Can't use zod v4

[JClackett]

Which project does this relate to?

Start

Describe the bug

If I try to use zod 4 in project I get errors when starting vite because router-generator and start-core relies on zod v3 api', the old z.function().returns, its now z.function({input: [], output:[]}).

Your Example Website or App

https://stackblitz.com/edit/github-9eq11eyj?file=package.json

Steps to Reproduce the Bug or Issue

npm install
npm run dev

Expected behavior

Server should start

Screenshots or Videos

Platform

• Router / Start Version: latest
• OS: macos
• Browser: all
• Browser Version: latest
• Bundler: vite
• Bundler Version: vite 7 and 8 beta

Additional context

I guess it's not possible to use zod v4 yet? otherwise get into weird issues where theres multiple versions of zod installed.

[schiller-manuel]

you need to use a package manager that uses isolated installs (e.g. pnpm).
otherwise, if router would use v4, someone could not use v3.

[JClackett]

yeah im using Bun which I thought handled this

[schiller-manuel]

needs to be enabled in bun. in your issue text you mention npm btw

[R5dan]

you need to use a package manager that uses isolated installs (e.g. pnpm). otherwise, if router would use v4, someone could not use v3.

You can support both zod 3 and zod 4 simultaneously: https://zod.dev/library-authors?id=how-to-support-zod-3-and-zod-4-simultaneously

Additionally, zod supports standard schema which is what I think tanstack start should support (rather than any particular version of zod etc)

[CarlosZiegler]

For some that has same issue with bun you can add that into project => https://bun.com/docs/pm/isolated-installs#configuration-file

[JClackett]

It is the default for new projects, but it's still occasionally not working for me