fix(start): don't log aborted server function requests as errors

[oztune]

Problem

serverFnFetcher's getResponse logs every non-Response error before rethrowing:

} catch (error) {
  if (error instanceof Response) {
    response = error
  } else {
    console.log(error) // <- logs even expected cancellations
    throw error
  }
}

This includes the AbortError thrown when the caller cancels a server-function request, which is normal, expected control flow — not a failure. The most common trigger is TanStack Query aborting a query when its component unmounts: navigating away while a server-fn-backed query is in flight spams the console with

AbortError: signal is aborted without reason

even though nothing is wrong — the request was intentionally cancelled.

Fix

Skip the log when the error is an abort (DOMException or any Error with name === 'AbortError'). The error is still rethrown, so callers (e.g. TanStack Query) handle the cancellation exactly as before, and genuine errors are still logged.

Tests

Added serverFnFetcher unit tests covering both branches:

• an aborted request is not logged, but is still rethrown
• a genuine error is logged and rethrown

A changeset is included (@tanstack/start-client-core, patch).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Aborted server-function requests no longer appear as logged errors.
  • Genuine server-function errors continue to be logged and rethrown.
  • Aborted requests and other errors preserve their original error details.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: c0d55729-ab29-4fc2-9dc8-a06ffa662706

📥 Commits

Reviewing files that changed from the base of the PR and between 6954a37 and aabf663.

📒 Files selected for processing (3)

• .changeset/serverfn-dont-log-aborts.md
• packages/start-client-core/src/client-rpc/serverFnFetcher.ts
• packages/start-client-core/tests/serverFnFetcher.test.ts

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

serverFnFetcher now suppresses logging for AbortError cancellations. It still logs genuine errors and rethrows every error. Tests verify both behaviors, and a patch changeset documents the change.

Changes

Server-function abort handling

Layer / File(s)	Summary
Abort error detection and handling packages/start-client-core/src/client-rpc/serverFnFetcher.ts	The fetcher detects errors with name === 'AbortError'. It skips logging for those errors and rethrows them. Other errors remain logged and rethrown.
Error handling validation and release note packages/start-client-core/tests/serverFnFetcher.test.ts, .changeset/serverfn-dont-log-aborts.md	Tests verify that abort errors are not logged and genuine errors are logged. Both errors are rethrown. The changeset records the patch release update.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to aabf6

Aborted requests avoid expected error-log noise while genuine failures remain visible and all errors are still rethrown. No merge-blocking risk is evident.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: preventing error logging for aborted server-function requests.
Description check	✅ Passed	The description explains the problem, fix, tests, and release impact. It omits the required checklist section and does not explicitly confirm the checklist items, but the main required change informat…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files. (1 skipped: 1 unsupported.)

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[Sheraff]

Probably the only test we need is this

Suggested change

	if (!isAbortError(error)) {
	if (!(error instanceof Error) || error.name !== 'AbortError') {