diff --git a/CMakeLists.txt b/CMakeLists.txt
index bff25696..5a52f109 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -100,7 +100,8 @@ add_subdirectory(xo-type)         # experiment w/ facet object model
 add_subdirectory(xo-procedure2)   # schematika procedure abstraction + runtime context (fomo)
 add_subdirectory(xo-numeric)      # schematika poly arithmetic w/ facet object model
 add_subdirectory(xo-tokenizer2)   # schematika tokenizer (w/ fomo)
-
+add_subdirectory(xo-expression2)  # schematika expressions (fomo)
+#
 add_subdirectory(xo-allocutil)    # xo-alloc api
 add_subdirectory(xo-alloc)        # arena allocator + incremental gc
 add_subdirectory(xo-ratio)
@@ -111,7 +112,6 @@ add_subdirectory(xo-callback)
 add_subdirectory(xo-object)
 add_subdirectory(xo-ordinaltree)
 #
-add_subdirectory(xo-expression2)  # schematika expressions (fomo)
 add_subdirectory(xo-reader2)      # schematika expression parser (fomo)
 add_subdirectory(xo-interpreter2) # schematika interpreter (fomo)
 #
diff --git a/ci.nix b/ci.nix
index 300e3854..a7b8b6a2 100644
--- a/ci.nix
+++ b/ci.nix
@@ -34,6 +34,7 @@ in
       xo-procedure2
       xo-numeric
       xo-tokenizer2
+      xo-expression2
       xo-allocutil
       xo-alloc
       xo-ratio
diff --git a/pkgs/xo-expression2.nix b/pkgs/xo-expression2.nix
new file mode 100644
index 00000000..a821464d
--- /dev/null
+++ b/pkgs/xo-expression2.nix
@@ -0,0 +1,45 @@
+{
+  # nixpkgs dependencies
+  lib, stdenv, cmake, catch2,
+
+  # xo dependencies
+  xo-gc,
+  xo-type,
+  xo-reflect,
+  xo-procedure2,
+  xo-printable2,
+  xo-flatstring,
+  xo-subsys,
+  xo-indentlog,
+  xo-cmake,
+
+  # config arguments
+  doCheck ? true
+} :
+
+stdenv.mmkDerivation (finalattrs :
+  {
+    name = "xo-expression2";
+
+    src = ../xo-expression2;
+
+    cmakeFlags = ["-DCMAKE_MODULE_PATH=${xo-cmake}/share/cmake"]
+                  ++ lib.optionals doCheck ["-DENABLE_TESTING=1"];
+
+    inherit doCheck;
+
+    nativeBuildInputs = [
+      cmake catch2
+      xo-cmake
+    ];
+    propagatedBuildInputs = [
+      xo-gc
+      xo-type
+      xo-reflect
+      xo-procedure2
+      xo-printable2
+      xo-flatstring
+      xo-subsys
+      xo-indentlog
+    ];
+  })
diff --git a/shells.nix b/shells.nix
index fb9a4dd8..7d563043 100644
--- a/shells.nix
+++ b/shells.nix
@@ -314,6 +314,9 @@ in
 {
   inherit pkgs;
 
+  # load-bearing for
+  #   $ nix-build -A xo.foo
+  #
   xo = {
     cmake          = pkgs.xo-cmake;
     subsys         = pkgs.xo-subsys;
@@ -337,6 +340,7 @@ in
     procedure2     = pkgs.xo-procedure2;
     numeric        = pkgs.xo-numeric;
     tokenizer2     = pkgs.xo-tokenizer2;
+    expression2    = pkgs.xo-expression2;
 
     allocutil      = pkgs.xo-allocutil;
     alloc          = pkgs.xo-alloc;
diff --git a/xo-cmake/etc/xo/subsystem-list b/xo-cmake/etc/xo/subsystem-list
index 6568ccbc..eea49525 100644
--- a/xo-cmake/etc/xo/subsystem-list
+++ b/xo-cmake/etc/xo/subsystem-list
@@ -20,6 +20,7 @@ xo-type
 xo-procedure2
 xo-numeric
 xo-tokenizer2
+xo-expression2
 xo-allocutil
 xo-alloc
 xo-object
diff --git a/xo.nix b/xo.nix
index c2e832b7..454e4081 100644
--- a/xo.nix
+++ b/xo.nix
@@ -47,6 +47,7 @@ let
     xo-procedure2     = callPackage pkgs/xo-procedure2.nix     { stdenv = jitStdenv; };
     xo-numeric        = callPackage pkgs/xo-numeric.nix        { stdenv = jitStdenv; };
     xo-tokenizer2     = callPackage pkgs/xo-tokenizer2.nix     { stdenv = jitStdenv;                   buildExamples = true; };
+    xo-expression2    = callPackage pkgs/xo-expression2.nix    { stdenv = jitStdenv; };
     xo-allocutil      = callPackage pkgs/xo-allocutil.nix      { stdenv = jitStdenv; };
     xo-alloc          = callPackage pkgs/xo-alloc.nix          { stdenv = jitStdenv; buildDocs = true; };
     xo-ratio          = callPackage pkgs/xo-ratio.nix          { stdenv = jitStdenv; buildDocs = true; buildExamples = true; };