From 8dd6f21b17b9eee8042a6f3dbfa03bff87a5f09f Mon Sep 17 00:00:00 2001
From: JPeer264 <jan.peer@sentry.io>
Date: Mon, 4 May 2026 14:42:57 +0200
Subject: [PATCH 1/2] test(tanstackstart): Add TanStack Start on Cloudflare
 Workers test app

---
 .../tanstackstart-react-cloudflare/.gitignore |  6 ++
 .../package.json                              | 44 ++++++++++
 .../playwright.config.ts                      |  6 ++
 .../src/env.d.ts                              |  3 +
 .../src/router.tsx                            | 23 +++++
 .../src/routes/__root.tsx                     | 52 ++++++++++++
 .../src/routes/api.error.ts                   | 11 +++
 .../src/routes/api.flush.ts                   | 13 +++
 .../src/routes/index.tsx                      | 31 +++++++
 .../src/routes/ssr-error.tsx                  |  8 ++
 .../src/server.ts                             | 13 +++
 .../start-event-proxy.mjs                     |  6 ++
 .../tests/index.test.ts                       | 83 +++++++++++++++++++
 .../tsconfig.json                             | 21 +++++
 .../vite.config.ts                            | 12 +++
 .../wrangler.jsonc                            | 10 +++
 16 files changed, 342 insertions(+)
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/.gitignore
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/package.json
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/playwright.config.ts
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/env.d.ts
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/router.tsx
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/api.error.ts
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/api.flush.ts
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/index.tsx
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/ssr-error.tsx
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/server.ts
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/start-event-proxy.mjs
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tests/index.test.ts
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tsconfig.json
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/vite.config.ts
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/wrangler.jsonc

diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/.gitignore b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/.gitignore
new file mode 100644
index 000000000000..f67821b00540
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/.gitignore
@@ -0,0 +1,6 @@
+node_modules
+dist
+.output
+.wrangler
+.tanstack
+src/routeTree.gen.ts
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/package.json b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/package.json
new file mode 100644
index 000000000000..415159f7afc1
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/package.json
@@ -0,0 +1,44 @@
+{
+  "name": "tanstackstart-react-cloudflare",
+  "private": true,
+  "version": "0.0.1",
+  "type": "module",
+  "scripts": {
+    "dev": "vite dev",
+    "build": "vite build",
+    "preview": "wrangler dev --var E2E_TEST_DSN:$E2E_TEST_DSN --log-level=$(test $CI && echo 'none' || echo 'log')",
+    "test": "playwright test",
+    "typecheck": "tsc --noEmit",
+    "test:build": "pnpm install && pnpm build",
+    "test:assert": "pnpm typecheck && pnpm test"
+  },
+  "dependencies": {
+    "@sentry/browser": "file:../../packed/sentry-browser-packed.tgz",
+    "@sentry/cloudflare": "file:../../packed/sentry-cloudflare-packed.tgz",
+    "@sentry/core": "file:../../packed/sentry-core-packed.tgz",
+    "@tanstack/react-start": "^1.136.0",
+    "@tanstack/react-router": "^1.136.0",
+    "react": "^19.2.0",
+    "react-dom": "^19.2.0"
+  },
+  "devDependencies": {
+    "@cloudflare/vite-plugin": "^1.35.0",
+    "@cloudflare/workers-types": "^4.20260504.0",
+    "@playwright/test": "~1.56.0",
+    "@sentry-internal/test-utils": "link:../../../test-utils",
+    "@types/react": "^19.2.0",
+    "@types/react-dom": "^19.2.0",
+    "@vitejs/plugin-react": "^4.5.0",
+    "typescript": "^5.9.0",
+    "vite": "7.3.1",
+    "vite-tsconfig-paths": "^5.1.4",
+    "wrangler": "^4.68.1"
+  },
+  "volta": {
+    "node": "24.15.0",
+    "extends": "../../package.json"
+  },
+  "sentryTest": {
+    "optional": true
+  }
+}
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/playwright.config.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/playwright.config.ts
new file mode 100644
index 000000000000..94d9558b37b6
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/playwright.config.ts
@@ -0,0 +1,6 @@
+import { getPlaywrightConfig } from '@sentry-internal/test-utils';
+
+export default getPlaywrightConfig({
+  startCommand: 'pnpm preview',
+  port: 8787,
+});
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/env.d.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/env.d.ts
new file mode 100644
index 000000000000..eb80bafb4834
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/env.d.ts
@@ -0,0 +1,3 @@
+interface Env {
+  E2E_TEST_DSN: string;
+}
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/router.tsx b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/router.tsx
new file mode 100644
index 000000000000..c18a1a0b8167
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/router.tsx
@@ -0,0 +1,23 @@
+import * as Sentry from '@sentry/browser';
+import { createRouter } from '@tanstack/react-router';
+import { routeTree } from './routeTree.gen';
+
+export const getRouter = () => {
+  const router = createRouter({
+    routeTree,
+    scrollRestoration: true,
+  });
+
+  if (!router.isServer) {
+    Sentry.init({
+      environment: 'qa',
+      dsn: 'https://public@dsn.ingest.sentry.io/1337',
+      integrations: [Sentry.browserTracingIntegration()],
+      tracesSampleRate: 1.0,
+      release: 'e2e-test',
+      tunnel: 'http://localhost:3031/',
+    });
+  }
+
+  return router;
+};
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx
new file mode 100644
index 000000000000..bf48b6e6cb69
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx
@@ -0,0 +1,52 @@
+import type { ReactNode } from 'react';
+import { Outlet, createRootRoute, HeadContent, Scripts } from '@tanstack/react-router';
+import { getTraceData } from '@sentry/core';
+
+export const Route = createRootRoute({
+  head: () => {
+    const traceData = getTraceData();
+    const sentryMeta = Object.entries(traceData).map(([key, value]) => ({
+      name: key,
+      content: value,
+    }));
+
+    return {
+      meta: [
+        {
+          charSet: 'utf-8',
+        },
+        {
+          name: 'viewport',
+          content: 'width=device-width, initial-scale=1',
+        },
+        {
+          title: 'TanStack Start Cloudflare E2E Test',
+        },
+        ...sentryMeta,
+      ],
+    };
+  },
+  component: RootComponent,
+});
+
+function RootComponent() {
+  return (
+    <RootDocument>
+      <Outlet />
+    </RootDocument>
+  );
+}
+
+function RootDocument({ children }: Readonly<{ children: ReactNode }>) {
+  return (
+    <html>
+      <head>
+        <HeadContent />
+      </head>
+      <body>
+        {children}
+        <Scripts />
+      </body>
+    </html>
+  );
+}
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/api.error.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/api.error.ts
new file mode 100644
index 000000000000..041fb175c1f1
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/api.error.ts
@@ -0,0 +1,11 @@
+import { createFileRoute } from '@tanstack/react-router';
+
+export const Route = createFileRoute('/api/error')({
+  server: {
+    handlers: {
+      GET: async () => {
+        throw new Error('Sentry API Route Test Error');
+      },
+    },
+  },
+});
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/api.flush.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/api.flush.ts
new file mode 100644
index 000000000000..b8f2313504e1
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/api.flush.ts
@@ -0,0 +1,13 @@
+import { createFileRoute } from '@tanstack/react-router';
+import { flush } from '@sentry/cloudflare';
+
+export const Route = createFileRoute('/api/flush')({
+  server: {
+    handlers: {
+      GET: async () => {
+        await flush();
+        return new Response('ok');
+      },
+    },
+  },
+});
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/index.tsx b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/index.tsx
new file mode 100644
index 000000000000..5be8873475ef
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/index.tsx
@@ -0,0 +1,31 @@
+import { createFileRoute } from '@tanstack/react-router';
+
+export const Route = createFileRoute('/')({
+  component: Home,
+});
+
+function Home() {
+  return (
+    <div>
+      <h1>TanStack Start Cloudflare E2E Test</h1>
+      <button
+        id="client-error-btn"
+        type="button"
+        onClick={() => {
+          throw new Error('Sentry Client Test Error');
+        }}
+      >
+        Break the client
+      </button>
+      <button
+        id="api-error-btn"
+        type="button"
+        onClick={async () => {
+          await fetch('/api/error');
+        }}
+      >
+        Break API route
+      </button>
+    </div>
+  );
+}
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/ssr-error.tsx b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/ssr-error.tsx
new file mode 100644
index 000000000000..71ba7ce92d29
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/ssr-error.tsx
@@ -0,0 +1,8 @@
+import { createFileRoute } from '@tanstack/react-router';
+
+export const Route = createFileRoute('/ssr-error')({
+  loader: () => {
+    throw new Error('Sentry SSR Test Error');
+  },
+  component: () => <div>SSR Error Page</div>,
+});
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/server.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/server.ts
new file mode 100644
index 000000000000..54bf854cba88
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/server.ts
@@ -0,0 +1,13 @@
+import * as Sentry from '@sentry/cloudflare';
+import handler from '@tanstack/react-start/server-entry';
+
+export default Sentry.withSentry(
+  (env: Env) => ({
+    dsn: env.E2E_TEST_DSN,
+    tunnel: 'http://localhost:3031/',
+    tracesSampleRate: 1.0,
+    environment: 'qa',
+  }),
+  // @ts-expect-error - handler is not typed as a Cloudflare handler
+  handler,
+);
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/start-event-proxy.mjs b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/start-event-proxy.mjs
new file mode 100644
index 000000000000..14ed61c3b9bd
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/start-event-proxy.mjs
@@ -0,0 +1,6 @@
+import { startEventProxyServer } from '@sentry-internal/test-utils';
+
+startEventProxyServer({
+  port: 3031,
+  proxyServerName: 'tanstackstart-react-cloudflare',
+});
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tests/index.test.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tests/index.test.ts
new file mode 100644
index 000000000000..3cc914b91514
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tests/index.test.ts
@@ -0,0 +1,83 @@
+import { expect, test } from '@playwright/test';
+import { waitForError, waitForTransaction } from '@sentry-internal/test-utils';
+
+test('Sends client-side error to Sentry', async ({ page }) => {
+  const errorEventPromise = waitForError('tanstackstart-react-cloudflare', errorEvent => {
+    return errorEvent?.exception?.values?.[0]?.value === 'Sentry Client Test Error';
+  });
+
+  await page.goto(`/`);
+
+  await expect(page.locator('#client-error-btn')).toBeVisible();
+
+  await page.locator('#client-error-btn').click();
+
+  const errorEvent = await errorEventPromise;
+
+  expect(errorEvent.exception?.values?.[0]).toEqual({
+    type: 'Error',
+    value: 'Sentry Client Test Error',
+    stacktrace: expect.objectContaining({
+      frames: expect.any(Array),
+    }),
+    mechanism: {
+      type: 'auto.browser.global_handlers.onerror',
+      handled: false,
+    },
+  });
+
+  expect(errorEvent.transaction).toBe('/');
+  expect(errorEvent.contexts?.trace?.trace_id).toEqual(expect.any(String));
+  expect(errorEvent.contexts?.trace?.span_id).toEqual(expect.any(String));
+});
+
+// Note: API route errors in TanStack Start are handled internally by the framework
+// and don't bubble up to the Cloudflare handler. @sentry/cloudflare cannot instrument
+// TanStack Start's internal error handling. For full server-side error capture,
+// users would need @sentry/tanstackstart-react middleware, which isn't compatible
+// with Cloudflare Workers.
+
+test('Sends server-side transaction for fetch request', async ({ baseURL }) => {
+  const transactionEventPromise = waitForTransaction('tanstackstart-react-cloudflare', transactionEvent => {
+    return transactionEvent?.contexts?.trace?.op === 'http.server' && transactionEvent?.transaction === 'GET /';
+  });
+
+  await fetch(`${baseURL}/`);
+
+  const transactionEvent = await transactionEventPromise;
+
+  expect(transactionEvent.transaction).toBe('GET /');
+  expect(transactionEvent.contexts?.trace).toEqual({
+    trace_id: expect.any(String),
+    span_id: expect.any(String),
+    op: 'http.server',
+    origin: 'auto.http.cloudflare',
+    status: 'ok',
+    data: expect.objectContaining({
+      'sentry.origin': 'auto.http.cloudflare',
+      'sentry.op': 'http.server',
+    }),
+  });
+});
+
+test('Propagates trace from server to client', async ({ page }) => {
+  const serverTransactionPromise = waitForTransaction('tanstackstart-react-cloudflare', transactionEvent => {
+    return transactionEvent?.contexts?.trace?.op === 'http.server' && transactionEvent?.transaction === 'GET /';
+  });
+
+  const clientTransactionPromise = waitForTransaction('tanstackstart-react-cloudflare', transactionEvent => {
+    return transactionEvent?.contexts?.trace?.op === 'pageload' && transactionEvent?.transaction === '/';
+  });
+
+  await page.goto('/');
+
+  const serverTransaction = await serverTransactionPromise;
+  const clientTransaction = await clientTransactionPromise;
+
+  const serverTraceId = serverTransaction.contexts?.trace?.trace_id;
+  const clientTraceId = clientTransaction.contexts?.trace?.trace_id;
+
+  expect(serverTraceId).toEqual(expect.any(String));
+  expect(clientTraceId).toEqual(expect.any(String));
+  expect(clientTraceId).toBe(serverTraceId);
+});
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tsconfig.json b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tsconfig.json
new file mode 100644
index 000000000000..ecf9f5694249
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tsconfig.json
@@ -0,0 +1,21 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "useDefineForClassFields": true,
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "module": "ESNext",
+    "skipLibCheck": true,
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "noEmit": true,
+    "jsx": "react-jsx",
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noFallthroughCasesInSwitch": true,
+    "types": ["@cloudflare/workers-types"]
+  },
+  "include": ["src"]
+}
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/vite.config.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/vite.config.ts
new file mode 100644
index 000000000000..8e749133c7d8
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/vite.config.ts
@@ -0,0 +1,12 @@
+import { defineConfig } from 'vite';
+import tsConfigPaths from 'vite-tsconfig-paths';
+import { tanstackStart } from '@tanstack/react-start/plugin/vite';
+import viteReact from '@vitejs/plugin-react';
+import { cloudflare } from '@cloudflare/vite-plugin';
+
+export default defineConfig({
+  server: {
+    port: 3030,
+  },
+  plugins: [cloudflare({ viteEnvironment: { name: 'ssr' } }), tsConfigPaths(), tanstackStart(), viteReact()],
+});
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/wrangler.jsonc b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/wrangler.jsonc
new file mode 100644
index 000000000000..cea7ef58657d
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/wrangler.jsonc
@@ -0,0 +1,10 @@
+{
+  "$schema": "node_modules/wrangler/config-schema.json",
+  "name": "tanstackstart-react-cloudflare",
+  "compatibility_date": "2026-05-04",
+  "compatibility_flags": ["nodejs_compat"],
+  "main": "src/server.ts",
+  "observability": {
+    "enabled": true,
+  },
+}

From 2d2ea64e52627d5a928fbd732d86d337b7c7cd80 Mon Sep 17 00:00:00 2001
From: JPeer264 <jan.peer@sentry.io>
Date: Tue, 5 May 2026 18:09:57 +0200
Subject: [PATCH 2/2] fixup! test(tanstackstart): Add TanStack Start on
 Cloudflare Workers test app

---
 .../package.json                              |  2 +-
 .../src/routes/__root.tsx                     |  2 +-
 .../src/start.ts                              |  9 ++++++
 .../tests/index.test.ts                       | 30 +++++++++++++++----
 4 files changed, 36 insertions(+), 7 deletions(-)
 create mode 100644 dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/start.ts

diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/package.json b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/package.json
index 415159f7afc1..b5450d0e198c 100644
--- a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/package.json
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/package.json
@@ -15,7 +15,7 @@
   "dependencies": {
     "@sentry/browser": "file:../../packed/sentry-browser-packed.tgz",
     "@sentry/cloudflare": "file:../../packed/sentry-cloudflare-packed.tgz",
-    "@sentry/core": "file:../../packed/sentry-core-packed.tgz",
+    "@sentry/tanstackstart-react": "file:../../packed/sentry-tanstackstart-react-packed.tgz",
     "@tanstack/react-start": "^1.136.0",
     "@tanstack/react-router": "^1.136.0",
     "react": "^19.2.0",
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx
index bf48b6e6cb69..bc3a376d7eba 100644
--- a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx
@@ -1,6 +1,6 @@
 import type { ReactNode } from 'react';
 import { Outlet, createRootRoute, HeadContent, Scripts } from '@tanstack/react-router';
-import { getTraceData } from '@sentry/core';
+import { getTraceData } from '@sentry/tanstackstart-react';
 
 export const Route = createRootRoute({
   head: () => {
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/start.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/start.ts
new file mode 100644
index 000000000000..719869f235ef
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/start.ts
@@ -0,0 +1,9 @@
+import { sentryGlobalFunctionMiddleware, sentryGlobalRequestMiddleware } from '@sentry/tanstackstart-react';
+import { createStart } from '@tanstack/react-start';
+
+export const startInstance = createStart(() => {
+  return {
+    requestMiddleware: [sentryGlobalRequestMiddleware],
+    functionMiddleware: [sentryGlobalFunctionMiddleware],
+  };
+});
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tests/index.test.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tests/index.test.ts
index 3cc914b91514..30daeaedc7fd 100644
--- a/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tests/index.test.ts
+++ b/dev-packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/tests/index.test.ts
@@ -31,11 +31,31 @@ test('Sends client-side error to Sentry', async ({ page }) => {
   expect(errorEvent.contexts?.trace?.span_id).toEqual(expect.any(String));
 });
 
-// Note: API route errors in TanStack Start are handled internally by the framework
-// and don't bubble up to the Cloudflare handler. @sentry/cloudflare cannot instrument
-// TanStack Start's internal error handling. For full server-side error capture,
-// users would need @sentry/tanstackstart-react middleware, which isn't compatible
-// with Cloudflare Workers.
+test('Sends API route error to Sentry', async ({ page }) => {
+  const errorEventPromise = waitForError('tanstackstart-react-cloudflare', errorEvent => {
+    return errorEvent?.exception?.values?.[0]?.value === 'Sentry API Route Test Error';
+  });
+
+  await page.goto('/');
+
+  await expect(page.locator('#api-error-btn')).toBeVisible();
+
+  await page.locator('#api-error-btn').click();
+
+  const errorEvent = await errorEventPromise;
+
+  expect(errorEvent.exception?.values?.[0]).toEqual({
+    type: 'Error',
+    value: 'Sentry API Route Test Error',
+    stacktrace: expect.objectContaining({
+      frames: expect.any(Array),
+    }),
+    mechanism: {
+      type: 'auto.middleware.tanstackstart.request',
+      handled: false,
+    },
+  });
+});
 
 test('Sends server-side transaction for fetch request', async ({ baseURL }) => {
   const transactionEventPromise = waitForTransaction('tanstackstart-react-cloudflare', transactionEvent => {