diff --git a/default.nix b/default.nix
index 07182293..f4897bf6 100644
--- a/default.nix
+++ b/default.nix
@@ -84,13 +84,19 @@ let
 #  };
 
   # Problem: builds *everything* with llvm18 toolchain, exposes too many compiler nits
-  llvm-overlay = self: super: {
+  llvm-overlay = self: super:
     # use 'super' when you want to override the terms of a package.
     # use 'self'  when pointing to an existing package
     #
 
-    llvmPackages = super.llvmPackages_18;
-  };
+    let
+      llvmPackages = super.llvmPackages_18;
+    in let
+      clangStdenv = super.overrideCC super.stdenv super.llvmPackages_18.clang;
+    in let
+      jitStdenv = if super.stdenv.isDarwin then clangStdenv else super.stdenv;
+    in
+      { inherit llvmPackages clangStdenv jitStdenv; };
 
   # tests excruciatingly slow
   mailutils-overlay = self: super: {
@@ -133,30 +139,31 @@ let
 
       in
         {
-            xo-cmake          = self.callPackage pkgs/xo-cmake.nix          {};
-            xo-indentlog      = self.callPackage pkgs/xo-indentlog.nix      { buildDocs = true; buildExamples = true; };
-            xo-subsys         = self.callPackage pkgs/xo-subsys.nix         {};
-            xo-randomgen      = self.callPackage pkgs/xo-randomgen.nix      {                   buildExamples = true; };
-            xo-reflectutil    = self.callPackage pkgs/xo-reflectutil.nix    {};
-            xo-arena          = self.callPackage pkgs/xo-arena.nix          { buildDocs = true; };
-            xo-facet          = self.callPackage pkgs/xo-facet.nix          {};
-            xo-allocutil      = self.callPackage pkgs/xo-allocutil.nix      {};
-            xo-alloc          = self.callPackage pkgs/xo-alloc.nix          { buildDocs = true; };
-            xo-alloc2         = self.callPackage pkgs/xo-alloc2.nix         { buildDocs = true; };
-            xo-gc             = self.callPackage pkgs/xo-gc.nix             { buildDocs = true; };
-            xo-refcnt         = self.callPackage pkgs/xo-refcnt.nix         {};
-            xo-ordinaltree    = self.callPackage pkgs/xo-ordinaltree.nix    {};
-            xo-flatstring     = self.callPackage pkgs/xo-flatstring.nix     { buildDocs = true; buildExamples = true; };
-            xo-pyutil         = self.callPackage pkgs/xo-pyutil.nix         {};
-            xo-reflect        = self.callPackage pkgs/xo-reflect.nix        {};
-            xo-pyreflect      = self.callPackage pkgs/xo-pyreflect.nix      {};
-            xo-ratio          = self.callPackage pkgs/xo-ratio.nix          { buildDocs = true; buildExamples = true; };
-            xo-unit           = self.callPackage pkgs/xo-unit.nix           { buildDocs = true; buildExamples = true; };
-            xo-pyunit         = self.callPackage pkgs/xo-pyunit.nix         {};
+            xo-cmake          = self.callPackage pkgs/xo-cmake.nix          { stdenv = jitStdenv; };
+            xo-indentlog      = self.callPackage pkgs/xo-indentlog.nix      { stdenv = jitStdenv; buildDocs = true; buildExamples = true; };
+            xo-subsys         = self.callPackage pkgs/xo-subsys.nix         { stdenv = jitStdenv; };
+            xo-randomgen      = self.callPackage pkgs/xo-randomgen.nix      { stdenv = jitStdenv;                   buildExamples = true; };
+            xo-reflectutil    = self.callPackage pkgs/xo-reflectutil.nix    { stdenv = jitStdenv; };
+            xo-flatstring     = self.callPackage pkgs/xo-flatstring.nix     { stdenv = jitStdenv; buildDocs = true; buildExamples = true; };
+            xo-arena          = self.callPackage pkgs/xo-arena.nix          { stdenv = jitStdenv; buildDocs = true; };
+            xo-facet          = self.callPackage pkgs/xo-facet.nix          { stdenv = jitStdenv; };
+            xo-allocutil      = self.callPackage pkgs/xo-allocutil.nix      { stdenv = jitStdenv; };
+            xo-alloc          = self.callPackage pkgs/xo-alloc.nix          { stdenv = jitStdenv; buildDocs = true; };
+            xo-alloc2         = self.callPackage pkgs/xo-alloc2.nix         { stdenv = jitStdenv; buildDocs = true; };
+            xo-gc             = self.callPackage pkgs/xo-gc.nix             { stdenv = jitStdenv; buildDocs = true; };
+            xo-object         = self.callPackage pkgs/xo-object.nix         { stdenv = jitStdenv; };
+            xo-refcnt         = self.callPackage pkgs/xo-refcnt.nix         { stdenv = jitStdenv; };
+            xo-ordinaltree    = self.callPackage pkgs/xo-ordinaltree.nix    { stdenv = jitStdenv; };
+            xo-pyutil         = self.callPackage pkgs/xo-pyutil.nix         { stdenv = jitStdenv; };
+            xo-reflect        = self.callPackage pkgs/xo-reflect.nix        { stdenv = jitStdenv; };
+            xo-pyreflect      = self.callPackage pkgs/xo-pyreflect.nix      { stdenv = jitStdenv; };
+            xo-ratio          = self.callPackage pkgs/xo-ratio.nix          { stdenv = jitStdenv; buildDocs = true; buildExamples = true; };
+            xo-unit           = self.callPackage pkgs/xo-unit.nix           { stdenv = jitStdenv; buildDocs = true; buildExamples = true; };
+            xo-pyunit         = self.callPackage pkgs/xo-pyunit.nix         { stdenv = jitStdenv; };
             #
-            xo-callback       = self.callPackage pkgs/xo-callback.nix       {};
-            xo-printable2     = self.callPackage pkgs/xo-printable2.nix     {};
-            xo-webutil        = self.callPackage pkgs/xo-webutil.nix        {};
+            xo-callback       = self.callPackage pkgs/xo-callback.nix       { stdenv = jitStdenv; };
+            xo-printable2     = self.callPackage pkgs/xo-printable2.nix     { stdenv = jitStdenv; };
+            xo-webutil        = self.callPackage pkgs/xo-webutil.nix        { stdenv = jitStdenv; };
             xo-pywebutil      = self.callPackage pkgs/xo-pywebutil.nix      {};
             xo-printjson      = self.callPackage pkgs/xo-printjson.nix      {};
             xo-pyprintjson    = self.callPackage pkgs/xo-pyprintjson.nix    {};
@@ -493,6 +500,7 @@ in
     alloc          = pkgs.xo-alloc;
     alloc2         = pkgs.xo-alloc2;
     gc             = pkgs.xo-gc;
+    object         = pkgs.xo-object;
     ordinaltree    = pkgs.xo-ordinaltree;
     flatstring     = pkgs.xo-flatstring;
     pyutil         = pkgs.xo-pyutil;
@@ -741,6 +749,7 @@ in
   #  1 - get this to work as standalone copy of shell4-assembly
   #  2 - merge to look like shell4-wsl / shell4-nvidia
   #
+  #shell4-osx = pkgs.mkShell.override { stdenv = pkgs.jitStdenv; } { .. } # very high attack surface area
   shell4-osx = pkgs.mkShell {
     buildInputs = docutils ++ xodeps ++ devutils ++ ideutils ++ x11utils ++ gldeps ++ vkdeps ++ imguideps;
 
diff --git a/pkgs/xo-object.nix b/pkgs/xo-object.nix
new file mode 100644
index 00000000..7d65efe7
--- /dev/null
+++ b/pkgs/xo-object.nix
@@ -0,0 +1,49 @@
+{
+  # nixpkgs dependencies
+  lib, stdenv, cmake, catch2,
+
+  # xo dependencies
+#  xo-reflect,
+#  xo-webutil,
+  xo-callback,
+  xo-unit,
+  xo-refcnt,
+  xo-reflectutil,
+  xo-alloc,
+  xo-randomgen,
+  xo-cmake,
+#  xo-printjson,
+#  xo-ordinaltree,
+  xo-indentlog,
+  doCheck ? true,
+} :
+
+stdenv.mkDerivation (finalattrs:
+  {
+    name = "xo-object";
+
+    src = ../xo-object;
+
+    cmakeFlags = ["-DCMAKE_MODULE_PATH=${xo-cmake}/share/cmake"]
+                 ++ lib.optionals doCheck ["-DENABLE_TESTING=1"];
+
+    inherit doCheck;
+
+    nativeBuildInputs = [
+      cmake catch2
+      xo-randomgen
+      xo-cmake
+    ];
+    propagatedBuildInputs = [
+      xo-callback
+      xo-unit
+      xo-refcnt
+#      xo-reflect
+#      xo-webutil
+#      xo-printjson
+#      xo-ordinaltree
+      xo-alloc
+      xo-reflectutil
+      xo-indentlog
+    ];
+  })