diff --git a/flake.nix b/flake.nix
index 4e11fbe..ab66e42 100644
--- a/flake.nix
+++ b/flake.nix
@@ -42,15 +42,31 @@
   }@inputs: let
     flake    = ./.;
     nixpkgs  = nixpkgs-25-05;
-    overlays = [ self.overlays.default ];
     self-lib = import ./lib { inherit flake self inputs; };
+    
+    # Create overlay that includes legacy packages
+    overlayWithLegacy = system: final: prev: 
+      let
+        baseOverlay = (import ./overlay { inherit flake self inputs nixpkgs; }) final prev;
+        legacyPackages = import ./legacy { inherit system pkgs self; };
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ (import rust-overlay) ];
+        };
+      in
+        baseOverlay // legacyPackages;
+    
+    overlays = [ self.overlays.default ];
   in self-lib.forAllSystemsWithPkgs ([(import rust-overlay)] ++ overlays) ({
     system,
     pkgs,
   }: {
-    packages.${system}         = import ./package      { inherit system pkgs self; };
-    legacyPackages.${system}   = import ./legacy       { inherit system pkgs self; };
-    devShells.${system}        = import ./devshell     { inherit system pkgs self; };
+    packages.${system}         = import ./package      { inherit system self pkgs; };
+    devShells.${system}        = import ./devshell     { inherit system self pkgs; };
+    legacyPackages.${system}   = import ./legacy       {
+      inherit system self;
+      pkgs = import nixpkgs { inherit system; };
+    };
     nixosConfigurations = {
       "devvm-manual|${system}" = import ./nixos/system/devvm-manual/default.nix 
         { inherit flake self inputs system; };
diff --git a/legacy/default.nix b/legacy/default.nix
index 6a3dda3..973e287 100644
--- a/legacy/default.nix
+++ b/legacy/default.nix
@@ -1,4 +1,7 @@
 { self, system, pkgs }:
-{
+let 
   writers = pkgs.callPackage ./writer { };
-}
+in {
+  # NOTE(yukkop): duplicate writers in root of legacyPackages and writers due nixpkgs legacyPackages consistency
+  writers = writers;
+} // writers
diff --git a/legacy/writer/default.nix b/legacy/writer/default.nix
index 4a9c488..8b2f29a 100644
--- a/legacy/writer/default.nix
+++ b/legacy/writer/default.nix
@@ -1,41 +1,11 @@
 {
-  lib,
-  writers,
-  gcc,
-}: let
-      writeC = name: argsOrScript:
-        if lib.isAttrs argsOrScript && !lib.isDerivation argsOrScript
-        then
-          writers.makeBinWriter (
-            argsOrScript
-            // {
-              compileScript = ''
-                # Force gcc to treat the input file as C code
-                ${gcc}/bin/gcc -fsyntax-only -xc $contentPath
-                if [ $? -ne 0 ]; then
-                  echo "Syntax check failed"
-                  exit 1
-                fi
-                ${gcc}/bin/gcc -xc -o $out $contentPath
-              '';
-            }
-          )
-          name
-        else
-          writers.makeBinWriter {
-            compileScript = ''
-              # Force gcc to treat the input file as C code
-              ${gcc}/bin/gcc -fsyntax-only -xc $contentPath
-              if [ $? -ne 0 ]; then
-                echo "Syntax check failed"
-                exit 1
-              fi
-              ${gcc}/bin/gcc -xc -o $out $contentPath
-            '';
-          }
-          name
-          argsOrScript;
-      writeMinC = name: includes: body:
+  callPackage
+}: rec {
+  writeShellApplication = callPackage ./writeShellApplication.nix  {};
+  writeC                = callPackage ./writeC.nix                 {};
+  writeCBin             = name: writeC "/bin/${name}";
+  writeMinCBin          = name: includes: body: writeMinC "/bin/${name}" includes body;
+  writeMinC             = name: includes: body:
         writeC name ''
           ${builtins.concatStringsSep "\n" (map (h: "#include " + h) includes)}
 
@@ -43,9 +13,4 @@
               ${body}
           }
         '';
-in {
-  writeCBin = name: writeC "/bin/${name}";
-  writeC = writeC;
-  writeMinCBin = name: includes: body: writeMinC "/bin/${name}" includes body;
-  writeMinC = writeMinC;
 }
diff --git a/legacy/writer/writeC.nix b/legacy/writer/writeC.nix
new file mode 100644
index 0000000..c802451
--- /dev/null
+++ b/legacy/writer/writeC.nix
@@ -0,0 +1,35 @@
+{ lib, writers, gcc }:
+name: argsOrScript:
+  if 
+    lib.isAttrs argsOrScript 
+    && !lib.isDerivation argsOrScript
+  then
+    writers.makeBinWriter (
+      argsOrScript
+      // {
+        compileScript = ''
+          # Force gcc to treat the input file as C code
+          ${gcc}/bin/gcc -fsyntax-only -xc $contentPath
+          if [ $? -ne 0 ]; then
+            echo "Syntax check failed"
+            exit 1
+          fi
+          ${gcc}/bin/gcc -xc -o $out $contentPath
+        '';
+      }
+    )
+    name
+  else
+    writers.makeBinWriter {
+      compileScript = ''
+        # Force gcc to treat the input file as C code
+        ${gcc}/bin/gcc -fsyntax-only -xc $contentPath
+        if [ $? -ne 0 ]; then
+          echo "Syntax check failed"
+          exit 1
+        fi
+        ${gcc}/bin/gcc -xc -o $out $contentPath
+      '';
+    }
+    name
+    argsOrScript
diff --git a/legacy/writer/writeDashApplication.nix b/legacy/writer/writeShellApplication.nix
similarity index 81%
rename from legacy/writer/writeDashApplication.nix
rename to legacy/writer/writeShellApplication.nix
index 1d7dbd4..ba1b80e 100644
--- a/legacy/writer/writeDashApplication.nix
+++ b/legacy/writer/writeShellApplication.nix
@@ -1,3 +1,10 @@
+{
+  writeTextFile,
+  lib,
+  shellcheck-minimal,
+  stdenv,
+  runtimeShell,
+}:
 {
   /*
      The name of the script to write.
@@ -87,6 +94,8 @@
      Type: Bool
   */
   inheritPath ? true,
+
+  shell ? runtimeShell,
 }:
 writeTextFile {
   inherit
@@ -99,27 +108,26 @@ writeTextFile {
   destination = "/bin/${name}";
   allowSubstitutes = true;
   preferLocalBuild = false;
-  text =
-    ''
-      #!${dash}/bin/dash
-      ${lib.concatMapStringsSep "\n" (option: "set -o ${option}") bashOptions}
-    ''
-    + lib.optionalString (runtimeEnv != null) (
-      lib.concatStrings (
-        lib.mapAttrsToList (name: value: ''
-          ${lib.toShellVar name value}
-          export ${name}
-        '') runtimeEnv
-      )
+  text = ''
+    #!${shell}
+    ${lib.concatMapStringsSep "\n" (option: "set -o ${option}") bashOptions}
+  ''
+  + lib.optionalString (runtimeEnv != null) (
+    lib.concatStrings (
+      lib.mapAttrsToList (name: value: ''
+        ${lib.toShellVar name value}
+        export ${name}
+      '') runtimeEnv
     )
-    + lib.optionalString (runtimeInputs != [ ]) ''
+  )
+  + lib.optionalString (runtimeInputs != [ ]) ''
 
-      export PATH="${lib.makeBinPath runtimeInputs}${lib.optionalString inheritPath ":$PATH"}"
-    ''
-    + ''
+    export PATH="${lib.makeBinPath runtimeInputs}${lib.optionalString inheritPath ":$PATH"}"
+  ''
+  + ''
 
-      ${text}
-    '';
+    ${text}
+  '';
 
   checkPhase =
     let
@@ -140,11 +148,10 @@ writeTextFile {
     if checkPhase == null then
       ''
         runHook preCheck
-	#dryrun
-	${dash}/bin/dash -n -O extglob "$target"
+        ${stdenv.shellDryRun} "$target"
         ${shellcheckCommand}
         runHook postCheck
       ''
     else
       checkPhase;
-};
+}
diff --git a/nixos/module/generic/postgresql.nix b/nixos/module/generic/postgresql.nix
index 992639c..d667a36 100644
--- a/nixos/module/generic/postgresql.nix
+++ b/nixos/module/generic/postgresql.nix
@@ -49,7 +49,7 @@ in {
       extensions = let
         packages = {
           inherit (cfg.package.pkgs) pg_net pgjwt pg_cron http pg_smtp_client plsh;
-          hemar = inputs.hutil.packages.${system}.pg-15-hemar;
+          hemar = self.packages.${system}.pg-15-hemar;
         };
       in
         lib.attrValues (
diff --git a/overlay/default.nix b/overlay/default.nix
index 0343fc9..8f74480 100644
--- a/overlay/default.nix
+++ b/overlay/default.nix
@@ -5,7 +5,7 @@ in final: prev: (
     packages = self.packages.${prev.system};
     legacyPackages = self.legacyPackages.${prev.system};
   in {
-    hectic = packages;
+    hectic = packages // legacyPackages;
     postgresql_17 = prev.postgresql_17 // {pkgs = prev.postgresql_17.pkgs // {
       http = packages.pg-17-ext-http;
       pg_smtp_client = packages.pg-17-ext-smtp-client;
@@ -27,6 +27,5 @@ in final: prev: (
       plsh = packages.pg-15-ext-plsh;
       hemar = packages.pg-15-ext-hemar;
     };};
-    writers = prev.writers // legacyPackages.writers;
   }
 )
diff --git a/overlay/writeDashApplication.nix b/overlay/writeDashApplication.nix
deleted file mode 100644
index 1d7dbd4..0000000
--- a/overlay/writeDashApplication.nix
+++ /dev/null
@@ -1,150 +0,0 @@
-{
-  /*
-     The name of the script to write.
-
-     Type: String
-  */
-  name,
-  /*
-     The shell script's text, not including a shebang.
-
-     Type: String
-  */
-  text,
-  /*
-     Inputs to add to the shell script's `$PATH` at runtime.
-
-     Type: [String|Derivation]
-  */
-  runtimeInputs ? [ ],
-  /*
-     Extra environment variables to set at runtime.
-
-     Type: AttrSet
-  */
-  runtimeEnv ? null,
-  /*
-     `stdenv.mkDerivation`'s `meta` argument.
-
-     Type: AttrSet
-  */
-  meta ? { },
-  /*
-     `stdenv.mkDerivation`'s `passthru` argument.
-
-     Type: AttrSet
-  */
-  passthru ? { },
-  /*
-     The `checkPhase` to run. Defaults to `shellcheck` on supported
-     platforms and `bash -n`.
-
-     The script path will be given as `$target` in the `checkPhase`.
-
-     Type: String
-  */
-  checkPhase ? null,
-  /*
-     Checks to exclude when running `shellcheck`, e.g. `[ "SC2016" ]`.
-
-     See <https://www.shellcheck.net/wiki/> for a list of checks.
-
-     Type: [String]
-  */
-  excludeShellChecks ? [ ],
-  /*
-     Extra command-line flags to pass to ShellCheck.
-
-     Type: [String]
-  */
-  extraShellCheckFlags ? [ ],
-  /*
-     Bash options to activate with `set -o` at the start of the script.
-
-     Defaults to `[ "errexit" "nounset" "pipefail" ]`.
-
-     Type: [String]
-  */
-  bashOptions ? [
-    "errexit"
-    "nounset"
-    "pipefail"
-  ],
-  /*
-    Extra arguments to pass to `stdenv.mkDerivation`.
-
-    :::{.caution}
-    Certain derivation attributes are used internally,
-    overriding those could cause problems.
-    :::
-
-    Type: AttrSet
-  */
-  derivationArgs ? { },
-  /*
-     Whether to inherit the current `$PATH` in the script.
-
-     Type: Bool
-  */
-  inheritPath ? true,
-}:
-writeTextFile {
-  inherit
-    name
-    meta
-    passthru
-    derivationArgs
-    ;
-  executable = true;
-  destination = "/bin/${name}";
-  allowSubstitutes = true;
-  preferLocalBuild = false;
-  text =
-    ''
-      #!${dash}/bin/dash
-      ${lib.concatMapStringsSep "\n" (option: "set -o ${option}") bashOptions}
-    ''
-    + lib.optionalString (runtimeEnv != null) (
-      lib.concatStrings (
-        lib.mapAttrsToList (name: value: ''
-          ${lib.toShellVar name value}
-          export ${name}
-        '') runtimeEnv
-      )
-    )
-    + lib.optionalString (runtimeInputs != [ ]) ''
-
-      export PATH="${lib.makeBinPath runtimeInputs}${lib.optionalString inheritPath ":$PATH"}"
-    ''
-    + ''
-
-      ${text}
-    '';
-
-  checkPhase =
-    let
-      excludeFlags = lib.optionals (excludeShellChecks != [ ]) [
-        "--exclude"
-        (lib.concatStringsSep "," excludeShellChecks)
-      ];
-      # GHC (=> shellcheck) isn't supported on some platforms (such as risc-v)
-      # but we still want to use writeShellApplication on those platforms
-      shellcheckCommand = lib.optionalString shellcheck-minimal.compiler.bootstrapAvailable ''
-        # use shellcheck which does not include docs
-        # pandoc takes long to build and documentation isn't needed for just running the cli
-        ${lib.getExe shellcheck-minimal} ${
-          lib.escapeShellArgs (excludeFlags ++ extraShellCheckFlags)
-        } "$target"
-      '';
-    in
-    if checkPhase == null then
-      ''
-        runHook preCheck
-	#dryrun
-	${dash}/bin/dash -n -O extglob "$target"
-        ${shellcheckCommand}
-        runHook postCheck
-      ''
-    else
-      checkPhase;
-};
diff --git a/package/sentinèlla/default.nix b/package/sentinèlla/default.nix
index 92e0ca4..90c1fbf 100644
--- a/package/sentinèlla/default.nix
+++ b/package/sentinèlla/default.nix
@@ -1,25 +1,35 @@
 { symlinkJoin, writeShellApplication, socat, dash, hectic, curl }:
 let
-  base64 = writeShellApplication {
+  shell = "${dash}/bin/dash";
+  bashOptions = [
+    "errexit"
+    "nounset"
+  ];
+
+  base64 = hectic.writeShellApplication {
+    inherit shell bashOptions;
     name = "base64";
     runtimeInputs = [ ];
     text = builtins.readFile ./base64.sh;
   };
 
   # TODO: writeDashApplication
-  probe = writeShellApplication {
+  probe = hectic.writeShellApplication {
+    inherit shell bashOptions;
     name = "probe";
     runtimeInputs = [ socat dash probe-loop ];
     text = builtins.readFile ./probe.sh;
   };
 
-  probe-loop = writeShellApplication {
+  probe-loop = hectic.writeShellApplication {
+    inherit shell bashOptions;
     name = "probe-loop";
     runtimeInputs = [ base64 ];
     text = builtins.readFile ./probe-loop.sh;
   };
 
-  sentinel = writeShellApplication {
+  sentinel = hectic.writeShellApplication {
+    inherit shell bashOptions;
     name = "sentinel";
     runtimeInputs = [ hectic.shellplot curl ];
     text = builtins.readFile ./sentinel.sh;
diff --git a/package/sentinèlla/probe.sh b/package/sentinèlla/probe.sh
index ffeb0d1..a89d185 100644
--- a/package/sentinèlla/probe.sh
+++ b/package/sentinèlla/probe.sh
@@ -1,15 +1,5 @@
 #!/usr/bin/env dash
 
-#
-#
-#
-#
-#
-#
-#
-#
-
-set -euo pipefail
 socat -V >/dev/null
 dash -c 'echo ok' >/dev/null