stream/iter pipeTo() does not observe abort while waiting for the next source chunk

[trivikr]

Version

main

Platform

macOS 26.5.0

Subsystem

stream

What steps will reproduce the bug?

import { pipeTo } from "node:stream/iter";
import { setTimeout } from "node:timers/promises";

async function* neverYieldingSource() {
  await new Promise(() => {});
}

const writer = {
  write() {},
};

const ac = new AbortController();

setTimeout(100).then(() => {
  ac.abort(new Error("abort reason"));
});

const result = await Promise.race([
  pipeTo(neverYieldingSource(), writer, { signal: ac.signal }).then(
    () => "pipeTo resolved",
    (error) => `pipeTo rejected: ${error.name}: ${error.message}`,
  ),
  setTimeout(1000, "timed out"),
]);

console.log(result);

How often does it reproduce? Is there a required condition?

Always

What is the expected behavior? Why is that the expected behavior?

pipeTo rejected: Error: abort reason

pipeTo() should reject promptly when options.signal aborts, even while waiting for the next source chunk in the no-transform path.

What do you see instead?

timed out

pipeTo() checks signal.throwIfAborted() only after for await produces a batch, so a pending source read that never settles prevents abort from being observed.

Additional information

No response