diff --git a/CHANGELOG.md b/CHANGELOG.md
index 419b81051685..0334e291efae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,10 @@ Work in this release was contributed by @zhongrenfei1-hub. Thank you for your co
 
   `@sentry/angular` now officially supports Angular 22.
 
+- **fix(node-core): Read `__SENTRY_SERVER_MODULES__` lazily so Turbopack injection is honored [#21339](https://github.com/getsentry/sentry-javascript/pull/21339)**
+
+  On Next.js 16 / Turbopack production builds, `modulesIntegration` captured `__SENTRY_SERVER_MODULES__` at module-evaluation time, before Turbopack's runtime `globalThis` assignment ran. This silently disabled module-detection-based auto integrations (Vercel AI, OpenAI, Anthropic, Google GenAI, LangChain, LangGraph) and left `event.modules` empty. The value is now read lazily, supporting both the webpack (`DefinePlugin`) and Turbopack (runtime global) injection styles.
+
 - **ref(core): Deprecate `sendDefaultPii` in favor of `dataCollection` [#21277](https://github.com/getsentry/sentry-javascript/pull/21277)**
 
   `sendDefaultPii` is deprecated and will be removed in v11. The new `dataCollection` option lets you control each category of collected data.
diff --git a/packages/node-core/src/integrations/modules.ts b/packages/node-core/src/integrations/modules.ts
index 7079f4a2fab8..701e413d55fd 100644
--- a/packages/node-core/src/integrations/modules.ts
+++ b/packages/node-core/src/integrations/modules.ts
@@ -1,6 +1,6 @@
 import { existsSync, readFileSync } from 'node:fs';
 import { dirname, join } from 'node:path';
-import type { IntegrationFn } from '@sentry/core';
+import { GLOBAL_OBJ, type IntegrationFn } from '@sentry/core';
 import { isCjs } from '../utils/detection';
 
 type ModuleInfo = Record<string, string>;
@@ -12,10 +12,24 @@ const INTEGRATION_NAME = 'Modules';
 declare const __SENTRY_SERVER_MODULES__: Record<string, string>;
 
 /**
- * `__SENTRY_SERVER_MODULES__` can be replaced at build time with the modules loaded by the server.
- * Right now, we leverage this in Next.js to circumvent the problem that we do not get access to these things at runtime.
+ * Reads the modules injected at build time into `__SENTRY_SERVER_MODULES__` (e.g. by the Next.js SDK).
+ *
+ * Must be read lazily (per call), not captured at module-eval time: webpack replaces the token via
+ * `DefinePlugin` (available immediately), but Turbopack assigns `globalThis.__SENTRY_SERVER_MODULES__`
+ * at runtime, *after* this module's imports are hoisted and evaluated. A `const` capture would be
+ * empty under Turbopack. See getsentry/sentry-javascript#19147.
  */
-const SERVER_MODULES = typeof __SENTRY_SERVER_MODULES__ === 'undefined' ? {} : __SENTRY_SERVER_MODULES__;
+function getServerModules(): Record<string, string> {
+  // webpack: the token is replaced with a literal at build time.
+  if (typeof __SENTRY_SERVER_MODULES__ !== 'undefined') {
+    return __SENTRY_SERVER_MODULES__;
+  }
+  // Turbopack: the value is assigned onto the global object at runtime.
+  return (
+    (GLOBAL_OBJ as typeof GLOBAL_OBJ & { __SENTRY_SERVER_MODULES__?: Record<string, string> })
+      .__SENTRY_SERVER_MODULES__ ?? {}
+  );
+}
 
 const _modulesIntegration = (() => {
   return {
@@ -52,7 +66,7 @@ function getRequireCachePaths(): string[] {
 /** Extract information about package.json modules */
 function collectModules(): ModuleInfo {
   return {
-    ...SERVER_MODULES,
+    ...getServerModules(),
     ...getModulesFromPackageJson(),
     ...(isCjs() ? collectRequireModules() : {}),
   };
diff --git a/packages/node-core/test/integrations/modules.test.ts b/packages/node-core/test/integrations/modules.test.ts
new file mode 100644
index 000000000000..31ee5671e40a
--- /dev/null
+++ b/packages/node-core/test/integrations/modules.test.ts
@@ -0,0 +1,36 @@
+import { GLOBAL_OBJ } from '@sentry/core';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+type GlobalWithModules = typeof GLOBAL_OBJ & { __SENTRY_SERVER_MODULES__?: Record<string, string> };
+
+describe('modulesIntegration', () => {
+  afterEach(() => {
+    delete (GLOBAL_OBJ as GlobalWithModules).__SENTRY_SERVER_MODULES__;
+    vi.resetModules();
+  });
+
+  it('includes modules injected onto the global AFTER this module was evaluated (Turbopack ordering)', async () => {
+    // Re-evaluate the integration module with no injected global present. This mirrors Turbopack:
+    // the instrumentation file's hoisted ESM imports evaluate this module *before* its
+    // `globalThis.__SENTRY_SERVER_MODULES__ = {...}` assignment runs. A module-level capture would
+    // freeze an empty value here and never see the injection (getsentry/sentry-javascript#19147).
+    vi.resetModules();
+    const { modulesIntegration } = await import('../../src/integrations/modules');
+
+    // The runtime injection happens only now — after the module is already evaluated.
+    (GLOBAL_OBJ as GlobalWithModules).__SENTRY_SERVER_MODULES__ = { '@sentry/turbopack-injected': '1.2.3' };
+
+    const modules = modulesIntegration().getModules?.() ?? {};
+    expect(modules['@sentry/turbopack-injected']).toBe('1.2.3');
+  });
+
+  it('reads modules already present before evaluation (webpack DefinePlugin / pre-set global)', async () => {
+    (GLOBAL_OBJ as GlobalWithModules).__SENTRY_SERVER_MODULES__ = { '@sentry/prebuilt-injected': '4.5.6' };
+
+    vi.resetModules();
+    const { modulesIntegration } = await import('../../src/integrations/modules');
+
+    const modules = modulesIntegration().getModules?.() ?? {};
+    expect(modules['@sentry/prebuilt-injected']).toBe('4.5.6');
+  });
+});