fix block history when using mirror offset

CHANGELOG.md

@@ -7,6 +7,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Fixed
 - Fix HLS Direct playback with Jellyfin 10.11
 - Fix remote stream scripts (parsing issue with spaces and quotes)
+- Fix block history being removed when it is still needed for mirror channel
+  - This caused playout build errors like "Unable to locate history for playout item"
 
 ## [25.8.0] - 2025-10-26
 ### Added

ErsatzTV.Application/Playouts/Commands/BuildPlayoutHandler.cs

@@ -367,8 +367,8 @@ public class BuildPlayoutHandler : IRequestHandler<BuildPlayout, Either<BaseErro
         {
             try
             {
-                await dbContext.PlayoutBuildStatus.AddAsync(newBuildStatus, cancellationToken);
-                await dbContext.SaveChangesAsync(cancellationToken);
+                await dbContext.PlayoutBuildStatus.AddAsync(newBuildStatus, CancellationToken.None);
+                await dbContext.SaveChangesAsync(CancellationToken.None);
             }
             catch (Exception)
             {

ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutBuilder.cs

@@ -397,7 +397,7 @@ public class BlockPlayoutBuilder(
         IEnumerable<PlayoutHistory> allItemsToDelete = referenceData.PlayoutHistory
             .GroupBy(h => h.Key)
             .SelectMany(group => group
-                .Filter(h => h.Finish < start.UtcDateTime)
+                .Filter(h => h.Finish < start.UtcDateTime - referenceData.MaxPlayoutOffset)
                 .OrderByDescending(h => h.Finish)
                 .Tail());