429 enforced_spend_limit_reached: why retrying never works

A 429 with no retry-after header can be a spend cap rather than a rate limit. Anthropic's rate-limit page says that once an organization reaches its monthly cap, requests return HTTP 429 with error_code enforced_spend_limit_reached, and retrying, including SDK automatic retries, fails until access resumes. Sume reports an empty balance as 402 insufficient_credits instead.

Anthropic facts are from its Rate limits page (cited under Sources) and Sume facts from Errors and rate limits, both read 2026-09-30.

How do I tell a spend cap from a rate limit?

Look for the header and the code. Anthropic's page lists the monthly caps by tier (Start $500 USD, Build $1,000 USD, Scale $200,000 USD) and says the cap response has no retry-after header, while an ordinary rate-limit 429 carries one.

What does Sume return when the money runs out?

Sume returns 402 insufficient_credits before provider work starts, when it cannot reserve the estimated cost from the workspace balance. The docs list the next action as upgrading the plan, waiting for included Gen$, or submitting a cheaper request, and the quota job error category says to add funds or lower the request cost. Waiting does not fix it, so a 402 is not a retry case.

Sume keeps the 429s for two other things: rate_limited for request volume, and queue_full when the workspace has no accepted generation capacity left. Both clear as time passes or jobs finish.

What should a retry loop do with each one?

Retry a 429 only when it carries retry-after, and never retry a 402. For paid submits, reuse the same Idempotency-Key on every retry so a repeat cannot bill twice.

def should_retry(status: int, headers: dict, error_code: str) -> bool:
    if status == 402:
        return False  # insufficient_credits: fund the wallet first
    if status == 429:
        return "retry-after" in headers  # a cap has none
    return False

print(should_retry(429, {"retry-after": "12"}, "rate_limited"))
print(should_retry(429, {}, "enforced_spend_limit_reached"))
print(should_retry(402, {}, "insufficient_credits"))

What are the limits of this comparison?

The caps and tiers above are Anthropic's on the day read; check its page before relying on them. Sume's docs do not describe a monthly spend cap, only the balance and reservation described in the spend-limit post.