createSumeClient custom fetch: log ratelimit-remaining as you go

The seam

createSumeClient takes three options: apiKey (required), baseUrl, and fetch. The docs describe fetch as the place to supply your own function for instrumentation, retries or tests. The default is the runtime's globalThis.fetch, and the package has no runtime dependencies, so a wrapper is all you need.

Every generated operation and every helper such as waitForJob goes through that one function, which makes it the right place to watch the rate-limit headers instead of sprinkling logging at call sites.

Headers worth logging (read 2026-10-05)

A logging fetch

The headers describe the budget the current request spent from, read or write, so log the method with the number. This wrapper warns under 50 remaining and passes the response through untouched, so the SDK's own retry logic still sees it.

import { createSumeClient } from "@sume-com/sdk";

const loggingFetch: typeof fetch = async (input, init) => {
  const res = await fetch(input, init);
  const left = res.headers.get("ratelimit-remaining");
  if (left !== null && Number(left) < 50) {
    console.warn(
      "sume budget low:", (init?.method ?? "GET"), left,
      "reset in", res.headers.get("ratelimit-reset"), "s",
    );
  }
  return res;
};

export const client = createSumeClient({
  apiKey: process.env.SUME_API_KEY!,
  fetch: loggingFetch,
});

Keep it a pure observer

Do not add your own retries inside this wrapper. The client already retries 408, 429 and 5xx twice with backoff and jitter, and it retries a POST only when the request carries an Idempotency-Key. Retrying a keyless POST here would start and bill a second job. Log, count, and return the response.