diff --git a/src/ScadaLink.CentralUI/Audit/AuditExportEndpoints.cs b/src/ScadaLink.CentralUI/Audit/AuditExportEndpoints.cs
index fdf34f6..4047763 100644
--- a/src/ScadaLink.CentralUI/Audit/AuditExportEndpoints.cs
+++ b/src/ScadaLink.CentralUI/Audit/AuditExportEndpoints.cs
@@ -116,10 +116,10 @@ public static class AuditExportEndpoints
         DateTime? toUtc = ParseUtcDate(query, "to");
 
         return new AuditLogQueryFilter(
-            Channel: channel,
-            Kind: kind,
-            Status: status,
-            SourceSiteId: site,
+            Channels: channel is { } c ? new[] { c } : null,
+            Kinds: kind is { } k ? new[] { k } : null,
+            Statuses: status is { } s ? new[] { s } : null,
+            SourceSiteIds: site is { } siteId ? new[] { siteId } : null,
             Target: target,
             Actor: actor,
             CorrelationId: correlationId,
diff --git a/src/ScadaLink.CentralUI/Components/Audit/AuditQueryModel.cs b/src/ScadaLink.CentralUI/Components/Audit/AuditQueryModel.cs
index 6ed9e70..f902c90 100644
--- a/src/ScadaLink.CentralUI/Components/Audit/AuditQueryModel.cs
+++ b/src/ScadaLink.CentralUI/Components/Audit/AuditQueryModel.cs
@@ -114,10 +114,10 @@ public sealed class AuditQueryModel
         var (fromUtc, toUtc) = ResolveTimeWindow(utcNow);
 
         return new AuditLogQueryFilter(
-            Channel: Channels.Count > 0 ? Channels.First() : null,
-            Kind: Kinds.Count > 0 ? Kinds.First() : null,
-            Status: status,
-            SourceSiteId: SiteIdentifiers.Count > 0 ? SiteIdentifiers.First() : null,
+            Channels: Channels.Count > 0 ? new[] { Channels.First() } : null,
+            Kinds: Kinds.Count > 0 ? new[] { Kinds.First() } : null,
+            Statuses: status is { } s ? new[] { s } : null,
+            SourceSiteIds: SiteIdentifiers.Count > 0 ? new[] { SiteIdentifiers.First() } : null,
             Target: string.IsNullOrWhiteSpace(TargetSearch) ? null : TargetSearch.Trim(),
             Actor: string.IsNullOrWhiteSpace(ActorSearch) ? null : ActorSearch.Trim(),
             CorrelationId: null,
diff --git a/src/ScadaLink.CentralUI/Components/Pages/Audit/AuditLogPage.razor.cs b/src/ScadaLink.CentralUI/Components/Pages/Audit/AuditLogPage.razor.cs
index b3c05ff..9653150 100644
--- a/src/ScadaLink.CentralUI/Components/Pages/Audit/AuditLogPage.razor.cs
+++ b/src/ScadaLink.CentralUI/Components/Pages/Audit/AuditLogPage.razor.cs
@@ -129,9 +129,9 @@ public partial class AuditLogPage
         }
 
         _currentFilter = new AuditLogQueryFilter(
-            Channel: channel,
-            Status: status,
-            SourceSiteId: site,
+            Channels: channel is { } ch ? new[] { ch } : null,
+            Statuses: status is { } st ? new[] { st } : null,
+            SourceSiteIds: site is { } siteId ? new[] { siteId } : null,
             Target: target,
             Actor: actor,
             CorrelationId: correlationId);
@@ -181,21 +181,24 @@ public partial class AuditLogPage
         }
 
         var parts = new List<KeyValuePair<string, string?>>(9);
-        if (filter.Channel is { } ch)
+        // Task 8: the filter dimensions are multi-value now; the export query-string
+        // is still single-value, so emit the first selected value of each list.
+        // Task 9 widens the query-string contract to carry the full set.
+        if (filter.Channels is { Count: > 0 } channels)
         {
-            parts.Add(new("channel", ch.ToString()));
+            parts.Add(new("channel", channels[0].ToString()));
         }
-        if (filter.Kind is { } kind)
+        if (filter.Kinds is { Count: > 0 } kinds)
         {
-            parts.Add(new("kind", kind.ToString()));
+            parts.Add(new("kind", kinds[0].ToString()));
         }
-        if (filter.Status is { } status)
+        if (filter.Statuses is { Count: > 0 } statuses)
         {
-            parts.Add(new("status", status.ToString()));
+            parts.Add(new("status", statuses[0].ToString()));
         }
-        if (!string.IsNullOrWhiteSpace(filter.SourceSiteId))
+        if (filter.SourceSiteIds is { Count: > 0 } sourceSiteIds && !string.IsNullOrWhiteSpace(sourceSiteIds[0]))
         {
-            parts.Add(new("site", filter.SourceSiteId));
+            parts.Add(new("site", sourceSiteIds[0]));
         }
         if (!string.IsNullOrWhiteSpace(filter.Target))
         {
diff --git a/src/ScadaLink.Commons/Types/Audit/AuditLogQueryFilter.cs b/src/ScadaLink.Commons/Types/Audit/AuditLogQueryFilter.cs
index 4e2001a..5399f48 100644
--- a/src/ScadaLink.Commons/Types/Audit/AuditLogQueryFilter.cs
+++ b/src/ScadaLink.Commons/Types/Audit/AuditLogQueryFilter.cs
@@ -4,16 +4,20 @@ namespace ScadaLink.Commons.Types.Audit;
 
 /// <summary>
 /// Filter predicate for <see cref="ScadaLink.Commons.Interfaces.Repositories.IAuditLogRepository.QueryAsync"/>.
-/// Any field left <c>null</c> means "do not constrain on that column". Time bounds
-/// are half-open in the spec sense — <see cref="FromUtc"/> is inclusive and
-/// <see cref="ToUtc"/> is inclusive of the upper bound; the repository SQL uses
-/// <c>&gt;=</c> / <c>&lt;=</c> respectively. All filter fields are AND-combined.
+/// Any field left <c>null</c> means "do not constrain on that column". The
+/// <see cref="Channels"/>, <see cref="Kinds"/>, <see cref="Statuses"/> and
+/// <see cref="SourceSiteIds"/> dimensions are multi-value: a <c>null</c> OR empty
+/// list means "do not constrain", and a non-empty list is OR-combined within the
+/// dimension (translated to a SQL <c>IN (…)</c>). Time bounds are half-open in
+/// the spec sense — <see cref="FromUtc"/> is inclusive and <see cref="ToUtc"/> is
+/// inclusive of the upper bound; the repository SQL uses <c>&gt;=</c> / <c>&lt;=</c>
+/// respectively. All filter dimensions are AND-combined with one another.
 /// </summary>
 public sealed record AuditLogQueryFilter(
-    AuditChannel? Channel = null,
-    AuditKind? Kind = null,
-    AuditStatus? Status = null,
-    string? SourceSiteId = null,
+    IReadOnlyList<AuditChannel>? Channels = null,
+    IReadOnlyList<AuditKind>? Kinds = null,
+    IReadOnlyList<AuditStatus>? Statuses = null,
+    IReadOnlyList<string>? SourceSiteIds = null,
     string? Target = null,
     string? Actor = null,
     Guid? CorrelationId = null,
diff --git a/src/ScadaLink.ConfigurationDatabase/Repositories/AuditLogRepository.cs b/src/ScadaLink.ConfigurationDatabase/Repositories/AuditLogRepository.cs
index f517a8e..4a6ce78 100644
--- a/src/ScadaLink.ConfigurationDatabase/Repositories/AuditLogRepository.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Repositories/AuditLogRepository.cs
@@ -116,25 +116,28 @@ VALUES
 
         var query = _context.Set<AuditEvent>().AsNoTracking();
 
-        if (filter.Channel is { } channel)
+        // Multi-value dimensions: a null OR empty list means "no constraint"
+        // (the { Count: > 0 } guard prevents an empty list collapsing to a
+        // WHERE 1=0). A non-empty list translates to a SQL IN (…) via EF Core's
+        // IReadOnlyList<T>.Contains support — server-side, no client-eval.
+        if (filter.Channels is { Count: > 0 } channels)
         {
-            query = query.Where(e => e.Channel == channel);
+            query = query.Where(e => channels.Contains(e.Channel));
         }
 
-        if (filter.Kind is { } kind)
+        if (filter.Kinds is { Count: > 0 } kinds)
         {
-            query = query.Where(e => e.Kind == kind);
+            query = query.Where(e => kinds.Contains(e.Kind));
         }
 
-        if (filter.Status is { } status)
+        if (filter.Statuses is { Count: > 0 } statuses)
         {
-            query = query.Where(e => e.Status == status);
+            query = query.Where(e => statuses.Contains(e.Status));
         }
 
-        if (!string.IsNullOrEmpty(filter.SourceSiteId))
+        if (filter.SourceSiteIds is { Count: > 0 } sourceSiteIds)
         {
-            var siteId = filter.SourceSiteId;
-            query = query.Where(e => e.SourceSiteId == siteId);
+            query = query.Where(e => e.SourceSiteId != null && sourceSiteIds.Contains(e.SourceSiteId));
         }
 
         if (!string.IsNullOrEmpty(filter.Target))
diff --git a/src/ScadaLink.ManagementService/AuditEndpoints.cs b/src/ScadaLink.ManagementService/AuditEndpoints.cs
index 18217eb..0cf58c3 100644
--- a/src/ScadaLink.ManagementService/AuditEndpoints.cs
+++ b/src/ScadaLink.ManagementService/AuditEndpoints.cs
@@ -401,11 +401,13 @@ public static class AuditEndpoints
             correlationId = parsedCorr;
         }
 
+        var sourceSiteId = TrimToNullable(query, "sourceSiteId");
+
         return new AuditLogQueryFilter(
-            Channel: channel,
-            Kind: kind,
-            Status: status,
-            SourceSiteId: TrimToNullable(query, "sourceSiteId"),
+            Channels: channel is { } c ? new[] { c } : null,
+            Kinds: kind is { } k ? new[] { k } : null,
+            Statuses: status is { } s ? new[] { s } : null,
+            SourceSiteIds: sourceSiteId is { } site ? new[] { site } : null,
             Target: TrimToNullable(query, "target"),
             Actor: TrimToNullable(query, "actor"),
             CorrelationId: correlationId,
diff --git a/tests/ScadaLink.AuditLog.Tests/Integration/DatabaseSyncEmissionEndToEndTests.cs b/tests/ScadaLink.AuditLog.Tests/Integration/DatabaseSyncEmissionEndToEndTests.cs
index 5a73256..21910f7 100644
--- a/tests/ScadaLink.AuditLog.Tests/Integration/DatabaseSyncEmissionEndToEndTests.cs
+++ b/tests/ScadaLink.AuditLog.Tests/Integration/DatabaseSyncEmissionEndToEndTests.cs
@@ -214,7 +214,7 @@ public class DatabaseSyncEmissionEndToEndTests : TestKit, IClassFixture<MsSqlMig
             await using var readContext = CreateContext();
             var readRepo = new AuditLogRepository(readContext);
             var rows = await readRepo.QueryAsync(
-                new AuditLogQueryFilter(SourceSiteId: siteId),
+                new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
                 new AuditLogPaging(PageSize: 10));
             var evt = Assert.Single(rows);
             Assert.Equal(AuditChannel.DbOutbound, evt.Channel);
@@ -282,7 +282,7 @@ public class DatabaseSyncEmissionEndToEndTests : TestKit, IClassFixture<MsSqlMig
             await using var readContext = CreateContext();
             var readRepo = new AuditLogRepository(readContext);
             var rows = await readRepo.QueryAsync(
-                new AuditLogQueryFilter(SourceSiteId: siteId),
+                new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
                 new AuditLogPaging(PageSize: 10));
             var evt = Assert.Single(rows);
             Assert.Equal(AuditChannel.DbOutbound, evt.Channel);
diff --git a/tests/ScadaLink.AuditLog.Tests/Integration/NotifyDispatcherAuditTrailTests.cs b/tests/ScadaLink.AuditLog.Tests/Integration/NotifyDispatcherAuditTrailTests.cs
index cfc5bcf..5560afa 100644
--- a/tests/ScadaLink.AuditLog.Tests/Integration/NotifyDispatcherAuditTrailTests.cs
+++ b/tests/ScadaLink.AuditLog.Tests/Integration/NotifyDispatcherAuditTrailTests.cs
@@ -241,7 +241,7 @@ public class NotifyDispatcherAuditTrailTests : TestKit, IClassFixture<MsSqlMigra
             await using var ctx = CreateContext();
             var repo = new AuditLogRepository(ctx);
             var rows = await repo.QueryAsync(
-                new AuditLogQueryFilter(SourceSiteId: siteId),
+                new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
                 new AuditLogPaging(PageSize: 50));
             // 1 Submit + 1 Attempted = 2 rows so far.
             Assert.Equal(2, rows.Count);
@@ -257,7 +257,7 @@ public class NotifyDispatcherAuditTrailTests : TestKit, IClassFixture<MsSqlMigra
             await using var ctx = CreateContext();
             var repo = new AuditLogRepository(ctx);
             var rows = await repo.QueryAsync(
-                new AuditLogQueryFilter(SourceSiteId: siteId),
+                new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
                 new AuditLogPaging(PageSize: 50));
             // 1 Submit + 2 Attempted + 1 Delivered terminal = 4 rows.
             Assert.InRange(rows.Count, 3, 4);
diff --git a/tests/ScadaLink.AuditLog.Tests/Integration/SyncCallEmissionEndToEndTests.cs b/tests/ScadaLink.AuditLog.Tests/Integration/SyncCallEmissionEndToEndTests.cs
index 3b55da3..99d5a7d 100644
--- a/tests/ScadaLink.AuditLog.Tests/Integration/SyncCallEmissionEndToEndTests.cs
+++ b/tests/ScadaLink.AuditLog.Tests/Integration/SyncCallEmissionEndToEndTests.cs
@@ -160,7 +160,7 @@ public class SyncCallEmissionEndToEndTests : TestKit, IClassFixture<MsSqlMigrati
             await using var readContext = CreateContext();
             var readRepo = new AuditLogRepository(readContext);
             var rows = await readRepo.QueryAsync(
-                new AuditLogQueryFilter(SourceSiteId: siteId),
+                new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
                 new AuditLogPaging(PageSize: 10));
             Assert.Single(rows);
             Assert.Equal(evt.EventId, rows[0].EventId);
@@ -207,7 +207,7 @@ public class SyncCallEmissionEndToEndTests : TestKit, IClassFixture<MsSqlMigrati
             await using var readContext = CreateContext();
             var readRepo = new AuditLogRepository(readContext);
             var rows = await readRepo.QueryAsync(
-                new AuditLogQueryFilter(SourceSiteId: siteId),
+                new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
                 new AuditLogPaging(PageSize: 10));
             Assert.Single(rows);
             Assert.Equal(evt.EventId, rows[0].EventId);
@@ -260,7 +260,7 @@ public class SyncCallEmissionEndToEndTests : TestKit, IClassFixture<MsSqlMigrati
             await using var readContext = CreateContext();
             var readRepo = new AuditLogRepository(readContext);
             var rows = await readRepo.QueryAsync(
-                new AuditLogQueryFilter(SourceSiteId: siteId),
+                new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
                 new AuditLogPaging(PageSize: 10));
             Assert.Single(rows);
             Assert.Equal(sharedId, rows[0].EventId);
diff --git a/tests/ScadaLink.CentralUI.Tests/Audit/AuditExportEndpointsTests.cs b/tests/ScadaLink.CentralUI.Tests/Audit/AuditExportEndpointsTests.cs
index 286198b..b91cc07 100644
--- a/tests/ScadaLink.CentralUI.Tests/Audit/AuditExportEndpointsTests.cs
+++ b/tests/ScadaLink.CentralUI.Tests/Audit/AuditExportEndpointsTests.cs
@@ -160,10 +160,10 @@ public class AuditExportEndpointsTests
 
             await repo.Received().QueryAsync(
                 Arg.Is<AuditLogQueryFilter>(f =>
-                    f.Channel == AuditChannel.ApiOutbound &&
-                    f.Kind == AuditKind.ApiCall &&
-                    f.Status == AuditStatus.Failed &&
-                    f.SourceSiteId == "plant-a" &&
+                    f.Channels != null && f.Channels.Count == 1 && f.Channels[0] == AuditChannel.ApiOutbound &&
+                    f.Kinds != null && f.Kinds.Count == 1 && f.Kinds[0] == AuditKind.ApiCall &&
+                    f.Statuses != null && f.Statuses.Count == 1 && f.Statuses[0] == AuditStatus.Failed &&
+                    f.SourceSiteIds != null && f.SourceSiteIds.Count == 1 && f.SourceSiteIds[0] == "plant-a" &&
                     f.Target == "PaymentApi" &&
                     f.Actor == "apikey-1" &&
                     f.CorrelationId == Guid.Parse(correlationId) &&
@@ -188,10 +188,10 @@ public class AuditExportEndpointsTests
 
             await repo.Received().QueryAsync(
                 Arg.Is<AuditLogQueryFilter>(f =>
-                    f.Channel == null &&
-                    f.Kind == null &&
-                    f.Status == null &&
-                    f.SourceSiteId == null &&
+                    f.Channels == null &&
+                    f.Kinds == null &&
+                    f.Statuses == null &&
+                    f.SourceSiteIds == null &&
                     f.Target == null &&
                     f.Actor == null &&
                     f.CorrelationId == null &&
@@ -216,7 +216,7 @@ public class AuditExportEndpointsTests
             _ = await response.Content.ReadAsStringAsync();
 
             await repo.Received().QueryAsync(
-                Arg.Is<AuditLogQueryFilter>(f => f.Channel == null),
+                Arg.Is<AuditLogQueryFilter>(f => f.Channels == null),
                 Arg.Any<AuditLogPaging>(),
                 Arg.Any<CancellationToken>());
         }
diff --git a/tests/ScadaLink.CentralUI.Tests/Components/Audit/AuditFilterBarTests.cs b/tests/ScadaLink.CentralUI.Tests/Components/Audit/AuditFilterBarTests.cs
index 282c49c..0c8c623 100644
--- a/tests/ScadaLink.CentralUI.Tests/Components/Audit/AuditFilterBarTests.cs
+++ b/tests/ScadaLink.CentralUI.Tests/Components/Audit/AuditFilterBarTests.cs
@@ -77,7 +77,9 @@ public class AuditFilterBarTests : BunitContext
         cut.Find("[data-test=\"filter-apply\"]").Click();
 
         Assert.NotNull(captured);
-        Assert.Equal(AuditChannel.ApiOutbound, captured!.Channel);
+        // Task 8: the filter dimension is multi-value now; ToFilter still collapses
+        // the chip selection to a single-element list (Task 9 widens that).
+        Assert.Equal(new[] { AuditChannel.ApiOutbound }, captured!.Channels);
         Assert.Equal("Plant-A-OPC", captured.Target);
     }
 
@@ -117,14 +119,14 @@ public class AuditFilterBarTests : BunitContext
         cut.Find("[data-test=\"filter-apply\"]").Click();
 
         Assert.NotNull(captured);
-        // Single-value filter contract: Failed leads the non-success set.
-        Assert.Equal(AuditStatus.Failed, captured!.Status);
+        // Single-value collapse contract (Task 8): Failed leads the non-success set.
+        Assert.Equal(new[] { AuditStatus.Failed }, captured!.Statuses);
 
         // Now pin an explicit Status chip — Errors-only must yield (chip wins).
         cut.Find("[data-test=\"chip-status-Delivered\"]").Click();
         cut.Find("[data-test=\"filter-apply\"]").Click();
 
-        Assert.Equal(AuditStatus.Delivered, captured!.Status);
+        Assert.Equal(new[] { AuditStatus.Delivered }, captured!.Statuses);
     }
 
     [Fact]
diff --git a/tests/ScadaLink.CentralUI.Tests/Pages/AuditLogPageExportUrlTests.cs b/tests/ScadaLink.CentralUI.Tests/Pages/AuditLogPageExportUrlTests.cs
index 136a929..6fad432 100644
--- a/tests/ScadaLink.CentralUI.Tests/Pages/AuditLogPageExportUrlTests.cs
+++ b/tests/ScadaLink.CentralUI.Tests/Pages/AuditLogPageExportUrlTests.cs
@@ -36,10 +36,10 @@ public class AuditLogPageExportUrlTests
     {
         var corr = Guid.Parse("aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa");
         var filter = new AuditLogQueryFilter(
-            Channel: AuditChannel.ApiOutbound,
-            Kind: AuditKind.ApiCall,
-            Status: AuditStatus.Failed,
-            SourceSiteId: "plant-a",
+            Channels: new[] { AuditChannel.ApiOutbound },
+            Kinds: new[] { AuditKind.ApiCall },
+            Statuses: new[] { AuditStatus.Failed },
+            SourceSiteIds: new[] { "plant-a" },
             Target: "PaymentApi",
             Actor: "apikey-1",
             CorrelationId: corr,
@@ -65,7 +65,7 @@ public class AuditLogPageExportUrlTests
     [Fact]
     public void BuildExportUrl_OnlyChannelSet_OmitsOtherParams()
     {
-        var filter = new AuditLogQueryFilter(Channel: AuditChannel.Notification);
+        var filter = new AuditLogQueryFilter(Channels: new[] { AuditChannel.Notification });
 
         var url = AuditLogPage.BuildExportUrl(filter);
 
diff --git a/tests/ScadaLink.CentralUI.Tests/Pages/AuditLogPageScaffoldTests.cs b/tests/ScadaLink.CentralUI.Tests/Pages/AuditLogPageScaffoldTests.cs
index 955c314..f117d20 100644
--- a/tests/ScadaLink.CentralUI.Tests/Pages/AuditLogPageScaffoldTests.cs
+++ b/tests/ScadaLink.CentralUI.Tests/Pages/AuditLogPageScaffoldTests.cs
@@ -197,7 +197,8 @@ public class AuditLogPageScaffoldTests : BunitContext
         cut.WaitForAssertion(() =>
         {
             _queryService.Received().QueryAsync(
-                Arg.Is<AuditLogQueryFilter>(f => f.SourceSiteId == "plant-a"),
+                Arg.Is<AuditLogQueryFilter>(f =>
+                    f.SourceSiteIds != null && f.SourceSiteIds.Count == 1 && f.SourceSiteIds[0] == "plant-a"),
                 Arg.Any<AuditLogPaging?>(),
                 Arg.Any<CancellationToken>());
         });
@@ -218,7 +219,8 @@ public class AuditLogPageScaffoldTests : BunitContext
         cut.WaitForAssertion(() =>
         {
             _queryService.Received().QueryAsync(
-                Arg.Is<AuditLogQueryFilter>(f => f.Status == AuditStatus.Failed),
+                Arg.Is<AuditLogQueryFilter>(f =>
+                    f.Statuses != null && f.Statuses.Count == 1 && f.Statuses[0] == AuditStatus.Failed),
                 Arg.Any<AuditLogPaging?>(),
                 Arg.Any<CancellationToken>());
         });
diff --git a/tests/ScadaLink.CentralUI.Tests/Services/AuditLogQueryServiceTests.cs b/tests/ScadaLink.CentralUI.Tests/Services/AuditLogQueryServiceTests.cs
index 3e86a0d..03e0e82 100644
--- a/tests/ScadaLink.CentralUI.Tests/Services/AuditLogQueryServiceTests.cs
+++ b/tests/ScadaLink.CentralUI.Tests/Services/AuditLogQueryServiceTests.cs
@@ -34,7 +34,7 @@ public class AuditLogQueryServiceTests
     public async Task QueryAsync_ForwardsFilterAndPaging_ToRepository()
     {
         var repo = Substitute.For<IAuditLogRepository>();
-        var filter = new AuditLogQueryFilter(Channel: AuditChannel.ApiOutbound);
+        var filter = new AuditLogQueryFilter(Channels: new[] { AuditChannel.ApiOutbound });
         var paging = new AuditLogPaging(PageSize: 25);
         var expected = new List<AuditEvent>
         {
@@ -179,7 +179,7 @@ public class AuditLogQueryServiceTests
         var scopeFactory = provider.GetRequiredService<IServiceScopeFactory>();
         var sut = new AuditLogQueryService(scopeFactory, EmptyAggregator());
 
-        var filter = new AuditLogQueryFilter(Channel: AuditChannel.ApiOutbound);
+        var filter = new AuditLogQueryFilter(Channels: new[] { AuditChannel.ApiOutbound });
 
         // Fire two QueryAsync calls in parallel. With scope-per-query each gets a
         // fresh DbContext, so this completes cleanly; with a shared scoped context
diff --git a/tests/ScadaLink.ConfigurationDatabase.Tests/Repositories/AuditLogRepositoryTests.cs b/tests/ScadaLink.ConfigurationDatabase.Tests/Repositories/AuditLogRepositoryTests.cs
index 775fb2e..0ee14f0 100644
--- a/tests/ScadaLink.ConfigurationDatabase.Tests/Repositories/AuditLogRepositoryTests.cs
+++ b/tests/ScadaLink.ConfigurationDatabase.Tests/Repositories/AuditLogRepositoryTests.cs
@@ -91,7 +91,7 @@ public class AuditLogRepositoryTests : IClassFixture<MsSqlMigrationFixture>
         await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(20)));
 
         var rows = await repo.QueryAsync(
-            new AuditLogQueryFilter(SourceSiteId: siteId),
+            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
             new AuditLogPaging(PageSize: 10));
 
         Assert.Equal(3, rows.Count);
@@ -114,13 +114,116 @@ public class AuditLogRepositoryTests : IClassFixture<MsSqlMigrationFixture>
         await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(2), channel: AuditChannel.Notification));
 
         var rows = await repo.QueryAsync(
-            new AuditLogQueryFilter(Channel: AuditChannel.Notification, SourceSiteId: siteId),
+            new AuditLogQueryFilter(
+                Channels: new[] { AuditChannel.Notification },
+                SourceSiteIds: new[] { siteId }),
             new AuditLogPaging(PageSize: 10));
 
         Assert.Equal(2, rows.Count);
         Assert.All(rows, r => Assert.Equal(AuditChannel.Notification, r.Channel));
     }
 
+    [SkippableFact]
+    public async Task QueryAsync_FilterByMultipleChannels_ReturnsUnion()
+    {
+        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+        var siteId = NewSiteId();
+        await using var context = CreateContext();
+        var repo = new AuditLogRepository(context);
+
+        var t0 = new DateTime(2026, 5, 2, 14, 0, 0, DateTimeKind.Utc);
+        // One row per channel; the multi-value filter must return the union of
+        // ApiOutbound + Notification and exclude DbOutbound.
+        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0, channel: AuditChannel.ApiOutbound));
+        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(1), channel: AuditChannel.Notification));
+        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(2), channel: AuditChannel.DbOutbound));
+
+        var rows = await repo.QueryAsync(
+            new AuditLogQueryFilter(
+                Channels: new[] { AuditChannel.ApiOutbound, AuditChannel.Notification },
+                SourceSiteIds: new[] { siteId }),
+            new AuditLogPaging(PageSize: 10));
+
+        Assert.Equal(2, rows.Count);
+        Assert.All(rows, r => Assert.Contains(r.Channel, new[] { AuditChannel.ApiOutbound, AuditChannel.Notification }));
+        Assert.DoesNotContain(rows, r => r.Channel == AuditChannel.DbOutbound);
+    }
+
+    [SkippableFact]
+    public async Task QueryAsync_FilterByMultipleStatuses_ReturnsUnion()
+    {
+        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+        var siteId = NewSiteId();
+        await using var context = CreateContext();
+        var repo = new AuditLogRepository(context);
+
+        var t0 = new DateTime(2026, 5, 2, 15, 0, 0, DateTimeKind.Utc);
+        // Failed + Parked are requested; Delivered must be excluded.
+        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0, status: AuditStatus.Failed));
+        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(1), status: AuditStatus.Parked));
+        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(2), status: AuditStatus.Delivered));
+
+        var rows = await repo.QueryAsync(
+            new AuditLogQueryFilter(
+                Statuses: new[] { AuditStatus.Failed, AuditStatus.Parked },
+                SourceSiteIds: new[] { siteId }),
+            new AuditLogPaging(PageSize: 10));
+
+        Assert.Equal(2, rows.Count);
+        Assert.All(rows, r => Assert.Contains(r.Status, new[] { AuditStatus.Failed, AuditStatus.Parked }));
+        Assert.DoesNotContain(rows, r => r.Status == AuditStatus.Delivered);
+    }
+
+    [SkippableFact]
+    public async Task QueryAsync_FilterByMultipleSourceSiteIds_ReturnsUnion()
+    {
+        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+        var siteA = NewSiteId();
+        var siteB = NewSiteId();
+        var siteC = NewSiteId();
+        await using var context = CreateContext();
+        var repo = new AuditLogRepository(context);
+
+        var t0 = new DateTime(2026, 5, 2, 16, 0, 0, DateTimeKind.Utc);
+        await repo.InsertIfNotExistsAsync(NewEvent(siteA, occurredAtUtc: t0));
+        await repo.InsertIfNotExistsAsync(NewEvent(siteB, occurredAtUtc: t0.AddMinutes(1)));
+        await repo.InsertIfNotExistsAsync(NewEvent(siteC, occurredAtUtc: t0.AddMinutes(2)));
+
+        var rows = await repo.QueryAsync(
+            new AuditLogQueryFilter(SourceSiteIds: new[] { siteA, siteB }),
+            new AuditLogPaging(PageSize: 10));
+
+        Assert.Equal(2, rows.Count);
+        Assert.All(rows, r => Assert.Contains(r.SourceSiteId, new[] { siteA, siteB }));
+        Assert.DoesNotContain(rows, r => r.SourceSiteId == siteC);
+    }
+
+    [SkippableFact]
+    public async Task QueryAsync_EmptyChannelList_DoesNotConstrain()
+    {
+        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+        var siteId = NewSiteId();
+        await using var context = CreateContext();
+        var repo = new AuditLogRepository(context);
+
+        var t0 = new DateTime(2026, 5, 2, 17, 0, 0, DateTimeKind.Utc);
+        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0, channel: AuditChannel.ApiOutbound));
+        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(1), channel: AuditChannel.Notification));
+
+        // An empty Channels list must mean "no filter" — NOT WHERE 1=0.
+        var rows = await repo.QueryAsync(
+            new AuditLogQueryFilter(
+                Channels: Array.Empty<AuditChannel>(),
+                SourceSiteIds: new[] { siteId }),
+            new AuditLogPaging(PageSize: 10));
+
+        Assert.Equal(2, rows.Count);
+    }
+
     [SkippableFact]
     public async Task QueryAsync_FilterBySourceSiteId()
     {
@@ -137,7 +240,7 @@ public class AuditLogRepositoryTests : IClassFixture<MsSqlMigrationFixture>
         await repo.InsertIfNotExistsAsync(NewEvent(otherSiteId, occurredAtUtc: t0.AddMinutes(2)));
 
         var rows = await repo.QueryAsync(
-            new AuditLogQueryFilter(SourceSiteId: siteId),
+            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
             new AuditLogPaging(PageSize: 10));
 
         Assert.Equal(2, rows.Count);
@@ -160,7 +263,7 @@ public class AuditLogRepositoryTests : IClassFixture<MsSqlMigrationFixture>
 
         var rows = await repo.QueryAsync(
             new AuditLogQueryFilter(
-                SourceSiteId: siteId,
+                SourceSiteIds: new[] { siteId },
                 FromUtc: t0.AddMinutes(10),
                 ToUtc: t0.AddHours(1)),
             new AuditLogPaging(PageSize: 10));
@@ -187,7 +290,7 @@ public class AuditLogRepositoryTests : IClassFixture<MsSqlMigrationFixture>
         }
 
         var page1 = await repo.QueryAsync(
-            new AuditLogQueryFilter(SourceSiteId: siteId),
+            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
             new AuditLogPaging(PageSize: 2));
 
         Assert.Equal(2, page1.Count);
@@ -196,7 +299,7 @@ public class AuditLogRepositoryTests : IClassFixture<MsSqlMigrationFixture>
 
         var cursor = page1[^1];
         var page2 = await repo.QueryAsync(
-            new AuditLogQueryFilter(SourceSiteId: siteId),
+            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
             new AuditLogPaging(
                 PageSize: 2,
                 AfterOccurredAtUtc: cursor.OccurredAtUtc,
@@ -208,7 +311,7 @@ public class AuditLogRepositoryTests : IClassFixture<MsSqlMigrationFixture>
 
         var cursor2 = page2[^1];
         var page3 = await repo.QueryAsync(
-            new AuditLogQueryFilter(SourceSiteId: siteId),
+            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
             new AuditLogPaging(
                 PageSize: 2,
                 AfterOccurredAtUtc: cursor2.OccurredAtUtc,
@@ -281,7 +384,7 @@ public class AuditLogRepositoryTests : IClassFixture<MsSqlMigrationFixture>
             await repo.InsertIfNotExistsAsync(e);
         }
 
-        var filter = new AuditLogQueryFilter(SourceSiteId: siteId);
+        var filter = new AuditLogQueryFilter(SourceSiteIds: new[] { siteId });
 
         var page1 = await repo.QueryAsync(filter, new AuditLogPaging(PageSize: 2));
         Assert.Equal(2, page1.Count);