Environment

│ ╭── Nuxt project info (copied to clipboard) ─────────────╮
│ │                                                        │
│ │  Operating system      Linux 7.0.10-2-cachyos          │
│ │  CPU                   AMD Ryzen 5 5500 (12 cores)     │
│ │  Node.js version       v24.14.0                        │
│ │  nuxt/cli version      3.36.0-20260608-223204-f869c61  │
│ │  Package manager       npm 11.9.0                      │
│ │  Nuxt version          5.0.0-29675450.fd7056aa         │
│ │  Nitro version         3.0.260522-beta                 │
│ │  Builder               vite 8.0.16                     │
│ │  Config                compatibilityDate               │
│ │  Modules               -                               │
│ │                                                        │
│ ╰────────────────────────────────────────────────────────╯
│

Reproduction

• Create a Nuxt v5 project
• Create a server route that fetches an external URL, I will be using https://jsonplaceholder.typicode.com/todos/1 in server/routes/test-fetch.get.ts

  import { defineEventHandler } from "nitro/h3";
  
  export default defineEventHandler(async () => {
    let externalResult: any;
    let externalError: any;
  
    try {
      const response = await globalThis.fetch(
        "https://jsonplaceholder.typicode.com/todos/1",
        {
          redirect: "error",
          headers: { accept: "application/json" },
        },
      );
      externalResult = await response.json();
    } catch (err: any) {
      externalError = {
        message: err.message,
        name: err.name,
      };
    }
  
    return {
      externalSuccess: !!externalResult,
      externalTitle: externalResult?.title,
      externalError,
    };
  });

• start the nuxt server
• curl localhost:3000/test-fetch and you will see externalTitle is delectus aut autem (the correct response)
• Trigger SSR by loading the index page curl localhost:3000
• curl localhost:3000/test-fetch: error. Furthermore, if you have a route at /todos/1 the response will be from that file rather than from jsonplaceholder

Describe the bug

After triggering a SSR, all server fetches will use the globalThis.fetch implementation that gets clobbered here

Additional context

No response

Logs