`unstable_cache` fails during build process with "Invariant: incrementalCache missing" error

[Lionel-Dutrieux]

Plugin version

0.8.2

Payload version

3.37.0

Auth.js version

5.0.0-beta.28

Describe the bug

When using unstable_cache from Next.js in combination with the payload-authjs plugin, the application fails during the build process (pnpm build && pnpm start) with the following error:

Error: Invariant: incrementalCache missing in unstable_cache async function s(){return await new Promise(e=>setTimeout(e,100)),Math.floor(1e3*Math.random())+1}
    at <unknown> (C:\repos\Win\test-cache\.next\server\chunks\1906.js:711:4902)
    at Object.onInit (C:\repos\Win\test-cache\.next\server\app\(payload)\api\[...slug]\route.js:1:1800)
    at tJ.init (C:\repos\Win\test-cache\.next\server\chunks\1906.js:588:18842)
    at async tQ (C:\repos\Win\test-cache\.next\server\chunks\1906.js:588:20621)
    at async (C:\repos\Win\test-cache\.next\server\chunks\1906.js:710:16006)

The error occurs specifically when calling a cached function within the onInit hook of the Payload configuration. This works perfectly fine in a vanilla PayloadCMS setup without the payload-authjs plugin.

To Reproduce

Steps to reproduce the behavior:

1. Create a Next.js 15.3.2 project with PayloadCMS 3.37.0

2. Install and configure payload-authjs@0.8.2 plugin

3. Create a cached function using unstable_cache:

   import { unstable_cache } from 'next/cache'
   
   async function generateRandomNumber(): Promise<number> {
     await new Promise((resolve) => setTimeout(resolve, 100))
     return Math.floor(Math.random() * 1000) + 1
   }
   
   export const getCachedRandomNumber = unstable_cache(generateRandomNumber, ['random-number'], {
     revalidate: 60,
     tags: ['random-number'],
   })

4. Use the cached function in the onInit hook:

   export default buildConfig({
     // ... other config
     onInit: async (payload) => {
       const randomNumber = await getCachedRandomNumber()
       console.log(randomNumber)
       payload.logger.info(`Random number: ${randomNumber}`)
     },
   })

5. Run pnpm build && pnpm start

6. The error occurs during the initialization process

Additional context / Screenshots

Expected behavior

The cached function should work normally during the build process, just as it does in development mode and in vanilla PayloadCMS setups.

Environment

• Node.js: 18.20.2+ / 20.9.0+
• Package Manager: pnpm
• Next.js: 15.3.2
• PayloadCMS: 3.37.0
• payload-authjs: 0.8.2
• next-auth: 5.0.0-beta.28

[CrawlerCode]

This happens because payload is initialized outside a component.

This could be avoid using lazy initialization of the authjs config inside auth.ts:

-export const { handlers, signIn, signOut, auth } = NextAuth(
+export const { handlers, signIn, signOut, auth } = NextAuth(() =>
  withPayload(authConfig, {
    payloadConfig,
  }),
);