diff --git a/idl/Collector.json5 b/idl/Collector.json5
index e7e53a0f..6cc82433 100644
--- a/idl/Collector.json5
+++ b/idl/Collector.json5
@@ -120,6 +120,25 @@
             noexcept: true,
             attributes: [],
         },
+        // bool report_types(obj<AAllocator> report_mm, obj<AAllocator> error_mm, obj<AGCObject> * output);
+        {
+            name: "report_object_types",
+            doc: [
+                "Report gc object types, at discretion of collector implementation.",
+                "Creates dictionary using memory from @p report_mm.",
+                "If unable to comply (e.g. oom), return runtime error allocated from @p error_mm.",
+                "Avoiding obj<AGCObject> return type to avoid #include cycle"
+            ],
+            return_type: "bool",
+            args: [
+                {type: "obj<AAllocator>", name: "report_mm"},
+                {type: "obj<AAllocator>", name: "error_mm"},
+                {type: "obj<AGCObject> *", name: "output"},
+            ],
+            const: true,
+            noexcept: true,
+            attributes: [],
+        },
     ],
     nonconst_methods: [
         // bool install_type(const AGCObject & iface)
diff --git a/include/xo/alloc2/gc/ACollector.hpp b/include/xo/alloc2/gc/ACollector.hpp
index f156a4e4..432d3820 100644
--- a/include/xo/alloc2/gc/ACollector.hpp
+++ b/include/xo/alloc2/gc/ACollector.hpp
@@ -74,6 +74,11 @@ Creates dictionary using memory from @p report_mm.
 If unable to comply (e.g. oom), return runtime error allocated from @p error_mm.
 Avoiding obj<AGCObject> return type to avoid #include cycle **/
     virtual bool report_statistics(Copaque data, obj<AAllocator> report_mm, obj<AAllocator> error_mm, obj<AGCObject> * output)  const  noexcept = 0;
+    /** Report gc object types, at discretion of collector implementation.
+Creates dictionary using memory from @p report_mm.
+If unable to comply (e.g. oom), return runtime error allocated from @p error_mm.
+Avoiding obj<AGCObject> return type to avoid #include cycle **/
+    virtual bool report_object_types(Copaque data, obj<AAllocator> report_mm, obj<AAllocator> error_mm, obj<AGCObject> * output)  const  noexcept = 0;
 
     // nonconst methods
     /** install interface @p iface for representation with typeseq @p tseq
diff --git a/include/xo/alloc2/gc/ICollector_Any.hpp b/include/xo/alloc2/gc/ICollector_Any.hpp
index 34f90356..d5789310 100644
--- a/include/xo/alloc2/gc/ICollector_Any.hpp
+++ b/include/xo/alloc2/gc/ICollector_Any.hpp
@@ -65,6 +65,7 @@ namespace mm {
         [[noreturn]] bool contains(Copaque, role, const void *)  const  noexcept override { _fatal(); }
         [[noreturn]] bool is_type_installed(Copaque, typeseq)  const  noexcept override { _fatal(); }
         [[noreturn]] bool report_statistics(Copaque, obj<AAllocator>, obj<AAllocator>, obj<AGCObject> *)  const  noexcept override { _fatal(); }
+        [[noreturn]] bool report_object_types(Copaque, obj<AAllocator>, obj<AAllocator>, obj<AGCObject> *)  const  noexcept override { _fatal(); }
 
         // nonconst methods
         [[noreturn]] bool install_type(Opaque, const AGCObject &)  override;
diff --git a/include/xo/alloc2/gc/ICollector_Xfer.hpp b/include/xo/alloc2/gc/ICollector_Xfer.hpp
index 2df60064..77cde5fc 100644
--- a/include/xo/alloc2/gc/ICollector_Xfer.hpp
+++ b/include/xo/alloc2/gc/ICollector_Xfer.hpp
@@ -64,6 +64,9 @@ namespace mm {
         bool report_statistics(Copaque data, obj<AAllocator> report_mm, obj<AAllocator> error_mm, obj<AGCObject> * output)  const  noexcept override {
             return I::report_statistics(_dcast(data), report_mm, error_mm, output);
         }
+        bool report_object_types(Copaque data, obj<AAllocator> report_mm, obj<AAllocator> error_mm, obj<AGCObject> * output)  const  noexcept override {
+            return I::report_object_types(_dcast(data), report_mm, error_mm, output);
+        }
 
         // non-const methods
         bool install_type(Opaque data, const AGCObject & iface)  override {
diff --git a/include/xo/alloc2/gc/RCollector.hpp b/include/xo/alloc2/gc/RCollector.hpp
index ad514854..be44e90e 100644
--- a/include/xo/alloc2/gc/RCollector.hpp
+++ b/include/xo/alloc2/gc/RCollector.hpp
@@ -97,6 +97,9 @@ public:
     bool report_statistics(obj<AAllocator> report_mm, obj<AAllocator> error_mm, obj<AGCObject> * output)  const  noexcept {
         return O::iface()->report_statistics(O::data(), report_mm, error_mm, output);
     }
+    bool report_object_types(obj<AAllocator> report_mm, obj<AAllocator> error_mm, obj<AGCObject> * output)  const  noexcept {
+        return O::iface()->report_object_types(O::data(), report_mm, error_mm, output);
+    }
 
     // non-const methods (still const in router!)
     bool install_type(const AGCObject & iface)  {