diff --git a/CMakeLists.txt b/CMakeLists.txt
index a07236de..1a3135bb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -85,6 +85,7 @@ add_subdirectory(xo-pywebutil)
 add_subdirectory(xo-printjson)
 add_subdirectory(xo-pyprintjson)
 add_subdirectory(xo-reactor)
+add_subdirectory(xo-pyreactor)
 #
 add_subdirectory(xo-expression)
 add_subdirectory(xo-pyexpression)
@@ -93,7 +94,6 @@ add_subdirectory(xo-reader)
 add_subdirectory(xo-jit)
 add_subdirectory(xo-pyjit)
 #
-#add_subdirectory(xo-pyreactor)
 #add_subdirectory(xo-websock)
 #add_subdirectory(xo-pywebsock)
 #add_subdirectory(xo-statistics)
diff --git a/default.nix b/default.nix
index 5dff4f87..1ddeeb7a 100644
--- a/default.nix
+++ b/default.nix
@@ -58,6 +58,7 @@ let
           xo-printjson      = self.callPackage pkgs/xo-printjson.nix      {};
           xo-pyprintjson    = self.callPackage pkgs/xo-pyprintjson.nix    {};
           xo-reactor        = self.callPackage pkgs/xo-reactor.nix        {};
+          xo-pyreactor      = self.callPackage pkgs/xo-pyreactor.nix      {};
 #
           xo-expression     = self.callPackage pkgs/xo-expression.nix     {};
           xo-pyexpression   = self.callPackage pkgs/xo-pyexpression.nix   {};
@@ -68,7 +69,6 @@ let
                                                                             clang = llvmPackages.clang;
                                                                             llvm = llvmPackages.llvm; };
           xo-pyjit          = self.callPackage pkgs/xo-pyjit.nix          {};
-#          xo-pyreactor      = self.callPackage pkgs/xo-pyreactor.nix      {};
 #          xo-websock        = self.callPackage pkgs/xo-websock.nix        {};
 #          xo-pywebsock      = self.callPackage pkgs/xo-pywebsock.nix      {};
 #          xo-statistics     = self.callPackage pkgs/xo-statistics.nix     {};
diff --git a/pkgs/xo-pyreactor.nix b/pkgs/xo-pyreactor.nix
new file mode 100644
index 00000000..41c29aa2
--- /dev/null
+++ b/pkgs/xo-pyreactor.nix
@@ -0,0 +1,61 @@
+{
+  # nixpkgs dependencies
+  stdenv, cmake, catch2, # ... other deps here
+
+  python3Packages,
+
+  # xo dependencies
+  xo-cmake,
+
+  xo-reactor,
+  #xo-webutil,
+  #xo-refcnt,
+  #xo-pyutil,
+  #xo-reflect,
+
+  xo-pyprintjson,
+
+  # args
+
+  #   attrset for fetching source code.
+  #    { type, owner, repo, ref }
+  #
+  #   e.g. type="github", owner="rconybea", repo="cmake-examples", ref="ex1b"
+  #
+  #   see [[../flake.nix]]
+  #
+  #cmake-examples-ex1-path
+
+  # someconfigurationoption ? false
+} :
+
+stdenv.mkDerivation (finalattrs:
+  {
+    name = "xo-pyreactor";
+    version = "1.0";
+
+    outputs = [
+      "out"
+    ];
+
+    src = ../xo-pyreactor;
+
+    cmakeFlags = ["-DCMAKE_MODULE_PATH=${xo-cmake}/share/cmake"];
+    doCheck = true;
+
+    propagatedBuildInputs = [
+#      xo-refcnt
+#      xo-pyutil
+      xo-pyprintjson
+      xo-reactor
+#      xo-reflect
+    ];
+
+    nativeBuildInputs = [
+      cmake
+#      catch2
+      xo-cmake
+#      python3Packages.pybind11
+    ];
+
+  })
diff --git a/pkgs/xo-userenv.nix b/pkgs/xo-userenv.nix
index 89195b56..4d524966 100644
--- a/pkgs/xo-userenv.nix
+++ b/pkgs/xo-userenv.nix
@@ -43,7 +43,7 @@
   xo-printjson,
   xo-pyprintjson,
   xo-reactor,
-#  xo-pyreactor,
+  xo-pyreactor,
 #  xo-simulator,
 #  xo-pysimulator, xo-distribution, xo-pydistribution, xo-process, xo-pyprocess, xo-statistics, xo-kalmanfilter,
 #  xo-pykalmanfilter, xo-websock, xo-pywebsock,
@@ -90,7 +90,7 @@ buildEnv {
             xo-pyjit
             xo-pyprintjson
             xo-reactor
-#            xo-pyreactor
+            xo-pyreactor
 #            xo-websock
 #            xo-pywebsock
 #            xo-statistics