diff --git a/xo-alloc2/idl/Collector.json5 b/xo-alloc2/idl/Collector.json5
index 99904f88..3912ecdc 100644
--- a/xo-alloc2/idl/Collector.json5
+++ b/xo-alloc2/idl/Collector.json5
@@ -283,25 +283,26 @@
             noexcept: false,
             attributes: [],
         },
-        // void forward_inplace(AGCObject * lhs_iface, void ** lhs_data);
-        {
-            name: "forward_inplace",
-            doc: [
-                "evacuate @p *lhs, that refers to state with interface @p lhs_iface,",
-                "to collector @p d's to-space. Replace *lhs_data with forwarding pointer",
-                "",
-                "Require: gc in progress",
-                "",
-            ],
-            return_type: "void",
-            args: [
-                {type: "AGCObject *", name: "lhs_iface"},
-                {type: "void **", name: "lhs_data"},
-            ],
-            const: false,
-            noexcept: false,
-            attributes: [],
-        },
+        // obsolete. use GCObjectVisitor.visit_child()
+//        // void forward_inplace(AGCObject * lhs_iface, void ** lhs_data);
+//        {
+//            name: "forward_inplace",
+//            doc: [
+//                "evacuate @p *lhs, that refers to state with interface @p lhs_iface,",
+//                "to collector @p d's to-space. Replace *lhs_data with forwarding pointer",
+//                "",
+//                "Require: gc in progress",
+//                "",
+//            ],
+//            return_type: "void",
+//            args: [
+//                {type: "AGCObject *", name: "lhs_iface"},
+//                {type: "void **", name: "lhs_data"},
+//            ],
+//            const: false,
+//            noexcept: false,
+//            attributes: [],
+//        },
     ],
     router_facet_explicit_content: [
         "/** convenience template for gc object copy **/",
diff --git a/xo-alloc2/include/xo/alloc2/gc/ACollector.hpp b/xo-alloc2/include/xo/alloc2/gc/ACollector.hpp
index 8d23384b..2765c6b2 100644
--- a/xo-alloc2/include/xo/alloc2/gc/ACollector.hpp
+++ b/xo-alloc2/include/xo/alloc2/gc/ACollector.hpp
@@ -123,12 +123,6 @@ Require: gc not in progress **/
 Source must be owned by this collector.
 Increments object age **/
     virtual void * alloc_copy(Opaque data, std::byte * src)  = 0;
-    /** evacuate @p *lhs, that refers to state with interface @p lhs_iface,
-to collector @p d's to-space. Replace *lhs_data with forwarding pointer
-
-Require: gc in progress
- **/
-    virtual void forward_inplace(Opaque data, AGCObject * lhs_iface, void ** lhs_data)  = 0;
     ///@}
 }; /*ACollector*/
 
diff --git a/xo-alloc2/include/xo/alloc2/gc/ICollector_Any.hpp b/xo-alloc2/include/xo/alloc2/gc/ICollector_Any.hpp
index 0a14751a..f4ab6bb0 100644
--- a/xo-alloc2/include/xo/alloc2/gc/ICollector_Any.hpp
+++ b/xo-alloc2/include/xo/alloc2/gc/ICollector_Any.hpp
@@ -76,7 +76,6 @@ namespace mm {
         [[noreturn]] void request_gc(Opaque, Generation)  override;
         [[noreturn]] void assign_member(Opaque, void *, obj<AGCObject> *, obj<AGCObject> &)  override;
         [[noreturn]] void * alloc_copy(Opaque, std::byte *)  override;
-        [[noreturn]] void forward_inplace(Opaque, AGCObject *, void **)  override;
 
         ///@}
 
diff --git a/xo-alloc2/include/xo/alloc2/gc/ICollector_Xfer.hpp b/xo-alloc2/include/xo/alloc2/gc/ICollector_Xfer.hpp
index 1a368235..50802f9d 100644
--- a/xo-alloc2/include/xo/alloc2/gc/ICollector_Xfer.hpp
+++ b/xo-alloc2/include/xo/alloc2/gc/ICollector_Xfer.hpp
@@ -93,9 +93,6 @@ namespace mm {
         void * alloc_copy(Opaque data, std::byte * src)  override {
             return I::alloc_copy(_dcast(data), src);
         }
-        void forward_inplace(Opaque data, AGCObject * lhs_iface, void ** lhs_data)  override {
-            return I::forward_inplace(_dcast(data), lhs_iface, lhs_data);
-        }
 
         ///@}
 
diff --git a/xo-alloc2/include/xo/alloc2/gc/RCollector.hpp b/xo-alloc2/include/xo/alloc2/gc/RCollector.hpp
index ac66a262..b7c54d44 100644
--- a/xo-alloc2/include/xo/alloc2/gc/RCollector.hpp
+++ b/xo-alloc2/include/xo/alloc2/gc/RCollector.hpp
@@ -142,9 +142,6 @@ public:
     void * alloc_copy(std::byte * src)  {
         return O::iface()->alloc_copy(O::data(), src);
     }
-    void forward_inplace(AGCObject * lhs_iface, void ** lhs_data)  {
-        return O::iface()->forward_inplace(O::data(), lhs_iface, lhs_data);
-    }
 
     ///@}
     /** @defgroup mm-collector-member-vars **/
diff --git a/xo-alloc2/src/alloc2/facet/ICollector_Any.cpp b/xo-alloc2/src/alloc2/facet/ICollector_Any.cpp
index 269d95bb..2743bfb4 100644
--- a/xo-alloc2/src/alloc2/facet/ICollector_Any.cpp
+++ b/xo-alloc2/src/alloc2/facet/ICollector_Any.cpp
@@ -71,12 +71,6 @@ ICollector_Any::alloc_copy(Opaque, std::byte *)  -> void *
     _fatal();
 }
 
-auto
-ICollector_Any::forward_inplace(Opaque, AGCObject *, void **)  -> void
-{
-    _fatal();
-}
-
 
 } /*namespace mm*/
 } /*namespace xo*/
diff --git a/xo-gc/include/xo/gc/DX1Collector.hpp b/xo-gc/include/xo/gc/DX1Collector.hpp
index aaa2b083..5eafa802 100644
--- a/xo-gc/include/xo/gc/DX1Collector.hpp
+++ b/xo-gc/include/xo/gc/DX1Collector.hpp
@@ -274,13 +274,18 @@ namespace xo {
             /** Execute gc immediately, for all generations < @p upto **/
             void execute_gc(Generation upto) noexcept;
 
+#ifdef OBSOLETE  // replaced by visit_child()
             /** Evacuate object at @p *lhs_data to to-space.
              *  Replace original with forwarding pointer to new location
              **/
             void forward_inplace(AGCObject * lhs_iface, void ** lhs_data);
+#endif
 
-            /** Supports the GCObjectVisitor facet.
-             *  Synonym for forward_inplace
+            /** Supports GCObjectVisitor facet.
+             *  During gc phase:
+             *  1. evacuate object at @p *lhs_data to to-space.
+             *  2. replace @p *lhs_data with forwarding pointer
+             *     to new location.
              **/
             void visit_child(AGCObject * lhs_iface, void ** lhs_data);
 
diff --git a/xo-gc/include/xo/gc/detail/ICollector_DX1Collector.hpp b/xo-gc/include/xo/gc/detail/ICollector_DX1Collector.hpp
index c81513f0..d9b43a5c 100644
--- a/xo-gc/include/xo/gc/detail/ICollector_DX1Collector.hpp
+++ b/xo-gc/include/xo/gc/detail/ICollector_DX1Collector.hpp
@@ -111,12 +111,6 @@ Require: gc not in progress **/
 Source must be owned by this collector.
 Increments object age **/
             static void * alloc_copy(DX1Collector & self, std::byte * src);
-            /** evacuate @p *lhs, that refers to state with interface @p lhs_iface,
-to collector @p d's to-space. Replace *lhs_data with forwarding pointer
-
-Require: gc in progress
- **/
-            static void forward_inplace(DX1Collector & self, AGCObject * lhs_iface, void ** lhs_data);
             ///@}
         };
 
diff --git a/xo-gc/src/gc/DX1Collector.cpp b/xo-gc/src/gc/DX1Collector.cpp
index 28636368..00bd9fb4 100644
--- a/xo-gc/src/gc/DX1Collector.cpp
+++ b/xo-gc/src/gc/DX1Collector.cpp
@@ -584,32 +584,13 @@ namespace xo {
             }
         }
 
-        void
-        DX1Collector::forward_inplace(AGCObject * lhs_iface,
-                                      void ** lhs_data)
-        {
-            // TODO: streamline once GCObject refactored so that
-            //       forward_children takes GCObjectVisitor instead of Collector
-            //       argument.
-
-            Generation upto = runstate_.gc_upto();
-
-            if (runstate_.is_running()) {
-                // called during collection phase
-                gco_store_.forward_inplace_aux(this->ref<AGCObjectVisitor>(), lhs_iface, lhs_data, upto);
-            } else if (runstate_.is_verify()) {
-                // called during verify_ok
-                this->_verify_aux(lhs_iface, *lhs_data);
-            } else {
-                // should be unreachable
-                assert(false);
-            }
-        }
-
         void
         DX1Collector::visit_child(AGCObject * lhs_iface,
                                   void ** lhs_data)
         {
+            // MAYBE: adapter distinct from DX1Collector that supports GCObjectVisitor facet,
+            //        calls DX1Collector::_verify_aux()
+
             if (runstate_.is_running()) {
                 Generation upto = runstate_.gc_upto();
 
@@ -661,17 +642,17 @@ namespace xo {
 
         auto
         DX1Collector::super_alloc(typeseq t, size_type z) noexcept -> value_type {
-            return with_facet<AAllocator>::mkobj(new_space()).super_alloc(t, z);
+            return with_facet<AAllocator>::mkobj(this->new_space()).super_alloc(t, z);
         }
 
         auto
         DX1Collector::sub_alloc(size_type z, bool complete) noexcept -> value_type {
-            return with_facet<AAllocator>::mkobj(new_space()).sub_alloc(z, complete);
+            return with_facet<AAllocator>::mkobj(this->new_space()).sub_alloc(z, complete);
         }
 
         auto
         DX1Collector::alloc_copy(value_type src) noexcept -> value_type {
-            return with_facet<AAllocator>::mkobj(new_space()).alloc_copy(src);
+            return with_facet<AAllocator>::mkobj(this->new_space()).alloc_copy(src);
         }
 
         bool
diff --git a/xo-gc/src/gc/facet/ICollector_DX1Collector.cpp b/xo-gc/src/gc/facet/ICollector_DX1Collector.cpp
index a656ca6b..a20a9744 100644
--- a/xo-gc/src/gc/facet/ICollector_DX1Collector.cpp
+++ b/xo-gc/src/gc/facet/ICollector_DX1Collector.cpp
@@ -99,11 +99,6 @@ namespace xo {
         {
             return self.alloc_copy(src);
         }
-        auto
-        ICollector_DX1Collector::forward_inplace(DX1Collector & self, AGCObject * lhs_iface, void ** lhs_data) -> void
-        {
-            self.forward_inplace(lhs_iface, lhs_data);
-        }
 
     } /*namespace mm*/
 } /*namespace xo*/
diff --git a/xo-gc/utest/CMakeLists.txt b/xo-gc/utest/CMakeLists.txt
index 5ffcac82..599e1ea1 100644
--- a/xo-gc/utest/CMakeLists.txt
+++ b/xo-gc/utest/CMakeLists.txt
@@ -9,9 +9,21 @@ set(UTEST_SRCS
     DX1CollectorIterator.test.cpp
     GCObjectStore.test.cpp
     Object2.test.cpp
+
+    DMockCollector.cpp
+    IGCObjectVisitor_DMockCollector.cpp
+
+    init_gc_utest.cpp
     random_allocs.cpp
 )
 
+# mock collector for unit test
+xo_add_genfacetimpl(
+    TARGET xo-gc-facetimpl-gcobjectvisitor-mockcollector
+    FACET_PKG xo_alloc2
+    INPUT idl/IGCObjectVisitor_DMockCollector.json5
+)
+
 if (ENABLE_TESTING)
     xo_add_utest_executable(${UTEST_EXE} ${UTEST_SRCS})
     xo_headeronly_dependency(${UTEST_EXE} randomgen)
diff --git a/xo-gc/utest/DMockCollector.cpp b/xo-gc/utest/DMockCollector.cpp
new file mode 100644
index 00000000..69f90508
--- /dev/null
+++ b/xo-gc/utest/DMockCollector.cpp
@@ -0,0 +1,37 @@
+/** @file DMockCollector.cpp
+ *
+ *  @author Roland Conybeare, Apr 2026
+ **/
+
+#include "MockCollector.hpp"
+
+namespace xo {
+    namespace mm {
+
+        Generation
+        DMockCollector::generation_of(Role r, const void * addr) const noexcept
+        {
+            return p_gco_store_->generation_of(r, addr);
+        }
+
+        AllocInfo
+        DMockCollector::alloc_info(void * mem) const noexcept
+        {
+            return p_gco_store_->alloc_info((std::byte *)mem);
+        }
+
+        void
+        DMockCollector::visit_child(AGCObject * lhs_iface, void ** lhs_data)
+        {
+            p_gco_store_->forward_inplace_aux(this->ref<AGCObjectVisitor>(), lhs_iface, lhs_data, upto_);
+        }
+
+        std::byte *
+        DMockCollector::alloc_copy(void * src) noexcept {
+            return p_gco_store_->new_space()->alloc_copy((std::byte *)src);
+        }
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end DMockCollector.cpp */
diff --git a/xo-gc/utest/DMockCollector.hpp b/xo-gc/utest/DMockCollector.hpp
new file mode 100644
index 00000000..ca1c0dfb
--- /dev/null
+++ b/xo-gc/utest/DMockCollector.hpp
@@ -0,0 +1,40 @@
+/** @file DMockCollector.hpp
+ *
+ *  @author Roland Conybeare, Apr 2026
+ **/
+
+#pragma once
+
+#include <xo/gc/GCObjectStore.hpp>
+#include <xo/arena/AllocInfo.hpp>
+
+namespace xo {
+    namespace mm {
+
+        /** @brief Mock Collector
+         *
+         *  Intended to help unit test a GCObjectSotre instance.
+         *  Mock a Collector in collection phase for generations 0 <= g < @ref upto_.
+         **/
+        class DMockCollector {
+        public:
+            explicit DMockCollector(GCObjectStore * gcos, Generation upto) : p_gco_store_{gcos}, upto_{upto} {}
+
+            template <typename AFacet>
+            obj<AFacet,DMockCollector> ref() { return obj<AFacet,DMockCollector>(this); }
+
+            Generation generation_of(Role r, const void * addr) const noexcept;
+            AllocInfo alloc_info(void * mem) const noexcept;
+
+            void visit_child(AGCObject * lhs_iface, void ** lhs_data);
+            std::byte * alloc_copy(void * src) noexcept;
+
+        private:
+            GCObjectStore * p_gco_store_ = nullptr;
+            Generation upto_;
+        };
+
+    } /*namespace mm*/
+} /*namespaace xo*/
+
+/* end DMockCollector.hpp */
diff --git a/xo-gc/utest/IGCObjectVisitor_DMockCollector.cpp b/xo-gc/utest/IGCObjectVisitor_DMockCollector.cpp
new file mode 100644
index 00000000..f4472874
--- /dev/null
+++ b/xo-gc/utest/IGCObjectVisitor_DMockCollector.cpp
@@ -0,0 +1,44 @@
+/** @file IGCObjectVisitor_DMockCollector.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObjectVisitor_DMockCollector.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObjectVisitor_DMockCollector.json5]
+**/
+
+#include "./IGCObjectVisitor_DMockCollector.hpp"
+
+namespace xo {
+    namespace mm {
+        auto
+        IGCObjectVisitor_DMockCollector::alloc_info(const DMockCollector & self, void * addr) -> AllocInfo
+        {
+            return self.alloc_info(addr);
+        }
+
+        auto
+        IGCObjectVisitor_DMockCollector::generation_of(const DMockCollector & self, Role r, const void * addr) noexcept -> Generation
+        {
+            return self.generation_of(r, addr);
+        }
+
+        auto
+        IGCObjectVisitor_DMockCollector::alloc_copy(DMockCollector & self, std::byte * src) -> void *
+        {
+            return self.alloc_copy(src);
+        }
+        auto
+        IGCObjectVisitor_DMockCollector::visit_child(DMockCollector & self, AGCObject * iface, void ** pp_data) noexcept -> void
+        {
+            self.visit_child(iface, pp_data);
+        }
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end IGCObjectVisitor_DMockCollector.cpp */
diff --git a/xo-gc/utest/IGCObjectVisitor_DMockCollector.hpp b/xo-gc/utest/IGCObjectVisitor_DMockCollector.hpp
new file mode 100644
index 00000000..ac9db2bb
--- /dev/null
+++ b/xo-gc/utest/IGCObjectVisitor_DMockCollector.hpp
@@ -0,0 +1,68 @@
+/** @file IGCObjectVisitor_DMockCollector.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObjectVisitor_DMockCollector.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObjectVisitor_DMockCollector.json5]
+ **/
+
+#pragma once
+
+#include "GCObjectVisitor.hpp"
+#include "DMockCollector.hpp"
+
+namespace xo { namespace mm { class IGCObjectVisitor_DMockCollector; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::mm::AGCObjectVisitor,
+                                   xo::mm::DMockCollector>
+        {
+            using ImplType = xo::mm::IGCObjectVisitor_Xfer
+              <xo::mm::DMockCollector,
+               xo::mm::IGCObjectVisitor_DMockCollector>;
+        };
+    }
+}
+
+namespace xo {
+    namespace mm {
+        /** @class IGCObjectVisitor_DMockCollector
+         **/
+        class IGCObjectVisitor_DMockCollector {
+        public:
+            /** @defgroup mm-gcobjectvisitor-dmockcollector-type-traits **/
+            ///@{
+            using Copaque = xo::mm::AGCObjectVisitor::Copaque;
+            using Opaque = xo::mm::AGCObjectVisitor::Opaque;
+            ///@}
+            /** @defgroup mm-gcobjectvisitor-dmockcollector-methods **/
+            ///@{
+            // const methods
+            /** allocation metadata for gc-aware data at address @p gco.
+@p gco must be the result of a call to collector's alloc() function **/
+            static AllocInfo alloc_info(const DMockCollector & self, void * addr);
+            /** generation to which pointer @p addr belongs, given role @p r;
+sentinel if @p addr is not owned by collector **/
+            static Generation generation_of(const DMockCollector & self, Role r, const void * addr) noexcept;
+
+            // non-const methods
+            /** allocate copy of source object at address @p src.
+Source must be owned by this collector.
+Increments object age **/
+            static void * alloc_copy(DMockCollector & self, std::byte * src);
+            /** visit child of a gc-aware object. May update child in-place! **/
+            static void visit_child(DMockCollector & self, AGCObject * iface, void ** pp_data) noexcept;
+            ///@}
+        };
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end */
\ No newline at end of file
diff --git a/xo-gc/utest/MockCollector.hpp b/xo-gc/utest/MockCollector.hpp
new file mode 100644
index 00000000..4e3f3d1b
--- /dev/null
+++ b/xo-gc/utest/MockCollector.hpp
@@ -0,0 +1,13 @@
+/** @file MockCollector.hpp
+ *
+ *  @author Roland Conybeare, Apr 2026
+ **/
+
+#pragma once
+
+#include "DMockCollector.hpp"
+#include "IGCObjectVisitor_DMockCollector.hpp"
+//#include "ICollector_DMockCollector.hpp"
+//#include "IAllocator_DMockCollector.hpp"
+
+/* end MockCollector.hpp */
diff --git a/xo-gc/utest/gc_utest_main.cpp b/xo-gc/utest/gc_utest_main.cpp
index cb1a31f3..5d4c4ea8 100644
--- a/xo-gc/utest/gc_utest_main.cpp
+++ b/xo-gc/utest/gc_utest_main.cpp
@@ -1,17 +1,19 @@
 /* file gc_utest_main.cpp */
 
-#include <xo/gc/init_gc.hpp>
+#include "init_gc_utest.hpp"
 #include <xo/subsys/Subsystem.hpp>
 
 #define CATCH_CONFIG_RUNNER
 #include <catch2/catch.hpp>
 
-using xo::S_gc_tag;
+using xo::S_gc_utest_tag;
 using xo::InitSubsys;
 using xo::InitEvidence;
 
-// ensure xo-gc properly initialized when Subsystem::initialize_all() runs
-static InitEvidence s_init = (InitSubsys<S_gc_tag>::require());
+// ensure xo-gc/utest as mock subsystem
+// properly initialized when Subsystem::initialize_all() runs
+//
+static InitEvidence s_init = (InitSubsys<S_gc_utest_tag>::require());
 
 int
 main(int argc, char* argv[])
diff --git a/xo-gc/utest/idl/IGCObjectVisitor_DMockCollector.json5 b/xo-gc/utest/idl/IGCObjectVisitor_DMockCollector.json5
new file mode 100644
index 00000000..9d104bf7
--- /dev/null
+++ b/xo-gc/utest/idl/IGCObjectVisitor_DMockCollector.json5
@@ -0,0 +1,27 @@
+{
+    mode: "implementation",
+    output_cpp_dir: ".",
+    output_hpp_dir: "./",
+    output_impl_subdir: ".",
+    includes: [
+//        "<xo/alloc2/GCObject.hpp>",
+//        "<xo/alloc2/Allocator.hpp>"
+    ],
+    local_types: [
+//        {
+//            name: "typeseq",
+//            doc: ["identifies a c++ type"],
+//            definition: "xo::reflect::typeseq"
+//        },
+    ],
+    namespace1: "xo",
+    namespace2: "mm",
+    facet_idl: "idl/GCObjectVisitor.json5",
+    brief: "provide AGCObjectVisitor interface for DMockCollector",
+    using_doxygen: true,
+    repr: "DMockCollector",
+    doc: [
+        "Implement AGCObjectVisitor for DMockCollector.",
+        "Evacuate object pointer (migrate to to-space) during collection phase"
+    ],
+}
diff --git a/xo-gc/utest/init_gc_utest.cpp b/xo-gc/utest/init_gc_utest.cpp
new file mode 100644
index 00000000..a88f6046
--- /dev/null
+++ b/xo-gc/utest/init_gc_utest.cpp
@@ -0,0 +1,48 @@
+/** @file init_gc_utest.cpp
+*
+ *  @author Roland Conybeare, Apr 2026
+ **/
+
+#include "init_gc_utest.hpp"
+#include "MockCollector.hpp"
+#include <xo/gc/init_gc.hpp>
+#include <xo/facet/FacetRegistry.hpp>
+#include <xo/indentlog/scope.hpp>
+
+namespace xo {
+    using xo::mm::SetupGcUtest;
+    using xo::facet::FacetRegistry;
+    using xo::reflect::typeseq;
+
+    bool
+    SetupGcUtest::register_facets()
+    {
+        scope log(XO_DEBUG(true));
+
+        FacetRegistry::register_impl<AGCObjectVisitor, DMockCollector>();
+
+        log && log(xtag("DMockCollector.tseq", typeseq::id<DMockCollector>()));
+
+        return true;
+    }
+
+    void
+    InitSubsys<S_gc_utest_tag>::init()
+    {
+        SetupGcUtest::register_facets();
+    }
+
+    InitEvidence
+    InitSubsys<S_gc_utest_tag>::require() {
+        InitEvidence retval;
+
+        /* recursive subsystem deps for xo-gc/utest */
+        retval ^= InitSubsys<S_gc_tag>::require();
+
+        /* xo-gc/utest/'s own initialization code */
+        retval ^= Subsystem::provide<S_gc_utest_tag>("gc-utest", &init);
+
+        return retval;
+    }
+
+}
diff --git a/xo-gc/utest/init_gc_utest.hpp b/xo-gc/utest/init_gc_utest.hpp
new file mode 100644
index 00000000..ccadf842
--- /dev/null
+++ b/xo-gc/utest/init_gc_utest.hpp
@@ -0,0 +1,34 @@
+/** @file init_gc_utest.hpp
+*
+ *  @author Roland Conybeare, Apr 2026
+ **/
+
+#pragma once
+
+#include <xo/subsys/Subsystem.hpp>
+
+namespace xo {
+    /* tag to represent xo-gc/utest/ as a mock subsystem within ordered initialization
+     *
+     * (so we can follow usual patterns for setting up facet tables)
+     */
+    enum S_gc_utest_tag {};
+
+    template <>
+    struct InitSubsys<S_gc_utest_tag> {
+        static void init();
+        static InitEvidence require();
+    };
+
+    namespace mm {
+
+        class SetupGcUtest {
+        public:
+            /** Register gc/utest (facet,impl) combinations with FacetRegistry **/
+            static bool register_facets();
+        };
+    } /*namespace mm*/
+
+} /*namespace xo*/
+
+/* end init_gc_utest.hpp */