fix(nuxt): Detect Nitro version via the app's Nuxt dependency chain

packages/nuxt/src/module.ts

@@ -94,7 +94,7 @@ export default defineNuxtModule<ModuleOptions>({
     }
 
     const serverConfigFile = await findDefaultSdkInitFile('server', nuxt, moduleOptions);
-    const isNitroV3 = (await getNitroMajorVersion()) >= 3;
+    const isNitroV3 = (await getNitroMajorVersion(nuxt.options.rootDir)) >= 3;
     const nuxtMajor = parseInt((nuxt as unknown as { _version: string })._version?.split('.')[0] ?? '3', 10);
     const isMinNuxtV4 = nuxtMajor >= 4;
 

packages/nuxt/src/vite/utils.ts

@@ -7,21 +7,37 @@ import type { SentryNuxtModuleOptions } from '../common/types';
 import { resolvePath } from '@nuxt/kit';
 
 /**
- * Gets the major version of the installed nitro package.
- * Returns 2 as the default if nitro is not found or the version cannot be determined.
+ * Gets the major version of the Nitro package used by the app's Nuxt installation.
+ * Returns 2 as the default if the version cannot be determined.
+ *
+ * Nitro v2 is published as `nitropack`, v3 as `nitro`. Resolving `nitro` directly is
+ * unreliable: module resolution walks up the directory tree, so in a monorepo an
+ * unrelated `nitro` v3 above the app wins even when the app's Nuxt uses `nitropack` v2.
+ * Instead, follow the dependency chain Nuxt itself imports Nitro through:
+ * `nuxt` -> (`@nuxt/nitro-server` ->) `nitro` | `nitropack`.
  */
-export async function getNitroMajorVersion(): Promise<number> {
+export async function getNitroMajorVersion(rootDir: string): Promise<number> {
   try {
     const { getPackageInfo } = await import('local-pkg');
-    const info = await getPackageInfo('nitro');
-    if (info?.version) {
-      const major = parseInt(info.version.split('.')[0] ?? '2', 10);
-      return isNaN(major) ? 2 : major;
+
+    // The package that declares the Nitro dependency: `nuxt` itself, or `@nuxt/nitro-server` (Nuxt >= 3.21) when nuxt delegates to it
+    let provider = await getPackageInfo('nuxt', { paths: [rootDir] });
+    if (provider?.packageJson.dependencies?.['@nuxt/nitro-server']) {
+      provider = (await getPackageInfo('@nuxt/nitro-server', { paths: [provider.rootPath] })) ?? provider;
     }
+
+    if (!provider?.packageJson.dependencies?.nitro) {
+      return 2;
+    }
+
+    const info = await getPackageInfo('nitro', { paths: [provider.rootPath] });
+    const major = parseInt(info?.version?.split('.')[0] ?? '', 10);
+    // The provider imports `nitro` (not `nitropack`), so it is at least v3 even if the version is unreadable
+    return isNaN(major) ? 3 : major;
   } catch {
-    // If local-pkg is unavailable or nitro is not found, default to v2
+    // If local-pkg is unavailable or resolution fails, default to v2
+    return 2;
   }
-  return 2;
 }
 
 /**

packages/nuxt/test/vite/nitroVersion.test.ts

@@ -0,0 +1,107 @@
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { getNitroMajorVersion } from '../../src/vite/utils';
+
+// Real filesystem fixtures instead of mocks: the bug this guards against lives in
+// module resolution walking up the directory tree, which mocks cannot reproduce.
+let monorepoRoot: string;
+
+function writePackage(dir: string, packageJson: Record<string, unknown>): void {
+  fs.mkdirSync(dir, { recursive: true });
+  fs.writeFileSync(path.join(dir, 'package.json'), JSON.stringify({ main: 'index.js', ...packageJson }));
+  fs.writeFileSync(path.join(dir, 'index.js'), '');
+}
+
+function createApp(appName: string, packages: Record<string, Record<string, unknown>>): string {
+  const appDir = path.join(monorepoRoot, 'apps', appName);
+  fs.mkdirSync(appDir, { recursive: true });
+  for (const [name, packageJson] of Object.entries(packages)) {
+    writePackage(path.join(appDir, 'node_modules', name), packageJson);
+  }
+  return appDir;
+}
+
+beforeAll(() => {
+  monorepoRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'sentry-nitro-version-'));
+  // An unrelated Nitro v3 above the apps, like a monorepo root devDependency
+  writePackage(path.join(monorepoRoot, 'node_modules', 'nitro'), { name: 'nitro', version: '3.0.0-beta.1' });
+});
+
+afterAll(() => {
+  fs.rmSync(monorepoRoot, { recursive: true, force: true });
+});
+
+describe('getNitroMajorVersion', () => {
+  it('detects v2 when nuxt depends on nitropack directly (Nuxt 3 / <=4.1), ignoring a nitro v3 higher up the tree', async () => {
+    const appDir = createApp('nuxt-4-old', {
+      nuxt: { name: 'nuxt', version: '4.1.0', dependencies: { nitropack: '^2.12.0' } },
+      nitropack: { name: 'nitropack', version: '2.12.0' },
+    });
+
+    await expect(getNitroMajorVersion(appDir)).resolves.toBe(2);
+  });
+
+  it('detects v2 through @nuxt/nitro-server when it depends on nitropack (Nuxt >=3.21 stable)', async () => {
+    const appDir = createApp('nuxt-4-stable', {
+      nuxt: { name: 'nuxt', version: '4.5.2', dependencies: { '@nuxt/nitro-server': '4.5.2' } },
+      '@nuxt/nitro-server': { name: '@nuxt/nitro-server', version: '4.5.2', dependencies: { nitropack: '^2.13.4' } },
+      nitropack: { name: 'nitropack', version: '2.13.4' },
+    });
+
+    await expect(getNitroMajorVersion(appDir)).resolves.toBe(2);
+  });
+
+  it('detects v3 through @nuxt/nitro-server when it depends on nitro (Nuxt 5)', async () => {
+    const appDir = createApp('nuxt-5', {
+      nuxt: {
+        name: 'nuxt',
+        version: '5.0.0',
+        dependencies: { '@nuxt/nitro-server': 'npm:@nuxt/nitro-server-nightly' },
+      },
+      '@nuxt/nitro-server': {
+        name: '@nuxt/nitro-server-nightly',
+        version: '5.0.0-nightly',
+        dependencies: { nitro: '^3.0.0-beta' },
+      },
+      nitro: { name: 'nitro', version: '3.0.0-beta.2' },
+    });
+
+    await expect(getNitroMajorVersion(appDir)).resolves.toBe(3);
+  });
+
+  it('detects v3 when nuxt depends on nitro directly, without @nuxt/nitro-server', async () => {
+    const appDir = createApp('nuxt-direct-nitro', {
+      nuxt: { name: 'nuxt', version: '5.1.0', dependencies: { nitro: '^3.1.0' } },
+      nitro: { name: 'nitro', version: '3.1.0' },
+    });
+
+    await expect(getNitroMajorVersion(appDir)).resolves.toBe(3);
+  });
+
+  it('falls back to v3 when the declared nitro package has no readable version (stub package)', async () => {
+    const appDir = createApp('nuxt-5-stub', {
+      nuxt: {
+        name: 'nuxt',
+        version: '5.0.0',
+        dependencies: { '@nuxt/nitro-server': 'npm:@nuxt/nitro-server-nightly' },
+      },
+      '@nuxt/nitro-server': {
+        name: '@nuxt/nitro-server-nightly',
+        version: '5.0.0-nightly',
+        dependencies: { nitro: '^3.0.0-beta' },
+      },
+      nitro: { name: 'nitro' },
+    });
+
+    await expect(getNitroMajorVersion(appDir)).resolves.toBe(3);
+  });
+
+  it('defaults to v2 when nuxt cannot be resolved', async () => {
+    const appDir = path.join(monorepoRoot, 'apps', 'no-nuxt');
+    fs.mkdirSync(appDir, { recursive: true });
+
+    await expect(getNitroMajorVersion(appDir)).resolves.toBe(2);
+  });
+});