redirect inside createServerFn handler isn't working

[nandcello]

Which project does this relate to?

Router

Describe the bug

So I have a button that when clicked, triggers a server function with a redirect inside. When I click the button, it doesn't redirect at all. I've tried throwing the redirect as well as setting throw: true but still isn't working. I've also tried with an external link via href option and also an internal link via to option but both aren't working as well. even tried reloadDocument: true and also replace: true.

Your Example Website or App

https://github.com/nandcello/repro-redirect-bug

Steps to Reproduce the Bug or Issue

1. bun create @tanstack/start@latest
2. add a button that calls a createServerFn with handler

  throw redirect({
    to: '/demo/start/ssr',
    // throw: true // this also doesn't work 
  })

3. click the button to trigger the server fn
4. nothing happens

Expected behavior

As a user, I expect to be redirected to the link.

Screenshots or Videos

No response

Platform

• Router / Start Version: 1.132.0
• OS: macOS
• Browser: Safari & Edge
• Browser Version: 142.0.3595.94 (Official build) (arm64)
• Bundler: vite
• Bundler Version: 7.1.7

Additional context

As per server fn docs, i should be able to do this

[brenelz]

You might need to use theuserServerFn hook.

https://tanstack.com/start/latest/docs/framework/react/guide/server-functions#where-to-call-server-functions

[khanhicetea]

You might need to use theuserServerFn hook.

https://tanstack.com/start/latest/docs/framework/react/guide/server-functions#where-to-call-server-functions

I faced the same issue, even using useServerFn hook. Root cause can be the the serializer try to act before checking redirect in the server

3423 |     return parseError2(ctx, id, current);
3424 |   }
3425 |   if (SYM_ITERATOR in current || SYM_ASYNC_ITERATOR in current) {
3426 |     return parsePlainObject2(ctx, id, current, !!currentClass);
3427 |   }
3428 |   throw new SerovalUnsupportedTypeError(current);
               ^
error: The value [object Response] of type "object" cannot be parsed/serialized.

There are few workarounds for this problem:
- Transform the value in a way that it can be serialized.
- If the reference is present on multiple runtimes (isomorphic), you can use the Reference API to map the references.
 value: Response (0 KB) {
  ok: false,
  url: "",
  status: 307,
  statusText: "",
  headers: Headers {},
  redirected: false,
  bodyUsed: false
},

[khanhicetea]

I think it related to #5929

[khanhicetea]

Updated, the redirect works normally if no middleware in the server function. (I used a global function middleware to catch the Zod error and it happens)

[khanhicetea]

temp fix : #5372 (comment)