concurrency_cap

HTTP 429 · type rate_limit. The account is already running as many sessions/extractions as it’s allowed to have in flight (new accounts start at 1). Expensive work is limited by concurrency, not requests-per-minute — a run holds real browsers and real model spend for minutes, so the cap is on simultaneous runs. Nothing was charged.

The shape

{
  "error": {
    "type": "rate_limit",
    "code": "concurrency_cap",
    "message": "1 run may be in flight; 1 is. Retry when it settles.",
    "doc_url": "https://docs.fiveninelabs.com/errors/concurrency_cap",
    "request_id": "req_5dd08r",
    "retry_after_s": 60,
    "limit": 1,
    "in_flight": 1
  }
}

limit is the account’s cap; in_flight is what’s running now. Retry-After is an estimate, not a promise — runs take minutes and finish when they finish.

How to fix

Find what’s running: GET /v1/sessions?status=running. Wait for its terminal (webhook, long-poll, or stream), or POST …/stop it if it’s no longer wanted.
Queue on your side: serialize run creation behind the session.answered / extraction.delivered webhook instead of retrying blind.
Note a batch extraction (urls[]) occupies concurrency per URL as passes dispatch — a 50-URL batch on a concurrency-1 account is a queue, not a parallel sweep.
Need real parallelism? Concurrency limits are raised per account — contact us; your current limit is visible in GET /v1/me (concurrency_limit).

Reproduce it

Requires a run genuinely in flight, so this one costs a real (small) run:

curl https://api.fiveninelabs.com/v1/sessions \
  -H "Authorization: Bearer $FIVENINE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"query": "vinyl records under $30 in Austin", "max_spend_usd": 1}'
# → while that run is in flight, create another:
curl https://api.fiveninelabs.com/v1/sessions \
  -H "Authorization: Bearer $FIVENINE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"query": "espresso machines under $400", "max_spend_usd": 1}'

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