Link to the code that reproduces this issue

https://codesandbox.io/p/devbox/metadata-server-action-dyq7yh?file=%2Fapp%2Fpage.tsx%3A8%2C5

To Reproduce

1. Run next dev.
2. Open your browser’s DevTools (Elements panel).
   You’ll see the <title> and the <meta name="description"> rendered twice.

Current vs. Expected behavior

Current: <title> and description are duplicated.

Expected: <title> and description are not duplicated.

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #1 SMP PREEMPT_DYNAMIC Sun Aug  6 20:05:33 UTC 2023
  Available memory (MB): 4102
  Available CPU cores: 2
Binaries:
  Node: 20.9.0
  npm: 9.8.1
  Yarn: 1.22.19
  pnpm: 8.10.2
Relevant Packages:
  next: 15.5.1-canary.30 // Latest available version is detected (15.5.1-canary.30).
  eslint-config-next: N/A
  react: 19.1.1
  react-dom: 19.1.1
  typescript: 5.3.3
Next.js Config:
  output: N/A

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

Server Actions, Metadata

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

next dev (local), next start (local), Vercel (Deployed), Other (Deployed)

Additional context

It might be because I’m triggering Server Action revalidation inside useEffect.