diff --git a/xo-alloc2/idl/GCObject.json5 b/xo-alloc2/idl/GCObject.json5
deleted file mode 100644
index e826af21..00000000
--- a/xo-alloc2/idl/GCObject.json5
+++ /dev/null
@@ -1,59 +0,0 @@
-{
-    mode: "facet",
-    includes: [],
-    namespace1: "xo",
-    namespace2: "scm",
-    facet: "GCObject",
-    detail_subdir: "detail",
-    brief: "xxx",
-    using_doxygen: true,
-    doc: [
-        "GC hooks for collector-aware data"
-    ],
-    types: [
-        // using size_type = std::size_t
-        {
-            name: "size_type",
-            doc: ["type for an amount of memory"],
-            definition: "std::size_t",
-        },
-    ],
-    const_methods: [
-        // size_type shallow_size() const noexcept
-        {
-            name: "shallow_size",
-            doc: ["memory consumption for this instance"],
-            return_type: "size_type",
-            args: [],
-            const: true,
-            noexcept: true,
-            attributes: [],
-        },
-        // Opaque shallow_copy(obj<AAllocator>>) const noexcept
-        {
-            name: "shallow_copy",
-            doc: ["copy instance using allocator"],
-            return_type: "Opaque",
-            args:[
-                {types: "obj<AAllocator>", name: "mm"},
-            ],
-            const: true,
-            noexcept: true,
-            attributes: [],
-        },
-    ],
-    nonconst_methods: [
-        // size_type forward_children(obj<ACollector>) const noexcept
-        {
-            name: "size_type",
-            doc: ["during GC: forward immdiate children"].
-            return_type: "size_type",
-            args: [
-                {types: "obj<ACollector>", name: "gc"},
-            ],
-            const: true,
-            noexcept: true,
-            attributes: [],
-        },
-    ],
-}
\ No newline at end of file
diff --git a/xo-facet/codegen/abstract_facet.hpp.j2 b/xo-facet/codegen/abstract_facet.hpp.j2
index e1fc17cf..76985b6a 100644
--- a/xo-facet/codegen/abstract_facet.hpp.j2
+++ b/xo-facet/codegen/abstract_facet.hpp.j2
@@ -43,6 +43,8 @@ public:
     // types
     /** integer identifying a type **/
     using typeseq = xo::facet::typeseq;
+    using Copaque = const void *;
+    using Opaque = void *;
     {% for ty in types %}
     /** {{ty.doc}} **/
     using {{ty.name}} = {{ty.definition}};
diff --git a/xo-facet/codegen/genfacet b/xo-facet/codegen/genfacet
index eef2eec1..788faf46 100755
--- a/xo-facet/codegen/genfacet
+++ b/xo-facet/codegen/genfacet
@@ -265,8 +265,8 @@ def gen_facet_impl(env,
     # doc section for facet
     facet_doc = '\n'.join(idl['doc'])
 
-    types = facet_idl['types']
-    for ty in types:
+    facet_types = facet_idl['types']
+    for ty in facet_types:
         ty['doc'] = '\n'.join(ty['doc'])
 
     const_methods = facet_idl['const_methods']
@@ -328,6 +328,8 @@ def gen_facet_impl(env,
     # repr_ns2: nested namespace for repr [e.g. scm].
     repr_ns2 = idl['namespace2']
 
+    # local_types: addition type defs (e.g. repr_ns2 != facet_ns2)
+    local_types = idl['local_types']
 
     # iface_facet_repr: IFoo_DRepr
     iface_facet_repr = f'{iface_facet}_{data_repr}'
@@ -379,7 +381,8 @@ def gen_facet_impl(env,
         'router_facet_hpp_j2': 'router_facet.hpp.j2',
         'router_facet_hpp_fname': router_facet_hpp_fname,
         #
-        'types': types,
+        'types': facet_types,
+        'local_types': local_types,
         #
         'const_methods': const_methods,
         #
diff --git a/xo-facet/codegen/iface_facet_repr.hpp.j2 b/xo-facet/codegen/iface_facet_repr.hpp.j2
index 55b7994b..221d6799 100644
--- a/xo-facet/codegen/iface_facet_repr.hpp.j2
+++ b/xo-facet/codegen/iface_facet_repr.hpp.j2
@@ -46,6 +46,11 @@ namespace {{repr_ns1}} {
             {% for ty in types %}
             using {{ty.name}} = {{facet_ns1}}::{{facet_ns2}}::{{abstract_facet}}::{{ty.name}};
             {% endfor %}
+            using Copaque = {{facet_ns1}}::{{facet_ns2}}::{{abstract_facet}}::Copaque;
+            using Opaque = {{facet_ns1}}::{{facet_ns2}}::{{abstract_facet}}::Opaque;
+            {% for ty in local_types %}
+            using {{ty.name}} = {{ty.definition}};
+            {% endfor %}
             {% if using_dox %}
             ///@}
             /** @defgroup {{repr_ns2}}-{{facet_name_lc}}-{{data_repr_lc}}-methods **/
diff --git a/xo-gc/idl/GCObject.json5 b/xo-gc/idl/GCObject.json5
index d35916b8..ef00b5d9 100644
--- a/xo-gc/idl/GCObject.json5
+++ b/xo-gc/idl/GCObject.json5
@@ -25,6 +25,16 @@
             doc: ["type for an amount of memory"],
             definition: "std::size_t",
         },
+        {
+            name: "AAllocator",
+            doc: ["fomo allocator type"],
+            definition: "xo::mm::AAllocator",
+        },
+        {
+            name: "ACollector",
+            doc: ["fomo collector type"],
+            definition: "xo::mm::ACollector",
+        },
     ],
     const_methods: [
         // size_type shallow_size() const noexcept
diff --git a/xo-gc/include/xo/gc/GCObject.hpp b/xo-gc/include/xo/gc/GCObject.hpp
index ebb6d26f..25834817 100644
--- a/xo-gc/include/xo/gc/GCObject.hpp
+++ b/xo-gc/include/xo/gc/GCObject.hpp
@@ -2,7 +2,7 @@
  *
  *  Generated automagically from ingredients:
  *  1. code generator:
- *       [/Users/roland/proj/xo-umbrella2/xo-facet/codegen/genfacet]
+ *       [/home/roland/proj/xo-umbrella2-claude1/xo-facet/codegen/genfacet]
  *     arguments:
  *       --input [idl/GCObject.json5]
  *  2. jinja2 template for facet .hpp file:
diff --git a/xo-gc/include/xo/gc/detail/AGCObject.hpp b/xo-gc/include/xo/gc/detail/AGCObject.hpp
index 5210dc97..b7a5ffa3 100644
--- a/xo-gc/include/xo/gc/detail/AGCObject.hpp
+++ b/xo-gc/include/xo/gc/detail/AGCObject.hpp
@@ -2,7 +2,7 @@
  *
  *  Generated automagically from ingredients:
  *  1. code generator:
- *       [/Users/roland/proj/xo-umbrella2/xo-facet/codegen/genfacet]
+ *       [/home/roland/proj/xo-umbrella2-claude1/xo-facet/codegen/genfacet]
  *     arguments:
  *       --input [idl/GCObject.json5]
  *  2. jinja2 template for abstract facet .hpp file:
@@ -40,8 +40,14 @@ public:
     // types
     /** integer identifying a type **/
     using typeseq = xo::facet::typeseq;
+    using Copaque = const void *;
+    using Opaque = void *;
     /** type for an amount of memory **/
     using size_type = std::size_t;
+    /** fomo allocator type **/
+    using AAllocator = xo::mm::AAllocator;
+    /** fomo collector type **/
+    using ACollector = xo::mm::ACollector;
     ///@}
 
     /** @defgroup mm-gcobject-methods **/
diff --git a/xo-gc/include/xo/gc/detail/IGCObject_Any.hpp b/xo-gc/include/xo/gc/detail/IGCObject_Any.hpp
index 9f086669..c930693f 100644
--- a/xo-gc/include/xo/gc/detail/IGCObject_Any.hpp
+++ b/xo-gc/include/xo/gc/detail/IGCObject_Any.hpp
@@ -2,7 +2,7 @@
  *
  *  Generated automagically from ingredients:
  *  1. code generator:
- *       [/Users/roland/proj/xo-umbrella2/xo-facet/codegen/genfacet]
+ *       [/home/roland/proj/xo-umbrella2-claude1/xo-facet/codegen/genfacet]
  *     arguments:
  *       --input [idl/GCObject.json5]
  *  2. jinja2 template for abstract facet .hpp file:
@@ -45,6 +45,8 @@ namespace mm {
         /** integer identifying a type **/
         using typeseq = xo::facet::typeseq;
         using size_type = AGCObject::size_type;
+        using AAllocator = AGCObject::AAllocator;
+        using ACollector = AGCObject::ACollector;
 
         ///@}
         /** @defgroup mm-gcobject-any-methods **/
diff --git a/xo-gc/include/xo/gc/detail/IGCObject_Xfer.hpp b/xo-gc/include/xo/gc/detail/IGCObject_Xfer.hpp
index 2ece6b01..655263bf 100644
--- a/xo-gc/include/xo/gc/detail/IGCObject_Xfer.hpp
+++ b/xo-gc/include/xo/gc/detail/IGCObject_Xfer.hpp
@@ -2,7 +2,7 @@
  *
  *  Generated automagically from ingredients:
  *  1. code generator:
- *       [/Users/roland/proj/xo-umbrella2/xo-facet/codegen/genfacet]
+ *       [/home/roland/proj/xo-umbrella2-claude1/xo-facet/codegen/genfacet]
  *     arguments:
  *       --input [idl/GCObject.json5]
  *  2. jinja2 template for abstract facet .hpp file:
@@ -32,6 +32,8 @@ namespace mm {
         /** integer identifying a type **/
         using typeseq = AGCObject::typeseq;
         using size_type = AGCObject::size_type;
+        using AAllocator = AGCObject::AAllocator;
+        using ACollector = AGCObject::ACollector;
         ///@}
 
         /** @defgroup mm-gcobject-xfer-methods **/
diff --git a/xo-gc/include/xo/gc/detail/RGCObject.hpp b/xo-gc/include/xo/gc/detail/RGCObject.hpp
index ace699c5..e54a2539 100644
--- a/xo-gc/include/xo/gc/detail/RGCObject.hpp
+++ b/xo-gc/include/xo/gc/detail/RGCObject.hpp
@@ -2,7 +2,7 @@
  *
  *  Generated automagically from ingredients:
  *  1. code generator:
- *       [/Users/roland/proj/xo-umbrella2/xo-facet/codegen/genfacet]
+ *       [/home/roland/proj/xo-umbrella2-claude1/xo-facet/codegen/genfacet]
  *     arguments:
  *       --input [idl/GCObject.json5]
  *  2. jinja2 template for abstract facet .hpp file:
@@ -32,6 +32,8 @@ public:
     using DataPtr = Object::DataPtr;
     using typeseq = xo::reflect::typeseq;
     using size_type = AGCObject::size_type;
+    using AAllocator = AGCObject::AAllocator;
+    using ACollector = AGCObject::ACollector;
     ///@}
 
     /** @defgroup mm-gcobject-router-ctors **/
diff --git a/xo-object2/CMakeLists.txt b/xo-object2/CMakeLists.txt
index 4dfdf4d8..556e6d66 100644
--- a/xo-object2/CMakeLists.txt
+++ b/xo-object2/CMakeLists.txt
@@ -64,6 +64,18 @@ xo_add_genfacetimpl(
     OUTPUT_CPP_DIR src/object2
 )
 
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-object2-facetimpl-gcobject-string
+    FACET_PKG xo_gc
+    FACET GCObject
+    REPR String
+    INPUT idl/IGCObject_DString.json5
+    OUTPUT_HPP_DIR include/xo/object2
+    OUTPUT_IMPL_SUBDIR string
+    OUTPUT_CPP_DIR src/object2
+)
+
 # ----------------------------------------------------------------
 
 # must complete definition of expression lib before configuring examples
diff --git a/xo-object2/idl/IGCObject_DString.json5 b/xo-object2/idl/IGCObject_DString.json5
new file mode 100644
index 00000000..b8fcfba5
--- /dev/null
+++ b/xo-object2/idl/IGCObject_DString.json5
@@ -0,0 +1,14 @@
+{
+    mode: "implementation",
+    includes: [ "<xo/gc/GCObject.hpp>",
+        "<xo/alloc2/Allocator.hpp>"
+    ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/GCObject.json5",
+    brief: "provide AGCObject interface for DString",
+    using_doxygen: true,
+    repr: "DString",
+    doc: [ "implement AGCObject for DString" ],
+}
diff --git a/xo-object2/include/xo/object2/DString.hpp b/xo-object2/include/xo/object2/DString.hpp
index 7f8e1eeb..accdd96d 100644
--- a/xo-object2/include/xo/object2/DString.hpp
+++ b/xo-object2/include/xo/object2/DString.hpp
@@ -6,7 +6,9 @@
 #pragma once
 
 #include <xo/alloc2/Allocator.hpp>
+#include <xo/gc/Collector.hpp>
 #include <xo/facet/obj.hpp>
+#include <xo/indentlog/print/ppindentinfo.hpp>
 #include <string_view>
 #include <cstdint>
 
@@ -38,11 +40,22 @@ namespace xo {
             using const_iterator = const char *;
             /** xo allocator **/
             using AAllocator = xo::mm::AAllocator;
-
+            /** garbage collector **/
+            using ACollector = xo::mm::ACollector;
+            /** ppindentinfo for APrintable **/
+            using ppindentinfo = xo::print::ppindentinfo;
             ///@}
             /** @defgroup dstring-ctors constructors **/
             ///@{
 
+            /** default ctor **/
+            DString() = default;
+
+            /** not simply copyable, because of flexible array.
+             *  Need allocator
+             **/
+            DString(const DString &) = delete;
+
             /** create empty string with space for @cap chars
              *  (including null terminator).
              *  Use memory from allocator @p mm
@@ -56,6 +69,17 @@ namespace xo {
             static DString * from_cstr(obj<AAllocator> mm,
                                        const char * cstr);
 
+            /** clone existing string **/
+            static DString * clone(obj<AAllocator> mm,
+                                   const DString * src);
+
+#ifdef NOT_YET
+            /** **/
+            static DString * concat(obj<AAllocator> mm,
+                                    DString * s1,
+                                    DString * s2);
+#endif
+
             ///@}
             /** @defgroup dstring-access access methods **/
             ///@{
@@ -141,6 +165,24 @@ namespace xo {
             operator const char * () const noexcept { return &(chars_[0]); }
 
             ///@}
+            /** @defgroup dstring-printable-methods printable facet methods **/
+            ///@{
+
+            bool pretty(const ppindentinfo & ppii) const;
+
+            ///@}
+            /** @defgroup dstring-gcobject-methods gcobject facet methods **/
+            ///@{
+
+            size_type shallow_size() const noexcept;
+
+            /** clone string, using memory from allocator @p mm **/
+            DString * shallow_copy(obj<AAllocator> mm) const noexcept;
+
+            /** fixup child pointers (trivial for DString, no children) **/
+            size_type forward_children(obj<ACollector> gc) noexcept;
+
+            ///@}
 
         private:
             /** @defgroup dstring-instance-variables instance variables **/
diff --git a/xo-object2/include/xo/object2/IGCObject_DString.hpp b/xo-object2/include/xo/object2/IGCObject_DString.hpp
new file mode 100644
index 00000000..ad12cb80
--- /dev/null
+++ b/xo-object2/include/xo/object2/IGCObject_DString.hpp
@@ -0,0 +1,66 @@
+/** @file IGCObject_DString.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [/home/roland/proj/xo-umbrella2-claude1/xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DString.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DString.json5]
+ **/
+
+#pragma once
+
+#include <xo/gc/GCObject.hpp>
+#include <xo/alloc2/Allocator.hpp>
+#include "DString.hpp"
+
+namespace xo { namespace scm { class IGCObject_DString; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::mm::AGCObject,
+                                   xo::scm::DString>
+        {
+            using ImplType = xo::mm::IGCObject_Xfer
+              <xo::scm::DString,
+               xo::scm::IGCObject_DString>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IGCObject_DString
+         **/
+        class IGCObject_DString {
+        public:
+            /** @defgroup scm-gcobject-dstring-type-traits **/
+            ///@{
+            using size_type = xo::mm::AGCObject::size_type;
+            using AAllocator = xo::mm::AGCObject::AAllocator;
+            using ACollector = xo::mm::AGCObject::ACollector;
+            using Copaque = xo::mm::AGCObject::Copaque;
+            using Opaque = xo::mm::AGCObject::Opaque;
+            ///@}
+            /** @defgroup scm-gcobject-dstring-methods **/
+            ///@{
+            // const methods
+            /** memory consumption for this instance **/
+            static size_type shallow_size(const DString & self) noexcept;
+            /** copy instance using allocator **/
+            static Opaque shallow_copy(const DString & self, obj<AAllocator> mm) noexcept;
+
+            // non-const methods
+            /** during GC: forward immdiate children **/
+            static size_type forward_children(DString & self, obj<ACollector> gc) noexcept;
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */
\ No newline at end of file
diff --git a/xo-object2/src/object2/CMakeLists.txt b/xo-object2/src/object2/CMakeLists.txt
index a3658925..4c74529f 100644
--- a/xo-object2/src/object2/CMakeLists.txt
+++ b/xo-object2/src/object2/CMakeLists.txt
@@ -5,6 +5,7 @@ set(SELF_SRCS
     IGCObject_DFloat.cpp
     IGCObject_DInteger.cpp
     IGCObject_DList.cpp
+    IGCObject_DString.cpp
     ISequence_Any.cpp
     ISequence_DList.cpp
     IPrintable_DList.cpp
diff --git a/xo-object2/src/object2/DString.cpp b/xo-object2/src/object2/DString.cpp
index c173d106..3278d258 100644
--- a/xo-object2/src/object2/DString.cpp
+++ b/xo-object2/src/object2/DString.cpp
@@ -52,6 +52,22 @@ namespace xo {
             return result;
         }
 
+        DString *
+        DString::clone(obj<AAllocator> mm, const DString * src)
+        {
+            size_type cap = src->capacity_;
+
+            void * mem = mm.alloc(typeseq::id<DString>(),
+                                  sizeof(DString) + cap);
+
+            DString * result = new (mem) DString();
+            result->capacity_ = cap;
+            result->size_ = src->size_;
+            std::memcpy(result->chars_, src->chars_, cap);
+
+            return result;
+        }
+
         DString &
         DString::assign(const DString & other)
         {
@@ -71,6 +87,32 @@ namespace xo {
             return this->size_;
         }
 
+        auto
+        DString::shallow_size() const noexcept -> size_type
+        {
+            return sizeof(DString) + capacity_;
+        }
+
+        DString *
+        DString::shallow_copy(obj<AAllocator> mm) const noexcept
+        {
+            DString * copy = (DString *)mm.alloc_copy((std::byte *)this);
+
+            if (copy) {
+                copy->capacity_ = capacity_;
+                copy->size_ = size_;
+                ::memcpy(copy->chars_, chars_, capacity_);
+            }
+
+            return copy;
+        }
+
+        auto
+        DString::forward_children(obj<ACollector>) noexcept -> size_type
+        {
+            return shallow_size();
+        }
+
     } /*namespace scm*/
 } /*namespace xo*/
 
diff --git a/xo-object2/src/object2/IGCObject_DString.cpp b/xo-object2/src/object2/IGCObject_DString.cpp
new file mode 100644
index 00000000..72a81244
--- /dev/null
+++ b/xo-object2/src/object2/IGCObject_DString.cpp
@@ -0,0 +1,39 @@
+/** @file IGCObject_DString.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [/home/roland/proj/xo-umbrella2-claude1/xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DString.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DString.json5]
+**/
+
+#include "IGCObject_DString.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IGCObject_DString::shallow_size(const DString & self) noexcept -> size_type
+        {
+            return self.shallow_size();
+        }
+
+        auto
+        IGCObject_DString::shallow_copy(const DString & self, obj<AAllocator> mm) noexcept -> Opaque
+        {
+            return self.shallow_copy(mm);
+        }
+
+        auto
+        IGCObject_DString::forward_children(DString & self, obj<ACollector> gc) noexcept -> size_type
+        {
+            return self.forward_children(gc);
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IGCObject_DString.cpp */
\ No newline at end of file
diff --git a/xo-object2/src/object2/object2_register_facets.cpp b/xo-object2/src/object2/object2_register_facets.cpp
index 210fb7c0..c33b0637 100644
--- a/xo-object2/src/object2/object2_register_facets.cpp
+++ b/xo-object2/src/object2/object2_register_facets.cpp
@@ -4,9 +4,11 @@
  **/
 
 #include "object2_register_facets.hpp"
+
 #include <xo/object2/IGCObject_DList.hpp>
 #include <xo/object2/IGCObject_DFloat.hpp>
 #include <xo/object2/IGCObject_DInteger.hpp>
+#include <xo/object2/IGCObject_DString.hpp>
 
 #include <xo/object2/IPrintable_DList.hpp>
 #include <xo/object2/IPrintable_DFloat.hpp>
@@ -23,6 +25,7 @@ namespace xo {
     using xo::mm::AGCObject;
     using xo::scm::DList;
     using xo::scm::DFloat;
+    using xo::scm::DString;
     using xo::facet::FacetRegistry;
     using xo::facet::typeseq;
 
@@ -41,9 +44,12 @@ namespace xo {
             FacetRegistry::register_impl<AGCObject, DInteger>();
             FacetRegistry::register_impl<APrintable, DInteger>();
 
+            FacetRegistry::register_impl<AGCObject, DString>();
+
             log && log(xtag("DList.tseq", typeseq::id<DList>()));
             log && log(xtag("DFloat.tseq", typeseq::id<DFloat>()));
             log && log(xtag("DInteger.tseq", typeseq::id<DInteger>()));
+            log && log(xtag("DString.tseq", typeseq::id<DString>()));
 
             log && log(xtag("AAllocator.tseq", typeseq::id<AAllocator>()));
             log && log(xtag("APrintable.tseq", typeseq::id<APrintable>()));
diff --git a/xo-object2/utest/DString.test.cpp b/xo-object2/utest/DString.test.cpp
index c6d217f1..b5f70f17 100644
--- a/xo-object2/utest/DString.test.cpp
+++ b/xo-object2/utest/DString.test.cpp
@@ -243,6 +243,23 @@ namespace xo {
 
             REQUIRE(std::strcmp(s->chars(), "HELLO") == 0);
         }
+
+        TEST_CASE("DString-clone", "[object2][DString]")
+        {
+            ArenaConfig cfg { .name_ = "testarena",
+                              .size_ = 4*1024 };
+            DArena arena = DArena::map(cfg);
+            auto alloc = with_facet<AAllocator>::mkobj(&arena);
+
+            DString * src = DString::from_cstr(alloc, "hello world");
+            DString * copy = DString::clone(alloc, src);
+
+            REQUIRE(copy != nullptr);
+            REQUIRE(copy != src);
+            REQUIRE(copy->size() == src->size());
+            REQUIRE(copy->capacity() == src->capacity());
+            REQUIRE(std::strcmp(copy->chars(), src->chars()) == 0);
+        }
     } /*namespace ut*/
 } /*namespace xo*/