diff --git a/tests/integration/release/version_consistency_test.ts b/tests/integration/release/version_consistency_test.ts
new file mode 100644
index 000000000..d252339db
--- /dev/null
+++ b/tests/integration/release/version_consistency_test.ts
@@ -0,0 +1,116 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+import {fileURLToPath} from 'node:url';
+import {describe, expect, it} from 'vitest';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+/** This file lives in tests/integration/release/, three levels below the root. */
+const REPO_ROOT = path.resolve(__dirname, '../../..');
+
+const MANIFEST = '.release-please-manifest.json';
+const CONFIG = 'release-please-config.json';
+
+/**
+ * release-please package path (as keyed in release-please-config.json and
+ * .release-please-manifest.json) -> its component name in the linked-versions
+ * group. Every package released with the group must be listed here.
+ */
+const LINKED_PACKAGES = {
+  '.': 'main',
+  core: 'adk',
+  dev: 'devtools',
+  integrations: 'integrations',
+} as const;
+
+/** Semver core with an optional prerelease suffix. */
+const VERSION_PATTERN = /^\d+\.\d+\.\d+(?:-[\w.]+)?$/;
+
+function isJsonObject(value: unknown): value is Record<string, unknown> {
+  return typeof value === 'object' && value !== null && !Array.isArray(value);
+}
+
+function isJsonArray(value: unknown): value is unknown[] {
+  return Array.isArray(value);
+}
+
+/** Narrows a parsed file so callers can index it without a cast. */
+function readJsonObject(relativePath: string): Record<string, unknown> {
+  const parsed: unknown = JSON.parse(
+    fs.readFileSync(path.resolve(REPO_ROOT, relativePath), 'utf8'),
+  );
+  if (!isJsonObject(parsed)) {
+    expect.fail(`Expected ${relativePath} to hold a JSON object`);
+  }
+  return parsed;
+}
+
+describe('release version consistency', () => {
+  it('pins every package.json and the release-please manifest to the same version', () => {
+    const manifest = readJsonObject(MANIFEST);
+    const versions: Record<string, unknown> = {};
+    for (const pkg of Object.keys(LINKED_PACKAGES)) {
+      const pkgJson = path.join(pkg, 'package.json');
+      versions[pkgJson] = readJsonObject(pkgJson).version;
+      versions[`${MANIFEST}#${pkg}`] = manifest[pkg];
+    }
+
+    // Guards the equality below from passing vacuously on a malformed value.
+    const rootVersion = versions['package.json'];
+    expect(rootVersion).toMatch(VERSION_PATTERN);
+
+    // Compared as one record so the diff names every file that drifted, not
+    // just the first one.
+    expect(versions).toEqual(
+      Object.fromEntries(
+        Object.keys(versions).map((source) => [source, rootVersion]),
+      ),
+    );
+  });
+
+  it('checks every package in the release-please linked-versions group', () => {
+    const config = readJsonObject(CONFIG);
+    const packagePaths = Object.keys(LINKED_PACKAGES).sort();
+
+    const packages = config.packages;
+    if (!isJsonObject(packages)) {
+      expect.fail(`Expected "packages" to be an object in ${CONFIG}`);
+    }
+    expect(Object.keys(packages).sort()).toEqual(packagePaths);
+    expect(Object.keys(readJsonObject(MANIFEST)).sort()).toEqual(packagePaths);
+
+    expect(packages).toEqual(
+      Object.fromEntries(
+        Object.entries(LINKED_PACKAGES).map(([pkg, component]) => [
+          pkg,
+          expect.objectContaining({component}),
+        ]),
+      ),
+    );
+
+    const plugins = config.plugins;
+    if (!isJsonArray(plugins)) {
+      expect.fail(`Expected "plugins" to be an array in ${CONFIG}`);
+    }
+    const linkedVersions = plugins.find(
+      (plugin) => isJsonObject(plugin) && plugin.type === 'linked-versions',
+    );
+    if (!isJsonObject(linkedVersions)) {
+      expect.fail(`Expected a "linked-versions" plugin in ${CONFIG}`);
+    }
+    const linkedComponents = linkedVersions.components;
+    if (!isJsonArray(linkedComponents)) {
+      expect.fail(`Expected "components" to be an array in ${CONFIG}`);
+    }
+    expect([...linkedComponents].sort()).toEqual(
+      Object.values(LINKED_PACKAGES).sort(),
+    );
+  });
+});