen channel — so the bar stays a row or
+           two tall instead of four stacked blocks of chip buttons. *@
+        <div class="row g-2 align-items-end">
+            @* Single-select: one channel at a time, so the Kind options below
+               narrow cleanly to that channel. "All channels" clears it. *@
+            <div class="col-auto" data-test="filter-channel">
+                <label class="form-label small mb-1" for="audit-channel">Channel</label>
+                <select id="audit-channel" data-test="filter-channel-select"
+                        class="form-select form-select-sm" @bind="SelectedChannel">
+                    <option value="">All channels</option>
+                    @foreach (var channel in _channels)
                     {
-                    var selected = _model.Channels.Contains(channel);
-                    <button type="button" data-test="chip-channel-@channel"
-                            class="@ChipClass(selected)"
-                            @onclick="() => ToggleChannel(channel)">
-                        @channel
-                    </button>
+                        <option value="@channel">@channel</option>
                     }
-            </div>
+                </select>
             </div>
 
-        @* Kind chip multi-select — narrowed by Channel selection. *@
-        <div class="mb-2" data-test="filter-kind">
+            @* Kind options are narrowed by the Channel selection (VisibleKinds). *@
+            <div class="col-auto" data-test="filter-kind">
                 <label class="form-label small mb-1">Kind</label>
                 <div>
-                @foreach (var kind in _model.VisibleKinds())
-                {
-                    var selected = _model.Kinds.Contains(kind);
-                    <button type="button" data-test="chip-kind-@kind"
-                            class="@ChipClass(selected)"
-                            @onclick="() => ToggleKind(kind)">
-                        @kind
-                    </button>
-                }
+                    <MultiSelectDropdown TValue="AuditKind"
+                                         Items="_model.VisibleKinds()"
+                                         Selected="_model.Kinds"
+                                         DataTest="filter-kind-ms" />
                 </div>
             </div>
 
-        @* Status chip multi-select. *@
-        <div class="mb-2" data-test="filter-status">
+            <div class="col-auto" data-test="filter-status">
                 <label class="form-label small mb-1">Status</label>
                 <div>
-                @foreach (var status in Enum.GetValues<AuditStatus>())
-                {
-                    var selected = _model.Statuses.Contains(status);
-                    <button type="button" data-test="chip-status-@status"
-                            class="@ChipClass(selected)"
-                            @onclick="() => ToggleStatus(status)">
-                        @status
-                    </button>
-                }
+                    <MultiSelectDropdown TValue="AuditStatus"
+                                         Items="_statuses"
+                                         Selected="_model.Statuses"
+                                         DataTest="filter-status-ms" />
                 </div>
             </div>
 
-        @* Site chip multi-select — populated from ISiteRepository. *@
-        <div class="mb-2" data-test="filter-site">
+            <div class="col-auto" data-test="filter-site">
                 <label class="form-label small mb-1">Site</label>
                 <div>
-                @if (_sites.Count == 0)
-                {
-                    <span class="text-muted small">No sites available.</span>
-                }
-                else
-                {
-                    @foreach (var site in _sites)
-                    {
-                        var selected = _model.SiteIdentifiers.Contains(site.SiteIdentifier);
-                        <button type="button" data-test="chip-site-@site.SiteIdentifier"
-                                class="@ChipClass(selected)"
-                                @onclick="() => ToggleSite(site.SiteIdentifier)">
-                            @site.Name
-                        </button>
-                    }
-                }
+                    <MultiSelectDropdown TValue="string"
+                                         Items="_siteIds"
+                                         Selected="_model.SiteIdentifiers"
+                                         Display="SiteName"
+                                         EmptyText="No sites available"
+                                         DataTest="filter-site-ms" />
                 </div>
             </div>
 
-        <div class="row g-2 align-items-end">
             <div class="col-auto" data-test="filter-time-range">
                 <label class="form-label small mb-1" for="audit-time-range">Time range</label>
                 <select id="audit-time-range" class="form-select form-select-sm"

src/ScadaLink.CentralUI/Components/Audit/AuditFilterBar.razor.cs

@@ -7,19 +7,32 @@ namespace ScadaLink.CentralUI.Components.Audit;
 
 /// <summary>
 /// Filter bar for the central Audit Log page (#23 M7-T2). Owns the
-/// <see cref="AuditQueryModel"/> binding state, renders the 10 filter elements
-/// plus the Errors-only toggle, and publishes a collapsed
-/// <see cref="AuditLogQueryFilter"/> via <see cref="OnFilterChanged"/> when the
-/// user clicks Apply. See <see cref="AuditQueryModel"/> for the multi-select →
-/// single-value collapse contract.
+/// <see cref="AuditQueryModel"/> binding state and renders the filter controls
+/// — Channel as a single-select (one channel at a time, so the Kind options
+/// narrow to it cleanly); Kind / Status / Site as compact
+/// <see cref="ScadaLink.CentralUI.Components.Shared.MultiSelectDropdown{TValue}"/>
+/// controls; plus the time range, free-text searches and the Errors-only
+/// toggle — and publishes an <see cref="AuditLogQueryFilter"/> via
+/// <see cref="OnFilterChanged"/> when the user clicks Apply. The selected
+/// dimensions map through to the filter's list fields; see
+/// <see cref="AuditQueryModel"/> for the Errors-only and time-range rules.
 /// </summary>
 public partial class AuditFilterBar
 {
     private readonly AuditQueryModel _model = new();
     private List<Site> _sites = new();
 
+    /// <summary>Channel options — the full enum, fixed for the component's lifetime.</summary>
+    private static readonly IReadOnlyList<AuditChannel> _channels = Enum.GetValues<AuditChannel>();
+
+    /// <summary>Status options — the full enum, fixed for the component's lifetime.</summary>
+    private static readonly IReadOnlyList<AuditStatus> _statuses = Enum.GetValues<AuditStatus>();
+
+    /// <summary>Site identifiers in display order; rebuilt once when sites load.</summary>
+    private IReadOnlyList<string> _siteIds = Array.Empty<string>();
+
     /// <summary>
-    /// Raised when the user clicks Apply. Carries the collapsed
+    /// Raised when the user clicks Apply. Carries the
     /// <see cref="AuditLogQueryFilter"/> the parent page hands to
     /// <see cref="ScadaLink.CentralUI.Services.IAuditLogQueryService"/>.
     /// </summary>
@@ -51,10 +64,9 @@ public partial class AuditFilterBar
             _model.InstanceSearch = InitialInstanceSearch.Trim();
         }
 
-
-        // Populate the Site chips at component init. Failure is non-fatal — the chip
-        // section just shows "No sites available." Sites are listed by Name to match
-        // operator expectations from the Notification Report.
+        // Populate the Site dropdown at component init. Failure is non-fatal — the
+        // dropdown just shows "No sites available." Sites are listed by Name to
+        // match operator expectations from the Notification Report.
         try
         {
             var sites = await SiteRepository.GetAllSitesAsync();
@@ -62,48 +74,52 @@ public partial class AuditFilterBar
         }
         catch
         {
-            // Swallowed: filter bar still renders without the Site chips. The page
+            // Swallowed: filter bar still renders without the Site options. The page
             // surfaces site-load errors elsewhere (the grid query path).
             _sites = new();
         }
+
+        _siteIds = _sites.Select(s => s.SiteIdentifier).ToArray();
     }
 
-    private void ToggleChannel(AuditChannel channel)
+    /// <summary>
+    /// Single-select Channel binding for the filter bar. The Audit Log filters one
+    /// channel at a time so the Kind options narrow cleanly to it; the model still
+    /// stores the selection as a set (0 or 1 entry) so <see cref="AuditQueryModel.ToFilter"/>
+    /// and <see cref="AuditQueryModel.VisibleKinds"/> are unchanged. <c>null</c> = all channels.
+    /// </summary>
+    private AuditChannel? SelectedChannel
     {
-        if (!_model.Channels.Add(channel))
+        get => _model.Channels.Count > 0 ? _model.Channels.First() : null;
+        set
         {
-            _model.Channels.Remove(channel);
+            _model.Channels.Clear();
+            if (value is { } channel)
+            {
+                _model.Channels.Add(channel);
             }
 
-        // Drop Kind chips that fall outside the new visible set. Keeps "Channel and
-        // Kind both picked" coherent — without this, removing a channel could leave
-        // stale Kind chips selected that no longer match any visible chip.
+            OnChannelsChanged();
+        }
+    }
+
+    /// <summary>
+    /// Runs after the Channel selection changes. Drops any Kind selections that fell
+    /// outside the new visible set — without this, changing the channel could leave
+    /// stale Kind selections that no longer match any visible option.
+    /// </summary>
+    private void OnChannelsChanged()
+    {
         var visible = _model.VisibleKinds().ToHashSet();
         _model.Kinds.RemoveWhere(k => !visible.Contains(k));
     }
 
-    private void ToggleKind(AuditKind kind)
+    /// <summary>Display label for a site identifier — its friendly Name, id as fallback.</summary>
+    private string SiteName(string siteIdentifier)
     {
-        if (!_model.Kinds.Add(kind))
-        {
-            _model.Kinds.Remove(kind);
-        }
-    }
-
-    private void ToggleStatus(AuditStatus status)
-    {
-        if (!_model.Statuses.Add(status))
-        {
-            _model.Statuses.Remove(status);
-        }
-    }
-
-    private void ToggleSite(string siteIdentifier)
-    {
-        if (!_model.SiteIdentifiers.Add(siteIdentifier))
-        {
-            _model.SiteIdentifiers.Remove(siteIdentifier);
-        }
+        var site = _sites.FirstOrDefault(s =>
+            string.Equals(s.SiteIdentifier, siteIdentifier, StringComparison.OrdinalIgnoreCase));
+        return site?.Name ?? siteIdentifier;
     }
 
     private void ClearFilters()
@@ -129,11 +145,6 @@ public partial class AuditFilterBar
         await OnFilterChanged.InvokeAsync(filter);
     }
 
-    private static string ChipClass(bool selected) =>
-        selected
-            ? "btn btn-sm btn-primary me-1 mb-1"
-            : "btn btn-sm btn-outline-secondary me-1 mb-1";
-
     private static string TimeRangeLabel(AuditTimeRangePreset preset) => preset switch
     {
         AuditTimeRangePreset.Last5Minutes => "now − 5 min → now",

src/ScadaLink.CentralUI/Components/Shared/MultiSelectDropdown.razor

@@ -0,0 +1,40 @@
+@typeparam TValue
+@*
+    Compact multi-select control: a Bootstrap dropdown whose toggle button
+    summarises the current selection over a checkbox menu. Replaces a wrapped
+    block of chip buttons with a single control of one row's height.
+*@
+<div class="dropdown msd" data-test="@DataTest">
+    <button type="button"
+            class="btn btn-sm btn-outline-secondary dropdown-toggle msd-toggle text-start"
+            data-bs-toggle="dropdown"
+            data-bs-auto-close="outside"
+            aria-expanded="false"
+            disabled="@(Items.Count == 0)"
+            data-test="@($"{DataTest}-toggle")">
+        <span class="msd-summary">@Summary()</span>
+    </button>
+    <ul class="dropdown-menu msd-menu">
+        @if (Items.Count == 0)
+        {
+            <li><span class="dropdown-item-text text-muted small">@EmptyText</span></li>
+        }
+        else
+        {
+            @foreach (var item in Items)
+            {
+                var isSelected = Selected.Contains(item);
+                <li>
+                    <label class="dropdown-item msd-item">
+                        <input type="checkbox"
+                               class="form-check-input msd-check"
+                               checked="@isSelected"
+                               @onchange="() => Toggle(item)"
+                               data-test="@($"{DataTest}-opt-{item}")" />
+                        <span>@Display(item)</span>
+                    </label>
+                </li>
+            }
+        }
+    </ul>
+</div>

src/ScadaLink.CentralUI/Components/Shared/MultiSelectDropdown.razor.cs

@@ -0,0 +1,95 @@
+using Microsoft.AspNetCore.Components;
+
+namespace ScadaLink.CentralUI.Components.Shared;
+
+/// <summary>
+/// A compact multi-select control: a Bootstrap dropdown whose toggle button
+/// summarises the current selection ("All" when empty, the single item's label
+/// when one is picked, or "N selected" otherwise) over a checkbox menu.
+///
+/// <para>
+/// It exists to keep multi-value filter controls one row tall instead of a
+/// wrapped block of chip buttons. The component mutates the caller-owned
+/// <see cref="Selected"/> collection in place and raises
+/// <see cref="SelectionChanged"/> after every toggle so the parent can react
+/// (re-render, prune dependent selections, …).
+/// </para>
+///
+/// <para>
+/// Requires the Bootstrap JS bundle (loaded in <c>App.razor</c>) for the
+/// dropdown toggle; <c>data-bs-auto-close="outside"</c> keeps the menu open
+/// while the operator ticks several boxes.
+/// </para>
+/// </summary>
+/// <typeparam name="TValue">The option value type (an enum or string).</typeparam>
+public partial class MultiSelectDropdown<TValue> where TValue : notnull
+{
+    /// <summary>The options shown in the menu, in display order.</summary>
+    [Parameter, EditorRequired]
+    public IReadOnlyList<TValue> Items { get; set; } = Array.Empty<TValue>();
+
+    /// <summary>
+    /// The caller-owned selection set. Mutated in place by <see cref="Toggle"/>.
+    /// </summary>
+    [Parameter, EditorRequired]
+    public ICollection<TValue> Selected { get; set; } = default!;
+
+    /// <summary>Maps an option to its display label. Defaults to <c>ToString()</c>.</summary>
+    [Parameter]
+    public Func<TValue, string> Display { get; set; } = static v => v.ToString() ?? string.Empty;
+
+    /// <summary>Raised after each toggle, once <see cref="Selected"/> has been updated.</summary>
+    [Parameter]
+    public EventCallback SelectionChanged { get; set; }
+
+    /// <summary>Summary text shown on the toggle button when nothing is selected.</summary>
+    [Parameter]
+    public string AllLabel { get; set; } = "All";
+
+    /// <summary>Text shown in the menu when there are no options.</summary>
+    [Parameter]
+    public string EmptyText { get; set; } = "None available";
+
+    /// <summary><c>data-test</c> root for this control, its toggle and its options.</summary>
+    [Parameter]
+    public string DataTest { get; set; } = "multi-select";
+
+    private async Task Toggle(TValue item)
+    {
+        // ICollection.Remove returns false when the item was absent — that is the
+        // "not currently selected" case, so add it. This is a plain toggle.
+        if (!Selected.Remove(item))
+        {
+            Selected.Add(item);
+        }
+
+        await SelectionChanged.InvokeAsync();
+    }
+
+    private string Summary()
+    {
+        var count = Selected.Count;
+        if (count == 0)
+        {
+            return AllLabel;
+        }
+
+        if (count == 1)
+        {
+            // Prefer the single selection's label over a bare "1 selected".
+            foreach (var item in Items)
+            {
+                if (Selected.Contains(item))
+                {
+                    return Display(item);
+                }
+            }
+
+            // The one selected value is not in the current Items list (e.g. a Kind
+            // narrowed out by a Channel change before the parent pruned it).
+            return "1 selected";
+        }
+
+        return $"{count} selected";
+    }
+}

src/ScadaLink.CentralUI/Components/Shared/MultiSelectDropdown.razor.css

@@ -0,0 +1,32 @@
+/* Compact multi-select dropdown. Tuned to sit inline with form-select-sm /
+   form-control-sm controls in a filter row. */
+
+.msd-toggle {
+    min-width: 9rem;
+    max-width: 15rem;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+}
+
+/* Keep a long option list from running off-screen — scroll within the menu. */
+.msd-menu {
+    max-height: 16rem;
+    overflow-y: auto;
+}
+
+/* The whole row is a <label> so a click anywhere toggles the checkbox; the
+   menu stays open thanks to data-bs-auto-close="outside". */
+.msd-item {
+    display: flex;
+    align-items: center;
+    gap: 0.5rem;
+    cursor: pointer;
+}
+
+/* Neutralise the default form-check-input top margin so the box lines up with
+   the option text inside the dropdown-item. */
+.msd-check {
+    flex: 0 0 auto;
+    margin: 0;
+}

src/ScadaLink.InboundAPI/Middleware/AuditWriteMiddleware.cs

@@ -145,6 +145,17 @@ public sealed class AuditWriteMiddleware
                 OccurredAtUtc = DateTime.UtcNow,
                 Channel = AuditChannel.ApiInbound,
                 Kind = kind,
+                // Audit Log #23: a fresh per-request correlation id so the
+                // inbound row carries a request identifier (closes the design
+                // gap that inbound rows should be correlatable).
+                //
+                // This id is intentionally request-local: it is NOT bridged to
+                // RouteHelper's routed-call correlation id or to
+                // HttpContext.TraceIdentifier. Threading an inbound request's
+                // correlation id through to the routed script execution (so an
+                // inbound call and the outbound API/DB rows it triggers share
+                // one id) is a deliberate future follow-up, out of scope here.
+                CorrelationId = Guid.NewGuid(),
                 Actor = actor,
                 Target = methodName,
                 Status = status,

src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs

@@ -30,6 +30,13 @@ public class NotificationOutboxActor : ReceiveActor, IWithTimers
     private const int FallbackMaxRetries = 10;
     private static readonly TimeSpan FallbackRetryDelay = TimeSpan.FromMinutes(1);
 
+    /// <summary>
+    /// Audit <c>Actor</c> stamped on central-dispatch (<c>NotifyDeliver</c>) rows.
+    /// The Actor-column spec assigns central-originated audit rows a system
+    /// identity — there is no per-call authenticated user at dispatch time.
+    /// </summary>
+    private const string SystemActor = "system";
+
     private readonly IServiceProvider _serviceProvider;
     private readonly NotificationOutboxOptions _options;
     private readonly ICentralAuditWriter _auditWriter;
@@ -500,9 +507,11 @@ public class NotificationOutboxActor : ReceiveActor, IWithTimers
             Channel = AuditChannel.Notification,
             Kind = AuditKind.NotifyDeliver,
             CorrelationId = correlationId,
-            // Central dispatch — no authenticated actor (the originating
-            // script's identity is captured on the upstream NotifySend row).
-            Actor = null,
+            // Central dispatch — a system identity per the Actor-column spec;
+            // there is no per-call authenticated user here. The originating
+            // script is still captured on SourceScript (and on the upstream
+            // NotifySend row).
+            Actor = SystemActor,
             SourceSiteId = notification.SourceSiteId,
             SourceInstanceId = notification.SourceInstanceId,
             SourceScript = notification.SourceScript,

src/ScadaLink.SiteRuntime/Scripts/AuditingDbCommand.cs

@@ -37,9 +37,13 @@ internal sealed class AuditingDbCommand : DbCommand
     private readonly string _siteId;
     private readonly string _instanceName;
     private readonly string? _sourceScript;
+    private readonly Guid _auditCorrelationId;
     private readonly ILogger _logger;
     private DbConnection? _wrappingConnection;
 
+    // Parameter ordering: auditCorrelationId sits immediately after the ILogger,
+    // consistent with the other three audit-threaded ctors (ExternalSystemHelper,
+    // DatabaseHelper, AuditingDbConnection).
     public AuditingDbCommand(
         DbCommand inner,
         IAuditWriter auditWriter,
@@ -47,7 +51,8 @@ internal sealed class AuditingDbCommand : DbCommand
         string siteId,
         string instanceName,
         string? sourceScript,
-        ILogger logger)
+        ILogger logger,
+        Guid auditCorrelationId)
     {
         _inner = inner ?? throw new ArgumentNullException(nameof(inner));
         _auditWriter = auditWriter ?? throw new ArgumentNullException(nameof(auditWriter));
@@ -56,6 +61,7 @@ internal sealed class AuditingDbCommand : DbCommand
         _instanceName = instanceName ?? string.Empty;
         _sourceScript = sourceScript;
         _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        _auditCorrelationId = auditCorrelationId;
     }
 
     // -- Forwarded surface ------------------------------------------------
@@ -426,11 +432,17 @@ internal sealed class AuditingDbCommand : DbCommand
             OccurredAtUtc = DateTime.SpecifyKind(occurredAtUtc, DateTimeKind.Utc),
             Channel = AuditChannel.DbOutbound,
             Kind = AuditKind.DbWrite,
-            CorrelationId = null,
+            // Audit Log #23: the execution-wide correlation id, so this sync
+            // DbWrite row shares an id with the other sync trust-boundary rows
+            // from the same script run.
+            CorrelationId = _auditCorrelationId,
             SourceSiteId = string.IsNullOrEmpty(_siteId) ? null : _siteId,
             SourceInstanceId = _instanceName,
             SourceScript = _sourceScript,
-            Actor = null,
+            // Outbound channel: per the Audit Log Actor-column spec the actor is
+            // the calling script. Null when no single script owns the call
+            // (e.g. a shared script running inline).
+            Actor = _sourceScript,
             Target = target,
             Status = status,
             HttpStatus = null,

src/ScadaLink.SiteRuntime/Scripts/AuditingDbConnection.cs

@@ -36,8 +36,12 @@ internal sealed class AuditingDbConnection : DbConnection
     private readonly string _siteId;
     private readonly string _instanceName;
     private readonly string? _sourceScript;
+    private readonly Guid _auditCorrelationId;
     private readonly ILogger _logger;
 
+    // Parameter ordering: auditCorrelationId sits immediately after the ILogger,
+    // consistent with the other three audit-threaded ctors (ExternalSystemHelper,
+    // DatabaseHelper, AuditingDbCommand).
     public AuditingDbConnection(
         DbConnection inner,
         IAuditWriter auditWriter,
@@ -45,7 +49,8 @@ internal sealed class AuditingDbConnection : DbConnection
         string siteId,
         string instanceName,
         string? sourceScript,
-        ILogger logger)
+        ILogger logger,
+        Guid auditCorrelationId)
     {
         _inner = inner ?? throw new ArgumentNullException(nameof(inner));
         _auditWriter = auditWriter ?? throw new ArgumentNullException(nameof(auditWriter));
@@ -54,6 +59,7 @@ internal sealed class AuditingDbConnection : DbConnection
         _instanceName = instanceName ?? string.Empty;
         _sourceScript = sourceScript;
         _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        _auditCorrelationId = auditCorrelationId;
     }
 
     // ConnectionString is settable on DbConnection — forward both halves.
@@ -92,7 +98,8 @@ internal sealed class AuditingDbConnection : DbConnection
             _siteId,
             _instanceName,
             _sourceScript,
-            _logger);
+            _logger,
+            _auditCorrelationId);
     }
 
     protected override void Dispose(bool disposing)

src/ScadaLink.SiteRuntime/Scripts/ScriptRuntimeContext.cs

@@ -105,6 +105,21 @@ public class ScriptRuntimeContext
     /// </summary>
     private readonly ICachedCallTelemetryForwarder? _cachedForwarder;
 
+    /// <summary>
+    /// Audit Log #23: the execution-wide audit correlation id. Every sync
+    /// trust-boundary audit row emitted by this script execution
+    /// (<c>ApiCall</c>, <c>DbWrite</c>) is stamped with this id so all the
+    /// rows from one script run can be correlated together.
+    /// </summary>
+    private readonly Guid _auditCorrelationId;
+
+    /// <param name="auditCorrelationId">
+    /// Audit Log #23: the execution-wide audit correlation id. When omitted
+    /// (tag-change / timer-triggered executions) a fresh id is generated; an
+    /// inbound caller may supply one to tie the execution to an upstream
+    /// request. Stamped on the sync <c>ApiCall</c>/<c>DbWrite</c> audit rows
+    /// this execution emits.
+    /// </param>
     public ScriptRuntimeContext(
         IActorRef instanceActor,
         IActorRef self,
@@ -122,7 +137,8 @@ public class ScriptRuntimeContext
         string? sourceScript = null,
         IAuditWriter? auditWriter = null,
         IOperationTrackingStore? operationTrackingStore = null,
-        ICachedCallTelemetryForwarder? cachedForwarder = null)
+        ICachedCallTelemetryForwarder? cachedForwarder = null,
+        Guid? auditCorrelationId = null)
     {
         _instanceActor = instanceActor;
         _self = self;
@@ -141,6 +157,7 @@ public class ScriptRuntimeContext
         _auditWriter = auditWriter;
         _operationTrackingStore = operationTrackingStore;
         _cachedForwarder = cachedForwarder;
+        _auditCorrelationId = auditCorrelationId ?? Guid.NewGuid();
     }
 
     /// <summary>
@@ -241,7 +258,7 @@ public class ScriptRuntimeContext
     /// ExternalSystem.CachedCall("systemName", "methodName", params)
     /// </summary>
     public ExternalSystemHelper ExternalSystem => new(
-        _externalSystemClient, _instanceName, _logger, _auditWriter, _siteId, _sourceScript,
+        _externalSystemClient, _instanceName, _logger, _auditCorrelationId, _auditWriter, _siteId, _sourceScript,
         // Audit Log #23 (M3 Bundle E — Task E3): emit CachedSubmit telemetry
         // on every ExternalSystem.CachedCall enqueue.
         _cachedForwarder);
@@ -255,6 +272,7 @@ public class ScriptRuntimeContext
         _databaseGateway,
         _instanceName,
         _logger,
+        _auditCorrelationId,
         // Audit Log #23 (M4 Bundle A): wire the IAuditWriter so
         // Database.Connection(name) returns an auditing decorator that
         // emits one DbOutbound/DbWrite row per script-initiated
@@ -362,6 +380,7 @@ public class ScriptRuntimeContext
         private readonly IExternalSystemClient? _client;
         private readonly string _instanceName;
         private readonly ILogger _logger;
+        private readonly Guid _auditCorrelationId;
         private readonly IAuditWriter? _auditWriter;
         private readonly string _siteId;
         private readonly string? _sourceScript;
@@ -370,10 +389,18 @@ public class ScriptRuntimeContext
         // Internal constructor for tests living in ScadaLink.SiteRuntime.Tests
         // (via InternalsVisibleTo). Production sites resolve the helper through
         // ScriptRuntimeContext.ExternalSystem.
+        //
+        // Parameter ordering: auditCorrelationId sits immediately after the
+        // ILogger across all four audit-threaded ctors (ExternalSystemHelper,
+        // DatabaseHelper, AuditingDbConnection, AuditingDbCommand) — a required
+        // Guid cannot follow the optional provenance params without a
+        // required-after-optional compile error, so the post-logger slot is the
+        // one consistent position that compiles cleanly everywhere.
         internal ExternalSystemHelper(
             IExternalSystemClient? client,
             string instanceName,
             ILogger logger,
+            Guid auditCorrelationId,
             IAuditWriter? auditWriter = null,
             string siteId = "",
             string? sourceScript = null,
@@ -382,6 +409,7 @@ public class ScriptRuntimeContext
             _client = client;
             _instanceName = instanceName;
             _logger = logger;
+            _auditCorrelationId = auditCorrelationId;
             _auditWriter = auditWriter;
             _siteId = siteId;
             _sourceScript = sourceScript;
@@ -420,7 +448,7 @@ public class ScriptRuntimeContext
             {
                 var elapsedMs = (int)((Stopwatch.GetTimestamp() - startTicks)
                     * 1000d / Stopwatch.Frequency);
-                EmitCallAudit(systemName, methodName, occurredAtUtc, elapsedMs, result, thrown);
+                EmitCallAudit(systemName, methodName, occurredAtUtc, elapsedMs, result, thrown, parameters);
             }
         }
 
@@ -458,7 +486,7 @@ public class ScriptRuntimeContext
             // Submitted row even if the immediate-delivery attempt happens to
             // resolve before this method returns.
             await EmitCachedSubmitTelemetryAsync(
-                systemName, methodName, target, trackedId, occurredAtUtc, cancellationToken)
+                systemName, methodName, target, trackedId, occurredAtUtc, parameters, cancellationToken)
                 .ConfigureAwait(false);
 
             // Hand off to the existing cached-call path. The TrackedOperationId
@@ -503,7 +531,7 @@ public class ScriptRuntimeContext
             if (result is { WasBuffered: false })
             {
                 await EmitImmediateTerminalTelemetryAsync(
-                    systemName, methodName, target, trackedId, result, cancellationToken)
+                    systemName, methodName, target, trackedId, result, parameters, cancellationToken)
                     .ConfigureAwait(false);
             }
 
@@ -521,6 +549,7 @@ public class ScriptRuntimeContext
             string target,
             TrackedOperationId trackedId,
             DateTime occurredAtUtc,
+            IReadOnlyDictionary<string, object?>? parameters,
             CancellationToken cancellationToken)
         {
             if (_cachedForwarder == null)
@@ -544,6 +573,8 @@ public class ScriptRuntimeContext
                         SourceScript = _sourceScript,
                         Target = target,
                         Status = AuditStatus.Submitted,
+                        // Submit precedes the call — request args only, no response yet.
+                        RequestSummary = SerializeRequest(parameters),
                         ForwardState = AuditForwardState.Pending,
                     },
                     Operational: new SiteCallOperational(
@@ -599,6 +630,7 @@ public class ScriptRuntimeContext
             string target,
             TrackedOperationId trackedId,
             ExternalCallResult result,
+            IReadOnlyDictionary<string, object?>? parameters,
             CancellationToken cancellationToken)
         {
             if (_cachedForwarder == null)
@@ -653,6 +685,8 @@ public class ScriptRuntimeContext
                         Status = AuditStatus.Attempted,
                         HttpStatus = httpStatus,
                         ErrorMessage = result.Success ? null : result.ErrorMessage,
+                        RequestSummary = SerializeRequest(parameters),
+                        ResponseSummary = result.ResponseJson,
                         ForwardState = AuditForwardState.Pending,
                     },
                     Operational: new SiteCallOperational(
@@ -712,6 +746,8 @@ public class ScriptRuntimeContext
                         Status = auditTerminalStatus,
                         HttpStatus = httpStatus,
                         ErrorMessage = result.Success ? null : result.ErrorMessage,
+                        RequestSummary = SerializeRequest(parameters),
+                        ResponseSummary = result.ResponseJson,
                         ForwardState = AuditForwardState.Pending,
                     },
                     Operational: new SiteCallOperational(
@@ -762,7 +798,8 @@ public class ScriptRuntimeContext
             DateTime occurredAtUtc,
             int durationMs,
             ExternalCallResult? result,
-            Exception? thrown)
+            Exception? thrown,
+            IReadOnlyDictionary<string, object?>? parameters)
         {
             if (_auditWriter == null)
             {
@@ -772,7 +809,8 @@ public class ScriptRuntimeContext
             AuditEvent evt;
             try
             {
-                evt = BuildCallAuditEvent(systemName, methodName, occurredAtUtc, durationMs, result, thrown);
+                evt = BuildCallAuditEvent(
+                    systemName, methodName, occurredAtUtc, durationMs, result, thrown, parameters);
             }
             catch (Exception buildEx)
             {
@@ -828,7 +866,8 @@ public class ScriptRuntimeContext
             DateTime occurredAtUtc,
             int durationMs,
             ExternalCallResult? result,
-            Exception? thrown)
+            Exception? thrown,
+            IReadOnlyDictionary<string, object?>? parameters)
         {
             // Status: Delivered on a Success result; Failed otherwise (the
             // ExternalSystemClient already maps HTTP non-2xx + transient
@@ -871,24 +910,57 @@ public class ScriptRuntimeContext
                 OccurredAtUtc = DateTime.SpecifyKind(occurredAtUtc, DateTimeKind.Utc),
                 Channel = AuditChannel.ApiOutbound,
                 Kind = AuditKind.ApiCall,
-                CorrelationId = null,
+                // Audit Log #23: the execution-wide correlation id, so all the
+                // sync ApiCall/DbWrite rows from one script run share an id.
+                CorrelationId = _auditCorrelationId,
                 SourceSiteId = string.IsNullOrEmpty(_siteId) ? null : _siteId,
                 SourceInstanceId = _instanceName,
                 SourceScript = _sourceScript,
-                Actor = null,
+                // Outbound channel: per the Audit Log Actor-column spec the actor
+                // is the calling script. Null when no single script owns the call
+                // (e.g. a shared script running inline).
+                Actor = _sourceScript,
                 Target = $"{systemName}.{methodName}",
                 Status = status,
                 HttpStatus = httpStatus,
                 DurationMs = durationMs,
                 ErrorMessage = errorMessage,
                 ErrorDetail = errorDetail,
-                RequestSummary = null,
-                ResponseSummary = null,
+                // Payload capture: the request arguments and the response body.
+                // The audit writer's payload filter applies the configured size
+                // cap and header/secret redaction downstream — the emitter just
+                // hands over the raw values.
+                RequestSummary = SerializeRequest(parameters),
+                ResponseSummary = result?.ResponseJson,
                 PayloadTruncated = false,
                 Extra = null,
                 ForwardState = AuditForwardState.Pending,
             };
         }
+
+        /// <summary>
+        /// Serialises the outbound-call argument dictionary into the JSON
+        /// <c>RequestSummary</c> stamped on <c>ApiOutbound</c> audit rows.
+        /// Returns <c>null</c> for a null/empty argument set. Serialization
+        /// failure is swallowed (returns <c>null</c>) — a payload that cannot be
+        /// summarised must never abort the best-effort audit emission.
+        /// </summary>
+        private static string? SerializeRequest(IReadOnlyDictionary<string, object?>? parameters)
+        {
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            try
+            {
+                return JsonSerializer.Serialize(parameters);
+            }
+            catch (Exception)
+            {
+                return null;
+            }
+        }
     }
 
     /// <summary>
@@ -907,6 +979,7 @@ public class ScriptRuntimeContext
         private readonly IDatabaseGateway? _gateway;
         private readonly string _instanceName;
         private readonly ILogger _logger;
+        private readonly Guid _auditCorrelationId;
         private readonly string _siteId;
         private readonly string? _sourceScript;
         private readonly ICachedCallTelemetryForwarder? _cachedForwarder;
@@ -923,10 +996,15 @@ public class ScriptRuntimeContext
         /// </summary>
         private readonly IAuditWriter? _auditWriter;
 
+        // Parameter ordering: auditCorrelationId sits immediately after the
+        // ILogger — see the note on ExternalSystemHelper's ctor for why the
+        // post-logger slot is the one consistent position across all four
+        // audit-threaded ctors.
         internal DatabaseHelper(
             IDatabaseGateway? gateway,
             string instanceName,
             ILogger logger,
+            Guid auditCorrelationId,
             IAuditWriter? auditWriter = null,
             string siteId = "",
             string? sourceScript = null,
@@ -935,6 +1013,7 @@ public class ScriptRuntimeContext
             _gateway = gateway;
             _instanceName = instanceName;
             _logger = logger;
+            _auditCorrelationId = auditCorrelationId;
             _auditWriter = auditWriter;
             _siteId = siteId;
             _sourceScript = sourceScript;
@@ -969,7 +1048,8 @@ public class ScriptRuntimeContext
                 siteId: _siteId,
                 instanceName: _instanceName,
                 sourceScript: _sourceScript,
-                logger: _logger);
+                logger: _logger,
+                auditCorrelationId: _auditCorrelationId);
         }
 
         /// <summary>
@@ -1355,7 +1435,10 @@ public class ScriptRuntimeContext
                     SourceSiteId = string.IsNullOrEmpty(_siteId) ? null : _siteId,
                     SourceInstanceId = _instanceName,
                     SourceScript = _sourceScript,
-                    Actor = null,
+                    // Outbound channel: per the Audit Log Actor-column spec the
+                    // actor is the calling script. Null when no single script
+                    // owns the call (e.g. a shared script running inline).
+                    Actor = _sourceScript,
                     Target = _listName,
                     Status = AuditStatus.Submitted,
                     HttpStatus = null,

tests/ScadaLink.AuditLog.Tests/Integration/AuditWriteFailureSafetyTests.cs

@@ -150,6 +150,7 @@ public class AuditWriteFailureSafetyTests : TestKit, IClassFixture<MsSqlMigratio
             client,
             instanceName: "Plant.Pump42",
             NullLogger.Instance,
+            Guid.NewGuid(),
             auditWriter: writer,
             siteId: "site-77",
             sourceScript: "ScriptActor:Sync",
@@ -193,6 +194,7 @@ public class AuditWriteFailureSafetyTests : TestKit, IClassFixture<MsSqlMigratio
             client,
             instanceName: "Plant.Pump42",
             NullLogger.Instance,
+            Guid.NewGuid(),
             auditWriter: writer,
             siteId: "site-77",
             sourceScript: "ScriptActor:Cached",
@@ -243,6 +245,7 @@ public class AuditWriteFailureSafetyTests : TestKit, IClassFixture<MsSqlMigratio
             gateway,
             instanceName,
             NullLogger.Instance,
+            Guid.NewGuid(),
             auditWriter: writer,
             siteId: "site-77",
             sourceScript: "ScriptActor:Db",

tests/ScadaLink.AuditLog.Tests/Integration/DatabaseSyncEmissionEndToEndTests.cs

@@ -157,6 +157,7 @@ public class DatabaseSyncEmissionEndToEndTests : TestKit, IClassFixture<MsSqlMig
             gateway,
             InstanceName,
             NullLogger.Instance,
+            Guid.NewGuid(),
             auditWriter: writer,
             siteId: siteId,
             sourceScript: SourceScript,

tests/ScadaLink.CentralUI.PlaywrightTests/Audit/AuditLogPageTests.cs

@@ -16,7 +16,7 @@ namespace ScadaLink.CentralUI.PlaywrightTests.Audit;
 /// <para>
 /// Scenarios covered (per the M7-T16 brief):
 /// <list type="bullet">
-///   <item><c>FilterNarrowing</c> — channel chip narrows the results grid.</item>
+///   <item><c>FilterNarrowing</c> — the channel filter narrows the results grid.</item>
 ///   <item><c>DrilldownDrawer_JsonPrettyPrint</c> — JSON request bodies pretty-print.</item>
 ///   <item><c>CopyAsCurlButton_VisibleOnApiInbound</c> — cURL action visible for API rows.</item>
 ///   <item><c>DrillInFromCorrelationId_AutoLoadsAuditLog</c> — query-string drill-in
@@ -45,7 +45,7 @@ public class AuditLogPageTests
     }
 
     [Fact]
-    public async Task FilterNarrowing_ChannelChipShrinksGrid()
+    public async Task FilterNarrowing_ChannelFilterShrinksGrid()
     {
         // Skip with a clear message when MSSQL is not reachable — the rest of
         // the Playwright suite is UI-only and does not need the DB, so this
@@ -91,13 +91,13 @@ public class AuditLogPageTests
             await page.WaitForLoadStateAsync(LoadState.NetworkIdle);
 
             // Pre-Apply, both rows are absent because the grid stays empty until
-            // the user filters. Click the ApiOutbound chip then Apply.
-            await page.Locator("[data-test='chip-channel-ApiOutbound']").ClickAsync();
+            // the user filters. Pick the ApiOutbound channel, then Apply.
+            await page.Locator("[data-test='filter-channel-select']").SelectOptionAsync("ApiOutbound");
             await page.Locator("[data-test='filter-apply']").ClickAsync();
             await page.WaitForLoadStateAsync(LoadState.NetworkIdle);
 
             // The seeded ApiOutbound row is visible; the DbOutbound row is not
-            // (it was filtered out by the channel chip).
+            // (it was filtered out by the channel filter).
             var apiRow = page.Locator($"[data-test='grid-row-{apiEventId}']");
             var dbRow = page.Locator($"[data-test='grid-row-{dbEventId}']");
             await Assertions.Expect(apiRow).ToBeVisibleAsync();

tests/ScadaLink.CentralUI.Tests/Components/Audit/AuditFilterBarTests.cs

@@ -13,13 +13,18 @@ namespace ScadaLink.CentralUI.Tests.Components.Audit;
 /// <summary>
 /// bUnit tests for <see cref="AuditFilterBar"/> (#23 M7-T2 / Bundle B).
 ///
-/// The bar carries the 10 spec filter elements plus the Errors-only toggle. Tests
-/// pin: (1) the full filter set renders; (2) Apply raises <c>OnFilterChanged</c>
-/// with collapsed values; (3) the Channel→Kind narrowing map drives Kind chip
-/// visibility; (4) the Errors-only toggle ORs <c>Failed</c> into Status when
-/// Status is otherwise empty; (5) the "Last hour" preset populates
-/// <c>FromUtc</c> to roughly an hour before "now" — proves the time-window
-/// collapse without freezing the clock.
+/// The bar carries the 10 spec filter elements plus the Errors-only toggle.
+/// Channel is a single-select <c>&lt;select data-test="filter-channel-select"&gt;</c>;
+/// Kind / Status / Site are
+/// <see cref="ScadaLink.CentralUI.Components.Shared.MultiSelectDropdown{TValue}"/>
+/// controls whose options are checkboxes tagged
+/// <c>data-test="filter-&lt;dim&gt;-ms-opt-&lt;value&gt;"</c>. Tests pin:
+/// (1) the full filter set renders; (2) Apply raises <c>OnFilterChanged</c> with
+/// the selected values; (3) the Channel→Kind narrowing map drives Kind option
+/// visibility; (4) the Errors-only toggle ORs the error statuses into Status when
+/// Status is otherwise empty; (5) the "Last hour" preset populates <c>FromUtc</c>
+/// to roughly an hour before "now" — proves the time-window collapse without
+/// freezing the clock.
 /// </summary>
 public class AuditFilterBarTests : BunitContext
 {
@@ -71,8 +76,8 @@ public class AuditFilterBarTests : BunitContext
         var cut = Render<AuditFilterBar>(p => p
             .Add(c => c.OnFilterChanged, EventCallback.Factory.Create<AuditLogQueryFilter>(this, f => captured = f)));
 
-        // Drive UI: toggle a Channel chip, type in the Target search box, click Apply.
-        cut.Find("[data-test=\"chip-channel-ApiOutbound\"]").Click();
+        // Drive UI: pick a Channel, type in the Target search box, click Apply.
+        cut.Find("[data-test=\"filter-channel-select\"]").Change("ApiOutbound");
         cut.Find("[data-test=\"filter-target\"] input").Change("Plant-A-OPC");
         cut.Find("[data-test=\"filter-apply\"]").Click();
 
@@ -82,23 +87,25 @@ public class AuditFilterBarTests : BunitContext
     }
 
     [Fact]
-    public void Apply_WithMultipleChannelChips_PassesAllSelectedChannels()
+    public void ChangingChannel_ReplacesTheSelection_SingleSelect()
     {
-        // Task 9: ToFilter no longer collapses the chip multi-select — every
-        // selected channel chip reaches the filter's Channels list.
+        // Channel is single-select: picking a second channel replaces the first
+        // rather than adding to it (the page filters one channel at a time).
         AuditLogQueryFilter? captured = null;
         var cut = Render<AuditFilterBar>(p => p
             .Add(c => c.OnFilterChanged, EventCallback.Factory.Create<AuditLogQueryFilter>(this, f => captured = f)));
 
-        cut.Find("[data-test=\"chip-channel-ApiOutbound\"]").Click();
-        cut.Find("[data-test=\"chip-channel-Notification\"]").Click();
+        cut.Find("[data-test=\"filter-channel-select\"]").Change("ApiOutbound");
+        cut.Find("[data-test=\"filter-channel-select\"]").Change("Notification");
         cut.Find("[data-test=\"filter-apply\"]").Click();
 
         Assert.NotNull(captured);
-        Assert.NotNull(captured!.Channels);
-        Assert.Equal(2, captured.Channels!.Count);
-        Assert.Contains(AuditChannel.ApiOutbound, captured.Channels);
-        Assert.Contains(AuditChannel.Notification, captured.Channels);
+        Assert.Equal(new[] { AuditChannel.Notification }, captured!.Channels);
+
+        // Selecting "All channels" clears the channel filter entirely.
+        cut.Find("[data-test=\"filter-channel-select\"]").Change(string.Empty);
+        cut.Find("[data-test=\"filter-apply\"]").Click();
+        Assert.Null(captured!.Channels);
     }
 
     [Fact]
@@ -106,23 +113,23 @@ public class AuditFilterBarTests : BunitContext
     {
         var cut = Render<AuditFilterBar>();
 
-        // With no Channel selected, every kind chip is in the DOM.
+        // With no Channel selected, every kind option is in the DOM.
         foreach (var kind in Enum.GetValues<AuditKind>())
         {
-            Assert.Contains($"data-test=\"chip-kind-{kind}\"", cut.Markup);
+            Assert.Contains($"data-test=\"filter-kind-ms-opt-{kind}\"", cut.Markup);
         }
 
-        // Select only ApiOutbound; Kind chips outside the channel-kind map drop out.
-        cut.Find("[data-test=\"chip-channel-ApiOutbound\"]").Click();
+        // Select ApiOutbound; Kind options outside the channel-kind map drop out.
+        cut.Find("[data-test=\"filter-channel-select\"]").Change("ApiOutbound");
 
         var apiKinds = AuditQueryModel.KindsByChannel[AuditChannel.ApiOutbound];
         foreach (var kind in apiKinds)
         {
-            Assert.Contains($"data-test=\"chip-kind-{kind}\"", cut.Markup);
+            Assert.Contains($"data-test=\"filter-kind-ms-opt-{kind}\"", cut.Markup);
         }
         // Sanity: an unrelated kind is gone.
-        Assert.DoesNotContain($"data-test=\"chip-kind-{AuditKind.NotifySend}\"", cut.Markup);
-        Assert.DoesNotContain($"data-test=\"chip-kind-{AuditKind.InboundRequest}\"", cut.Markup);
+        Assert.DoesNotContain($"data-test=\"filter-kind-ms-opt-{AuditKind.NotifySend}\"", cut.Markup);
+        Assert.DoesNotContain($"data-test=\"filter-kind-ms-opt-{AuditKind.InboundRequest}\"", cut.Markup);
     }
 
     [Fact]
@@ -144,8 +151,8 @@ public class AuditFilterBarTests : BunitContext
         Assert.Contains(AuditStatus.Parked, captured.Statuses);
         Assert.Contains(AuditStatus.Discarded, captured.Statuses);
 
-        // Now pin an explicit Status chip — Errors-only must yield (chip wins).
-        cut.Find("[data-test=\"chip-status-Delivered\"]").Click();
+        // Now pin an explicit Status option — Errors-only must yield (explicit wins).
+        cut.Find("[data-test=\"filter-status-ms-opt-Delivered\"]").Change(true);
         cut.Find("[data-test=\"filter-apply\"]").Click();
 
         Assert.Equal(new[] { AuditStatus.Delivered }, captured!.Statuses);
@@ -160,8 +167,8 @@ public class AuditFilterBarTests : BunitContext
         var cut = Render<AuditFilterBar>(p => p
             .Add(c => c.OnFilterChanged, EventCallback.Factory.Create<AuditLogQueryFilter>(this, f => captured = f)));
 
-        cut.Find("[data-test=\"chip-status-Delivered\"]").Click();
-        cut.Find("[data-test=\"chip-status-Failed\"]").Click();
+        cut.Find("[data-test=\"filter-status-ms-opt-Delivered\"]").Change(true);
+        cut.Find("[data-test=\"filter-status-ms-opt-Failed\"]").Change(true);
         cut.Find("[data-test=\"filter-apply\"]").Click();
 
         Assert.NotNull(captured);

tests/ScadaLink.InboundAPI.Tests/Middleware/AuditWriteMiddlewareTests.cs

@@ -350,6 +350,46 @@ public class AuditWriteMiddlewareTests
         Assert.Equal(requestJson, evt.RequestSummary);
     }
 
+    // ---------------------------------------------------------------------
+    // Correlation id — Audit Log #23: each inbound row carries a fresh
+    // per-request correlation id so inbound rows are correlatable.
+    // ---------------------------------------------------------------------
+
+    [Fact]
+    public async Task InboundRow_CarriesNonNull_CorrelationId()
+    {
+        var writer = new RecordingAuditWriter();
+        var ctx = BuildContext();
+        var mw = CreateMiddleware(_ =>
+        {
+            ctx.Response.StatusCode = 200;
+            return Task.CompletedTask;
+        }, writer);
+
+        await mw.InvokeAsync(ctx);
+
+        var evt = Assert.Single(writer.Events);
+        Assert.NotNull(evt.CorrelationId);
+        Assert.NotEqual(Guid.Empty, evt.CorrelationId!.Value);
+    }
+
+    [Fact]
+    public async Task SeparateRequests_GetDistinct_CorrelationIds()
+    {
+        var writer = new RecordingAuditWriter();
+        var mw = CreateMiddleware(hc =>
+        {
+            hc.Response.StatusCode = 200;
+            return Task.CompletedTask;
+        }, writer);
+
+        await mw.InvokeAsync(BuildContext());
+        await mw.InvokeAsync(BuildContext());
+
+        Assert.Equal(2, writer.Events.Count);
+        Assert.NotEqual(writer.Events[0].CorrelationId, writer.Events[1].CorrelationId);
+    }
+
     [Fact]
     public async Task DurationMs_IsRecorded()
     {

tests/ScadaLink.NotificationOutbox.Tests/NotificationOutboxActorAttemptEmissionTests.cs

@@ -155,8 +155,8 @@ public class NotificationOutboxActorAttemptEmissionTests : TestKit
             Assert.Equal("site-alpha", evt.SourceSiteId);
             Assert.Equal("instance-42", evt.SourceInstanceId);
             Assert.Equal("AlarmScript", evt.SourceScript);
-            // Central dispatch: actor is null (no authenticated end-user).
-            Assert.Null(evt.Actor);
+            // Central dispatch: Actor is the system identity (no per-call user).
+            Assert.Equal("system", evt.Actor);
             // Successful attempt: no error message.
             Assert.Null(evt.ErrorMessage);
         });

tests/ScadaLink.SiteRuntime.Tests/Scripts/DatabaseCachedWriteEmissionTests.cs

@@ -47,6 +47,9 @@ public class DatabaseCachedWriteEmissionTests
             gateway,
             InstanceName,
             NullLogger.Instance,
+            // Audit Log #23: execution-wide correlation id. Cached rows keep
+            // CorrelationId = TrackedOperationId, so any value works here.
+            Guid.NewGuid(),
             siteId: SiteId,
             sourceScript: SourceScript,
             cachedForwarder: forwarder);

tests/ScadaLink.SiteRuntime.Tests/Scripts/DatabaseSyncEmissionTests.cs

@@ -48,14 +48,28 @@ public class DatabaseSyncEmissionTests
     private const string SourceScript = "ScriptActor:Sync";
     private const string ConnectionName = "machineData";
 
+    /// <summary>
+    /// Audit Log #23: a fixed execution-wide correlation id used by the
+    /// default <see cref="CreateHelper(IDatabaseGateway, IAuditWriter?)"/>
+    /// overload so assertions can compare against a known value.
+    /// </summary>
+    private static readonly Guid TestCorrelationId = Guid.NewGuid();
+
     private static ScriptRuntimeContext.DatabaseHelper CreateHelper(
         IDatabaseGateway gateway,
         IAuditWriter? auditWriter)
+        => CreateHelper(gateway, auditWriter, TestCorrelationId);
+
+    private static ScriptRuntimeContext.DatabaseHelper CreateHelper(
+        IDatabaseGateway gateway,
+        IAuditWriter? auditWriter,
+        Guid correlationId)
     {
         return new ScriptRuntimeContext.DatabaseHelper(
             gateway,
             InstanceName,
             NullLogger.Instance,
+            correlationId,
             auditWriter: auditWriter,
             siteId: SiteId,
             sourceScript: SourceScript,
@@ -266,11 +280,36 @@ public class DatabaseSyncEmissionTests
         Assert.Equal(SiteId, evt.SourceSiteId);
         Assert.Equal(InstanceName, evt.SourceInstanceId);
         Assert.Equal(SourceScript, evt.SourceScript);
-        Assert.Null(evt.Actor);
-        Assert.Null(evt.CorrelationId);
+        // Outbound channel: Actor carries the calling script identity.
+        Assert.Equal(SourceScript, evt.Actor);
+        // Audit Log #23: the sync DbWrite row now carries the execution-wide
+        // correlation id the helper was constructed with.
+        Assert.Equal(TestCorrelationId, evt.CorrelationId);
         Assert.NotEqual(Guid.Empty, evt.EventId);
     }
 
+    [Fact]
+    public async Task SyncDbWrite_StampsExecutionCorrelationId()
+    {
+        using var keepAlive = new SqliteConnection("Data Source=kc;Mode=Memory;Cache=Shared");
+        var inner = NewInMemoryDb(out var _);
+        var gateway = new Mock<IDatabaseGateway>();
+        gateway
+            .Setup(g => g.GetConnectionAsync(ConnectionName, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(inner);
+        var writer = new CapturingAuditWriter();
+        var correlationId = Guid.NewGuid();
+
+        var helper = CreateHelper(gateway.Object, writer, correlationId);
+        await using var conn = await helper.Connection(ConnectionName);
+        await using var cmd = conn.CreateCommand();
+        cmd.CommandText = "INSERT INTO t (id, name) VALUES (7, 'eta')";
+        await cmd.ExecuteNonQueryAsync();
+
+        var evt = Assert.Single(writer.Events);
+        Assert.Equal(correlationId, evt.CorrelationId);
+    }
+
     [Fact]
     public async Task DurationMs_NonZero()
     {

tests/ScadaLink.SiteRuntime.Tests/Scripts/ExecutionCorrelationContextTests.cs

@@ -0,0 +1,179 @@
+using Akka.Actor;
+using Microsoft.Data.Sqlite;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using ScadaLink.Commons.Entities.Audit;
+using ScadaLink.Commons.Interfaces.Services;
+using ScadaLink.Commons.Types.Enums;
+using ScadaLink.SiteRuntime.Scripts;
+
+namespace ScadaLink.SiteRuntime.Tests.Scripts;
+
+/// <summary>
+/// Audit Log #23 — execution-correlation tests exercised through a full
+/// <see cref="ScriptRuntimeContext"/>:
+///
+/// <list type="bullet">
+/// <item><description>
+/// The <c>?? Guid.NewGuid()</c> fallback in the <see cref="ScriptRuntimeContext"/>
+/// ctor: when no audit correlation id is supplied (tag-change / timer-triggered
+/// executions) a fresh, non-empty id is minted and stamped on the emitted rows.
+/// </description></item>
+/// <item><description>
+/// The execution-wide contract: an <c>ExternalSystem.Call</c> and a sync
+/// <c>Database</c> write performed through ONE context share a single
+/// <see cref="AuditEvent.CorrelationId"/>.
+/// </description></item>
+/// </list>
+/// </summary>
+public class ExecutionCorrelationContextTests
+{
+    /// <summary>
+    /// In-memory <see cref="IAuditWriter"/> capturing every emitted event
+    /// (mirrors the <c>CapturingAuditWriter</c> stubs in
+    /// <see cref="ExternalSystemCallAuditEmissionTests"/> /
+    /// <see cref="DatabaseSyncEmissionTests"/>).
+    /// </summary>
+    private sealed class CapturingAuditWriter : IAuditWriter
+    {
+        public List<AuditEvent> Events { get; } = new();
+
+        public Task WriteAsync(AuditEvent evt, CancellationToken ct = default)
+        {
+            Events.Add(evt);
+            return Task.CompletedTask;
+        }
+    }
+
+    private const string InstanceName = "Plant.Pump42";
+    private const string ConnectionName = "machineData";
+
+    /// <summary>
+    /// Builds a full <see cref="ScriptRuntimeContext"/> wired with the external
+    /// system client, database gateway and audit writer the cross-helper test
+    /// needs. The actor refs are <see cref="ActorRefs.Nobody"/> — the
+    /// integration helpers (ExternalSystem / Database) never touch them — and
+    /// <paramref name="auditCorrelationId"/> defaults to null so the ctor's
+    /// <c>?? Guid.NewGuid()</c> fallback is exercised unless a test supplies one.
+    /// </summary>
+    private static ScriptRuntimeContext CreateContext(
+        IExternalSystemClient? externalSystemClient,
+        IDatabaseGateway? databaseGateway,
+        IAuditWriter? auditWriter,
+        Guid? auditCorrelationId = null)
+    {
+        var compilationService = new ScriptCompilationService(
+            NullLogger<ScriptCompilationService>.Instance);
+        var sharedScriptLibrary = new SharedScriptLibrary(
+            compilationService, NullLogger<SharedScriptLibrary>.Instance);
+
+        return new ScriptRuntimeContext(
+            ActorRefs.Nobody,
+            ActorRefs.Nobody,
+            sharedScriptLibrary,
+            currentCallDepth: 0,
+            maxCallDepth: 10,
+            askTimeout: TimeSpan.FromSeconds(5),
+            instanceName: InstanceName,
+            logger: NullLogger.Instance,
+            externalSystemClient: externalSystemClient,
+            databaseGateway: databaseGateway,
+            storeAndForward: null,
+            siteCommunicationActor: null,
+            siteId: "site-77",
+            sourceScript: "ScriptActor:OnTick",
+            auditWriter: auditWriter,
+            operationTrackingStore: null,
+            cachedForwarder: null,
+            auditCorrelationId: auditCorrelationId);
+    }
+
+    /// <summary>
+    /// Spin up a fresh in-memory SQLite database with a tiny single-table
+    /// schema. The keep-alive root must outlive any auditing wrapper the test
+    /// exercises (mirrors <c>DatabaseSyncEmissionTests.NewInMemoryDb</c>).
+    /// </summary>
+    private static SqliteConnection NewInMemoryDb(out SqliteConnection keepAlive)
+    {
+        var dbName = $"db-{Guid.NewGuid():N}";
+        var connStr = $"Data Source={dbName};Mode=Memory;Cache=Shared";
+
+        keepAlive = new SqliteConnection(connStr);
+        keepAlive.Open();
+        using (var seed = keepAlive.CreateCommand())
+        {
+            seed.CommandText =
+                "CREATE TABLE t (id INTEGER PRIMARY KEY, name TEXT NOT NULL);";
+            seed.ExecuteNonQuery();
+        }
+
+        var live = new SqliteConnection(connStr);
+        live.Open();
+        return live;
+    }
+
+    [Fact]
+    public async Task NoCorrelationIdSupplied_SyncCall_StampsFreshNonEmptyCorrelationId()
+    {
+        // No auditCorrelationId argument — the ScriptRuntimeContext ctor's
+        // `?? Guid.NewGuid()` fallback must mint one (this is the unsupplied-id
+        // branch every other audit test bypasses by passing an explicit id).
+        var client = new Mock<IExternalSystemClient>();
+        client
+            .Setup(c => c.CallAsync("ERP", "GetOrder", It.IsAny<IReadOnlyDictionary<string, object?>?>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(new ExternalCallResult(true, "{}", null));
+        var writer = new CapturingAuditWriter();
+
+        var context = CreateContext(client.Object, databaseGateway: null, writer);
+        await context.ExternalSystem.Call("ERP", "GetOrder");
+
+        var evt = Assert.Single(writer.Events);
+        Assert.NotNull(evt.CorrelationId);
+        Assert.NotEqual(Guid.Empty, evt.CorrelationId!.Value);
+    }
+
+    [Fact]
+    public async Task SameContext_ApiCallAndDbWrite_ShareTheSameCorrelationId()
+    {
+        // The execution-wide contract: an ExternalSystem.Call AND a sync
+        // Database write performed through ONE ScriptRuntimeContext must both
+        // carry the same execution correlation id, so an audit reader can tie
+        // every trust-boundary action from one script run together.
+        using var keepAlive = new SqliteConnection("Data Source=ecc;Mode=Memory;Cache=Shared");
+        var innerDb = NewInMemoryDb(out var _);
+
+        var client = new Mock<IExternalSystemClient>();
+        client
+            .Setup(c => c.CallAsync("ERP", "GetOrder", It.IsAny<IReadOnlyDictionary<string, object?>?>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(new ExternalCallResult(true, "{}", null));
+
+        var gateway = new Mock<IDatabaseGateway>();
+        gateway
+            .Setup(g => g.GetConnectionAsync(ConnectionName, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(innerDb);
+
+        var writer = new CapturingAuditWriter();
+        var context = CreateContext(client.Object, gateway.Object, writer);
+
+        // 1) outbound API call through the context's ExternalSystem helper.
+        await context.ExternalSystem.Call("ERP", "GetOrder");
+
+        // 2) sync DB write through the SAME context's Database helper.
+        await using (var conn = await context.Database.Connection(ConnectionName))
+        await using (var cmd = conn.CreateCommand())
+        {
+            cmd.CommandText = "INSERT INTO t (id, name) VALUES (1, 'alpha')";
+            await cmd.ExecuteNonQueryAsync();
+        }
+
+        Assert.Equal(2, writer.Events.Count);
+        var apiRow = Assert.Single(writer.Events, e => e.Channel == AuditChannel.ApiOutbound);
+        var dbRow = Assert.Single(writer.Events, e => e.Channel == AuditChannel.DbOutbound);
+
+        Assert.NotNull(apiRow.CorrelationId);
+        Assert.NotEqual(Guid.Empty, apiRow.CorrelationId!.Value);
+        // The ApiCall row and the DbWrite row, emitted by two different helpers
+        // resolved off one context, carry the identical execution correlation id.
+        Assert.Equal(apiRow.CorrelationId, dbRow.CorrelationId);
+    }
+}

tests/ScadaLink.SiteRuntime.Tests/Scripts/ExternalSystemCachedCallEmissionTests.cs

@@ -49,6 +49,9 @@ public class ExternalSystemCachedCallEmissionTests
             client,
             InstanceName,
             NullLogger.Instance,
+            // Audit Log #23: execution-wide correlation id. Cached rows keep
+            // CorrelationId = TrackedOperationId, so any value works here.
+            Guid.NewGuid(),
             auditWriter: null,
             siteId: SiteId,
             sourceScript: SourceScript,
@@ -94,6 +97,42 @@ public class ExternalSystemCachedCallEmissionTests
         Assert.Null(packet.Operational.TerminalAtUtc);
     }
 
+    [Fact]
+    public async Task CachedCall_ImmediateCompletion_CapturesRequestArgs_AndResponseBody()
+    {
+        var client = new Mock<IExternalSystemClient>();
+        client
+            .Setup(c => c.CachedCallAsync(
+                "ERP", "GetOrder",
+                It.IsAny<IReadOnlyDictionary<string, object?>?>(),
+                InstanceName,
+                It.IsAny<CancellationToken>(),
+                It.IsAny<TrackedOperationId?>()))
+            .ReturnsAsync(new ExternalCallResult(true, "{\"ok\":true}", null, WasBuffered: false));
+        var forwarder = new CapturingForwarder();
+
+        var helper = CreateHelper(client.Object, forwarder);
+        var args = new Dictionary<string, object?> { ["orderId"] = 42 };
+        await helper.CachedCall("ERP", "GetOrder", args);
+
+        // Immediate completion (WasBuffered=false) emits Submit, Attempted, Resolve.
+        Assert.Equal(3, forwarder.Telemetry.Count);
+        var submit = forwarder.Telemetry.Single(t => t.Audit.Kind == AuditKind.CachedSubmit);
+        var attempted = forwarder.Telemetry.Single(t => t.Audit.Kind == AuditKind.ApiCallCached);
+        var resolve = forwarder.Telemetry.Single(t => t.Audit.Kind == AuditKind.CachedResolve);
+
+        // Every row carries the request args; the two post-call rows also carry
+        // the response body (Submit precedes the call, so it has no response).
+        Assert.Equal("{\"orderId\":42}", submit.Audit.RequestSummary);
+        Assert.Null(submit.Audit.ResponseSummary);
+
+        Assert.Equal("{\"orderId\":42}", attempted.Audit.RequestSummary);
+        Assert.Equal("{\"ok\":true}", attempted.Audit.ResponseSummary);
+
+        Assert.Equal("{\"orderId\":42}", resolve.Audit.RequestSummary);
+        Assert.Equal("{\"ok\":true}", resolve.Audit.ResponseSummary);
+    }
+
     [Fact]
     public async Task CachedCall_ReturnsTrackedOperationId()
     {

tests/ScadaLink.SiteRuntime.Tests/Scripts/ExternalSystemCallAuditEmissionTests.cs

@@ -45,14 +45,28 @@ public class ExternalSystemCallAuditEmissionTests
     private const string InstanceName = "Plant.Pump42";
     private const string SourceScript = "ScriptActor:CheckPressure";
 
+    /// <summary>
+    /// Audit Log #23: a fixed execution-wide correlation id used by the
+    /// default <see cref="CreateHelper(IExternalSystemClient, IAuditWriter?)"/>
+    /// overload so assertions can compare against a known value.
+    /// </summary>
+    private static readonly Guid TestCorrelationId = Guid.NewGuid();
+
     private static ScriptRuntimeContext.ExternalSystemHelper CreateHelper(
         IExternalSystemClient client,
         IAuditWriter? auditWriter)
+        => CreateHelper(client, auditWriter, TestCorrelationId);
+
+    private static ScriptRuntimeContext.ExternalSystemHelper CreateHelper(
+        IExternalSystemClient client,
+        IAuditWriter? auditWriter,
+        Guid correlationId)
     {
         return new ScriptRuntimeContext.ExternalSystemHelper(
             client,
             InstanceName,
             NullLogger.Instance,
+            correlationId,
             auditWriter,
             SiteId,
             SourceScript);
@@ -81,6 +95,29 @@ public class ExternalSystemCallAuditEmissionTests
         Assert.Equal(DateTimeKind.Utc, evt.OccurredAtUtc.Kind);
         Assert.NotEqual(Guid.Empty, evt.EventId);
         Assert.False(evt.PayloadTruncated);
+        // No call arguments → null request summary; the response body is captured.
+        Assert.Null(evt.RequestSummary);
+        Assert.Equal("{}", evt.ResponseSummary);
+    }
+
+    [Fact]
+    public async Task Call_CapturesRequestArgs_AndResponseBody_OnTheAuditRow()
+    {
+        var client = new Mock<IExternalSystemClient>();
+        client
+            .Setup(c => c.CallAsync("Weather", "GetCurrent", It.IsAny<IReadOnlyDictionary<string, object?>?>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(new ExternalCallResult(true, "{\"tempC\":11.4}", null));
+        var writer = new CapturingAuditWriter();
+
+        var helper = CreateHelper(client.Object, writer);
+        var args = new Dictionary<string, object?> { ["city"] = "Dublin" };
+        await helper.Call("Weather", "GetCurrent", args);
+
+        var evt = Assert.Single(writer.Events);
+        // RequestSummary is the serialized argument dictionary; ResponseSummary
+        // is the verbatim response body. (Cap + redaction are the writer's job.)
+        Assert.Equal("{\"city\":\"Dublin\"}", evt.RequestSummary);
+        Assert.Equal("{\"tempC\":11.4}", evt.ResponseSummary);
     }
 
     [Fact]
@@ -186,8 +223,49 @@ public class ExternalSystemCallAuditEmissionTests
         Assert.Equal(SiteId, evt.SourceSiteId);
         Assert.Equal(InstanceName, evt.SourceInstanceId);
         Assert.Equal(SourceScript, evt.SourceScript);
-        Assert.Null(evt.Actor);
-        Assert.Null(evt.CorrelationId);
+        // Outbound channel: Actor carries the calling script identity.
+        Assert.Equal(SourceScript, evt.Actor);
+        // Audit Log #23: the sync ApiCall row now carries the execution-wide
+        // correlation id the helper was constructed with.
+        Assert.Equal(TestCorrelationId, evt.CorrelationId);
+    }
+
+    [Fact]
+    public async Task Call_SyncApiCall_StampsExecutionCorrelationId()
+    {
+        var client = new Mock<IExternalSystemClient>();
+        client
+            .Setup(c => c.CallAsync("ERP", "GetOrder", It.IsAny<IReadOnlyDictionary<string, object?>?>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(new ExternalCallResult(true, "{}", null));
+        var writer = new CapturingAuditWriter();
+        var correlationId = Guid.NewGuid();
+
+        var helper = CreateHelper(client.Object, writer, correlationId);
+        await helper.Call("ERP", "GetOrder");
+
+        var evt = Assert.Single(writer.Events);
+        Assert.Equal(correlationId, evt.CorrelationId);
+    }
+
+    [Fact]
+    public async Task Call_TwoCallsOnSameHelper_ShareTheSameCorrelationId()
+    {
+        var client = new Mock<IExternalSystemClient>();
+        client
+            .Setup(c => c.CallAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<IReadOnlyDictionary<string, object?>?>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(new ExternalCallResult(true, "{}", null));
+        var writer = new CapturingAuditWriter();
+        var correlationId = Guid.NewGuid();
+
+        var helper = CreateHelper(client.Object, writer, correlationId);
+        await helper.Call("ERP", "GetOrder");
+        await helper.Call("ERP", "GetCustomer");
+
+        Assert.Equal(2, writer.Events.Count);
+        // Both sync ApiCall rows from one execution carry the same id.
+        Assert.Equal(correlationId, writer.Events[0].CorrelationId);
+        Assert.Equal(correlationId, writer.Events[1].CorrelationId);
+        Assert.Equal(writer.Events[0].CorrelationId, writer.Events[1].CorrelationId);
     }
 
     [Fact]

tests/ScadaLink.SiteRuntime.Tests/Scripts/NotifySendAuditEmissionTests.cs

@@ -127,7 +127,8 @@ public class NotifySendAuditEmissionTests : TestKit, IAsyncLifetime, IDisposable
         Assert.Null(evt.HttpStatus);
         Assert.Null(evt.ErrorMessage);
         Assert.Null(evt.ErrorDetail);
-        Assert.Null(evt.Actor);
+        // Outbound channel: Actor carries the calling script identity.
+        Assert.Equal(SourceScript, evt.Actor);
     }
 
     [Fact]
@@ -199,7 +200,8 @@ public class NotifySendAuditEmissionTests : TestKit, IAsyncLifetime, IDisposable
         Assert.Equal(SiteId, evt.SourceSiteId);
         Assert.Equal(InstanceName, evt.SourceInstanceId);
         Assert.Equal(SourceScript, evt.SourceScript);
-        Assert.Null(evt.Actor);
+        // Outbound channel: Actor carries the calling script identity.
+        Assert.Equal(SourceScript, evt.Actor);
     }
 
     [Fact]