getsentry · JPeer264 · Aug 31, 2026
diff --git a/dev-packages/e2e-tests/test-applications/solidstart-2/tests/trace-propagation.test.ts b/dev-packages/e2e-tests/test-applications/solidstart-2/tests/trace-propagation.test.ts
@@ -0,0 +1,11 @@
+import { expect, test } from '@playwright/test';
+
+test('injects trace meta tags on pageload', async ({ page }) => {
+  await page.goto('/');
+
+  const sentryTraceContent = await page.getAttribute('meta[name="sentry-trace"]', 'content');
+  expect(sentryTraceContent).toMatch(/^[a-f0-9]{32}-[a-f0-9]{16}-[01]$/);
+
+  const baggageContent = await page.getAttribute('meta[name="baggage"]', 'content');
+  expect(baggageContent).toContain('sentry-trace_id=');
+});
diff --git a/...packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx b/...packages/e2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/__root.tsx
@@ -1,5 +1,5 @@
 import type { ReactNode } from 'react';
-import { Outlet, createRootRoute, HeadContent, Scripts } from '@tanstack/react-router';
+import { Outlet, createRootRoute, HeadContent, Scripts, useRouterState } from '@tanstack/react-router';
 
 export const Route = createRootRoute({
   head: () => ({
@@ -19,6 +19,10 @@ export const Route = createRootRoute({
   component: RootComponent,
 });
 
+// Long enough that the SSR stream flushes a chunk boundary inside this attribute, ahead of
+// the head. See https://github.com/getsentry/sentry-javascript/issues/23468.
+const LONG_ATTRIBUTE = 'x'.repeat(3000);
+
 function RootComponent() {
   return (
     <RootDocument>
@@ -28,8 +32,10 @@ function RootComponent() {
 }
 
 function RootDocument({ children }: Readonly<{ children: ReactNode }>) {
+  const pathname = useRouterState({ select: state => state.location.pathname });
+
   return (
-    <html>
+    <html {...(pathname.startsWith('/split-head-chunk') ? { 'data-long': LONG_ATTRIBUTE } : {})}>
       <head>
         <HeadContent />
       </head>

diff --git a/...2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/split-head-chunk.tsx b/...2e-tests/test-applications/tanstackstart-react-cloudflare/src/routes/split-head-chunk.tsx
@@ -0,0 +1,14 @@
+import { createFileRoute } from '@tanstack/react-router';
+
+export const Route = createFileRoute('/split-head-chunk')({
+  component: SplitHeadChunk,
+});
+
+function SplitHeadChunk() {
+  return (
+    <main>
+      <h1>Split head chunk</h1>
+      <p>The root document carries a long attribute ahead of the head, so the SSR stream splits inside it.</p>
+    </main>
+  );
+}
diff --git a/...2e-tests/test-applications/tanstackstart-react-cloudflare/tests/trace-propagation.test.ts b/...2e-tests/test-applications/tanstackstart-react-cloudflare/tests/trace-propagation.test.ts
@@ -17,6 +17,19 @@ test.describe('Trace propagation', () => {
     expect(baggageContent).toContain('sentry-sampled=');
   });
 
+  test('should inject metatags when the SSR stream splits ahead of the head', async ({ page }) => {
+    await page.goto('/split-head-chunk');
+
+    const sentryTraceContent = await page.getAttribute('meta[name="sentry-trace"]', 'content');
+    expect(sentryTraceContent).toMatch(/^[a-f0-9]{32}-[a-f0-9]{16}-[01]$/);
+
+    const baggageContent = await page.getAttribute('meta[name="baggage"]', 'content');
+    expect(baggageContent).toContain('sentry-trace_id=');
+
+    // The attribute that forces the chunk boundary must survive the rewrite intact.
+    expect(await page.getAttribute('html', 'data-long')).toHaveLength(3000);
+  });
+
   test('should have trace connection between server and client', async ({ page }) => {
     const serverTxPromise = waitForTransaction('tanstackstart-react-cloudflare', transactionEvent => {
       return transactionEvent?.contexts?.trace?.op === 'http.server' && transactionEvent?.transaction === 'GET /';

diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react/src/routes/__root.tsx b/dev-packages/e2e-tests/test-applications/tanstackstart-react/src/routes/__root.tsx
@@ -1,5 +1,9 @@
 import { useEffect, type ReactNode } from 'react';
-import { Outlet, createRootRoute, HeadContent, Scripts } from '@tanstack/react-router';
+import { Outlet, createRootRoute, HeadContent, Scripts, useRouterState } from '@tanstack/react-router';
+
+// Long enough that the SSR stream flushes a chunk boundary inside this attribute, ahead of
+// the head. See https://github.com/getsentry/sentry-javascript/issues/23468.
+const LONG_ATTRIBUTE = 'x'.repeat(3000);
 
 export const Route = createRootRoute({
   head: () => ({
@@ -36,8 +40,10 @@ function RootComponent() {
 }
 
 function RootDocument({ children }: Readonly<{ children: ReactNode }>) {
+  const pathname = useRouterState({ select: state => state.location.pathname });
+
   return (
-    <html>
+    <html {...(pathname.startsWith('/split-head-chunk') ? { 'data-long': LONG_ATTRIBUTE } : {})}>
       <head>
         <HeadContent />
       </head>

diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react/src/routes/split-head-chunk.tsx b/dev-packages/e2e-tests/test-applications/tanstackstart-react/src/routes/split-head-chunk.tsx
@@ -0,0 +1,14 @@
+import { createFileRoute } from '@tanstack/react-router';
+
+export const Route = createFileRoute('/split-head-chunk')({
+  component: SplitHeadChunk,
+});
+
+function SplitHeadChunk() {
+  return (
+    <main>
+      <h1>Split head chunk</h1>
+      <p>The root document carries a long attribute ahead of the head, so the SSR stream splits inside it.</p>
+    </main>
+  );
+}
diff --git a/dev-packages/e2e-tests/test-applications/tanstackstart-react/tests/trace-propagation.test.ts b/dev-packages/e2e-tests/test-applications/tanstackstart-react/tests/trace-propagation.test.ts
@@ -22,6 +22,22 @@ test.describe('Trace propagation', () => {
     expect(baggageContent).toContain('sentry-sampled=');
   });
 
+  // The SSR stream splits inside the long attribute that sits ahead of the head, so the meta
+  // tags are only injected if the transform carries its state across chunks.
+  // See https://github.com/getsentry/sentry-javascript/issues/23468.
+  test('should inject metatags when the SSR stream splits ahead of the head', async ({ page }) => {
+    await page.goto('/split-head-chunk');
+
+    const sentryTraceContent = await page.getAttribute('meta[name="sentry-trace"]', 'content');
+    expect(sentryTraceContent).toMatch(/^[a-f0-9]{32}-[a-f0-9]{16}-[01]$/);
+
+    const baggageContent = await page.getAttribute('meta[name="baggage"]', 'content');
+    expect(baggageContent).toContain('sentry-trace_id=');
+
+    // The attribute that forces the chunk boundary must survive the rewrite.
+    expect(await page.getAttribute('html', 'data-long')).toHaveLength(3000);
+  });
+
   test('should have trace connection between server and client', async ({ page }) => {
     const serverTxPromise = waitForTransaction('tanstackstart-react', transactionEvent => {
       return transactionEvent?.contexts?.trace?.op === 'http.server' && transactionEvent?.transaction === 'GET /';

@@ -39,7 +39,7 @@ import {
   winterCGHeadersToDict,
   withIsolationScope,
 } from '@sentry/node';
-import { setHttpServerSpanRouteAttribute } from '@sentry/server-utils';
+import { injectHtmlIntoHead, setHttpServerSpanRouteAttribute } from '@sentry/server-utils';
 import type { APIContext, MiddlewareHandler, MiddlewareNext, RoutePart } from 'astro';
 
 type MiddlewareOptions = {
@@ -279,26 +279,6 @@ async function instrumentRequestStartHttpServerSpan(
   });
 }
 
-/**
- * This function optimistically assumes that the HTML coming in chunks will not be split
- * within the <head> tag. If this still happens, we simply won't replace anything.
- */
-function addMetaTagToHead(htmlChunk: string, metaTagsStr: string): string {
-  if (typeof htmlChunk !== 'string' || !metaTagsStr) {
-    return htmlChunk;
-  }
-
-  // Skip quoted attribute values so we don't match <head> inside e.g. data-code="...<head>..."
-  let replaced = false;
-  return htmlChunk.replace(/"[^"]*"|'[^']*'|(<head>)/g, (match, headTag) => {
-    if (headTag && !replaced) {
-      replaced = true;
-      return `<head>${metaTagsStr}`;
-    }
-    return match;
-  });
-}
-
 function getMetaTagsStr({
   injectTraceData,
   parametrizedRoute,
@@ -463,63 +443,5 @@ function getParametrizedRoute(ctx: APIContext & { routePattern?: string }): stri
 }
 
 function injectMetaTagsInResponse(originalResponse: Response, metaTagsStr: string): Response {
-  try {
-    const contentType = originalResponse.headers.get('content-type');
-
-    const isPageloadRequest = contentType?.startsWith('text/html');
-    if (!isPageloadRequest) {
-      return originalResponse;
-    }
-
-    // Type case necessary b/c the body's ReadableStream type doesn't include
-    // the async iterator that is actually available in Node
-    // We later on use the async iterator to read the body chunks
-    // see https://github.com/microsoft/TypeScript/issues/39051
-    const originalBody = originalResponse.body as NodeJS.ReadableStream | null;
-    if (!originalBody) {
-      return originalResponse;
-    }
-
-    const decoder = new TextDecoder();
-
-    const newResponseStream = new ReadableStream({
-      start: async controller => {
-        // Assign to a new variable to avoid TS losing the narrower type checked above.
-        const body = originalBody;
-
-        async function* bodyReporter(): AsyncGenerator<string | Buffer> {
-          try {
-            for await (const chunk of body) {
-              yield chunk;
-            }
-          } catch (e) {
-            // Report stream errors coming from user code or Astro rendering.
-            sendErrorToSentry(e);
-            throw e;
-          }
-        }
-
-        try {
-          for await (const chunk of bodyReporter()) {
-            const html = typeof chunk === 'string' ? chunk : decoder.decode(chunk, { stream: true });
-            const modifiedHtml = addMetaTagToHead(html, metaTagsStr);
-            controller.enqueue(new TextEncoder().encode(modifiedHtml));
-          }
-        } catch (e) {
-          controller.error(e);
-        } finally {
-          controller.close();
-        }
-      },
-    });
-
-    return new Response(newResponseStream, {
-      status: originalResponse.status,
-      statusText: originalResponse.statusText,
-      headers: new Headers(originalResponse.headers),
-    });
-  } catch (e) {
-    sendErrorToSentry(e);
-    throw e;
-  }
+  return injectHtmlIntoHead(originalResponse, metaTagsStr, sendErrorToSentry);
 }
@@ -389,9 +389,9 @@ describe('sentryMiddleware', () => {
     const html = await resultFromNext?.text();
 
     expect(html).toContain('<head>');
-    expect(html).toContain('<meta name="something" content=""/></head>');
-    // parametrized route is injected
-    expect(html).toContain('<meta name="sentry-route-name" content="%2Fusers"/>');
+    expect(html).toContain('<meta name="something" content=""/>');
+    // parametrized route is injected, directly before the closing head tag
+    expect(html).toContain('<meta name="sentry-route-name" content="%2Fusers"/></head>');
     // trace data is not injected
     expect(html).not.toContain('<meta name="sentry-trace" content="');
     expect(html).not.toContain('<meta name="baggage" content="');
@@ -449,7 +449,7 @@ describe('sentryMiddleware', () => {
     const html = await resultFromNext?.text();
 
     expect(html).toContain('<head>');
-    expect(html).toContain('<meta name="something" content=""/></head>');
+    expect(html).toContain('<meta name="something" content=""/>');
     expect(html).toContain('<meta name="sentry-route-name" content="%2Fusers"/>');
     expect(html).toContain('<meta name="sentry-trace" content="');
     expect(html).toContain('<meta name="baggage" content="');

@@ -1,5 +1,6 @@
 // Shared exports not using diagnostics channels
 export { setHttpServerSpanRouteAttribute } from './utils/setHttpServerSpanRouteAttribute';
+export { injectHtmlIntoHead, injectHtmlIntoHeadStream } from './utils/htmlInjection';
 export { setAsyncLocalStorageAsyncContextStrategy } from './async-context';
 export { otlpIntegration, getOtlpTracesEndpoint } from './otlp';
 export * from './ai';