OpenAI 429 slow_down vs 503 server_is_overloaded, and Sume

OpenAI's changelog, read 2026-09-30, says traffic that increases too quickly can return a 429 with the code slow_down, while temporary model overload returns a 503 with server_is_overloaded. On Sume the two ideas live in different places: a 429 rate_limited names the budget in error.details.scope, and a provider_capacity_exceeded response means Sume's provider dispatch queue is full.

These are Sume's own error contracts. They do not translate OpenAI's codes, and Sume does not return slow_down or server_is_overloaded on this page's evidence.

What does OpenAI say to do?

The changelog says both responses may include Retry-After. When present, wait at least that long before retrying; when missing, use exponential backoff.

How does each case map to Sume?

Sume's rate limit docs give reads and writes separate budgets, so "a tight status-poll loop cannot 429 your own submits". A 429 says which budget it spent in error.details.scope, either read or write, and the response carries retry-after. For capacity, the errors page lists provider_capacity_exceeded.

How should my retry code differ?

For a 429, read ratelimit-remaining and back off on retry-after instead of counting requests yourself. For provider_capacity_exceeded, retry later but keep the same Idempotency-Key, so a job that was in fact created is not created twice; see idempotency keys for AI video APIs.

async function withRetry(call, tries = 4) {
  for (let i = 0; i < tries; i++) {
    const res = await call();
    if (res.status !== 429 && res.status !== 503) return res;
    const wait = Number(res.headers.get("retry-after")) || 2 ** i;
    await new Promise((r) => setTimeout(r, wait * 1000));
  }
  throw new Error("still rate limited or at capacity");
}

Is every Sume 429 a request-rate problem?

No. queue_full also arrives as a 429 and means Sume cannot accept another paid job for the workspace until one finishes or is canceled; see queue full vs concurrency full. Request rate and generation concurrency are separate limits, and raising one does not raise the other.