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Pick a model with the provider/model convention and pass it as the model field. The live, authoritative list (with current pricing) is always at GET /v1/models.

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Available models

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Audio transcription

See Audio transcription for a copy-paste file upload and streaming example.

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Image generation

openai/gpt-image-2 generates images via POST /v1/images/generations, billed per token at the rates in the table below (text input plus image output tokens). See Image generation for the request shape and options.

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Token-priced models

Token prices are USD per 1M tokens. More providers and models are added over time. anthropic/claude-sonnet-5 is currently promo-priced at 2.00/2.00 / 10.00 (through 2026-08-31) — GET /v1/models always returns the effective price you’re billed at. Fireworks also supports serverless passthrough for any public serverless model in the Fireworks catalog. Use either fireworks/<model-slug> or the full fireworks/accounts/fireworks/models/<model-slug> id. Unlisted passthrough models are billed at the conservative fallback price configured in the gateway.

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Credits

Usage is billed from a prepaid credit balance. Credits are denominated in micro-USD:
  • 1 credit = 0.000001∗∗,so∗∗0.000001**, so **1.00 = 1,000,000 credits
  • Buying 10increditsadds10,000,000credits.Thefixed510 in credits adds 10,000,000 credits. The fixed 5% platform fee is 0.50, making the pre-tax total $10.50
  • New accounts get a signup bonus so the first call works immediately

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How a request is priced

where input_price / output_price are the per-1M-token prices above. Provider usage is billed at the provider’s list price with no usage markup (PRICE_MARKUP=1.0). Because a credit is one micro-USD, the “per 1M” division cancels: tokens × price is already micro-USD. The amount is rounded up, deducted atomically when the request finishes, and recorded in the usage ledger (GET /v1/usage). Some models carry more than the two base rates, and the formula extends the same way — each token class times its own rate, summed, rounded up once. GET /v1/models reports every rate that applies to a model:
  • audio_input_per_mtok_usd — audio input tokens priced above the text rate (see Audio & video input)
  • cached_input_per_mtok_usd / cache_write_per_mtok_usd — prompt-cache reads and writes
  • context_price_tiers — long-context brackets: once the prompt crosses a tier’s threshold, its rates apply to the request
Audio transcription uses duration instead:
The gateway prefers duration usage reported by OpenAI and otherwise reads the uploaded audio file’s duration. It charges only after the transcription completes successfully.
Example — gpt-4o-mini, 11 input + 3 output tokens: ⌈11 × 0.15 + 3 × 0.60⌉ = ⌈3.45⌉ = 4 credits ($0.000004).
For self-hosted deployments, PRICE_MARKUP multiplies this provider-usage formula to set a margin. AI API production keeps it at 1.0. The separate fixed 5% platform fee applies only when prepaid credits are purchased. If your balance is empty, model endpoints return 402 (see Errors). Check your balance with GET /v1/account.
Requests routed through your own provider credential (BYOK) skip this formula entirely — they’re billed 0 credits, since the provider charges you directly.

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Topping up

Buy credits with a hosted Stripe Invoice:
Open invoice_url and pay. Credits are added automatically once the invoice is paid, and Stripe retries cannot double-credit them. The minimum top-up is **5∗∗,andfractionalamountsareroundeddowntoawholedollar.Afixed5feeisaddedtothenetcreditamount,so5**, and fractional amounts are rounded down to a whole dollar. A fixed 5% platform fee is added to the net credit amount, so 10 of credits has a 0.50feeandcosts0.50 fee and costs 10.50 before tax. The invoice has a single Impossible Credits line item covering the credits and fee. Stripe Tax adds VAT or sales tax on top when enabled. GET /v1/billing shows your balance, the minimum top-up, the fixed platform fee rate, and the provider-usage multiplier.