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API usage is billed in credits worth $0.01 each. Per-model rates are on protoface.com/pricing. GET /v1/billing/plans returns published plan limits and GET /v1/billing/quota returns where your account stands against them. balance_credits is your spendable total, and can_start_session accounts for that and your concurrency.

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Model inference

A generation reserves credit_estimate.maximum_reserved_credits against your balance up front. A completed run is charged that amount, and a failed run releases it. Canceling before the run starts releases the reservation. Canceling after it starts charges the full reserved amount. A request Protoface rejects outright reserves nothing.

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Concurrency

Concurrency is based on platform spend over the last 30 days: the price of your current plan plus any credits you buy. Refunded purchases do not count. Workers is how many generations can run at the same time. Requested is how many runs you can have queued or running. Extra runs wait until a worker is free. If you hit the requested limit, the API returns 429 with error.code: "run.concurrency_exceeded". Run submissions are separately capped at 60 per minute per key, and exceeding that returns 429 with error.code: "run.rate_limited". Need higher limits? Contact us.

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Realtime sessions

Your plan sets how long each session lasts, and — except on Scale — how many sessions you can run at once. Every session response carries the effective limits for that session. *Uncapped means no artificial cap on simultaneous sessions. Ramp and system technical limits still apply, and uncapped does not imply guaranteed concurrency. On capped plans, exceeding your concurrency returns 429 with error.type: "quota_exceeded" and error.code: "concurrent_sessions". Session starts are ramp rate-limited on all plans to prevent abuse (see create rate limit below); this affects ramp-up speed only, not your total concurrency budget. If production frequently hits ramp limits, contact us to discuss higher ramp limits. If you send max_duration_seconds, Protoface applies the lower of your request and your plan limit. For early capacity planning, divide daily active users by 250 to estimate concurrent sessions.

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Realtime credits

Session time rounds up to the nearest minute, at one credit per minute. If your balance is empty, session creation returns 402 with error.code: "insufficient_credit_balance". Free monthly credits do not roll over. Purchased credits roll over without expiry.

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Metadata keys

metadata is customer-owned JSON with two reservations. Session keys beginning with _avatar. are managed by Protoface and reserved for support-directed use. Model-run keys beginning with protoface_ are rejected.