diff --git a/.envrc b/.envrc
new file mode 100644
index 0000000..3550a30
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/flake.lock b/flake.lock
index e12ff47..710e4d1 100644
--- a/flake.lock
+++ b/flake.lock
@@ -1,5 +1,28 @@
 {
   "nodes": {
+    "alejandra": {
+      "inputs": {
+        "fenix": "fenix",
+        "flakeCompat": "flakeCompat",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1744324181,
+        "narHash": "sha256-Oi1n2ncF4/AWeY6X55o2FddIRICokbciqFYK64XorYk=",
+        "owner": "kamadorueda",
+        "repo": "alejandra",
+        "rev": "3e2a85506627062313e131bf8a85315f3387c8e0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "kamadorueda",
+        "ref": "4.0.0",
+        "repo": "alejandra",
+        "type": "github"
+      }
+    },
     "elisp-helpers": {
       "inputs": {
         "fromElisp": "fromElisp"
@@ -53,6 +76,28 @@
         "type": "github"
       }
     },
+    "fenix": {
+      "inputs": {
+        "nixpkgs": [
+          "alejandra",
+          "nixpkgs"
+        ],
+        "rust-analyzer-src": "rust-analyzer-src"
+      },
+      "locked": {
+        "lastModified": 1730615655,
+        "narHash": "sha256-2HBR3zLn57LXKNRtxBb+O+uDqHM4n0pz51rPayMl4cg=",
+        "owner": "nix-community",
+        "repo": "fenix",
+        "rev": "efeb50e2535b17ffd4a135e6e3e5fd60a525180c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "fenix",
+        "type": "github"
+      }
+    },
     "flake-parts": {
       "inputs": {
         "nixpkgs-lib": "nixpkgs-lib"
@@ -89,6 +134,22 @@
         "type": "github"
       }
     },
+    "flakeCompat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
     "fromElisp": {
       "flake": false,
       "locked": {
@@ -239,6 +300,7 @@
     },
     "root": {
       "inputs": {
+        "alejandra": "alejandra",
         "emacs-builtins": "emacs-builtins",
         "epkgs": "epkgs",
         "flake-parts": "flake-parts_2",
@@ -251,6 +313,23 @@
         "twist": "twist"
       }
     },
+    "rust-analyzer-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1730555913,
+        "narHash": "sha256-KNHZUlqsEibg3YtfUyOFQSofP8hp1HKoY+laoesBxRM=",
+        "owner": "rust-lang",
+        "repo": "rust-analyzer",
+        "rev": "f17a5bbfd0969ba2e63a74505a80e55ecb174ed9",
+        "type": "github"
+      },
+      "original": {
+        "owner": "rust-lang",
+        "ref": "nightly",
+        "repo": "rust-analyzer",
+        "type": "github"
+      }
+    },
     "systems": {
       "locked": {
         "lastModified": 1681028828,
diff --git a/flake.nix b/flake.nix
index 6be36f5..cff555e 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,5 +1,11 @@
 {
   inputs = {
+    alejandra = {
+      url = "github:kamadorueda/alejandra/4.0.0";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+      };
+    };
     flake-parts.url = "github:hercules-ci/flake-parts";
     systems.url = "github:nix-systems/default";
     twist.url = "github:emacs-twist/twist.nix";
@@ -38,6 +44,13 @@
       perSystem = { config, pkgs, ... }:
         let emacs-package = pkgs.emacs;
         in {
+          devShells.default = pkgs.mkShell {
+            buildInputs = with pkgs; [
+              nil
+              just
+              alejandra
+            ];
+          };
           packages = {
             emacs = (inputs.twist.lib.makeEnv {
               inherit pkgs;
diff --git a/justfile b/justfile
new file mode 100644
index 0000000..8cf65b5
--- /dev/null
+++ b/justfile
@@ -0,0 +1,6 @@
+lock *args:
+    @nix run '.#lock' --impure -- {{args}}
+update *args:
+    @nix run '.#update' --impure -- {{args}}
+test *args:
+    @nix run '.#emacs' -- --init-directory . {{args}}