diff --git a/.github/workflows/cross-language-integration.yml b/.github/workflows/cross-language-integration.yml
index 9ba2a2d7b..e679af069 100644
--- a/.github/workflows/cross-language-integration.yml
+++ b/.github/workflows/cross-language-integration.yml
@@ -16,6 +16,8 @@ jobs:
 
       - name: Use Node.js
         uses: actions/setup-node@v6
+        with:
+          node-version: '24.x'
 
       - name: Setup Go
         uses: actions/setup-go@v5
diff --git a/.github/workflows/validation.yaml b/.github/workflows/validation.yaml
index 7bb00098e..a926b2309 100644
--- a/.github/workflows/validation.yaml
+++ b/.github/workflows/validation.yaml
@@ -15,6 +15,14 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
+        node: ['24.x']
+        include:
+          # The exact lower bound of engines.node in core/dev/integrations
+          # package.json. Pinned to the patch so a Node API added later in the
+          # 20.x line cannot pass CI while breaking a consumer who is still
+          # inside the declared range. Keep the two in sync.
+          - os: ubuntu-latest
+            node: '20.19.0'
 
     steps:
       - name: Checkout code
@@ -22,6 +30,8 @@ jobs:
 
       - name: Use Node.js
         uses: actions/setup-node@v6
+        with:
+          node-version: ${{ matrix.node }}
 
       - name: Setup Python
         uses: actions/setup-python@v5
diff --git a/core/package.json b/core/package.json
index 678f8c0c9..3b22cf762 100644
--- a/core/package.json
+++ b/core/package.json
@@ -8,6 +8,9 @@
     "type": "git",
     "url": "https://github.com/google/adk-js"
   },
+  "engines": {
+    "node": ">=20.19.0"
+  },
   "files": [
     "package.json",
     "README.md",
diff --git a/dev/package.json b/dev/package.json
index 6117df13a..a81465f2d 100644
--- a/dev/package.json
+++ b/dev/package.json
@@ -8,6 +8,9 @@
     "type": "git",
     "url": "https://github.com/google/adk-js"
   },
+  "engines": {
+    "node": ">=20.19.0"
+  },
   "files": [
     "package.json",
     "README.md",
diff --git a/integrations/package.json b/integrations/package.json
index b7c467b4c..cbf6cc338 100644
--- a/integrations/package.json
+++ b/integrations/package.json
@@ -8,6 +8,9 @@
     "type": "git",
     "url": "https://github.com/google/adk-js"
   },
+  "engines": {
+    "node": ">=20.19.0"
+  },
   "files": [
     "package.json",
     "README.md",
diff --git a/package-lock.json b/package-lock.json
index e29a4a190..b314c866a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -81,6 +81,9 @@
         "@types/lodash-es": "^4.17.12",
         "openapi-types": "^12.1.3"
       },
+      "engines": {
+        "node": ">=20.19.0"
+      },
       "peerDependencies": {
         "@mikro-orm/mariadb": "^6.6.6",
         "@mikro-orm/mssql": "^6.6.6",
@@ -130,6 +133,9 @@
         "tslib": "^2.6.2",
         "typescript": "^5.9.2",
         "vitest": "^3.2.4"
+      },
+      "engines": {
+        "node": ">=20.19.0"
       }
     },
     "dev/node_modules/@eslint/js": {
@@ -335,6 +341,9 @@
       "license": "Apache-2.0",
       "dependencies": {
         "@google/adk": "^1.5.0"
+      },
+      "engines": {
+        "node": ">=20.19.0"
       }
     },
     "node_modules/@a2a-js/sdk": {
diff --git a/tests/integration/package_manifests/engines_test.ts b/tests/integration/package_manifests/engines_test.ts
new file mode 100644
index 000000000..e4e5121a1
--- /dev/null
+++ b/tests/integration/package_manifests/engines_test.ts
@@ -0,0 +1,45 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import {readFile} from 'node:fs/promises';
+import path from 'node:path';
+import {describe, expect, it} from 'vitest';
+
+/**
+ * Workspace directories published to npm. The root manifest is the workspace
+ * container, is never published, and deliberately declares no engines: npm
+ * already validates a workspace package's engines during a root install.
+ */
+const PUBLISHED_WORKSPACES = ['core', 'dev', 'integrations'];
+
+interface Manifest {
+  engines?: {node?: string};
+}
+
+async function readEnginesNode(workspace: string): Promise<string | undefined> {
+  const manifestPath = path.join(process.cwd(), workspace, 'package.json');
+  const manifest = JSON.parse(await readFile(manifestPath, 'utf8')) as Manifest;
+  return manifest.engines?.node;
+}
+
+describe('published package manifests', () => {
+  it('declare one agreed engines.node range', async () => {
+    const entries = await Promise.all(
+      PUBLISHED_WORKSPACES.map(
+        async (workspace) =>
+          [workspace, await readEnginesNode(workspace)] as const,
+      ),
+    );
+    const declared = Object.fromEntries(entries);
+    const [reference] = Object.values(declared);
+
+    expect(reference).toBeDefined();
+    expect(declared).toEqual(
+      Object.fromEntries(
+        PUBLISHED_WORKSPACES.map((workspace) => [workspace, reference]),
+      ),
+    );
+  });
+});