Error serialization issue

[oguzgelal]

Which project does this relate to?

Start

Describe the bug

Errors thrown on server side does not serialize correctly. Here's an example:

class TestError extends Error {
  constructor(message: string = 'Test error') {
    super(message)
    this.name = 'TestError' // ← Error name set to 'TestError'
  }
}

export const testError = createServerFn().handler(async () => {
  throw new TestError('This is a test')
})

and on the client side:

const testErrorMutation = useServerFn(testError);

// ...

<Button
  onClick={async () => {
    try {
      await testErrorMutation()
    } catch (err) {
      const error = err as Error
      console.log(error.name) // prints 'Error' instead of 'TestError'
    }
  }}
>
  Throw server error
</Button>

While the error thrown has the name 'TestError', this information gets lost in serialization/deserialization.

Your Example Website or App

https://stackblitz.com/edit/github-egpnw7wu-6dmvze6t?file=src%2Froutes%2Findex.tsx

Steps to Reproduce the Bug or Issue

N/A

Expected behavior

It should print 'TestError'

Screenshots or Videos

No response

Platform

• Router / Start Version: 1.132.0
• OS: macOS
• Browser: Chrome
• Browser Version: 141.0.7390.122
• Bundler: Vite
• Bundler Version: 7.1.7

Additional context

No response

[hokkyss]

You have to provide the serialization logic yourself

try this: https://github.com/TanStack/router/blob/main/e2e/react-start/serialization-adapters/src/start.tsx

[oguzgelal]

@hokkyss This is exactly what I was looking! I must've missed this in the documentation, or perhaps not documented yet. Thanks for the pointer 🙏

[hokkyss]

It was not documented yet.

I am not a maintainer so probably cannot say this, but feel free to write the docs if you want to!