diff --git a/flake.nix b/flake.nix
index 2207708..1ad11b6 100644
--- a/flake.nix
+++ b/flake.nix
@@ -11,112 +11,104 @@
       self,
       nixpkgs,
       flake-utils,
+      ...
     }:
     flake-utils.lib.eachDefaultSystem (
       system:
       let
         pkgs = import nixpkgs { inherit system; };
+
+        # patched proot (relative interp + rpath)
+        prootPatched = (pkgs.proot.override { enablePython = false; }).overrideAttrs (prev: {
+          postFixup = (prev.postFixup or "") + ''
+            exe=$out/bin/proot
+            if interp="$(${pkgs.patchelf}/bin/patchelf --print-interpreter "$exe" 2>/dev/null)"; then
+              ${pkgs.patchelf}/bin/patchelf --set-interpreter ."$interp" "$exe"
+            fi
+            if rpath="$(${pkgs.patchelf}/bin/patchelf --print-rpath "$exe" 2>/dev/null)"; then
+              ${pkgs.patchelf}/bin/patchelf \
+                --set-rpath "$(printf %s "$rpath" | sed 's|/nix/store/|./nix/store/|g')" "$exe"
+            fi
+          '';
+        });
       in
       {
-        bundlers = rec {
-          proot-bundler =
-            drv:
-            pkgs.stdenvNoCC.mkDerivation {
-              name = "myApp.run";
-              nativeBuildInputs = [
-                pkgs.nix
-                pkgs.coreutils
-                pkgs.findutils
-                pkgs.gnutar
-                pkgs.gzip
-                pkgs.patchelf
+        bundlers.proot-bundler =
+          drv:
+          let
+            ci = pkgs.closureInfo {
+              rootPaths = [
+                drv
+                prootPatched
               ];
-              # patch proot as you described
-              prootPatched = (pkgs.proot.override { enablePython = false; }).overrideAttrs (_: {
-                postFixup = ''
-                  exe=$out/bin/proot
-                  ${pkgs.patchelf}/bin/patchelf \
-                    --set-interpreter ."$(${pkgs.patchelf}/bin/patchelf --print-interpreter $exe)" \
-                    --set-rpath "$(${pkgs.patchelf}/bin/patchelf --print-rpath $exe | sed 's|/nix/store/|./nix/store/|g')" \
-                    $exe
-                '';
-              });
-
-              buildCommand = ''
-                set -euo pipefail
-                # 1) Make payload dir that mirrors the bundle runtime layout
-                PAY="$PWD/payload"
-                mkdir -p "$PAY/nix/store"
-
-                # include app + patched proot in the payload closure
-                app=${drv}
-                proot=${
-                  self.bundlers.${system}.selfExtracting.prootPatched or ""
-                } # not callable; we want the attr above
-                proot=${
-                  pkgs.proot.overrideAttrs (_: {
-                    postFixup = "${pkgs.patchelf}/bin/patchelf --set-interpreter .\"$(${pkgs.patchelf}/bin/patchelf --print-interpreter $out/bin/proot)\" --set-rpath \"$( ${pkgs.patchelf}/bin/patchelf --print-rpath $out/bin/proot | sed 's|/nix/store/|./nix/store/|g')\" $out/bin/proot";
-                  })
-                }
-
-                # copy closure of app + proot into ./nix/store
-                paths=$( ${pkgs.nix}/bin/nix-store --query --requisites "$app" "$proot" )
-                for p in $paths; do
-                  cp -a --no-preserve=ownership "$p" "$PAY/nix/store/"
-                done
-
-                # discover targets for the launcher
-                APP_BIN=$(find "$app/bin" -maxdepth 1 -type f -perm -111 | head -n1)
-                APP_REL="/nix/store/$(basename "$(dirname "$APP_BIN")")/$(basename "$APP_BIN")"
-                PROOT_REL="/nix/store/$(basename "$proot")/bin/proot"
-
-                # 2) Tar.gz the payload
-                ( cd "$PAY" && tar -czf "$PWD/payload.tar.gz" . )
-
-                # 3) Assemble a self-extracting script at $out
-                cat > $out <<'SH'
-                #!/bin/sh
-                set -euf
-                # extract to temp dir
-                : "''${TMPDIR:=/tmp}"
-                EXTRACT_DIR="$(mktemp -d "''${TMPDIR%/}/nxbdl.XXXXXX")"
-                cleanup() { [ -n "''${KEEP_BUNDLE:-}" ] || rm -rf "$EXTRACT_DIR"; }
-                trap cleanup EXIT INT TERM
-
-                # locate embedded archive (line after marker)
-                ARCHIVE_LINE=$(awk '/^__ARCHIVE_BELOW__/ {print NR+1; exit 0}' "$0")
-                tail -n +$ARCHIVE_LINE "$0" | tar -xzf - -C "$EXTRACT_DIR"
-
-                cd "$EXTRACT_DIR"
-                # vars substituted by bundler at build time:
-                APP_REL='__APP_REL__'
-                PROOT_REL='__PROOT_REL__'
-
-                # run via proot
-                BUNDLE_PWD="''${BUNDLE_PWD:-$PWD}"
-                exec ".$PROOT_REL" \
-                  -b ./nix:nix \
-                  -R / \
-                  -w "$BUNDLE_PWD" \
-                  ".$APP_REL" "$@"
-
-                __ARCHIVE_BELOW__
-                SH
-
-                # substitute the program + proot paths into the stub
-                sed -i \
-                  -e "s|__APP_REL__|$APP_REL|g" \
-                  -e "s|__PROOT_REL__|$PROOT_REL|g" \
-                  $out
-                chmod +x $out
-
-                # 4) Append the payload bytes after the marker
-                cat payload.tar.gz >> $out
-              '';
             };
+            # resolve these now so we can hardcode into the runner
+            appBinGuess = "${drv}/bin";
+            prootBin = "${prootPatched}/bin/proot";
+            PROOT_REL = "/nix/store/${builtins.baseNameOf (builtins.dirOf prootBin)}/bin/proot";
+          in
+          pkgs.stdenvNoCC.mkDerivation {
+            name = "myApp.run";
+            nativeBuildInputs = [
+              pkgs.coreutils
+              pkgs.findutils
+              pkgs.gnutar
+              pkgs.gzip
+            ];
+            buildCommand = ''
+              set -euo pipefail
+              PAY="$PWD/payload"
+              mkdir -p "$PAY/nix/store"
 
-          default = proot-bundler;
-        };
+              # copy closure paths from closureInfo (no nix calls here)
+              while IFS= read -r p; do
+                cp -a --no-preserve=ownership "$p" "$PAY/nix/store/"
+              done < ${ci}/store-paths
+
+              # pick an app binary
+              APP_BIN=$(find ${appBinGuess} -maxdepth 1 -type f -perm -111 | head -n1)
+              if [ -z "''${APP_BIN:-}" ]; then
+                echo "no executable found in ${appBinGuess}" >&2
+                exit 1
+              fi
+              APP_REL="/nix/store/$(basename "$(dirname "$APP_BIN")")/$(basename "$APP_BIN")"
+
+              ( cd "$PAY" && tar -czf "$PWD/payload.tar.gz" . )
+
+              cat > $out <<'SH'
+              #!/bin/sh
+              set -euf
+              : "''${TMPDIR:=/tmp}"
+              EXTRACT_DIR="$(mktemp -d "''${TMPDIR%/}/nxbdl.XXXXXX")"
+              cleanup() { [ -n "''${KEEP_BUNDLE:-}" ] || rm -rf "$EXTRACT_DIR"; }
+              trap cleanup EXIT INT TERM
+
+              ARCHIVE_LINE=$(awk '/^__ARCHIVE_BELOW__/ {print NR+1; exit 0}' "$0")
+              tail -n +"$ARCHIVE_LINE" "$0" | tar -xzf - -C "$EXTRACT_DIR"
+
+              cd "$EXTRACT_DIR"
+              APP_REL='__APP_REL__'
+              PROOT_REL='__PROOT_REL__'
+
+              BUNDLE_PWD="''${BUNDLE_PWD:-$PWD}"
+              exec ".${PROOT_REL}" \
+                -b ./nix:nix \
+                -R / \
+                -w "$BUNDLE_PWD" \
+                ".$APP_REL" "$@"
+
+              __ARCHIVE_BELOW__
+              SH
+              sed -i \
+                -e "s|__APP_REL__|$APP_REL|g" \
+                -e "s|__PROOT_REL__|${PROOT_REL}|g" \
+                $out
+              chmod +x $out
+              cat payload.tar.gz >> $out
+            '';
+          };
+
+        default = self.bundlers.${system}.proot-bundler;
       }
     );
 }