diff --git a/flake.nix b/flake.nix
index 99fcaaf..2e4403a 100644
--- a/flake.nix
+++ b/flake.nix
@@ -10,20 +10,23 @@
 
   outputs =
     inputs:
-    (
+    {
+      overlays.default = import ./overlay;
+    }
+    // (
       let
         system = "x86_64-linux";
 
         pkgs = import inputs.nixpkgs {
           inherit system;
           config.allowUnfree = true;
+          overlays = [ inputs.self.overlays.default ];
         };
 
         treefmt = inputs.treefmt-nix.lib.evalModule pkgs ./treefmt.nix;
       in
       {
-        lib.${system} = import ./lib { inherit pkgs; };
-
+        packages.${system} = pkgs;
         formatter.${system} = treefmt.config.build.wrapper;
         checks.${system}.formatting = treefmt.config.build.check inputs.self;
       }
diff --git a/lib/default.nix b/lib/default.nix
deleted file mode 100644
index f613ba1..0000000
--- a/lib/default.nix
+++ /dev/null
@@ -1,8 +0,0 @@
-{ pkgs, ... }:
-let
-  callPackage = pkgs.lib.callPackageWith { inherit pkgs; };
-in
-{
-  fetchers = callPackage ./fetchers { };
-  runtime = callPackage ./runtime { };
-}
diff --git a/lib/fetchers/default.nix b/lib/fetchers/default.nix
deleted file mode 100644
index 4640293..0000000
--- a/lib/fetchers/default.nix
+++ /dev/null
@@ -1,7 +0,0 @@
-{ pkgs, ... }:
-let
-  callPackage = pkgs.lib.callPackageWith { inherit pkgs; };
-in
-{
-  sshKnownHosts = callPackage ./sshKnownHosts { };
-}
diff --git a/lib/runtime/default.nix b/lib/runtime/default.nix
deleted file mode 100644
index 27040c2..0000000
--- a/lib/runtime/default.nix
+++ /dev/null
@@ -1,7 +0,0 @@
-{ pkgs, ... }:
-let
-  callPackage = pkgs.lib.callPackageWith { inherit pkgs; };
-in
-{
-  merge = callPackage ./merge { };
-}
diff --git a/lib/runtime/merge/default.nix b/lib/runtime/merge/default.nix
deleted file mode 100644
index 9324954..0000000
--- a/lib/runtime/merge/default.nix
+++ /dev/null
@@ -1,7 +0,0 @@
-{ pkgs, ... }:
-let
-  callPackage = pkgs.lib.callPackageWith { inherit pkgs; };
-in
-{
-  keyValue = callPackage ./keyValue { };
-}
diff --git a/overlay/default.nix b/overlay/default.nix
new file mode 100644
index 0000000..658b7f3
--- /dev/null
+++ b/overlay/default.nix
@@ -0,0 +1,14 @@
+final: prev:
+{
+  lib = prev.lib.recursiveUpdate prev.lib {
+    fetchers = {
+      sshKnownHosts = import ./fetchers/sshKnownHosts final prev;
+    };
+
+    runtime = {
+      merge = {
+        keyValue = import ./runtime/merge/keyValue final prev;
+      };
+    };
+  };
+}
diff --git a/lib/fetchers/sshKnownHosts/default.nix b/overlay/fetchers/sshKnownHosts/default.nix
similarity index 71%
rename from lib/fetchers/sshKnownHosts/default.nix
rename to overlay/fetchers/sshKnownHosts/default.nix
index 440c1c0..3532183 100644
--- a/lib/fetchers/sshKnownHosts/default.nix
+++ b/overlay/fetchers/sshKnownHosts/default.nix
@@ -1,5 +1,5 @@
-{ pkgs, ... }:
-pkgs.lib.fetchers.withNormalizedHash { } (
+final: prev:
+prev.lib.fetchers.withNormalizedHash { } (
   {
     host,
     name ? "ssh-known-hosts-${host}",
@@ -13,15 +13,15 @@ pkgs.lib.fetchers.withNormalizedHash { } (
     ],
   }:
   let
-    keyTypeArgs = pkgs.lib.concatStringsSep "," keyTypes;
+    keyTypeArgs = prev.lib.concatStringsSep "," keyTypes;
   in
-  pkgs.runCommandLocal name
+  prev.runCommandLocal name
     {
       inherit outputHash outputHashAlgo;
       outputHashMode = "flat";
       preferLocalBuild = true;
 
-      nativeBuildInputs = with pkgs; [
+      nativeBuildInputs = with final; [
         openssh
         gnugrep
         coreutils
diff --git a/lib/runtime/merge/keyValue/default.nix b/overlay/runtime/merge/keyValue/default.nix
similarity index 63%
rename from lib/runtime/merge/keyValue/default.nix
rename to overlay/runtime/merge/keyValue/default.nix
index e4504c8..710c26f 100644
--- a/lib/runtime/merge/keyValue/default.nix
+++ b/overlay/runtime/merge/keyValue/default.nix
@@ -1,8 +1,8 @@
-{ pkgs, ... }:
+final: prev:
 "${
-  pkgs.writeShellApplication {
+  prev.writeShellApplication {
     name = "merge-key-value";
-    runtimeInputs = with pkgs; [
+    runtimeInputs = with final; [
       coreutils
       gawk
     ];
diff --git a/lib/runtime/merge/keyValue/key-value.sh b/overlay/runtime/merge/keyValue/key-value.sh
similarity index 100%
rename from lib/runtime/merge/keyValue/key-value.sh
rename to overlay/runtime/merge/keyValue/key-value.sh