diff --git a/idl/GCObject.json5 b/idl/GCObject.json5
index 234b3d0..fc63bf5 100644
--- a/idl/GCObject.json5
+++ b/idl/GCObject.json5
@@ -62,10 +62,10 @@
 //        },
     ],
     nonconst_methods: [
-        // Opaque shallow_move(obj<AAllocator>>) noexcept
+        // Opaque shallow_move(obj<ACollector>) noexcept
         {
             name: "shallow_move",
-            doc: ["move instance using allocator"],
+            doc: ["move instance using collector"],
             return_type: "Opaque",
             args:[
                 {type: "obj<ACollector>", name: "gc"},
diff --git a/idl/GCObjectVisitor.json5 b/idl/GCObjectVisitor.json5
index 2e8344d..9307219 100644
--- a/idl/GCObjectVisitor.json5
+++ b/idl/GCObjectVisitor.json5
@@ -57,6 +57,22 @@
 //        },
     ],
     nonconst_methods: [
+        // void alloc_copy(void * src)
+        {
+            name: "alloc_copy",
+            doc: [
+                "allocate copy of source object at address @p src.",
+                "Source must be owned by this collector.",
+                "Increments object age"
+            ],
+            return_type: "void *",
+            args: [
+                {type: "std::byte *", name: "src"},
+            ],
+            const: false,
+            noexcept: false,
+            attributes: [],
+        },
         // void visit_child(AGCObject * iface, void ** pp_data) noexcept;
         {
             name: "visit_child",
diff --git a/include/xo/alloc2/gc/AGCObject.hpp b/include/xo/alloc2/gc/AGCObject.hpp
index 3c0fed0..098d0c5 100644
--- a/include/xo/alloc2/gc/AGCObject.hpp
+++ b/include/xo/alloc2/gc/AGCObject.hpp
@@ -67,7 +67,7 @@ public:
     virtual void _drop(Opaque d) const noexcept = 0;
 
     // nonconst methods
-    /** move instance using allocator **/
+    /** move instance using collector **/
     virtual Opaque shallow_move(Opaque data, obj<ACollector> gc)  const  noexcept = 0;
     /** Invoke fn.visit_child(iface,data) for each child GCObject pointer.
 Context: provides address of data pointer so it can be updated in place
diff --git a/include/xo/alloc2/gc/AGCObjectVisitor.hpp b/include/xo/alloc2/gc/AGCObjectVisitor.hpp
index b533076..efedbfe 100644
--- a/include/xo/alloc2/gc/AGCObjectVisitor.hpp
+++ b/include/xo/alloc2/gc/AGCObjectVisitor.hpp
@@ -55,6 +55,10 @@ public:
     virtual void _drop(Opaque d) const noexcept = 0;
 
     // nonconst methods
+    /** allocate copy of source object at address @p src.
+Source must be owned by this collector.
+Increments object age **/
+    virtual void * alloc_copy(Opaque data, std::byte * src)  = 0;
     /** visit child of a gc-aware object. May update child in-place! **/
     virtual void visit_child(Opaque data, AGCObject * iface, void ** pp_data)  const  noexcept = 0;
     ///@}
diff --git a/include/xo/alloc2/gc/IGCObjectVisitor_Any.hpp b/include/xo/alloc2/gc/IGCObjectVisitor_Any.hpp
index 287252c..7297239 100644
--- a/include/xo/alloc2/gc/IGCObjectVisitor_Any.hpp
+++ b/include/xo/alloc2/gc/IGCObjectVisitor_Any.hpp
@@ -60,6 +60,7 @@ namespace mm {
         // const methods
 
         // nonconst methods
+        [[noreturn]] void * alloc_copy(Opaque, std::byte *)  override;
         [[noreturn]] void visit_child(Opaque, AGCObject *, void **)  const  noexcept override;
 
         ///@}
diff --git a/include/xo/alloc2/gc/IGCObjectVisitor_Xfer.hpp b/include/xo/alloc2/gc/IGCObjectVisitor_Xfer.hpp
index aa9b476..2786ed4 100644
--- a/include/xo/alloc2/gc/IGCObjectVisitor_Xfer.hpp
+++ b/include/xo/alloc2/gc/IGCObjectVisitor_Xfer.hpp
@@ -44,6 +44,9 @@ namespace mm {
         // const methods
 
         // non-const methods
+        void * alloc_copy(Opaque data, std::byte * src)  override {
+            return I::alloc_copy(_dcast(data), src);
+        }
         void visit_child(Opaque data, AGCObject * iface, void ** pp_data)  const  noexcept override {
             return I::visit_child(_dcast(data), iface, pp_data);
         }
diff --git a/include/xo/alloc2/gc/RGCObjectVisitor.hpp b/include/xo/alloc2/gc/RGCObjectVisitor.hpp
index 7fbf907..b0f2f5b 100644
--- a/include/xo/alloc2/gc/RGCObjectVisitor.hpp
+++ b/include/xo/alloc2/gc/RGCObjectVisitor.hpp
@@ -74,6 +74,9 @@ public:
     // const methods
 
     // non-const methods (still const in router!)
+    void * alloc_copy(std::byte * src)  {
+        return O::iface()->alloc_copy(O::data(), src);
+    }
     void visit_child(AGCObject * iface, void ** pp_data)  noexcept {
         return O::iface()->visit_child(O::data(), iface, pp_data);
     }
diff --git a/src/alloc2/facet/IGCObjectVisitor_Any.cpp b/src/alloc2/facet/IGCObjectVisitor_Any.cpp
index 53d13ca..e60cc31 100644
--- a/src/alloc2/facet/IGCObjectVisitor_Any.cpp
+++ b/src/alloc2/facet/IGCObjectVisitor_Any.cpp
@@ -35,6 +35,12 @@ IGCObjectVisitor_Any::_valid
 
 // nonconst methods
 
+auto
+IGCObjectVisitor_Any::alloc_copy(Opaque, std::byte *)  -> void *
+{
+    _fatal();
+}
+
 auto
 IGCObjectVisitor_Any::visit_child(Opaque, AGCObject *, void **)  const  noexcept -> void
 {