diff --git a/World/Persistence/InMemoryChunkModificationStore.cs b/World/Persistence/InMemoryChunkModificationStore.cs
index 5928276..e22809c 100644
--- a/World/Persistence/InMemoryChunkModificationStore.cs
+++ b/World/Persistence/InMemoryChunkModificationStore.cs
@@ -10,7 +10,9 @@ public sealed class InMemoryChunkModificationStore : IChunkModificationStore
     {
         if (this._diffs.TryGetValue(chunkPos, out Dictionary<int, ushort>? d))
         {
-            diff = d;
+            // Returned snapshot: callers may safely retain and enumerate even
+            // after concurrent RecordEdit on the same chunk.
+            diff = new Dictionary<int, ushort>(d);
             return true;
         }
         diff = null;
diff --git a/World/Streaming/ChunkJob.cs b/World/Streaming/ChunkJob.cs
index e643aa1..58bf9fc 100644
--- a/World/Streaming/ChunkJob.cs
+++ b/World/Streaming/ChunkJob.cs
@@ -3,12 +3,12 @@ using VoxelEngine.World.Chunk;
 
 namespace VoxelEngine.World.Streaming;
 
-// Job dispatched to an IJobExecutor. For a fresh load, ExistingChunk is null
-// and the worker generates + applies diff + meshes. For a remesh-only job,
-// ExistingChunk holds the chunk and the worker only meshes (no generation).
+// Job dispatched to an IJobExecutor for a fresh chunk load. The worker
+// generates the chunk, applies any modification diff, and meshes the result.
+// Remesh-only jobs are dispatched separately by DispatchRemesh and capture
+// their state via closures, so they do not use this record.
 internal sealed record ChunkJob(
     Vector3i Pos,
-    Chunk.Chunk? ExistingChunk,
     NeighborSnapshots Neighbors,
     IReadOnlyDictionary<int, ushort>? Diff);
 
diff --git a/World/Streaming/ChunkStreamer.cs b/World/Streaming/ChunkStreamer.cs
index c9a61ca..8a4b3ea 100644
--- a/World/Streaming/ChunkStreamer.cs
+++ b/World/Streaming/ChunkStreamer.cs
@@ -299,15 +299,9 @@ public sealed class ChunkStreamer : IDisposable
     private void DispatchLoad(Vector3i pos)
     {
         NeighborSnapshots neighbors = this.SnapshotNeighbors(pos);
-        IReadOnlyDictionary<int, ushort>? diff = null;
-        if (this._world.ModificationStore.TryGetDiff(pos, out var d) && d != null)
-        {
-            // Copy: TryGetDiff returns the live internal dictionary, which the
-            // main thread may mutate via World.SetBlock while the worker iterates.
-            diff = new Dictionary<int, ushort>(d);
-        }
+        this._world.ModificationStore.TryGetDiff(pos, out IReadOnlyDictionary<int, ushort>? diff);
 
-        var job = new ChunkJob(pos, ExistingChunk: null, neighbors, diff);
+        var job = new ChunkJob(pos, neighbors, diff);
         this._inFlight++;
 
         IChunkMesher mesher = this._mesher;