Memoization during permanentRedirect

[mcAnastasiou]

Link to the code that reproduces this issue

https://github.com/mcAnastasiou/nextjs-memoization-issue

To Reproduce

1. Run the application
2. Visit http://localhost:3000/1 or any odd number
   Should see

   --- Rendering ---
   --- Fetching data ---
   --- Generating metadata ---
   

3. Visit
   Should see

    === Will redirect ===
    --- Rendering ---
    --- Fetching data ---
    --- Generating metadata ---
    --- Generating metadata ---
    --- Fetching data ---
   
   

Metadata is called twice. Second time is not during the same server request and cache is not working

Current vs. Expected behavior

There is intentionally a timeout in fetch data. During these 2 seconds monitor network responses. While waiting for the page to load, the type changes from document to document / Redirect. This is when metadata is being changed by permanentRedirect and is causing the second call of generateMetadata.

Expecting to either not call generateMetadata twice or have an indicator to understand that it is the second request and not call fetch data

This has a high impact in our servers as we are not doing a single cached fetched

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.4.0: Fri Apr 11 18:32:50 PDT 2025; root:xnu-11417.101.15~117/RELEASE_ARM64_T6041
  Available memory (MB): 24576
  Available CPU cores: 12
Binaries:
  Node: 20.11.1
  npm: 10.2.4
  Yarn: 1.22.22
  pnpm: 10.9.0
Relevant Packages:
  next: 15.2.3 // There is a newer version (15.3.2) available, upgrade recommended! 
  eslint-config-next: N/A
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.8.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Metadata

Which stage(s) are affected? (Select all that apply)

next start (local)

Additional context

I tested it also in the latest version and it happening there too

[gaojude]

It's expected that generateMetadata is called twice here, because the server receives two requests (one for the even number, and the other for the odd number param after the redirect roundtrip).

generateMetadata function has access to params (see https://nextjs.org/docs/app/api-reference/functions/generate-metadata#generatemetadata-function), so you could shortcircuit the execution of generateMetadata by checking params in the same way as you did for the page component.