diff --git a/CMakeLists.txt b/CMakeLists.txt
index ac63701..b4cc8fb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -46,6 +46,35 @@ xo_add_genfacetimpl(
 
 # ----------------------------------------------------------------
 
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-procedure2-facetimpl-procedure-primitive_gco_0
+    FACET_PKG xo_procedure2
+    FACET Procedure
+    REPR DPrimitive_gco_0
+    INPUT idl/IProcedure_DPrimitive_gco_0.json5
+)
+
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-procedure2-facetimpl-gcobject-primitive_gco_0
+    FACET_PKG xo_gc
+    FACET GCObject
+    REPR Primitive_gco_0
+    INPUT idl/IGCObject_DPrimitive_gco_0.json5
+)
+
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-procedure2-facetimpl-printable-primitive_gco_0
+    FACET_PKG xo_printable2
+    FACET Printable
+    REPR Primitive_gco_0
+    INPUT idl/IPrintable_DPrimitive_gco_0.json5
+)
+
+# ----------------------------------------------------------------
+
 # note: manual target; generated code committed to git
 xo_add_genfacetimpl(
     TARGET xo-procedure2-facetimpl-procedure-primitive_gco_2_gco_gco
diff --git a/idl/IGCObject_DPrimitive_gco_0.json5 b/idl/IGCObject_DPrimitive_gco_0.json5
new file mode 100644
index 0000000..27557c2
--- /dev/null
+++ b/idl/IGCObject_DPrimitive_gco_0.json5
@@ -0,0 +1,19 @@
+{
+    mode: "implementation",
+    output_cpp_dir: "src/procedure2",
+    output_hpp_dir: "include/xo/procedure2",
+    output_impl_subdir: "detail",
+    includes: [
+        //<xo/procedure2/GCObjectConversion_DPrimitive_gco_0.hpp>
+        "<xo/gc/GCObject.hpp>",
+        "<xo/alloc2/Allocator.hpp>",
+    ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/GCObject.json5",
+    brief: "provide AGCobject interface for Primitive _ -> gco",
+    using_doxygen: true,
+    repr: "DPrimitive_gco_0",
+    doc: [ "implement AGCObject for DPrimitive _ -> gco" ],
+}
diff --git a/idl/IPrintable_DPrimitive_gco_0.json5 b/idl/IPrintable_DPrimitive_gco_0.json5
new file mode 100644
index 0000000..830078c
--- /dev/null
+++ b/idl/IPrintable_DPrimitive_gco_0.json5
@@ -0,0 +1,18 @@
+{
+    mode: "implementation",
+    output_cpp_dir: "src/procedure2",
+    output_hpp_dir: "include/xo/procedure2",
+    output_impl_subdir: "detail",
+    includes: [
+        "<xo/printable2/Printable.hpp>",
+        "<xo/printable2/detail/IPrintable_Xfer.hpp>",
+    ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/Printable.json5",
+    brief: "provide APrintable interface for DPrimitive _ -> gco",
+    using_doxygen: true,
+    repr: "DPrimitive_gco_0",
+    doc: [ "implement APrintable for DPrimitive _ -> gco" ],
+}
diff --git a/idl/IProcedure_DPrimitive_gco_0.json5 b/idl/IProcedure_DPrimitive_gco_0.json5
new file mode 100644
index 0000000..757e5f5
--- /dev/null
+++ b/idl/IProcedure_DPrimitive_gco_0.json5
@@ -0,0 +1,20 @@
+{
+    mode: "implementation",
+    output_cpp_dir: "src/procedure2",
+    output_hpp_dir: "include/xo/procedure2",
+    output_impl_subdir: "detail",
+    includes: [
+        "<xo/procedure2/RuntimeContext.hpp>",
+        "<xo/procedure2/detail/IRuntimeContext_Xfer.hpp>",
+        "<xo/procedure2/Procedure.hpp>",
+        "<xo/procedure2/detail/IProcedure_Xfer.hpp>",
+    ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/Procedure.json5",
+    brief: "provide AProcedure interface for Primitive _ -> gco",
+    using_doxygen: true,
+    repr: "DPrimitive_gco_0",
+    doc: [ "implement AProcedure for DPrimitive _ -> gco" ],
+}
diff --git a/include/xo/procedure2/DPrimitive_gco_0.hpp b/include/xo/procedure2/DPrimitive_gco_0.hpp
new file mode 100644
index 0000000..7e5633c
--- /dev/null
+++ b/include/xo/procedure2/DPrimitive_gco_0.hpp
@@ -0,0 +1,20 @@
+/** @file DPrimitive_gco_0.hpp
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include <xo/gc/GCObject.hpp>
+#include "DPrimitive.hpp"
+
+namespace xo {
+    namespace scm {
+        using xo::mm::AGCObject;
+        using xo::facet::obj;
+
+        using DPrimitive_gco_0 = Primitive<obj<AGCObject> (*)(obj<ARuntimeContext>)>;
+    }
+}
+
+/* end DPrimitive_gco_0.hpp */
diff --git a/include/xo/procedure2/Primitive_gco_0.hpp b/include/xo/procedure2/Primitive_gco_0.hpp
new file mode 100644
index 0000000..00b2d86
--- /dev/null
+++ b/include/xo/procedure2/Primitive_gco_0.hpp
@@ -0,0 +1,11 @@
+/** @file Primitive_gco_0_gco_gco.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#include "DPrimitive_gco_0.hpp"
+#include "detail/IProcedure_DPrimitive_gco_0.hpp"
+#include "detail/IGCObject_DPrimitive_gco_0.hpp"
+#include "detail/IPrintable_DPrimitive_gco_0.hpp"
+
+/* end Primitive_gco_2_gco_gco.hpp */
diff --git a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_0.hpp b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_0.hpp
new file mode 100644
index 0000000..91ff183
--- /dev/null
+++ b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_0.hpp
@@ -0,0 +1,67 @@
+/** @file IGCObject_DPrimitive_gco_0.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DPrimitive_gco_0.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DPrimitive_gco_0.json5]
+ **/
+
+#pragma once
+
+#include "GCObject.hpp"
+#include <xo/gc/GCObject.hpp>
+#include <xo/alloc2/Allocator.hpp>
+#include "DPrimitive_gco_0.hpp"
+
+namespace xo { namespace scm { class IGCObject_DPrimitive_gco_0; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::mm::AGCObject,
+                                   xo::scm::DPrimitive_gco_0>
+        {
+            using ImplType = xo::mm::IGCObject_Xfer
+              <xo::scm::DPrimitive_gco_0,
+               xo::scm::IGCObject_DPrimitive_gco_0>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IGCObject_DPrimitive_gco_0
+         **/
+        class IGCObject_DPrimitive_gco_0 {
+        public:
+            /** @defgroup scm-gcobject-dprimitive_gco_0-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-dprimitive_gco_0-methods **/
+            ///@{
+            // const methods
+            /** memory consumption for this instance **/
+            static size_type shallow_size(const DPrimitive_gco_0 & self) noexcept;
+            /** copy instance using allocator **/
+            static Opaque shallow_copy(const DPrimitive_gco_0 & self, obj<AAllocator> mm) noexcept;
+
+            // non-const methods
+            /** during GC: forward immdiate children **/
+            static size_type forward_children(DPrimitive_gco_0 & self, obj<ACollector> gc) noexcept;
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */
\ No newline at end of file
diff --git a/include/xo/procedure2/detail/IPrintable_DPrimitive_gco_0.hpp b/include/xo/procedure2/detail/IPrintable_DPrimitive_gco_0.hpp
new file mode 100644
index 0000000..d8b3012
--- /dev/null
+++ b/include/xo/procedure2/detail/IPrintable_DPrimitive_gco_0.hpp
@@ -0,0 +1,62 @@
+/** @file IPrintable_DPrimitive_gco_0.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IPrintable_DPrimitive_gco_0.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IPrintable_DPrimitive_gco_0.json5]
+ **/
+
+#pragma once
+
+#include "Printable.hpp"
+#include <xo/printable2/Printable.hpp>
+#include <xo/printable2/detail/IPrintable_Xfer.hpp>
+#include "DPrimitive_gco_0.hpp"
+
+namespace xo { namespace scm { class IPrintable_DPrimitive_gco_0; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::print::APrintable,
+                                   xo::scm::DPrimitive_gco_0>
+        {
+            using ImplType = xo::print::IPrintable_Xfer
+              <xo::scm::DPrimitive_gco_0,
+               xo::scm::IPrintable_DPrimitive_gco_0>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IPrintable_DPrimitive_gco_0
+         **/
+        class IPrintable_DPrimitive_gco_0 {
+        public:
+            /** @defgroup scm-printable-dprimitive_gco_0-type-traits **/
+            ///@{
+            using ppindentinfo = xo::print::APrintable::ppindentinfo;
+            using Copaque = xo::print::APrintable::Copaque;
+            using Opaque = xo::print::APrintable::Opaque;
+            ///@}
+            /** @defgroup scm-printable-dprimitive_gco_0-methods **/
+            ///@{
+            // const methods
+            /** Pretty-printing support for this object.
+See [xo-indentlog/xo/indentlog/pretty.hpp] **/
+            static bool pretty(const DPrimitive_gco_0 & self, const ppindentinfo & ppii);
+
+            // non-const methods
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */
\ No newline at end of file
diff --git a/include/xo/procedure2/detail/IProcedure_DPrimitive_gco_0.hpp b/include/xo/procedure2/detail/IProcedure_DPrimitive_gco_0.hpp
new file mode 100644
index 0000000..cd1a9b3
--- /dev/null
+++ b/include/xo/procedure2/detail/IProcedure_DPrimitive_gco_0.hpp
@@ -0,0 +1,67 @@
+/** @file IProcedure_DPrimitive_gco_0.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IProcedure_DPrimitive_gco_0.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IProcedure_DPrimitive_gco_0.json5]
+ **/
+
+#pragma once
+
+#include "Procedure.hpp"
+#include <xo/procedure2/RuntimeContext.hpp>
+#include <xo/procedure2/detail/IRuntimeContext_Xfer.hpp>
+#include <xo/procedure2/Procedure.hpp>
+#include <xo/procedure2/detail/IProcedure_Xfer.hpp>
+#include "DPrimitive_gco_0.hpp"
+
+namespace xo { namespace scm { class IProcedure_DPrimitive_gco_0; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::scm::AProcedure,
+                                   xo::scm::DPrimitive_gco_0>
+        {
+            using ImplType = xo::scm::IProcedure_Xfer
+              <xo::scm::DPrimitive_gco_0,
+               xo::scm::IProcedure_DPrimitive_gco_0>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IProcedure_DPrimitive_gco_0
+         **/
+        class IProcedure_DPrimitive_gco_0 {
+        public:
+            /** @defgroup scm-procedure-dprimitive_gco_0-type-traits **/
+            ///@{
+            using AGCObject = xo::scm::AProcedure::AGCObject;
+            using Copaque = xo::scm::AProcedure::Copaque;
+            using Opaque = xo::scm::AProcedure::Opaque;
+            ///@}
+            /** @defgroup scm-procedure-dprimitive_gco_0-methods **/
+            ///@{
+            // const methods
+            /** true iff procedure takes n arguments **/
+            static bool is_nary(const DPrimitive_gco_0 & self) noexcept;
+            /** number of arguments. -1 for n-ary **/
+            static std::int32_t n_args(const DPrimitive_gco_0 & self) noexcept;
+
+            // non-const methods
+            /** invoke procedure; assume arguments satisfy type system **/
+            static obj<AGCObject> apply_nocheck(DPrimitive_gco_0 & self, obj<ARuntimeContext> rcx, const DArray * args);
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */
\ No newline at end of file
diff --git a/src/procedure2/CMakeLists.txt b/src/procedure2/CMakeLists.txt
index 45f41bd..44a4fad 100644
--- a/src/procedure2/CMakeLists.txt
+++ b/src/procedure2/CMakeLists.txt
@@ -11,6 +11,9 @@ set(SELF_SRCS
     IRuntimeContext_DSimpleRcx.cpp
     IProcedure_Any.cpp
     DPrimitive.cpp
+    IGCObject_DPrimitive_gco_0.cpp
+    IProcedure_DPrimitive_gco_0.cpp
+    IPrintable_DPrimitive_gco_0.cpp
     IGCObject_DPrimitive_gco_2_gco_gco.cpp
     IProcedure_DPrimitive_gco_2_gco_gco.cpp
     IPrintable_DPrimitive_gco_2_gco_gco.cpp
diff --git a/src/procedure2/IGCObject_DPrimitive_gco_0.cpp b/src/procedure2/IGCObject_DPrimitive_gco_0.cpp
new file mode 100644
index 0000000..1864246
--- /dev/null
+++ b/src/procedure2/IGCObject_DPrimitive_gco_0.cpp
@@ -0,0 +1,39 @@
+/** @file IGCObject_DPrimitive_gco_0.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DPrimitive_gco_0.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DPrimitive_gco_0.json5]
+**/
+
+#include "detail/IGCObject_DPrimitive_gco_0.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IGCObject_DPrimitive_gco_0::shallow_size(const DPrimitive_gco_0 & self) noexcept -> size_type
+        {
+            return self.shallow_size();
+        }
+
+        auto
+        IGCObject_DPrimitive_gco_0::shallow_copy(const DPrimitive_gco_0 & self, obj<AAllocator> mm) noexcept -> Opaque
+        {
+            return self.shallow_copy(mm);
+        }
+
+        auto
+        IGCObject_DPrimitive_gco_0::forward_children(DPrimitive_gco_0 & self, obj<ACollector> gc) noexcept -> size_type
+        {
+            return self.forward_children(gc);
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IGCObject_DPrimitive_gco_0.cpp */
diff --git a/src/procedure2/IPrintable_DPrimitive_gco_0.cpp b/src/procedure2/IPrintable_DPrimitive_gco_0.cpp
new file mode 100644
index 0000000..af23021
--- /dev/null
+++ b/src/procedure2/IPrintable_DPrimitive_gco_0.cpp
@@ -0,0 +1,28 @@
+/** @file IPrintable_DPrimitive_gco_0.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IPrintable_DPrimitive_gco_0.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IPrintable_DPrimitive_gco_0.json5]
+**/
+
+#include "detail/IPrintable_DPrimitive_gco_0.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IPrintable_DPrimitive_gco_0::pretty(const DPrimitive_gco_0 & self, const ppindentinfo & ppii) -> bool
+        {
+            return self.pretty(ppii);
+        }
+
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IPrintable_DPrimitive_gco_0.cpp */
diff --git a/src/procedure2/IProcedure_DPrimitive_gco_0.cpp b/src/procedure2/IProcedure_DPrimitive_gco_0.cpp
new file mode 100644
index 0000000..220f566
--- /dev/null
+++ b/src/procedure2/IProcedure_DPrimitive_gco_0.cpp
@@ -0,0 +1,39 @@
+/** @file IProcedure_DPrimitive_gco_0.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IProcedure_DPrimitive_gco_0.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IProcedure_DPrimitive_gco_0.json5]
+**/
+
+#include "detail/IProcedure_DPrimitive_gco_0.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IProcedure_DPrimitive_gco_0::is_nary(const DPrimitive_gco_0 & self) noexcept -> bool
+        {
+            return self.is_nary();
+        }
+
+        auto
+        IProcedure_DPrimitive_gco_0::n_args(const DPrimitive_gco_0 & self) noexcept -> std::int32_t
+        {
+            return self.n_args();
+        }
+
+        auto
+        IProcedure_DPrimitive_gco_0::apply_nocheck(DPrimitive_gco_0 & self, obj<ARuntimeContext> rcx, const DArray * args) -> obj<AGCObject>
+        {
+            return self.apply_nocheck(rcx, args);
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IProcedure_DPrimitive_gco_0.cpp */
diff --git a/src/procedure2/procedure2_register_facets.cpp b/src/procedure2/procedure2_register_facets.cpp
index 6905e0b..111a307 100644
--- a/src/procedure2/procedure2_register_facets.cpp
+++ b/src/procedure2/procedure2_register_facets.cpp
@@ -5,6 +5,7 @@
 
 #include "Procedure.hpp"
 #include "SimpleRcx.hpp"
+#include "Primitive_gco_0.hpp"
 #include "Primitive_gco_2_gco_gco.hpp"
 
 #include <xo/gc/GCObject.hpp>
@@ -25,6 +26,10 @@ namespace xo {
 
             FacetRegistry::register_impl<ARuntimeContext, DSimpleRcx>();
 
+            FacetRegistry::register_impl<AProcedure, DPrimitive_gco_0>();
+            FacetRegistry::register_impl<AGCObject, DPrimitive_gco_0>();
+            FacetRegistry::register_impl<APrintable, DPrimitive_gco_0>();
+
             FacetRegistry::register_impl<AProcedure, DPrimitive_gco_2_gco_gco>();
             FacetRegistry::register_impl<AGCObject, DPrimitive_gco_2_gco_gco>();
             FacetRegistry::register_impl<APrintable, DPrimitive_gco_2_gco_gco>();
diff --git a/src/procedure2/procedure2_register_types.cpp b/src/procedure2/procedure2_register_types.cpp
index 497773d..a6467be 100644
--- a/src/procedure2/procedure2_register_types.cpp
+++ b/src/procedure2/procedure2_register_types.cpp
@@ -5,6 +5,7 @@
 
 #include "procedure2_register_types.hpp"
 
+#include "detail/IGCObject_DPrimitive_gco_0.hpp"
 #include "detail/IGCObject_DPrimitive_gco_2_gco_gco.hpp"
 #include <xo/indentlog/scope.hpp>
 
@@ -25,6 +26,7 @@ namespace xo {
 
             // (note: don't currently intend to support AGCObject for DSimpleRcx)
 
+            ok &= gc.install_type(impl_for<AGCObject, DPrimitive_gco_0>());
             ok &= gc.install_type(impl_for<AGCObject, DPrimitive_gco_2_gco_gco>());
 
             return ok;