# Credits & billing

> How metering works, packs, refunds on failure.

Credits are the single unit: prepaid, flat-priced per call, shared by every key on the account. No subscription, no token arithmetic.

Packs: Starter $10 → 1,000 credits · Builder $50 → 5,500 credits · Scale $100 → 12,000 credits. Larger packs carry bonus credits, per-call prices never change. Credits do not expire.

Metering: a call charges before the engine runs and refunds itself if the engine returns nothing (negative row in the ledger). Every JSON response carries:

```json
"usage": { "credits_spent": 3, "credits_remaining": 997 }
```

Binary responses carry `X-Credits-Spent` / `X-Credits-Remaining` headers. Poll `GET /v1/account` for the balance. A call that costs more than the balance fails with HTTP 402 and charges nothing.

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Canonical: https://eroq.ai/docs/credits · Index for agents: https://eroq.ai/llms.txt · OpenAPI: https://eroq.ai/openapi.json