diff --git a/src/AcDream.App/Streaming/LandblockStreamJob.cs b/src/AcDream.App/Streaming/LandblockStreamJob.cs
index aff6500..e5b9602 100644
--- a/src/AcDream.App/Streaming/LandblockStreamJob.cs
+++ b/src/AcDream.App/Streaming/LandblockStreamJob.cs
@@ -10,7 +10,7 @@ namespace AcDream.App.Streaming;
 /// </summary>
 public abstract record LandblockStreamJob(uint LandblockId)
 {
-    public sealed record Load(uint LandblockId) : LandblockStreamJob(LandblockId);
+    public sealed record Load(uint LandblockId, LandblockStreamJobKind Kind) : LandblockStreamJob(LandblockId);
     public sealed record Unload(uint LandblockId) : LandblockStreamJob(LandblockId);
 }
 
diff --git a/src/AcDream.App/Streaming/LandblockStreamer.cs b/src/AcDream.App/Streaming/LandblockStreamer.cs
index fff7fc6..a325fb6 100644
--- a/src/AcDream.App/Streaming/LandblockStreamer.cs
+++ b/src/AcDream.App/Streaming/LandblockStreamer.cs
@@ -88,7 +88,7 @@ public sealed class LandblockStreamer : IDisposable
         // Synchronous mode: invoke the load delegate inline. The result lands
         // in the outbox and DrainCompletions picks it up later in the same
         // (or next) frame.
-        HandleJob(new LandblockStreamJob.Load(landblockId));
+        HandleJob(new LandblockStreamJob.Load(landblockId, LandblockStreamJobKind.LoadNear));
     }
 
     public void EnqueueUnload(uint landblockId)
diff --git a/src/AcDream.App/Streaming/TwoTierDiff.cs b/src/AcDream.App/Streaming/TwoTierDiff.cs
new file mode 100644
index 0000000..2a24dab
--- /dev/null
+++ b/src/AcDream.App/Streaming/TwoTierDiff.cs
@@ -0,0 +1,15 @@
+using System.Collections.Generic;
+
+namespace AcDream.App.Streaming;
+
+/// <summary>
+/// Output of <see cref="StreamingRegion.RecenterTo"/> for the two-tier model.
+/// Five disjoint lists describe what changed since the previous Tick. Per
+/// Phase A.5 spec §4.2.
+/// </summary>
+public readonly record struct TwoTierDiff(
+    IReadOnlyList<uint> ToLoadFar,    // entered far window from null (terrain only)
+    IReadOnlyList<uint> ToLoadNear,   // entered near window from null (terrain + entities — first-tick or teleport)
+    IReadOnlyList<uint> ToPromote,    // entered near window from far-resident (entities only)
+    IReadOnlyList<uint> ToDemote,     // exited near window past hysteresis (drop entities)
+    IReadOnlyList<uint> ToUnload);    // exited far window past hysteresis (drop terrain)