feat(auditlog): wire IAuditPayloadFilter into all writer paths (#23 M5)

Bundle C task M5-T6 — plugs the IAuditPayloadFilter singleton into the
three audit writer entry points so every event is truncated + redacted
before persistence, regardless of which path it took to disk:

  - FallbackAuditWriter (site hot path): filter runs before the primary
    SQLite write AND the ring-buffer enqueue, so a recovery drain replays
    rows that are already capped/redacted.
  - CentralAuditWriter (central direct-write): filter runs before the
    per-call IAuditLogRepository.InsertIfNotExistsAsync.
  - AuditLogIngestActor (site→central telemetry):
      - OnIngestAsync resolves the filter from the per-message scope and
        applies it to each row before IngestedAtUtc stamping.
      - OnCachedTelemetryAsync (M3 dual-write) applies the filter to the
        audit half of every CachedTelemetryEntry before the audit-insert
        + site-call-upsert transaction.

Filter parameter is optional (nullable) on each constructor so the
existing test composition roots that don't pass one keep working unchanged
— production DI wiring in AddAuditLog always passes the real filter
through. ICentralAuditWriter registration switched from the open-ctor
form to a factory so the filter flows through it.

Tests: FilterIntegrationTests covers all three writer paths end-to-end
(4 tests). Full ScadaLink.AuditLog.Tests suite: 146 passed, 0 failed,
0 skipped.

src/ScadaLink.AuditLog/Central/AuditLogIngestActor.cs

@@ -1,6 +1,7 @@
 using Akka.Actor;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
+using ScadaLink.AuditLog.Payload;
 using ScadaLink.Commons.Entities.Audit;
 using ScadaLink.Commons.Interfaces.Repositories;
 using ScadaLink.Commons.Messages.Audit;
@@ -114,8 +115,15 @@ public class AuditLogIngestActor : ReceiveActor
         // Resolve the repository for the whole batch — one DbContext per
         // message, mirroring NotificationOutboxActor. The injected-repository
         // mode (Bundle D tests) skips the scope entirely.
+        // Bundle C (M5-T6): the IAuditPayloadFilter is also resolved from the
+        // per-message scope when one is available so the row is truncated +
+        // redacted before InsertIfNotExistsAsync. The single-repository test
+        // ctor has no service provider — it falls through with no filter,
+        // which preserves the small-payload assumptions baked into the
+        // existing D2 fixtures.
         IServiceScope? scope = null;
         IAuditLogRepository repository;
+        IAuditPayloadFilter? filter = null;
         if (_injectedRepository is not null)
         {
             repository = _injectedRepository;
@@ -124,6 +132,7 @@ public class AuditLogIngestActor : ReceiveActor
         {
             scope = _serviceProvider!.CreateScope();
             repository = scope.ServiceProvider.GetRequiredService<IAuditLogRepository>();
+            filter = scope.ServiceProvider.GetService<IAuditPayloadFilter>();
         }
 
         try
@@ -136,7 +145,11 @@ public class AuditLogIngestActor : ReceiveActor
                     // repository hardening already swallows duplicate-key races,
                     // so the same id arriving twice (site retry, reconciliation)
                     // is a silent no-op.
-                    var ingested = evt with { IngestedAtUtc = nowUtc };
+                    // Filter BEFORE the IngestedAtUtc stamp so the redacted
+                    // copy carries the central-side ingest timestamp. Filter
+                    // is contract-bound to never throw; null = pass-through.
+                    var filtered = filter?.Apply(evt) ?? evt;
+                    var ingested = filtered with { IngestedAtUtc = nowUtc };
                     await repository.InsertIfNotExistsAsync(ingested).ConfigureAwait(false);
                     accepted.Add(evt.EventId);
                 }
@@ -185,6 +198,12 @@ public class AuditLogIngestActor : ReceiveActor
             var auditRepo = scope.ServiceProvider.GetRequiredService<IAuditLogRepository>();
             var siteCallRepo = scope.ServiceProvider.GetRequiredService<ISiteCallAuditRepository>();
             var dbContext = scope.ServiceProvider.GetRequiredService<ScadaLinkDbContext>();
+            // Bundle C (M5-T6): resolve the filter for the whole batch from
+            // the scope; null = pass-through for test composition roots that
+            // skip the filter registration. The filter is contract-bound to
+            // never throw, so we can apply it inside the per-entry try
+            // without risking an unbounded blast radius.
+            var filter = scope.ServiceProvider.GetService<IAuditPayloadFilter>();
 
             foreach (var entry in cmd.Entries)
             {
@@ -199,7 +218,12 @@ public class AuditLogIngestActor : ReceiveActor
                     // matching timestamps (debugging convenience, not a
                     // correctness invariant).
                     var ingestedAt = DateTime.UtcNow;
-                    var auditStamped = entry.Audit with { IngestedAtUtc = ingestedAt };
+                    // Filter the audit half BEFORE the dual-write — only the
+                    // AuditLog row's payload columns are filterable; SiteCalls
+                    // carries operational state only (status, retry count) and
+                    // is left untouched.
+                    var filteredAudit = filter?.Apply(entry.Audit) ?? entry.Audit;
+                    var auditStamped = filteredAudit with { IngestedAtUtc = ingestedAt };
                     var siteCallStamped = entry.SiteCall with { IngestedAtUtc = ingestedAt };
 
                     await auditRepo.InsertIfNotExistsAsync(auditStamped)

src/ScadaLink.AuditLog/Central/CentralAuditWriter.cs

@@ -1,5 +1,6 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
+using ScadaLink.AuditLog.Payload;
 using ScadaLink.Commons.Entities.Audit;
 using ScadaLink.Commons.Interfaces.Repositories;
 using ScadaLink.Commons.Interfaces.Services;
@@ -40,11 +41,24 @@ public sealed class CentralAuditWriter : ICentralAuditWriter
 {
     private readonly IServiceProvider _services;
     private readonly ILogger<CentralAuditWriter> _logger;
+    private readonly IAuditPayloadFilter? _filter;
 
-    public CentralAuditWriter(IServiceProvider services, ILogger<CentralAuditWriter> logger)
+    /// <summary>
+    /// Bundle C (M5-T6) — the central direct-write path used by the
+    /// NotificationOutboxActor dispatch and the Inbound API middleware also
+    /// needs to truncate + redact before the row hits MS SQL. The filter is
+    /// optional so the M4 test composition roots that don't pass one keep
+    /// working (they only ever write small payloads); production DI registers
+    /// the real filter via <see cref="ServiceCollectionExtensions.AddAuditLog"/>.
+    /// </summary>
+    public CentralAuditWriter(
+        IServiceProvider services,
+        ILogger<CentralAuditWriter> logger,
+        IAuditPayloadFilter? filter = null)
     {
         _services = services ?? throw new ArgumentNullException(nameof(services));
         _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        _filter = filter;
     }
 
     /// <summary>
@@ -65,9 +79,14 @@ public sealed class CentralAuditWriter : ICentralAuditWriter
 
         try
         {
+            // Filter BEFORE stamping IngestedAtUtc + handing to the repo. The
+            // filter contract is "never throws"; the null-coalesce keeps the
+            // M4 test composition roots (no filter passed) working unchanged.
+            var filtered = _filter?.Apply(evt) ?? evt;
+
             await using var scope = _services.CreateAsyncScope();
             var repo = scope.ServiceProvider.GetRequiredService<IAuditLogRepository>();
-            var stamped = evt with { IngestedAtUtc = DateTime.UtcNow };
+            var stamped = filtered with { IngestedAtUtc = DateTime.UtcNow };
             await repo.InsertIfNotExistsAsync(stamped, ct).ConfigureAwait(false);
         }
         catch (Exception ex)

src/ScadaLink.AuditLog/ServiceCollectionExtensions.cs

@@ -106,11 +106,16 @@ public static class ServiceCollectionExtensions
         // The script-thread surface is FallbackAuditWriter (primary + ring +
         // counter), not the raw SqliteAuditWriter — primary failures must NEVER
         // abort the user-facing action.
+        // Bundle C (M5-T6): the IAuditPayloadFilter singleton above is wired
+        // through the factory so every event written through this surface is
+        // truncated + redacted before it hits SQLite (and the ring on
+        // failure).
         services.AddSingleton<IAuditWriter>(sp => new FallbackAuditWriter(
             primary: sp.GetRequiredService<SqliteAuditWriter>(),
             ring: sp.GetRequiredService<RingBufferFallback>(),
             failureCounter: sp.GetRequiredService<IAuditWriteFailureCounter>(),
-            logger: sp.GetRequiredService<ILogger<FallbackAuditWriter>>()));
+            logger: sp.GetRequiredService<ILogger<FallbackAuditWriter>>(),
+            filter: sp.GetRequiredService<IAuditPayloadFilter>()));
 
         // ISiteStreamAuditClient: NoOp default. M6's reconciliation work brings
         // the real gRPC-backed implementation (no site→central gRPC channel
@@ -155,7 +160,13 @@ public static class ServiceCollectionExtensions
         // is intentionally distinct from IAuditWriter so site composition roots
         // do not accidentally bind it; central composition roots that include
         // AddConfigurationDatabase get a working implementation transparently.
-        services.AddSingleton<ICentralAuditWriter, CentralAuditWriter>();
+        // Bundle C (M5-T6): wire the IAuditPayloadFilter into the factory so
+        // NotificationOutboxActor + Inbound API rows are truncated + redacted
+        // before they hit MS SQL.
+        services.AddSingleton<ICentralAuditWriter>(sp => new CentralAuditWriter(
+            sp,
+            sp.GetRequiredService<ILogger<CentralAuditWriter>>(),
+            sp.GetRequiredService<IAuditPayloadFilter>()));
 
         return services;
     }

src/ScadaLink.AuditLog/Site/FallbackAuditWriter.cs

@@ -1,4 +1,5 @@
 using Microsoft.Extensions.Logging;
+using ScadaLink.AuditLog.Payload;
 using ScadaLink.Commons.Entities.Audit;
 using ScadaLink.Commons.Interfaces.Services;
 
@@ -30,27 +31,48 @@ public sealed class FallbackAuditWriter : IAuditWriter
     private readonly RingBufferFallback _ring;
     private readonly IAuditWriteFailureCounter _failureCounter;
     private readonly ILogger<FallbackAuditWriter> _logger;
+    private readonly IAuditPayloadFilter? _filter;
     private readonly SemaphoreSlim _drainGate = new(1, 1);
 
+    /// <summary>
+    /// Bundle C (M5-T6) wires the singleton <see cref="IAuditPayloadFilter"/>
+    /// here so every event written via the site hot path is truncated +
+    /// header/body/SQL-param redacted before it hits both the primary SQLite
+    /// writer AND the ring fallback. The parameter is optional (defaults to
+    /// no filtering) so the long tail of test composition roots that don't
+    /// care about the filter need no change — the production
+    /// <see cref="ServiceCollectionExtensions.AddAuditLog"/> registration
+    /// always passes the real filter through.
+    /// </summary>
     public FallbackAuditWriter(
         IAuditWriter primary,
         RingBufferFallback ring,
         IAuditWriteFailureCounter failureCounter,
-        ILogger<FallbackAuditWriter> logger)
+        ILogger<FallbackAuditWriter> logger,
+        IAuditPayloadFilter? filter = null)
     {
         _primary = primary ?? throw new ArgumentNullException(nameof(primary));
         _ring = ring ?? throw new ArgumentNullException(nameof(ring));
         _failureCounter = failureCounter ?? throw new ArgumentNullException(nameof(failureCounter));
         _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        _filter = filter; // null = no-op pass-through; see WriteAsync.
     }
 
     public async Task WriteAsync(AuditEvent evt, CancellationToken ct = default)
     {
         ArgumentNullException.ThrowIfNull(evt);
 
+        // Filter once, up-front. The filtered event flows BOTH to the primary
+        // and (on failure) to the ring buffer — so a primary outage that
+        // drains later still hands the SqliteAuditWriter a row that has
+        // already been truncated and redacted. The filter contract is
+        // "MUST NOT throw"; the null-coalesce keeps test composition roots
+        // that don't wire a filter working unchanged.
+        var filtered = _filter?.Apply(evt) ?? evt;
+
         try
         {
-            await _primary.WriteAsync(evt, ct).ConfigureAwait(false);
+            await _primary.WriteAsync(filtered, ct).ConfigureAwait(false);
         }
         catch (Exception ex)
         {
@@ -62,8 +84,12 @@ public sealed class FallbackAuditWriter : IAuditWriter
             _failureCounter.Increment();
             _logger.LogWarning(ex,
                 "Primary audit writer threw; routing EventId {EventId} to drop-oldest ring.",
-                evt.EventId);
-            _ring.TryEnqueue(evt);
+                filtered.EventId);
+            // Ring stores the filtered copy so the eventual drain replays a
+            // payload that has already been capped/redacted — no second
+            // filter pass needed on recovery, and no risk of the ring
+            // holding the raw oversized blob in memory.
+            _ring.TryEnqueue(filtered);
             return;
         }
 

tests/ScadaLink.AuditLog.Tests/Payload/FilterIntegrationTests.cs

@@ -0,0 +1,301 @@
+using System.Text;
+using Akka.Actor;
+using Akka.TestKit.Xunit2;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+using NSubstitute;
+using ScadaLink.AuditLog.Central;
+using ScadaLink.AuditLog.Configuration;
+using ScadaLink.AuditLog.Payload;
+using ScadaLink.AuditLog.Site;
+using ScadaLink.Commons.Entities.Audit;
+using ScadaLink.Commons.Interfaces.Repositories;
+using ScadaLink.Commons.Interfaces.Services;
+using ScadaLink.Commons.Messages.Audit;
+using ScadaLink.Commons.Types;
+using ScadaLink.Commons.Types.Enums;
+using ScadaLink.ConfigurationDatabase;
+using ScadaLink.ConfigurationDatabase.Repositories;
+using ScadaLink.ConfigurationDatabase.Tests.Migrations;
+
+namespace ScadaLink.AuditLog.Tests.Payload;
+
+/// <summary>
+/// Bundle C (M5-T6) integration tests verifying that the
+/// <see cref="IAuditPayloadFilter"/> wires correctly into each of the three
+/// writer entry points — <see cref="FallbackAuditWriter"/> on the site hot
+/// path, <see cref="CentralAuditWriter"/> on the central direct-write path,
+/// and <see cref="AuditLogIngestActor"/> on the site→central telemetry ingest
+/// path (both the per-row <c>IngestAuditEventsCommand</c> handler and the
+/// combined <c>IngestCachedTelemetryCommand</c> dual-write handler).
+/// </summary>
+/// <remarks>
+/// Bundle B established the filter's behaviour in isolation (truncation,
+/// header redaction, body-regex redaction, SQL-parameter redaction). Bundle C
+/// proves that filtering actually happens before persistence — a 10 KB
+/// RequestSummary on a Delivered row must land on disk capped to 8192 bytes
+/// with <c>PayloadTruncated=true</c>, regardless of whether the row was
+/// written via the site's SQLite hot path, the central direct-write path, or
+/// the site→central ingest pipeline. We use the production
+/// <see cref="DefaultAuditPayloadFilter"/> through every test so the
+/// integration is real end-to-end, not a fake-filter assertion.
+/// </remarks>
+public class FilterIntegrationTests
+{
+    /// <summary>
+    /// Default-options filter — 8 KiB cap on success rows, 64 KiB on error
+    /// rows. Cached and reused; the filter is stateless w.r.t. the per-event
+    /// inputs and the regex cache is happy under sharing.
+    /// </summary>
+    private static IAuditPayloadFilter NewDefaultFilter()
+    {
+        var monitor = Microsoft.Extensions.Options.Options.Create(new AuditLogOptions());
+        return new DefaultAuditPayloadFilter(
+            new StaticMonitor(monitor.Value),
+            NullLogger<DefaultAuditPayloadFilter>.Instance);
+    }
+
+    private static AuditEvent NewEvent(string? request = null, Guid? eventId = null) => new()
+    {
+        EventId = eventId ?? Guid.NewGuid(),
+        OccurredAtUtc = new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc),
+        Channel = AuditChannel.ApiOutbound,
+        Kind = AuditKind.ApiCall,
+        // Delivered = success cap (8 KiB). Picking a success status so the
+        // 10 KB payload reliably trips the filter.
+        Status = AuditStatus.Delivered,
+        RequestSummary = request,
+        PayloadTruncated = false,
+        ForwardState = AuditForwardState.Pending,
+    };
+
+    // -- C1.1: FallbackAuditWriter applies the filter before SQLite write ----
+
+    [Fact]
+    public async Task FallbackAuditWriter_AppliesFilter_BeforeSqliteWrite()
+    {
+        var dataSource =
+            $"file:filter-fbw-{Guid.NewGuid():N}?mode=memory&cache=shared";
+        // Hold the in-memory database alive for the verifier connection —
+        // SQLite frees a Cache=Shared in-memory DB when the last connection
+        // closes, so without this keep-alive the FallbackAuditWriter's
+        // dispose would wipe the data before we could query it.
+        using var keepAlive = new SqliteConnection($"Data Source={dataSource};Cache=Shared");
+        keepAlive.Open();
+
+        var sqliteWriter = new SqliteAuditWriter(
+            Microsoft.Extensions.Options.Options.Create(new SqliteAuditWriterOptions { DatabasePath = dataSource }),
+            NullLogger<SqliteAuditWriter>.Instance,
+            connectionStringOverride: $"Data Source={dataSource};Cache=Shared");
+        await using var _disposeSqlite = sqliteWriter;
+
+        var fallback = new FallbackAuditWriter(
+            sqliteWriter,
+            new RingBufferFallback(),
+            new NoOpAuditWriteFailureCounter(),
+            NullLogger<FallbackAuditWriter>.Instance,
+            NewDefaultFilter());
+
+        var bigRequest = new string('a', 10 * 1024);
+        var evt = NewEvent(request: bigRequest);
+        await fallback.WriteAsync(evt);
+
+        // Read back via a fresh connection so we observe what actually
+        // landed in SQLite — not what the writer was handed.
+        using var verifier = new SqliteConnection($"Data Source={dataSource};Cache=Shared");
+        verifier.Open();
+        using var cmd = verifier.CreateCommand();
+        cmd.CommandText = "SELECT RequestSummary, PayloadTruncated FROM AuditLog WHERE EventId = $id;";
+        cmd.Parameters.AddWithValue("$id", evt.EventId.ToString());
+        using var reader = cmd.ExecuteReader();
+        Assert.True(reader.Read());
+        var persistedRequest = reader.GetString(0);
+        var truncatedFlag = reader.GetInt32(1);
+
+        Assert.Equal(8192, Encoding.UTF8.GetByteCount(persistedRequest));
+        Assert.Equal(1, truncatedFlag);
+    }
+
+    // -- C1.2: CentralAuditWriter applies the filter before repo insert ------
+
+    [Fact]
+    public async Task CentralAuditWriter_AppliesFilter_BeforeRepoInsert()
+    {
+        var repo = Substitute.For<IAuditLogRepository>();
+        var services = new ServiceCollection();
+        services.AddScoped(_ => repo);
+        services.AddSingleton(NewDefaultFilter());
+        var provider = services.BuildServiceProvider();
+
+        var writer = new CentralAuditWriter(
+            provider, NullLogger<CentralAuditWriter>.Instance, NewDefaultFilter());
+
+        var bigRequest = new string('b', 10 * 1024);
+        var evt = NewEvent(request: bigRequest);
+        await writer.WriteAsync(evt);
+
+        // Verify the repository saw the FILTERED event, not the raw one.
+        // The filter caps RequestSummary to 8192 bytes on a Delivered row
+        // and flags PayloadTruncated.
+        await repo.Received(1).InsertIfNotExistsAsync(
+            Arg.Is<AuditEvent>(e =>
+                e.EventId == evt.EventId
+                && e.RequestSummary != null
+                && Encoding.UTF8.GetByteCount(e.RequestSummary) == 8192
+                && e.PayloadTruncated == true),
+            Arg.Any<CancellationToken>());
+    }
+
+    // -- C1.3 + C1.4: AuditLogIngestActor applies the filter on both paths ---
+
+    public class IngestActorTests : TestKit, IClassFixture<MsSqlMigrationFixture>
+    {
+        private readonly MsSqlMigrationFixture _fixture;
+
+        public IngestActorTests(MsSqlMigrationFixture fixture)
+        {
+            _fixture = fixture;
+        }
+
+        private ScadaLinkDbContext CreateReadContext()
+        {
+            var options = new DbContextOptionsBuilder<ScadaLinkDbContext>()
+                .UseSqlServer(_fixture.ConnectionString)
+                .Options;
+            return new ScadaLinkDbContext(options);
+        }
+
+        private static string NewSiteId() =>
+            "test-bundle-c1-filter-" + Guid.NewGuid().ToString("N").Substring(0, 8);
+
+        /// <summary>
+        /// Build the IServiceProvider in the production-flavoured shape —
+        /// scoped repositories + a singleton <see cref="IAuditPayloadFilter"/>
+        /// resolved per-message from the actor's scope. Matches the
+        /// AddAuditLog registrations Bundle B established.
+        /// </summary>
+        private IServiceProvider BuildServiceProvider()
+        {
+            var services = new ServiceCollection();
+            services.AddDbContext<ScadaLinkDbContext>(opts =>
+                opts.UseSqlServer(_fixture.ConnectionString)
+                    .ConfigureWarnings(w => w.Ignore(
+                        Microsoft.EntityFrameworkCore.Diagnostics.RelationalEventId.PendingModelChangesWarning)));
+            services.AddScoped<IAuditLogRepository>(sp =>
+                new AuditLogRepository(sp.GetRequiredService<ScadaLinkDbContext>()));
+            services.AddScoped<ISiteCallAuditRepository>(sp =>
+                new SiteCallAuditRepository(sp.GetRequiredService<ScadaLinkDbContext>()));
+            services.AddSingleton(NewDefaultFilter());
+            return services.BuildServiceProvider();
+        }
+
+        [SkippableFact]
+        public async Task AuditLogIngestActor_AppliesFilter_BeforeBatchInsert()
+        {
+            Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+            var siteId = NewSiteId();
+            var bigRequest = new string('c', 10 * 1024);
+            var evt = new AuditEvent
+            {
+                EventId = Guid.NewGuid(),
+                OccurredAtUtc = new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc),
+                Channel = AuditChannel.ApiOutbound,
+                Kind = AuditKind.ApiCall,
+                Status = AuditStatus.Delivered,
+                SourceSiteId = siteId,
+                RequestSummary = bigRequest,
+                PayloadTruncated = false,
+            };
+
+            var sp = BuildServiceProvider();
+            var actor = Sys.ActorOf(Props.Create(() => new AuditLogIngestActor(
+                sp, NullLogger<AuditLogIngestActor>.Instance)));
+
+            actor.Tell(new IngestAuditEventsCommand(new[] { evt }), TestActor);
+            ExpectMsg<IngestAuditEventsReply>(TimeSpan.FromSeconds(15));
+
+            // Verify the persisted row was filtered before INSERT.
+            await using var read = CreateReadContext();
+            var row = await read.Set<AuditEvent>()
+                .SingleAsync(e => e.EventId == evt.EventId);
+            Assert.NotNull(row.RequestSummary);
+            Assert.Equal(8192, Encoding.UTF8.GetByteCount(row.RequestSummary!));
+            Assert.True(row.PayloadTruncated);
+        }
+
+        [SkippableFact]
+        public async Task AuditLogIngestActor_CachedTelemetry_AppliesFilter()
+        {
+            Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+            var siteId = NewSiteId();
+            var trackedId = TrackedOperationId.New();
+            var bigRequest = new string('d', 10 * 1024);
+            var audit = new AuditEvent
+            {
+                EventId = Guid.NewGuid(),
+                OccurredAtUtc = new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc),
+                Channel = AuditChannel.ApiOutbound,
+                Kind = AuditKind.CachedSubmit,
+                Status = AuditStatus.Submitted,
+                SourceSiteId = siteId,
+                CorrelationId = trackedId.Value,
+                RequestSummary = bigRequest,
+                PayloadTruncated = false,
+            };
+            var siteCall = new SiteCall
+            {
+                TrackedOperationId = trackedId,
+                Channel = "ApiOutbound",
+                Target = "ERP.GetOrder",
+                SourceSite = siteId,
+                Status = "Submitted",
+                RetryCount = 0,
+                CreatedAtUtc = new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc),
+                UpdatedAtUtc = new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc),
+                IngestedAtUtc = new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc),
+            };
+
+            var sp = BuildServiceProvider();
+            var actor = Sys.ActorOf(Props.Create(() => new AuditLogIngestActor(
+                sp, NullLogger<AuditLogIngestActor>.Instance)));
+
+            actor.Tell(
+                new IngestCachedTelemetryCommand(new[] { new CachedTelemetryEntry(audit, siteCall) }),
+                TestActor);
+            ExpectMsg<IngestCachedTelemetryReply>(TimeSpan.FromSeconds(15));
+
+            await using var read = CreateReadContext();
+            var auditRow = await read.Set<AuditEvent>()
+                .SingleAsync(e => e.EventId == audit.EventId);
+            Assert.NotNull(auditRow.RequestSummary);
+            // Bundle C filter must run before the dual-write transaction
+            // commits, so the persisted AuditLog row carries the truncated
+            // payload.
+            Assert.Equal(8192, Encoding.UTF8.GetByteCount(auditRow.RequestSummary!));
+            Assert.True(auditRow.PayloadTruncated);
+        }
+    }
+
+    /// <summary>
+    /// IOptionsMonitor test double — returns the same snapshot on every read,
+    /// no change-token plumbing required for these tests. Mirrors the helper
+    /// used in <c>TruncationTests</c>.
+    /// </summary>
+    private sealed class StaticMonitor : IOptionsMonitor<AuditLogOptions>
+    {
+        private readonly AuditLogOptions _value;
+
+        public StaticMonitor(AuditLogOptions value) => _value = value;
+
+        public AuditLogOptions CurrentValue => _value;
+
+        public AuditLogOptions Get(string? name) => _value;
+
+        public IDisposable? OnChange(Action<AuditLogOptions, string?> listener) => null;
+    }
+}