Using `$env/dynamic/private` in top level might result in build error

Describe the bug

When reading environment variable in global scope, and the environment variable doesn't exists, it errors out during build time:

import { env } from "$env/dynamic/private";

if (!env.API_URL) {
  throw new Error('API_URL is not defined in the environment variables');
}

export const load = async ({ }) => {
  console.log('Loading page...');
}

output of vite build:

vite v6.3.5 building SSR bundle for production...
✓ 174 modules transformed.

node:internal/event_target:1101
  process.nextTick(() => { throw err; });
                           ^
Error: API_URL is not defined in the environment variables
    at file:///home/filip/tmp/foo/app/.svelte-kit/output/server/entries/pages/_page.server.js:3:9
    at ModuleJob.run (node:internal/modules/esm/module_job:273:25)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:600:26)
    at async Promise.all (index 2)
    at async analyse (file:///home/filip/tmp/foo/app/node_modules/.pnpm/@sveltejs+kit@2.20.8_@sveltejs+vite-plugin-svelte@5.0.3_svelte@5.28.2_vite@6.3.5__svelte@5.28.2_vite@6.3.5/node_modules/@sveltejs/kit/src/core/postbuild/analyse.js:67:16)
    at async MessagePort.<anonymous> (file:///home/filip/tmp/foo/app/node_modules/.pnpm/@sveltejs+kit@2.20.8_@sveltejs+vite-plugin-svelte@5.0.3_svelte@5.28.2_vite@6.3.5__svelte@5.28.2_vite@6.3.5/node_modules/@sveltejs/kit/src/utils/fork.js:23:16)

Node.js v23.9.0
 ELIFECYCLE  Command failed with exit code 1.

If the variable is present, the build ends up fine. Not sure if this is intended behavior, but I would expect the environment variables to be read only when running the app, not during build, when using $env/dynamic

It seems that vite dev works fine.

Reproduction

https://github.com/Gregofi/svelte-env-vars

pnpm install
pnpm run build

Logs

System Info

System:
    OS: Linux 6.14 Arch Linux
    CPU: (16) x64 AMD Ryzen 7 PRO 5850U with Radeon Graphics
    Memory: 22.37 GB / 30.66 GB
    Container: Yes
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 23.9.0 - /usr/bin/node
    Yarn: 1.22.22 - /usr/bin/yarn
    npm: 11.3.0 - /usr/bin/npm
    pnpm: 10.9.0 - /usr/bin/pnpm
    bun: 1.0.26 - ~/.bun/bin/bun
  Browsers:
    Chromium: 135.0.7049.95
  npmPackages:
    @sveltejs/adapter-auto: ^6.0.0 => 6.0.0
    @sveltejs/adapter-node: ^5.2.12 => 5.2.12
    @sveltejs/kit: ^2.20.8 => 2.20.8
    @sveltejs/vite-plugin-svelte: ^5.0.3 => 5.0.3
    svelte: ^5.28.2 => 5.28.2
    vite: ^6.3.5 => 6.3.5

Severity

annoyance

Additional Information

No response

Start with the linked reproduction and run pnpm install followed by pnpm run build; compare this with vite dev. Trace the build-time failure through @sveltejs/kit/src/core/postbuild/analyse.js and the generated server entry, then verify that an absent dynamic private environment variable does not cause a build failure while still being available at runtime.