Auto-activate package.json packageManager via Corepack in nodejs plugin

examples/development/nodejs/nodejs-npm/devbox.lock

@@ -1,8 +1,13 @@
 {
   "lockfile_version": "1",
   "packages": {
+    "github:NixOS/nixpkgs/nixpkgs-unstable": {
+      "last_modified": "2026-06-01T17:55:45Z",
+      "resolved": "github:NixOS/nixpkgs/4df1b885d76a54e1aa1a318f8d16fd6005b6401f?lastModified=1780336545&narHash=sha256-vhVhuXzFrIOfcssC%2F9hDHx7MHzDKjF3keHuREOQqQiQ%3D"
+    },
     "nodejs@18": {
       "last_modified": "2024-02-15T12:53:33Z",
+      "plugin_version": "0.0.3",
       "resolved": "github:NixOS/nixpkgs/085589047343aad800c4d305cf7b98e8a3d51ae2#nodejs_18",
       "source": "devbox-search",
       "version": "18.19.1",

examples/development/nodejs/nodejs-pnpm/devbox.json

@@ -8,7 +8,11 @@
       "pnpm install"
     ],
     "scripts": {
-      "run_test": "pnpm run start"
+      "run_test": [
+        "echo \"Expecting pnpm $(node -e \"console.log(require('./package.json').packageManager.split('@')[1])\")\"",
+        "test \"$(pnpm --version)\" = \"$(node -e \"console.log(require('./package.json').packageManager.split('@')[1])\")\"",
+        "pnpm run start"
+      ]
     }
   }
 }

examples/development/nodejs/nodejs-pnpm/devbox.lock

@@ -1,8 +1,13 @@
 {
   "lockfile_version": "1",
   "packages": {
+    "github:NixOS/nixpkgs/nixpkgs-unstable": {
+      "last_modified": "2026-06-01T17:55:45Z",
+      "resolved": "github:NixOS/nixpkgs/4df1b885d76a54e1aa1a318f8d16fd6005b6401f?lastModified=1780336545&narHash=sha256-vhVhuXzFrIOfcssC%2F9hDHx7MHzDKjF3keHuREOQqQiQ%3D"
+    },
     "nodejs@latest": {
       "last_modified": "2024-02-24T23:06:34Z",
+      "plugin_version": "0.0.3",
       "resolved": "github:NixOS/nixpkgs/9a9dae8f6319600fa9aebde37f340975cab4b8c0#nodejs_21",
       "source": "devbox-search",
       "version": "21.6.2",

examples/development/nodejs/nodejs-yarn/devbox.lock

@@ -1,9 +1,13 @@
 {
   "lockfile_version": "1",
   "packages": {
+    "github:NixOS/nixpkgs/nixpkgs-unstable": {
+      "last_modified": "2026-06-01T17:55:45Z",
+      "resolved": "github:NixOS/nixpkgs/4df1b885d76a54e1aa1a318f8d16fd6005b6401f?lastModified=1780336545&narHash=sha256-vhVhuXzFrIOfcssC%2F9hDHx7MHzDKjF3keHuREOQqQiQ%3D"
+    },
     "nodejs@latest": {
       "last_modified": "2024-02-24T23:06:34Z",
-      "plugin_version": "0.0.1",
+      "plugin_version": "0.0.3",
       "resolved": "github:NixOS/nixpkgs/9a9dae8f6319600fa9aebde37f340975cab4b8c0#nodejs_21",
       "source": "devbox-search",
       "version": "21.6.2",

plugins/nodejs.json

@@ -1,15 +1,19 @@
 {
     "$schema": "https://raw.githubusercontent.com/jetify-com/devbox/main/.schema/devbox-plugin.schema.json",
-    "version": "0.0.2",
+    "version": "0.0.3",
     "name": "nodejs",
-    "readme": "Devbox automatically configures Corepack for Nodejs when DEVBOX_COREPACK_ENABLED=1. You can install Yarn or Pnpm by adding them to your `package.json` file using `packageManager`\nCorepack binaries will be installed in your local `.devbox` directory",
+    "readme": "Devbox automatically configures Corepack for Nodejs when DEVBOX_COREPACK_ENABLED=1. You can install Yarn or Pnpm by adding them to your `package.json` file using `packageManager`\nCorepack binaries will be installed in your local `.devbox` directory\n\nWhen Corepack is enabled, Devbox also activates the package manager pinned in your `package.json` `packageManager` field automatically. Set DEVBOX_DISABLE_NODEJS_PACKAGE_MANAGER_AUTODETECT=1 to disable this behavior.",
+    "env": {
+        "DEVBOX_COREPACK_BIN_DIR": "{{ .Virtenv }}/corepack-bin",
+        "PATH": "{{ .Virtenv }}/corepack-bin:$PATH"
+    },
     "shell": {
         "init_hook": [
-            "test -z $DEVBOX_COREPACK_ENABLED || corepack enable --install-directory \"{{ .Virtenv }}/corepack-bin/\"",
-            "test -z $DEVBOX_COREPACK_ENABLED || export PATH=\"{{ .Virtenv }}/corepack-bin/:$PATH\""
+            "node \"{{ .Virtenv }}/bin/setup-corepack.js\""
         ]
     },
     "create_files": {
-      "{{ .Virtenv }}/corepack-bin": ""
+      "{{ .Virtenv }}/corepack-bin": "",
+      "{{ .Virtenv }}/bin/setup-corepack.js": "nodejs/setup-corepack.js"
     }
 }

plugins/nodejs/setup-corepack.js

@@ -0,0 +1,63 @@
+// Configures Corepack for the Devbox shell. This is the nodejs plugin's
+// init_hook, invoked as: node setup-corepack.js
+//
+// It is a no-op unless DEVBOX_COREPACK_ENABLED is set, in which case it:
+//   1. Enables Corepack, installing its package-manager shims into the
+//      directory given by DEVBOX_COREPACK_BIN_DIR (which the plugin also puts
+//      on PATH via its `env` block, so no PATH export is needed here).
+//   2. Activates the package manager pinned in the project's package.json
+//      "packageManager" field (pnpm, yarn, npm, ...), unless
+//      DEVBOX_DISABLE_NODEJS_PACKAGE_MANAGER_AUTODETECT is set.
+
+const { execFileSync } = require("node:child_process");
+const path = require("node:path");
+
+if (!process.env.DEVBOX_COREPACK_ENABLED) {
+  process.exit(0);
+}
+
+const corepackBinDir = process.env.DEVBOX_COREPACK_BIN_DIR;
+if (!corepackBinDir) {
+  process.exit(0);
+}
+
+// Enable Corepack, installing the pnpm/yarn/npm shims into corepackBinDir.
+run("corepack", ["enable", "--install-directory", corepackBinDir]);
+
+// Activate the package manager pinned in package.json's "packageManager" field.
+activatePinnedPackageManager();
+
+function activatePinnedPackageManager() {
+  if (process.env.DEVBOX_DISABLE_NODEJS_PACKAGE_MANAGER_AUTODETECT) {
+    return;
+  }
+
+  const projectRoot = process.env.DEVBOX_PROJECT_ROOT;
+  if (!projectRoot) {
+    return;
+  }
+
+  let packageManager;
+  try {
+    ({ packageManager } = require(path.join(projectRoot, "package.json")));
+  } catch {
+    // No package.json (or it is unreadable) — nothing to autodetect.
+    return;
+  }
+
+  if (!packageManager) {
+    return;
+  }
+
+  run("corepack", ["prepare", "--activate", packageManager]);
+}
+
+// Run a command, inheriting stdio so Corepack's output is visible. Failures
+// must not block shell initialization.
+function run(command, args) {
+  try {
+    execFileSync(command, args, { stdio: "inherit" });
+  } catch {
+    // Ignore: e.g. Corepack unavailable, or offline during activation.
+  }
+}

testscripts/plugin/nodejs_corepack_autodetect.test.txt

@@ -0,0 +1,30 @@
+# Tests the nodejs plugin's packageManager autodetect via Corepack.
+#
+# When Corepack is enabled, the plugin's init_hook activates the package
+# manager pinned in package.json's "packageManager" field. It must gracefully
+# no-op (without breaking shell init) when package.json is missing or has no
+# "packageManager" field.
+
+env DEVBOX_COREPACK_ENABLED=1
+
+# Pin to a Node version that still bundles Corepack (unbundled as of Node 25).
+exec devbox init
+exec devbox add nodejs@22
+
+# Case 1: package.json does not exist.
+# The autodetect hook must be skipped and shell init must still succeed.
+! exists package.json
+exec devbox run -- node -e 'console.log("case1-ok")'
+stdout 'case1-ok'
+
+# Case 2: package.json exists but has no "packageManager" field.
+# The autodetect hook must no-op and shell init must still succeed.
+cp package-no-pkgmgr.json package.json
+exec devbox run -- node -e 'console.log("case2-ok")'
+stdout 'case2-ok'
+
+-- package-no-pkgmgr.json --
+{
+  "name": "nodejs-corepack-autodetect",
+  "version": "1.0.0"
+}