This is a submission for .

Every codebase has that one bug that looks tiny on paper and behaves like a small landmine underneath. This is the story of one of those bugs, and the fix I shipped for it in .

Bug Fix or Performance Improvement

Here is the problem in plain words.

fetchWithTimeout accepts a normal RequestInit object as one of its parameters, the same shape you would pass to the native fetch function. A caller can put anything in there, including their own AbortSignal, if they already have a reason to cancel the request early. Maybe the user pressed stop. Maybe the session ended. Maybe a parent operation was cancelled and everything underneath it should stop too.

The trouble was in how the utility built its own internal signal for the timeout. Internally it spread the caller's init object first, and then added its own timeout signal on top of it. That ordering meant the caller's signal was silently thrown away every single time. Whatever cancellation logic the calling code thought it had wired up simply did not exist anymore once the request reached fetchWithTimeout.

The practical effect was not a crash. It was quieter and arguably worse. A request that the rest of the system believed had been cancelled would keep running in the background until either it finished naturally or the internal timeout eventually caught up with it. Under normal load you would not notice. Under real load, with many concurrent sessions and channels, this is exactly the kind of leak that piles up, ties up connections, and makes the gateway feel sluggish for reasons that are hard to trace back to a root cause.

Code

Here is the pull request with the actual change.

export async function fetchWithTimeout(

  url: string,

  init: RequestInit,

  timeoutMs: number,

  fetchFn: typeof fetch = fetch,

): Promise<Response> {

  const { signal, cleanup } = buildTimeoutAbortSignal({

    timeoutMs: Math.max(1, timeoutMs),

    operation: "fetchWithTimeout",

    url,

  });

  try {

    return await fetchFn(url, { ...init, signal });

  } finally {

    cleanup();

  }

}

  const { signal, cleanup } = buildTimeoutAbortSignal({

    timeoutMs: Math.max(1, timeoutMs),

    operation: "fetchWithTimeout",

    url,

    signal: init.signal,

  });