Upgrading Remix Fails: Server-only module referenced by client ./sessions.server' imported by route 'src/root.tsx'

[Ankish76]

Reproduction

I'm trying to upgrade Remix to latest one, which uses vite plugin. Upgrade fail with error:

Server-only module referenced by client

  './sessions.server' imported by route 'src/root.tsx'

  Remix automatically removes server-code from these exports:
    `loader`, `action`, `headers`

  But other route exports in 'src/root.tsx' depend on './sessions.server'.

exports from ./sessions.server is used inside root loader

old remix version was able to handle this and was not bundling server code to client
but newer one is not able to do so

I have tried creating a vite plugin to resolve .server.ts file for client side code as empty module.
It didn't helped

System Info

System:
    OS: macOS 15.2
    CPU: (8) arm64 Apple M1
    Memory: 161.73 MB / 8.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.18.0 - ~/.nvm/versions/node/v20.18.0/bin/node
    Yarn: 1.22.19 - /opt/homebrew/bin/yarn
    npm: 10.8.2 - ~/.nvm/versions/node/v20.18.0/bin/npm
    bun: 1.0.3 - ~/.bun/bin/bun
  Browsers:
    Chrome: 131.0.6778.140
    Edge: 131.0.2903.99
    Safari: 18.2
  npmPackages:
    vite: ^6.0.3 => 6.0.3

Used Package Manager

yarn

Expected Behavior

This should not throw error and handle it like old remix was doing.

Actual Behavior

It throws error mentioned above.

[DiederikvandenB]

I was seeing the same error, but it seems to have resolved itself. Possibly because of an rm -rf node_modules.

[nichtsam]

Hey, check if you've done this replacement:
https://github.com/remix-run/remix/blob/main/CHANGELOG.md#patch-changes-2

[sparkida]

There's a few solutions covered in the latest docs @Ankish76. Additionally, if the file is in your routes like ./routes/foo.server.js then the warning doesn't seem to happen.

[Ankish76]

I have tried suggested solutions. It's not working for my monorepo setup.

Although when I created a single remix app. I'm not able to reproduce the issue in it.

Not sure why it's not working in monorepo.

I'm trying to debug. Any suggestions will be very helpful.

Thanks