Start: serverFnFetcher unconditionally console.logs every server-function error, including benign cancellation AbortErrors

Inizia in packages/start-client-core/src/client-rpc/serverFnFetcher.ts, in getResponse, e ispeziona il blocco catch che registra gli errori che non sono Response. Usa la riproduzione collegata e i passaggi per l'annullamento per verificare il comportamento. Il lavoro è completato quando gli errori delle funzioni server rilanciati, inclusi gli AbortErrors, non producono più il log estraneo nella console.

Which project does this relate to?

Start

Describe the bug

serverFnFetcher's getResponse logs every non-Response error thrown by a server-function call via console.log, then re-throws it. In packages/start-client-core/src/client-rpc/serverFnFetcher.ts:

async function getResponse(fn) {
  let response
  try {
    response = await fn()
  } catch (error) {
    if (error instanceof Response) response = error
    else {
      console.log(error)   // ← logs every error, incl. benign cancellations
      throw error
    }
  }
  // ...
}

Two problems:

1. It's unconditional — there is no process.env.NODE_ENV guard, so it also runs in production builds (bundlers don't strip console.log by default), spamming the browser console for real users.
2. It logs benign cancellations. When a caller passes an AbortSignal to a server function and aborts it (e.g. a request cancelled on navigation/unmount), the RPC fetch rejects with DOMException: signal is aborted without reason (AbortError). getResponse console.logs it and re-throws. The
   re-thrown error is then handled by the caller (who deliberately aborted and no longer cares about the result), so the throw itself is fine — but the console.log leaves a stray, stack-trace-bearing console entry with no context.

Because it's console.log (not console.error) on a caught-and-rethrown error, it can't be intercepted from application code: it never reaches a framework error hook or error boundary, and it isn't an unhandled promise rejection, so a window unhandledrejection listener doesn't catch it either.
The only app-side workarounds are monkey-patching console or patching the package.

Complete minimal reproducer

https://codesandbox.io/p/devbox/condescending-diffie-z59y9f

Steps to Reproduce the Bug

1. Start Dev Server
2. Open preview browser.
3. Click the button
4. examine browser dev console logs

Expected behavior

Cancelling a server-function call should not log to the console. More generally, getResponse should not console.log errors it re-throws — the caller is responsible for handling and reporting them. At minimum the log should be removed; if diagnostic logging is intended, gate it behind
process.env.NODE_ENV !== 'production' and skip cancellation errors (AbortError / CancelledError).

Screenshots or Videos

No response

Platform

• @tanstack/react-start 1.168.30 (@tanstack/start-client-core 1.170.13)
• React 19, Vite 8
• Browser: Chrome (reproduces in both dev and production builds)

Additional context

No response