diff --git a/Engine/src/Renderer/SceneRenderer.cpp b/Engine/src/Renderer/SceneRenderer.cpp
index 8422b4e..1003394 100644
--- a/Engine/src/Renderer/SceneRenderer.cpp
+++ b/Engine/src/Renderer/SceneRenderer.cpp
@@ -303,8 +303,12 @@ namespace Engine
                             instanceTruncated = true;
                             return;
                         }
+                        // lookup 值 = batches 索引（此前误存 worlds 索引：
+                        // 单实体时两序号恰好恒等，多实体共享 mesh 后分叉
+                        // → batches[worldsIdx] 越界）。batch.first（GPU
+                        // firstInstance 基址）才是 worlds 索引，语义别混
                         const auto [it, inserted] = s.lookup.emplace(
-                            mesh.get(), static_cast<u32>(s.worlds.size()));
+                            mesh.get(), static_cast<u32>(s.result.batches.size()));
                         if (inserted) {
                             s.result.batches.push_back({mesh.get(),
                                 static_cast<u32>(s.worlds.size()), 0});