fix(v10/cloudflare): auto-instrument when wrangler main is a package (#25430)

Backport of: #25343

## Differences to the original PR

- `packages/cloudflare/src/vite/transform.ts`: on v10, a local class
already wrapped by a named export keeps its binding (which now points at
the wrapped class), so `export { Foo as default }` stays as written
instead of being re-pointed at a wrapper name.
- `packages/cloudflare/src/vite/autoInstrument.ts`, tests and the
`cloudflare-autoinstrument-package-entry` e2e app: small adjustments to
fit v10's code layout.

Heads-up: this conflicts with #25407 (backport of #25345) in
`packages/cloudflare/src/vite/transform.ts` and its test. Whichever
lands second needs a rebase.

This branch was prepared by the v10 backport automation, which was
blocked at PR creation; it's opened manually now.

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via **Jan Peer Stöcklmair**.
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---------

Co-authored-by: sentry-junior[bot] <264270552+sentry-junior[bot]@users.noreply.github.com>
Co-authored-by: Nicolas Hrubec <nicolas.hrubec@outlook.com>

Author: sentry-junior[bot]

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/.gitignore

@@ -0,0 +1,4 @@
+dist
+.wrangler
+test-results
+pnpm-lock.yaml

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/instrument.server.ts

@@ -0,0 +1,10 @@
+import { defineCloudflareOptions } from '@sentry/cloudflare';
+
+// The worker entry is a package, so the plugin reads this file from beside
+// the wrangler config.
+export default defineCloudflareOptions((env: { E2E_TEST_DSN: string }) => ({
+  dsn: env.E2E_TEST_DSN,
+  environment: 'qa',
+  tunnel: 'http://localhost:3031/',
+  tracesSampleRate: 1.0,
+}));

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/package.json

@@ -0,0 +1,29 @@
+{
+  "name": "cloudflare-autoinstrument-package-entry",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "build": "vite build",
+    "preview": "wrangler dev --var \"E2E_TEST_DSN:$E2E_TEST_DSN\" --log-level=$(test $CI && echo 'none' || echo 'log')",
+    "test": "playwright test",
+    "test:build": "pnpm install && pnpm build",
+    "test:assert": "pnpm test"
+  },
+  "dependencies": {
+    "@sentry/cloudflare": "file:../../packed/sentry-cloudflare-packed.tgz",
+    "worker-entry": "file:../../test-applications/cloudflare-autoinstrument-package-entry/worker-entry"
+  },
+  "devDependencies": {
+    "@cloudflare/vite-plugin": "^1.47.0",
+    "@cloudflare/workers-types": "^5.20260727.1",
+    "@playwright/test": "~1.56.0",
+    "@sentry-internal/test-utils": "link:../../../test-utils",
+    "vite": "^8.1.5",
+    "wrangler": "^4.114.0"
+  },
+  "volta": {
+    "node": "24.15.0",
+    "extends": "../../package.json"
+  }
+}

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/playwright.config.ts

@@ -0,0 +1,12 @@
+import { getPlaywrightConfig } from '@sentry-internal/test-utils';
+
+export default getPlaywrightConfig(
+  {
+    startCommand: 'pnpm preview',
+    port: 8787,
+  },
+  {
+    workers: '100%',
+    retries: 0,
+  },
+);

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/start-event-proxy.mjs

@@ -0,0 +1,6 @@
+import { startEventProxyServer } from '@sentry-internal/test-utils';
+
+startEventProxyServer({
+  port: 3031,
+  proxyServerName: 'cloudflare-autoinstrument-package-entry',
+});

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/tests/package-entry.test.ts

@@ -0,0 +1,32 @@
+import { expect, test } from '@playwright/test';
+import { waitForError, waitForTransaction } from '@sentry-internal/test-utils';
+
+// The worker entry is a package with no Sentry calls. Any event that arrives
+// proves the plugin wrapped the module that wrangler's `main` resolved to.
+
+test('wraps a package entry with withSentry (options from instrument.server.ts)', async ({ baseURL }) => {
+  const transactionPromise = waitForTransaction('cloudflare-autoinstrument-package-entry', event => {
+    return event.contexts?.trace?.op === 'http.server';
+  });
+
+  const res = await fetch(baseURL!);
+  expect(res.status).toBe(200);
+
+  const transaction = await transactionPromise;
+  expect(transaction.contexts?.trace?.origin).toBe('auto.http.cloudflare');
+  // Only `instrument.server.ts` sets this environment.
+  expect(transaction.environment).toBe('qa');
+});
+
+test('captures an error thrown by a package entry', async ({ baseURL }) => {
+  const errorPromise = waitForError(
+    'cloudflare-autoinstrument-package-entry',
+    event => event.exception?.values?.[0]?.value === 'Thrown from a package entry',
+  );
+
+  const res = await fetch(`${baseURL}/throw`);
+  expect(res.status).toBe(500);
+
+  const error = await errorPromise;
+  expect(error.environment).toBe('qa');
+});

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/vite.config.ts

@@ -0,0 +1,15 @@
+import { cloudflare } from '@cloudflare/vite-plugin';
+import { sentryCloudflareVitePlugin } from '@sentry/cloudflare/vite';
+import { defineConfig } from 'vite';
+
+export default defineConfig({
+  plugins: [
+    cloudflare(),
+    // On v10, auto-instrumentation is opt-in.
+    sentryCloudflareVitePlugin({
+      _experimental: {
+        autoInstrumentation: true,
+      },
+    }),
+  ],
+});

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/worker-entry/fetch-handler.js

@@ -0,0 +1,11 @@
+// Shaped like bundler output (e.g. `@astrojs/cloudflare`): the default export
+// is a specifier, not `export default <expr>`.
+var fetch_handler_default = {
+  async fetch(request) {
+    if (new URL(request.url).pathname === '/throw') {
+      throw new Error('Thrown from a package entry');
+    }
+    return new Response('ok');
+  },
+};
+export { fetch_handler_default as default };

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/worker-entry/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "worker-entry",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "exports": {
+    "./fetch-handler": "./fetch-handler.js"
+  }
+}

dev-packages/e2e-tests/test-applications/cloudflare-autoinstrument-package-entry/wrangler.jsonc

@@ -0,0 +1,8 @@
+{
+  "$schema": "node_modules/wrangler/config-schema.json",
+  "name": "cloudflare-autoinstrument-package-entry",
+  // A package export, not a file path. The Sentry plugin resolves it with Vite.
+  "main": "worker-entry/fetch-handler",
+  "compatibility_date": "2026-05-20",
+  "compatibility_flags": ["nodejs_compat"],
+}