diff --git a/src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs b/src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs
index 5ee496b..d0dbd82 100644
--- a/src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs
+++ b/src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs
@@ -74,6 +74,11 @@ public sealed unsafe class WbDrawDispatcher : IDisposable
     // miss-populate / hit-fast-path through the loop.
     private readonly EntityClassificationCache _cache;
 
+    // ACDREAM_DISABLE_TIER1_CACHE=1 A/B diagnostic — forces every static
+    // entity through the slow path. Read once in ctor.
+    private readonly bool _tier1CacheDisabled =
+        string.Equals(Environment.GetEnvironmentVariable("ACDREAM_DISABLE_TIER1_CACHE"), "1", StringComparison.Ordinal);
+
     /// <summary>
     /// A.5 T22.5: gate for GL_SAMPLE_ALPHA_TO_COVERAGE around the opaque pass.
     /// Default true matches T20 behavior. Set false for Low/Medium presets that
@@ -423,6 +428,14 @@ public sealed unsafe class WbDrawDispatcher : IDisposable
         // some parts missing permanently. Reset on entity change.
         bool currentEntityIncomplete = false;
 
+        // Per-tuple entity tracker used purely for entity-change detection.
+        // Updated UNCONDITIONALLY at end of every tuple (including tuples that
+        // skip via null renderData), so the flag-reset block below correctly
+        // distinguishes "new entity" from "same entity, different tuple."
+        // populateEntityId can't be used for this because it's only set after
+        // a successful slow-path classification.
+        uint? prevTupleEntityId = null;
+
         foreach (var (entity, partIdx, landblockId) in _walkScratch)
         {
             if (diag) _entitiesSeen++;
@@ -454,12 +467,26 @@ public sealed unsafe class WbDrawDispatcher : IDisposable
             // the tracker so MaybeFlushOnEntityChange sees the cleaned state
             // and no-ops for this entity. Reset the incomplete flag for the
             // new entity so each one gets a fresh measurement.
-            if (populateEntityId.HasValue && populateEntityId.Value != entity.Id && currentEntityIncomplete)
+            //
+            // CRITICAL: the flag reset must fire ONLY on entity change, not
+            // every tuple. Resetting per-tuple within the same entity would
+            // undo a null-renderData flag set by a previous tuple of the same
+            // entity → if the missing MeshRef sits in the MIDDLE of the
+            // entity's MeshRefs list, a later valid tuple's reset would
+            // re-mark the entity "complete" and let partial data populate
+            // the cache. Trees with [trunk valid, branches null, leaves
+            // valid] hit this exactly — branches never recover.
+            bool isNewEntity = !prevTupleEntityId.HasValue || prevTupleEntityId.Value != entity.Id;
+            if (isNewEntity)
             {
-                _populateScratch.Clear();
-                populateEntityId = null;
+                if (populateEntityId.HasValue && currentEntityIncomplete)
+                {
+                    _populateScratch.Clear();
+                    populateEntityId = null;
+                }
+                currentEntityIncomplete = false;
             }
-            currentEntityIncomplete = false;
+            prevTupleEntityId = entity.Id;
 
             // Flush-on-entity-change: if the previous entity accumulated any
             // batches AND this iteration is for a different entity, populate
@@ -489,7 +516,7 @@ public sealed unsafe class WbDrawDispatcher : IDisposable
             // ApplyCacheHit, sets lastHitEntityId, and continues. Subsequent
             // tuples of the same entity short-circuit at the top of the loop
             // body via the lastHitEntityId == entity.Id check above.
-            if (!isAnimated && _cache.TryGet(entity.Id, landblockId, out var cachedEntry))
+            if (!isAnimated && !_tier1CacheDisabled && _cache.TryGet(entity.Id, landblockId, out var cachedEntry))
             {
                 ApplyCacheHit(cachedEntry!, entityWorld, AppendInstanceToGroup);