diff --git a/src/ariadne/BUILD b/src/ariadne/BUILD
index cc4bfff..e40b023 100644
--- a/src/ariadne/BUILD
+++ b/src/ariadne/BUILD
@@ -1,4 +1,5 @@
 sh_binary(
     name = "extract_and_decompile",
     srcs = ["extract-and-decompile.sh"],
+    data = ["extract-tools.nix"],
 )
diff --git a/src/ariadne/README.md b/src/ariadne/README.md
index 1075ba1..1d25d73 100644
--- a/src/ariadne/README.md
+++ b/src/ariadne/README.md
@@ -18,7 +18,7 @@ The script defaults to `<workspace>/src/ariadne/output`.
 This path stays stable when you run the command from inside `src/ariadne`.
 Use the game installation directory as the game root.
 One run processes all installed season directories.
-If `rpycdec` is not available, the script re-runs itself inside a Nix shell.
+If `rpycdec` is not available, the script uses `extract-tools.nix` to enter a Nix shell.
 
 Keep the script as a thin orchestration layer.
 Bazel owns stable inputs and wrappers.
diff --git a/src/ariadne/extract-and-decompile.sh b/src/ariadne/extract-and-decompile.sh
index 5788541..0249baa 100755
--- a/src/ariadne/extract-and-decompile.sh
+++ b/src/ariadne/extract-and-decompile.sh
@@ -46,45 +46,20 @@ enter_nix_shell_if_needed() {
 
   require_tool nix
 
-  local rpycdec_installable
-  rpycdec_installable=$(cat <<'NIX'
-let
-  pkgs = import (builtins.getFlake "nixpkgs") { system = builtins.currentSystem; };
-  rpycdec = pkgs.python3Packages.buildPythonApplication {
-    pname = "rpycdec";
-    version = "0.0.0+1000bd1";
-    pyproject = true;
-    src = pkgs.fetchFromGitHub {
-      owner = "cnfatal";
-      repo = "rpycdec";
-      rev = "1000bd1da10ef07e82f6fa560c621e6a4b55d1b8";
-      hash = "sha256-VoVbIKs8xz5x2s0OGqdHbY55fWDruqMAX8YYjEQhwTQ=";
-    };
-    nativeBuildInputs = with pkgs.python3Packages; [
-      hatch-vcs
-      hatchling
-    ];
-    env.SETUPTOOLS_SCM_PRETEND_VERSION_FOR_RPYCDEC = "0.0.0+1000bd1";
-  };
-in
-  pkgs.buildEnv {
-    name = "ariadne-extract-and-decompile-tools";
-    paths = [
-      pkgs.bash
-      pkgs.coreutils
-      pkgs.findutils
-      rpycdec
-    ];
-  }
-NIX
-)
+  local tools_nix
+  if [[ -n "${BUILD_WORKSPACE_DIRECTORY:-}" ]]; then
+    tools_nix=$BUILD_WORKSPACE_DIRECTORY/src/ariadne/extract-tools.nix
+  else
+    tools_nix=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)/extract-tools.nix
+  fi
+
+  [[ -f "$tools_nix" ]] || fail "missing Ariadne tool definition: $tools_nix"
 
   say "entering Nix shell for rpycdec"
   export ARIADNE_NIX_SHELL=1
   exec nix shell \
     --extra-experimental-features 'nix-command flakes' \
-    --impure \
-    --expr "$rpycdec_installable" \
+    --file "$tools_nix" \
     --command bash "$0" "$@"
 }
 
diff --git a/src/ariadne/extract-tools.nix b/src/ariadne/extract-tools.nix
new file mode 100644
index 0000000..70bd6b9
--- /dev/null
+++ b/src/ariadne/extract-tools.nix
@@ -0,0 +1,28 @@
+let
+  pkgs = import (builtins.getFlake "nixpkgs") { system = builtins.currentSystem; };
+  rpycdec = pkgs.python3Packages.buildPythonApplication {
+    pname = "rpycdec";
+    version = "0.0.0+1000bd1";
+    pyproject = true;
+    src = pkgs.fetchFromGitHub {
+      owner = "cnfatal";
+      repo = "rpycdec";
+      rev = "1000bd1da10ef07e82f6fa560c621e6a4b55d1b8";
+      hash = "sha256-VoVbIKs8xz5x2s0OGqdHbY55fWDruqMAX8YYjEQhwTQ=";
+    };
+    nativeBuildInputs = with pkgs.python3Packages; [
+      hatch-vcs
+      hatchling
+    ];
+    env.SETUPTOOLS_SCM_PRETEND_VERSION_FOR_RPYCDEC = "0.0.0+1000bd1";
+  };
+in
+pkgs.buildEnv {
+  name = "ariadne-extract-and-decompile-tools";
+  paths = [
+    pkgs.bash
+    pkgs.coreutils
+    pkgs.findutils
+    rpycdec
+  ];
+}