diff --git a/DSequenceExpr.hpp b/DSequenceExpr.hpp
new file mode 100644
index 00000000..12caf649
--- /dev/null
+++ b/DSequenceExpr.hpp
@@ -0,0 +1,77 @@
+/** @file DSequenceExpr.hpp
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include "TypeRef.hpp"
+#include <xo/object2/DArray.hpp>
+
+namespace xo {
+    namespace scm {
+
+        /** syntax for a sequence of expressions
+         *   {
+         *      expr(1);
+         *      expr(2);
+         *      ...
+         *      expr(n);
+         *   }
+         **/
+        class DSequenceExpr {
+        public:
+            using size_type = DArray::size_type;
+            using ppindentinfo = xo::print::ppindentinfo;
+
+        public:
+            DSequenceExpr() = default;
+            DSequenceExpr(DArray * xv) : expr_v_{xv} {}
+
+            /** create empty sequence using memory from @p mm **/
+            static obj<AExpression,DSequenceExpr> make_empty(obj<AAllocator> mm);
+
+            /** create empty sequence expression using mmeory from @p mm **/
+            static DSequenceExpr * _make_empty(obj<AAllocator> mm);
+
+            size_type size() const noexcept;
+            obj<AExpression> operator[](std::size_t i) const;
+
+            /** append @p expr to the end of this sequence **/
+            void push_back(obj<AExpression> expr);
+
+            // get_free_variables();
+            // visit_preorder();
+            // visit_layer();
+            // xform_layer()
+            // attach_envs()
+
+            /** @defgroup scm-ifelseexpr-expression-facets **/
+            ///@{
+
+            exprtype extype() const noexcept { return exprtype::sequence; }
+            TypeRef typeref() const noexcept { return typeref_; }
+            TypeDescr valuetype() const noexcept { return typeref_.td(); }
+            void assign_valuetype(TypeDescr td) noexcept;
+
+            ///@}
+            /** @defgroup scm-sequenceexpr-printable-facet printable facet methods **/
+            ///@{
+
+            /** pretty-printing driver; combine layout+printing **/
+            bool pretty(const ppindentinfo & ppii) const;
+
+            ///@}
+
+        private:
+            /** expression value always has type consistent with this description
+             **/
+            TypeRef typeref_;
+            /** array of expressions **/
+            DArray * expr_v_ = nullptr;
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DSequenceExpr.hpp */
diff --git a/include/xo/expression2/exprtype.hpp b/include/xo/expression2/exprtype.hpp
index 861d62bd..3bcda3c4 100644
--- a/include/xo/expression2/exprtype.hpp
+++ b/include/xo/expression2/exprtype.hpp
@@ -40,10 +40,10 @@ namespace xo {
             variable,
             /** if-then-else **/
             ifexpr,
-#ifdef NOT_YET
             /** sequence **/
             sequence,
-            /** type conversion **/
+#ifdef NOT_YET
+            )            /** type conversion **/
             convert,
 #endif
 
diff --git a/src/expression2/DSequenceExpr.cpp b/src/expression2/DSequenceExpr.cpp
new file mode 100644
index 00000000..c5abf27b
--- /dev/null
+++ b/src/expression2/DSequenceExpr.cpp
@@ -0,0 +1,88 @@
+/** @file DSequenceExpr.cpp
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#include "DSequenceExpr.hpp"
+
+namespace xo {
+    namespace scm {
+
+        obj<AExpression,DSequenceExpr>
+        DSequenceExpr::make_empty(obj<AAllocator> mm)
+        {
+            return obj<AExpression,DSequenceExpr>(_make_empty(mm));
+        }
+
+        DSequenceExpr *
+        DSequenceExpr::_make_empty(obj<AAllocator> mm)
+        {
+            void * mem = mm.alloc(typeseq::id<DSequenceExpr>(),
+                                  sizeof(DSequenceExpr));
+
+            DSequenceExpr * expr = new (mem) DSequenceExpr();
+
+            constexpr size_type c_hint_capacity = 8;
+
+            /** allocate 2nd, so it comes after DSequenceExpr in
+             *  memory.  This may later allow realloc
+             **/
+            DArray * expr_v = DArray::empty(mm,
+                                            c_hint_capacity);
+
+            expr->expr_v_ = expr_v;
+
+            return expr;
+        }
+
+        size_type
+        DSequenceExpr::size() const noexcept
+        {
+            return expr_v_->size();
+        }
+
+        obj<AExpression>
+        DSequenceExpr::operator[](std::size_t i) const
+        {
+            return (*expr_v_)[i];
+        }
+
+        void
+        DSequenceExpr::push_back(obj<AAllocator> mm,
+                                 obj<AExpression> expr)
+        {
+            if (expr_v_->size() == expr_v_->capacity()) {
+                /* reallocate+expand */
+
+                DArray * expr_2x_v
+                    = DArray::empty(mm, 2 * expr_v_->capacity());
+
+                for (size_type i = 0, z = expr_v_->size(); i < z; ++i) {
+                    expr_2x_v->push_back((*expr_2x_v)[i]);
+                }
+
+                this->expr_v_ = expr_2x_v;
+            }
+
+            this->expr_v_->push_back(expr);
+        }
+
+        void
+        DSequenceExpr::assign_valuetype(TypeDescr td) noexcept
+        {
+            typeref_.resolve(td);
+        }
+
+        void
+        DSequenceExpr::pretty(const ppindentinfo & ppii) const
+        {
+            using xo::print::ppstate;
+
+            ppstate * pps = ppii.pps();
+
+                        xxx;
+        }
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DSequenceExpr.cpp */