diff --git a/src/GameCult.Mesh/CultMeshCdn.cs b/src/GameCult.Mesh/CultMeshCdn.cs
index 7aaf7eba..6ea4696f 100644
--- a/src/GameCult.Mesh/CultMeshCdn.cs
+++ b/src/GameCult.Mesh/CultMeshCdn.cs
@@ -42,7 +42,7 @@ namespace GameCult.Mesh
     public sealed class CultMeshCdnPackOptions
     {
         /// <summary>Default CDN chunk size.</summary>
-        public const int DefaultChunkSizeBytes = 256 * 1024;
+        public const int DefaultChunkSizeBytes = 4 * 1024 * 1024;
 
         /// <summary>Maximum bytes per content chunk.</summary>
         public int ChunkSizeBytes { get; set; } = DefaultChunkSizeBytes;
diff --git a/src/GameCult.Mesh/CultMeshContentTransfer.cs b/src/GameCult.Mesh/CultMeshContentTransfer.cs
index f6a426b8..b7f8c505 100644
--- a/src/GameCult.Mesh/CultMeshContentTransfer.cs
+++ b/src/GameCult.Mesh/CultMeshContentTransfer.cs
@@ -263,16 +263,37 @@ namespace GameCult.Mesh
                     {
                         await pending.Copy.ConfigureAwait(false);
                         verified.Add(pending.Item.Index);
-                        await SaveStateAsync(contentHash, fingerprint, manifest.SizeBytes, verified, stateKey).ConfigureAwait(false);
+                        await SaveStateAsync(
+                            contentHash,
+                            fingerprint,
+                            manifest.SizeBytes,
+                            verified,
+                            stateKey,
+                            flush: false).ConfigureAwait(false);
                     }
+                    await _stateCache.FlushAsync().ConfigureAwait(false);
                 }
                 catch
                 {
                     foreach (var pending in window)
                     {
-                        try { await pending.Copy.ConfigureAwait(false); }
+                        try
+                        {
+                            await pending.Copy.ConfigureAwait(false);
+                            if (verified.Add(pending.Item.Index))
+                            {
+                                await SaveStateAsync(
+                                    contentHash,
+                                    fingerprint,
+                                    manifest.SizeBytes,
+                                    verified,
+                                    stateKey,
+                                    flush: false).ConfigureAwait(false);
+                            }
+                        }
                         catch { }
                     }
+                    await _stateCache.FlushAsync().ConfigureAwait(false);
                     throw;
                 }
             }
@@ -450,7 +471,8 @@ namespace GameCult.Mesh
             string fingerprint,
             long sizeBytes,
             HashSet<int> verified,
-            CultRecordKey stateKey)
+            CultRecordKey stateKey,
+            bool flush)
         {
             var state = new CultMeshContentTransferStateDocument
             {
@@ -461,7 +483,7 @@ namespace GameCult.Mesh
                 UpdatedAtUtc = DateTimeOffset.UtcNow.ToString("O", CultureInfo.InvariantCulture)
             };
             await _stateCache.UpsertAsync(typeof(CultMeshContentTransferStateDocument), state, stateKey).ConfigureAwait(false);
-            await _stateCache.FlushAsync().ConfigureAwait(false);
+            if (flush) await _stateCache.FlushAsync().ConfigureAwait(false);
         }
 
         private static CultRecordKey StateKey(string contentHash) => new CultRecordKey("mesh:content-transfer:" + contentHash);
diff --git a/tests/GameCult.Mesh.Tests/CultMeshContentTransferTests.cs b/tests/GameCult.Mesh.Tests/CultMeshContentTransferTests.cs
index 04c6e283..6b5212c3 100644
--- a/tests/GameCult.Mesh.Tests/CultMeshContentTransferTests.cs
+++ b/tests/GameCult.Mesh.Tests/CultMeshContentTransferTests.cs
@@ -192,7 +192,7 @@ public sealed class CultMeshContentTransferTests
     }
 
     [Test]
-    public async Task FetchAsync_ObservesRemainingWindowTasksWhenEarlierFetchFails()
+    public async Task FetchAsync_CheckpointsVerifiedWindowPeersWhenEarlierFetchFails()
     {
         var artifact = Artifact("failed-window", 2);
         using var cache = Cache();
@@ -210,7 +210,8 @@ public sealed class CultMeshContentTransferTests
             .Should().ThrowAsync<InvalidDataException>();
 
         provider.ActiveRequests.Should().Be(0, "the failed window must observe every task before returning");
-        cache.Get<CultMeshContentTransferStateDocument>(StateKey(artifact.Manifest)).Should().BeNull();
+        cache.Get<CultMeshContentTransferStateDocument>(StateKey(artifact.Manifest))!
+            .VerifiedChunkIndexes.Should().Equal(1, 2);
         File.Exists(Path.Combine(_directory, artifact.Manifest.ContentHash + ".body")).Should().BeFalse();
     }