cases / next-15-async-headers

next-15-async-headers

next 14.2.3 → 15.0.0

Next 15 made the request-scoped helpers cookies() and headers() asynchronous, breaking every synchronous call site.

npm fixture evals/fixtures/next-15-async-cookies

grep-baseline

2 right 2 wrong 1 unjudged

<0.1s · $0.00

agent · deepseek-v4-flash-free

2 right 0 wrong

19.8s · $0.00

Release notes

The input. Checked in with the case so a scoring run measures the detector, not whether upstream's site is reachable.

Next.js 15

Breaking: async request APIs

The cookies and headers helpers exported from next/headers are now asynchronous and return a Promise. draftMode is likewise async.

// Before
const cookieStore = cookies();

// After
const cookieStore = await cookies();

Any synchronous call site must be awaited, and the enclosing function must become async.

What each detector said

One row per (file, symbol) site — the unit the scorer compares on. Ground truth comes from the case's hand-written labels.

5 sites · 3 where a detector is wrong only show mistakes

unlabeled app/dashboard/page.tsx :headers grep-baseline flagged agent · deepseek-v4-flash-free silent
1 matched line · reasoning
```
   1  import { cookies } from 'next/headers';
```
grep-baseline conf 0.50
'headers' is named in the release notes and appears in 7 place(s) in this repo. No check was made that these are real call sites.
not broken lib/parse.ts :cookies grep-baseline flagged agent · deepseek-v4-flash-free silent

A local Record variable named cookies. Not the next/headers helper.
4 matched lines · reasoning
```
   1  // A local variable named `cookies`, parsed off a raw header string. Nothing to
   4  const cookies: Record<string, string> = {};
   7  if (k) cookies[k] = decodeURIComponent(v ?? '');
   9  return cookies;
```
grep-baseline conf 0.50
'cookies' is named in the release notes and appears in 7 place(s) in this repo. No check was made that these are real call sites.
not broken lib/parse.ts :headers grep-baseline flagged agent · deepseek-v4-flash-free silent

A plain object literal named headers. Not the next/headers helper.
3 matched lines · reasoning
```
   2  // do with next/headers, and unaffected by the Next 15 async change.
  14  const headers = { authorization: `Bearer ${token}` };
  15  return headers;
```
grep-baseline conf 0.50
'headers' is named in the release notes and appears in 7 place(s) in this repo. No check was made that these are real call sites.
breaks app/api/session/route.ts :headers grep-baseline flagged agent · deepseek-v4-flash-free flagged

Synchronous headers() call.
3 matched lines · reasoning
```
   1  import { headers } from 'next/headers';
   4  // headers() is async in Next 15 as well.
   5  const h = headers();
```
grep-baseline conf 0.50
'headers' is named in the release notes and appears in 7 place(s) in this repo. No check was made that these are real call sites.
breaks app/dashboard/page.tsx :cookies grep-baseline flagged agent · deepseek-v4-flash-free flagged

Synchronous cookies() call in a non-async component.
3 matched lines · reasoning
```
   1  import { cookies } from 'next/headers';
   4  // Next 15 made cookies() async — this synchronous read breaks.
   5  const store = cookies();
```
grep-baseline conf 0.50
'cookies' is named in the release notes and appears in 7 place(s) in this repo. No check was made that these are real call sites.