generated `env.js` is missing a cache buster

[TorstenDittmann]

Describe the bug

We have been running into issues with deployments and realized that /_app/env.js is cached by cloudflare due to a missing cache buster in the filename.

A similiar issue could happen with /_app/version.json, but JSON files are usually not cached by the common cloudflare presets.

For now we have disabled cache for that path 👍🏻

Reproduction

https://stackblitz.com/edit/sveltejs-kit-template-default-fsrnypku?file=build%2F_app%2Fenv.js

Using the static adapter and a public static env var.

Logs

# not important

System Info

System:
    OS: macOS 15.4.1
    CPU: (11) arm64 Apple M3 Pro
    Memory: 95.47 MB / 18.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.19.1 - ~/.nvm/versions/node/v20.19.1/bin/node
    npm: 10.8.2 - ~/.nvm/versions/node/v20.19.1/bin/npm
    pnpm: 10.7.0 - ~/.nvm/versions/node/v20.19.1/bin/pnpm
    bun: 1.2.13 - ~/.bun/bin/bun
  Browsers:
    Chrome: 136.0.7103.114
    Safari: 18.4
  npmPackages:
    @sveltejs/adapter-static: ^3.0.8 => 3.0.8
    @sveltejs/kit: ^2.20.2 => 2.20.2
    @sveltejs/vite-plugin-svelte: ^5.0.3 => 5.0.3
    svelte: ^5.25.3 => 5.25.3
    vite: ^6.2.3 => 6.2.3

Severity

serious, but I can work around it

Additional Information

No response

[TorstenDittmann]

Actually I just saw what the node adapter is doing by only adding cache headers to /_app/immutable/ files:

https://github.com/sveltejs/kit/blob/main/packages/adapter-node/src/handler.js#L57-L59

This looks to be intended and should probably be mentioned in the docs for static adapters 👍🏻