Parallel routes are rendered unnecessarily

Why this is a good first issue

Parallel routes are rendering unnecessarily, requiring conditional logic fixes.

AI Summary

The issue involves parallel routes rendering unnecessarily, even when conditional logic should prevent it. This affects routing behavior and requires understanding Next.js's parallel routes implementation. The problem is reproducible but lacks clear guidance on expected behavior or fixes.

Issue Description

Verify canary release

I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
      Platform: darwin
      Arch: arm64
      Version: Darwin Kernel Version 22.5.0: Thu Jun  8 22:22:20 PDT 2023; root:xnu-8796.121.3~7/RELEASE_ARM64_T6000
    Binaries:
      Node: 18.16.0
      npm: 9.8.1
      Yarn: 1.22.19
      pnpm: 8.6.10
    Relevant Packages:
      next: 13.4.13-canary.5
      eslint-config-next: 13.4.12
      react: 18.2.0
      react-dom: 18.2.0
      typescript: 5.1.6
    Next.js Config:
      output: N/A

Which area(s) of Next.js are affected? (leave empty if unsure)

Routing (next/router, next/navigation, next/link)

Link to the code that reproduces this issue or a replay of the bug

https://github.com/slvstr-dev/test-parallel

To Reproduce

Install project
Run project locally
Check console for logs of both routes

Describe the Bug

In layout.tsx I want to render conditionally render a parallel route, f.e. if a user is logged in or not. Currently it runs code from both routes. Console.log's of both page.tsx in root and page.tsx in @auth are being run.

Expected Behavior

Based on the condition I only expect the console.log from the returned page to run.

Which browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)