diff --git a/.envrc b/.envrc
index 3550a30..4c6160f 100644
--- a/.envrc
+++ b/.envrc
@@ -1 +1 @@
-use flake
+use flake ./dev
diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index afdb7b2..3594b62 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -21,4 +21,4 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - uses: cachix/install-nix-action@v31
-      - run: nix flake check
+      - run: nix flake check ./dev
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 672e522..0e82542 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -1,5 +1,5 @@
 {
   "[nix]": {
-    "editor.defaultFormatter": "brettm12345.nixfmt-vscode"
+    "editor.defaultFormatter": "VanCoding.vscode-treefmt-nix"
   }
 }
diff --git a/dev/checks.nix b/dev/checks.nix
new file mode 100644
index 0000000..92dd442
--- /dev/null
+++ b/dev/checks.nix
@@ -0,0 +1,80 @@
+{
+  perSystem =
+    { pkgs, ... }:
+    let
+      prisma-factory = import ../prisma.nix;
+      yarn-v1 = pkgs.writeShellApplication {
+        name = "yarn-v1";
+        checkPhase = "";
+        runtimeInputs = [ pkgs.yarn ];
+        text = "yarn $@";
+      };
+      yarn-berry = pkgs.writeShellApplication {
+        name = "yarn-berry";
+        checkPhase = "";
+        runtimeInputs = [ pkgs.yarn-berry ];
+        text = "yarn $@";
+      };
+    in
+    {
+      checks =
+        (pkgs.callPackages ../tests.nix {
+          fetcherMode = "new";
+          inherit
+            pkgs
+            prisma-factory
+            yarn-v1
+            yarn-berry
+            ;
+        })
+        // (pkgs.callPackages ../tests.nix {
+          fetcherMode = "legacy";
+          inherit
+            pkgs
+            prisma-factory
+            yarn-v1
+            yarn-berry
+            ;
+        })
+        // {
+          fetcher-assert-npm =
+            let
+              # force download debian for consistent hash across systems
+              binaryTargetBySystem = {
+                x86_64-linux = "debian";
+                aarch64-linux = "debian";
+                x86_64-darwin = "debian";
+                aarch64-darwin = "debian";
+              };
+              prisma-legacy = prisma-factory {
+                inherit pkgs binaryTargetBySystem;
+                hash = "sha256-R9PG286KQTbzF0r/PPcShUkMiYam2prRh/JICjmhCZA=";
+              };
+              prisma-new =
+                lockName: lockFile:
+                prisma-factory {
+                  inherit pkgs binaryTargetBySystem;
+                  hash = "sha256-R9PG286KQTbzF0r/PPcShUkMiYam2prRh/JICjmhCZA=";
+                  ${lockName} = lockFile;
+                };
+            in
+            assert
+              (prisma-legacy.fromNpmLock ../npm/package-lock.json).env
+              == (prisma-new "npmLock" ../npm/package-lock.json).env;
+            pkgs.hello;
+          prisma-next =
+            (prisma-factory {
+              pkgs = pkgs;
+              versionString = "6.20.0-16.next-0c19ccc313cf9911a90d99d2ac2eb0280c76c513";
+              hash =
+                {
+                  x86_64-linux = "sha256-JWX+N/mmp9uJLcv4XFbQ3yg34fFf2BLIUpOLrrfTjEM=";
+                  x86_64-darwin = "sha256-WNwFOoeDOebbfAh4y/NvZCyE9otaJdg2hHb4ifEFD+Y=";
+                  aarch64-linux = "sha256-f9FuPZaGx0FwKo4pA9f8g82MTcAzYLwWslxjb7oqk6E=";
+                  aarch64-darwin = "sha256-NMI+JcP3epBO3V37D19TDgzivMnPekgrYqUrXB6qNV0=";
+                }
+                .${pkgs.system};
+            }).package;
+        };
+    };
+}
diff --git a/dev/flake.lock b/dev/flake.lock
new file mode 100644
index 0000000..0ffbdbb
--- /dev/null
+++ b/dev/flake.lock
@@ -0,0 +1,82 @@
+{
+  "nodes": {
+    "flake-parts": {
+      "inputs": {
+        "nixpkgs-lib": "nixpkgs-lib"
+      },
+      "locked": {
+        "lastModified": 1775087534,
+        "narHash": "sha256-91qqW8lhL7TLwgQWijoGBbiD4t7/q75KTi8NxjVmSmA=",
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "rev": "3107b77cd68437b9a76194f0f7f9c55f2329ca5b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1775095191,
+        "narHash": "sha256-CsqRiYbgQyv01LS0NlC7shwzhDhjNDQSrhBX8VuD3nM=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "106eb93cbb9d4e4726bf6bc367a3114f7ed6b32f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-lib": {
+      "locked": {
+        "lastModified": 1774748309,
+        "narHash": "sha256-+U7gF3qxzwD5TZuANzZPeJTZRHS29OFQgkQ2kiTJBIQ=",
+        "owner": "nix-community",
+        "repo": "nixpkgs.lib",
+        "rev": "333c4e0545a6da976206c74db8773a1645b5870a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "nixpkgs.lib",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-parts": "flake-parts",
+        "nixpkgs": "nixpkgs",
+        "treefmt-nix": "treefmt-nix"
+      }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1775125835,
+        "narHash": "sha256-2qYcPgzFhnQWchHo0SlqLHrXpux5i6ay6UHA+v2iH4U=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "75925962939880974e3ab417879daffcba36c4a3",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/dev/flake.nix b/dev/flake.nix
new file mode 100644
index 0000000..fea8285
--- /dev/null
+++ b/dev/flake.nix
@@ -0,0 +1,23 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    flake-parts.url = "github:hercules-ci/flake-parts";
+    treefmt-nix.url = "github:numtide/treefmt-nix";
+    treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
+  };
+  outputs =
+    inputs:
+    inputs.flake-parts.lib.mkFlake { inherit inputs; } {
+      systems = [
+        "x86_64-linux"
+        "aarch64-linux"
+        "x86_64-darwin"
+        "aarch64-darwin"
+      ];
+      imports = [
+        ./treefmt.nix
+        ./shell.nix
+        ./checks.nix
+      ];
+    };
+}
diff --git a/dev/shell.nix b/dev/shell.nix
new file mode 100644
index 0000000..71afca7
--- /dev/null
+++ b/dev/shell.nix
@@ -0,0 +1,15 @@
+{
+  perSystem =
+    { pkgs, config, ... }:
+    {
+      devShells.default = pkgs.mkShell {
+        buildInputs = [
+          pkgs.nodejs_24
+          pkgs.pnpm
+          pkgs.bun
+          pkgs.stdenv.cc.cc.lib
+          config.treefmt.build.wrapper
+        ];
+      };
+    };
+}
diff --git a/dev/treefmt.nix b/dev/treefmt.nix
new file mode 100644
index 0000000..928e039
--- /dev/null
+++ b/dev/treefmt.nix
@@ -0,0 +1,7 @@
+{ inputs, ... }:
+{
+  imports = [ inputs.treefmt-nix.flakeModule ];
+  perSystem.treefmt = {
+    programs.nixfmt.enable = true;
+  };
+}
diff --git a/flake.lock b/flake.lock
index 3665d48..5999137 100644
--- a/flake.lock
+++ b/flake.lock
@@ -1,81 +1,6 @@
 {
   "nodes": {
-    "flake-utils": {
-      "inputs": {
-        "systems": "systems"
-      },
-      "locked": {
-        "lastModified": 1731533236,
-        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
-    },
-    "nixpkgs": {
-      "locked": {
-        "lastModified": 1738703096,
-        "narHash": "sha256-1MABVDwNpAUrUDvyM6PlHlAB1eTWAX0eNYCzdsZ54NI=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "f7384aacd0ecd28681a99269ac0dff2c3a805d63",
-        "type": "github"
-      },
-      "original": {
-        "owner": "NixOS",
-        "ref": "nixpkgs-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
-    "root": {
-      "inputs": {
-        "flake-utils": "flake-utils",
-        "nixpkgs": "nixpkgs",
-        "treefmt-nix": "treefmt-nix"
-      }
-    },
-    "systems": {
-      "locked": {
-        "lastModified": 1681028828,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
-        "owner": "nix-systems",
-        "repo": "default",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-systems",
-        "repo": "default",
-        "type": "github"
-      }
-    },
-    "treefmt-nix": {
-      "inputs": {
-        "nixpkgs": [
-          "nixpkgs"
-        ]
-      },
-      "locked": {
-        "lastModified": 1738070913,
-        "narHash": "sha256-j6jC12vCFsTGDmY2u1H12lMr62fnclNjuCtAdF1a4Nk=",
-        "owner": "numtide",
-        "repo": "treefmt-nix",
-        "rev": "bebf27d00f7d10ba75332a0541ac43676985dea3",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "treefmt-nix",
-        "type": "github"
-      }
-    }
+    "root": {}
   },
   "root": "root",
   "version": 7
diff --git a/flake.nix b/flake.nix
index bde0b4b..2939b73 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,138 +1,7 @@
 {
-  inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
-    flake-utils.url = "github:numtide/flake-utils";
-    treefmt-nix.url = "github:numtide/treefmt-nix";
-    treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
-  };
-  outputs =
-    {
-      self,
-      nixpkgs,
-      flake-utils,
-      treefmt-nix,
-    }:
-    let
+  outputs = inputs: {
+    lib = {
       prisma-factory = import ./prisma.nix;
-    in
-    flake-utils.lib.eachDefaultSystem (
-      system:
-      let
-        pkgs = nixpkgs.legacyPackages.${system};
-
-        yarn-v1 = pkgs.writeShellApplication {
-          name = "yarn-v1";
-          checkPhase = "";
-          runtimeInputs = [ pkgs.yarn ];
-          text = "yarn $@";
-        };
-        yarn-berry = pkgs.writeShellApplication {
-          name = "yarn-berry";
-          checkPhase = "";
-          runtimeInputs = [ pkgs.yarn-berry ];
-          text = "yarn $@";
-        };
-        treefmt = treefmt-nix.lib.evalModule pkgs {
-          # nixfmt is nixfmt-rfc-style
-          programs.nixfmt.enable = true;
-        };
-      in
-      {
-        formatter = treefmt.config.build.wrapper;
-        checks =
-          (pkgs.callPackages ./tests.nix {
-            fetcherMode = "new";
-            inherit
-              pkgs
-              prisma-factory
-              yarn-v1
-              yarn-berry
-              ;
-          })
-          // (pkgs.callPackages ./tests.nix {
-            fetcherMode = "legacy";
-            inherit
-              pkgs
-              prisma-factory
-              yarn-v1
-              yarn-berry
-              ;
-          })
-          // {
-            format = treefmt.config.build.check self;
-            fetcher-assert-npm =
-              let
-                # force download debian for consistent hash across systems
-                binaryTargetBySystem = {
-                  x86_64-linux = "debian";
-                  aarch64-linux = "debian";
-                  x86_64-darwin = "debian";
-                  aarch64-darwin = "debian";
-                };
-                prisma-legacy = prisma-factory {
-                  inherit pkgs binaryTargetBySystem;
-                  hash = "sha256-R9PG286KQTbzF0r/PPcShUkMiYam2prRh/JICjmhCZA=";
-                };
-                prisma-new =
-                  lockName: lockFile:
-                  prisma-factory {
-                    inherit pkgs binaryTargetBySystem;
-                    hash = "sha256-R9PG286KQTbzF0r/PPcShUkMiYam2prRh/JICjmhCZA=";
-                    ${lockName} = lockFile;
-                  };
-              in
-              assert
-                (prisma-legacy.fromNpmLock ./npm/package-lock.json).env
-                == (prisma-new "npmLock" ./npm/package-lock.json).env;
-              pkgs.hello;
-            prisma-next =
-              (self.lib.prisma-factory {
-                pkgs = pkgs;
-                versionString = "6.20.0-16.next-0c19ccc313cf9911a90d99d2ac2eb0280c76c513";
-                hash =
-                  {
-                    x86_64-linux = "sha256-JWX+N/mmp9uJLcv4XFbQ3yg34fFf2BLIUpOLrrfTjEM=";
-                    x86_64-darwin = "sha256-WNwFOoeDOebbfAh4y/NvZCyE9otaJdg2hHb4ifEFD+Y=";
-                    aarch64-linux = "sha256-f9FuPZaGx0FwKo4pA9f8g82MTcAzYLwWslxjb7oqk6E=";
-                    aarch64-darwin = "sha256-NMI+JcP3epBO3V37D19TDgzivMnPekgrYqUrXB6qNV0=";
-                  }
-                  .${pkgs.system};
-              }).package;
-          };
-        packages.default =
-          (prisma-factory {
-            inherit pkgs;
-            hash = "sha256-R9PG286KQTbzF0r/PPcShUkMiYam2prRh/JICjmhCZA=";
-            versionString = "5.1.1-1.6a3747c37ff169c90047725a05a6ef02e32ac97e";
-          }).package;
-        devShells.default =
-          let
-            prisma = (
-              prisma-factory {
-                inherit pkgs;
-                hash = "sha256-R9PG286KQTbzF0r/PPcShUkMiYam2prRh/JICjmhCZA=";
-                versionString = "5.1.1-1.6a3747c37ff169c90047725a05a6ef02e32ac97e";
-              }
-            );
-          in
-          pkgs.mkShell {
-            buildInputs = [
-              pkgs.nodejs-18_x
-              pkgs.pnpm
-              pkgs.bun
-              pkgs.stdenv.cc.cc.lib
-              prisma.package
-              pkgs.nixfmt-rfc-style
-              yarn-v1
-              yarn-berry
-            ];
-            env = prisma.env;
-          };
-      }
-    )
-    // {
-      lib = {
-        inherit prisma-factory;
-      };
     };
+  };
 }
diff --git a/lib/fetcher.nix b/lib/fetcher.nix
index f336111..985cf31 100644
--- a/lib/fetcher.nix
+++ b/lib/fetcher.nix
@@ -51,7 +51,8 @@ let
       zlib
       openssl
       stdenv.cc.cc.lib
-    ] ++ lib.optionals (!isDarwin) [ autoPatchelfHook ];
+    ]
+    ++ lib.optionals (!isDarwin) [ autoPatchelfHook ];
     phases = [
       "installPhase"
       "postFixupHooks"
diff --git a/lib/legacyFetcher.nix b/lib/legacyFetcher.nix
index 8180cb4..4f48349 100644
--- a/lib/legacyFetcher.nix
+++ b/lib/legacyFetcher.nix
@@ -89,7 +89,8 @@ rec {
       zlib
       openssl
       stdenv.cc.cc.lib
-    ] ++ lib.optionals (!isDarwin) [ autoPatchelfHook ];
+    ]
+    ++ lib.optionals (!isDarwin) [ autoPatchelfHook ];
     phases = [
       "buildPhase"
       "postFixupHooks"
diff --git a/readme.md b/readme.md
index 80e711b..8dc14ae 100644
--- a/readme.md
+++ b/readme.md
@@ -67,13 +67,13 @@ The [Legacy API](./legacy-api.md) (with fromNpmLock, fromYarnLock, etc.) is now
 Before contributing, please make sure that your code is formatted correctly by running
 
 ```sh
-nix fmt
+treefmt
 ```
 
 All tests (including format check) can be run by
 
 ```sh
-nix flake check
+nix flake check ./dev
 ```
 
 ## License