diff --git a/.envrc b/.envrc
new file mode 100644
index 0000000..894571b
--- /dev/null
+++ b/.envrc
@@ -0,0 +1,3 @@
+source_url "https://raw.githubusercontent.com/cachix/devenv/82c0147677e510b247d8b9165c54f73d32dfd899/direnvrc" "sha256-7u4iDd1nZpxL4tCzmPG0dQgC5V+/44Ba+tHkPob1v2k="
+
+use devenv
diff --git a/.gitignore b/.gitignore
index 01d9ebb..e8c6064 100644
--- a/.gitignore
+++ b/.gitignore
@@ -40,3 +40,10 @@ web/web.config
 .env
 docker-compose.override.yaml
 
+
+!/phpstan.neon
+!/tests/Architecture/**
+.devenv*
+devenv.local.nix
+.direnv
+.pre-commit-config.yaml
diff --git a/build.yaml b/build.yaml
index 151acf1..e2c7b7a 100644
--- a/build.yaml
+++ b/build.yaml
@@ -45,6 +45,10 @@ git:
   ignore:
     - '!/phpstan.neon'
     - '!/tests/Architecture/**'
+    - .devenv*
+    - devenv.local.nix
+    - .direnv
+    - .pre-commit-config.yaml
 
 experimental:
   createGitHubActionsConfiguration: true
diff --git a/devenv.lock b/devenv.lock
new file mode 100644
index 0000000..1c84c63
--- /dev/null
+++ b/devenv.lock
@@ -0,0 +1,116 @@
+{
+  "nodes": {
+    "devenv": {
+      "locked": {
+        "dir": "src/modules",
+        "lastModified": 1732585607,
+        "owner": "cachix",
+        "repo": "devenv",
+        "rev": "a520f05c40ebecaf5e17064b27e28ba8e70c49fb",
+        "type": "github"
+      },
+      "original": {
+        "dir": "src/modules",
+        "owner": "cachix",
+        "repo": "devenv",
+        "type": "github"
+      }
+    },
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1696426674,
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "gitignore": {
+      "inputs": {
+        "nixpkgs": [
+          "pre-commit-hooks",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1709087332,
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "rev": "637db329424fd7e46cf4185293b9cc8c88c95394",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1716977621,
+        "owner": "cachix",
+        "repo": "devenv-nixpkgs",
+        "rev": "4267e705586473d3e5c8d50299e71503f16a6fb6",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "ref": "rolling",
+        "repo": "devenv-nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-stable": {
+      "locked": {
+        "lastModified": 1731797254,
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "e8c38b73aeb218e27163376a2d617e61a2ad9b59",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-24.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "pre-commit-hooks": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "gitignore": "gitignore",
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "nixpkgs-stable": "nixpkgs-stable"
+      },
+      "locked": {
+        "lastModified": 1732021966,
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "rev": "3308484d1a443fc5bc92012435d79e80458fe43c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "devenv": "devenv",
+        "nixpkgs": "nixpkgs",
+        "pre-commit-hooks": "pre-commit-hooks"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/devenv.nix b/devenv.nix
new file mode 100644
index 0000000..84792ae
--- /dev/null
+++ b/devenv.nix
@@ -0,0 +1,92 @@
+{ pkgs, ... }:
+
+let
+  drupal = {
+    docroot = "web";
+    theme = {
+      name = "opdavies";
+      path = "${drupal.docroot}/themes/custom/${drupal.theme.name}";
+    };
+  };
+in
+{
+  packages = with pkgs; [ git ];
+
+  dotenv.disableHint = true;
+
+  languages = {
+    javascript = {
+      enable = true;
+      npm.enable = true;
+    };
+
+    php = {
+      enable = true;
+      version = "8.2";
+
+      ini = ''
+        memory_limit = 256M
+      '';
+
+      fpm.pools.web = {
+        listen = "127.0.0.1:9000";
+
+        settings = {
+          "pm" = "dynamic";
+          "pm.max_children" = 75;
+          "pm.max_requests" = 500;
+          "pm.max_spare_servers" = 20;
+          "pm.min_spare_servers" = 5;
+          "pm.start_servers" = 10;
+        };
+      };
+    };
+  };
+
+  services = {
+    caddy = {
+      enable = true;
+
+      config = ''
+        {
+          http_port 8080
+        }
+
+        localhost:8080 {
+          root * ${drupal.docroot}
+          encode gzip
+          php_fastcgi localhost:9000
+          file_server
+        }
+      '';
+    };
+
+    mysql = {
+      enable = true;
+      initialDatabases = [ { name = "app"; } ];
+    };
+  };
+
+  processes = {
+    tailwind.exec = ''
+      cd ${drupal.theme.path}
+      watchexec --exts css,twig tailwindcss --config assets/tailwind.config.ts \
+        --output dist/tailwind.css
+    '';
+  };
+
+  enterShell = ''
+    if [[ ! -d vendor ]]; then
+      composer install
+    fi
+
+    if [[ ! -d ${drupal.theme.path}/node_modules ]]; then
+      cd "${drupal.theme.path}" \
+        && npm clean-install
+    fi
+  '';
+
+  enterTest = ''
+    phpunit --testdox
+  '';
+}
diff --git a/devenv.yaml b/devenv.yaml
new file mode 100644
index 0000000..116a2ad
--- /dev/null
+++ b/devenv.yaml
@@ -0,0 +1,15 @@
+# yaml-language-server: $schema=https://devenv.sh/devenv.schema.json
+inputs:
+  nixpkgs:
+    url: github:cachix/devenv-nixpkgs/rolling
+
+# If you're using non-OSS software, you can set allowUnfree to true.
+# allowUnfree: true
+
+# If you're willing to use a package that's vulnerable
+# permittedInsecurePackages:
+#  - "openssl-1.1.1w"
+
+# If you have more than one devenv you can merge them
+#imports:
+# - ./backend
diff --git a/web/themes/custom/opdavies/flake.lock b/web/themes/custom/opdavies/flake.lock
deleted file mode 100644
index e99f60b..0000000
--- a/web/themes/custom/opdavies/flake.lock
+++ /dev/null
@@ -1,27 +0,0 @@
-{
-  "nodes": {
-    "nixpkgs": {
-      "locked": {
-        "lastModified": 1712192574,
-        "narHash": "sha256-LbbVOliJKTF4Zl2b9salumvdMXuQBr2kuKP5+ZwbYq4=",
-        "owner": "nixos",
-        "repo": "nixpkgs",
-        "rev": "f480f9d09e4b4cf87ee6151eba068197125714de",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nixos",
-        "ref": "nixpkgs-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
-    "root": {
-      "inputs": {
-        "nixpkgs": "nixpkgs"
-      }
-    }
-  },
-  "root": "root",
-  "version": 7
-}
diff --git a/web/themes/custom/opdavies/flake.nix b/web/themes/custom/opdavies/flake.nix
deleted file mode 100644
index 84f207d..0000000
--- a/web/themes/custom/opdavies/flake.nix
+++ /dev/null
@@ -1,13 +0,0 @@
-{
-  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
-
-  outputs = { nixpkgs, ... }:
-    let
-      system = "x86_64-linux";
-      pkgs = nixpkgs.legacyPackages.${system};
-
-      inherit (pkgs) just mkShell nodejs;
-    in {
-      devShells.${system}.default = mkShell { buildInputs = [ just nodejs ]; };
-    };
-}
diff --git a/web/themes/custom/opdavies/justfile b/web/themes/custom/opdavies/justfile
deleted file mode 100644
index a7d0c58..0000000
--- a/web/themes/custom/opdavies/justfile
+++ /dev/null
@@ -1,9 +0,0 @@
-_default:
-    just --list
-
-build-css *args:
-    npx tailwind --config assets/tailwind.config.ts \
-      --output dist/tailwind.css {{ args }}
-
-clean:
-    rm -fr node_modules dist/*