Calling any server function from the client entry point breaks custom serialization adapters

Which project does this relate to?

Start

Describe the bug

Calling a server function that uses a custom serialization adapter throws a SerovalDeserializationError when any server function is called from the client entry point (client.tsx).

1. Define a startInstance with custom serializationAdapters in start.ts
2. Call any server function from the client entry point
3. Call a server function that uses a custom serialization adapter
4. A SerovalDeserializationError occurs

Complete minimal reproducer

https://github.com/roccomaniscalco/tanstack-start-createSerializationAdapter

Steps to Reproduce the Bug

1. pnpm i && pnpm dev
2. open localhost:3000
3. Click "Get Animal" button
4. Observe SerovalDeserializationError in console

Expected behavior

As a user, I expected custom serialization adapters to deserialize successfully, but instead I am seeing a SerovalDeserializationError.

Screenshots or Videos

No response

Platform

• Router / Start Version:

  "@tanstack/react-router": "1.170.16",
  "@tanstack/react-start": "1.168.26",
  

• OS: macOS
• Browser: Chrome
• Browser Version: 149.0.7827.156 (Official Build) (arm64)
• Bundler: vite
• Bundler Version: ^8.0.0

Additional context

No response

Start with the client.tsx and start.ts entry points described in the reproduction, then run the linked minimal reproducer with pnpm i && pnpm dev. Trace the server-function calls and custom serialization adapter usage until the SerovalDeserializationError occurs; done means the Get Animal flow deserializes successfully after another server function is called from the client entry point.