Billing & limits

Implementation target. This guide specifies the intended product surface. The current frontend uses local samples; it does not call an inference service or collect funds. An endpoint is enabled only after its adapter, ownership, usage, and payment behavior are qualified.

Pay for the inference you use

Noemad charges a request according to the selected model’s rate and attributable usage. The user keeps tokens in their own wallet; the app does not create a prepaid balance.

Model prices are shown in USD using official sources where the exact model and billing unit can be verified. The final payment quote is denominated in USDC on Monad. An unverified model price is shown as Price not verified, never a guessed rate or a free offer.

The operator’s provider account and the user’s activity remain separate. /v1/usage must return owner-scoped usage, not the balance or logs of a shared service account.

What a quote freezes

Use integer or fixed-point accounting. Preserve both the pre-rounding amount and the final token atomic amount. A rate change applies to future quotes; an operator must absorb an unplanned difference or reject before dispatch.

A public price table helps comparison. It is not a request-specific quote, a guaranteed availability signal, or permission to spend from a wallet.

Authorize a maximum; settle actual usage

The target x402 v2 upto mechanism authorizes a maximum and collects the actual amount after reliable usage is known. It uses the pinned Permit2/proxy mechanism from the chosen SDK. The maximum is not transferred to the merchant before inference.

1. 1
   Validate the request and obtain an immutable quote.
2. 2
   Review origin, model, limits, rates, maximum, network, asset, recipient, expiry, facilitator, and proxy.
3. 3
   Complete any required wallet allowance, then sign the bounded authorization.
4. 4
   Bind the nonce once to the owner, operation, and request hash before dispatch.
5. 5
   Deliver inference and durably record attributable usage.
6. 6
   Calculate the final amount and persist one settlement job.
7. 7
   Verify the bound onchain receipt before marking collection settled.

The unused maximum stays in the wallet. Authorization does not reserve funds, so a balance or allowance can change before collection. An inference can succeed while collection fails; those states must remain separate.

Compute the USD cost from the right units

ordinary_input = total_input - included_cache_read
USD_cost = ordinary_input × USD_input_rate
         + cache_read × USD_cache_rate
         + output × USD_output_rate
         + other documented model-specific units

Token rates are often quoted per one million tokens; divide the measured count by the stated unit before applying the rate. Only subtract cached input when the provider’s total-input definition already includes it. Reasoning and cache-write units follow the exact model contract.

Prefer a verified, request-correlated provider receipt where available. Otherwise calculate from validated usage and the pinned rate snapshot. A change in a shared provider account balance cannot attribute one request’s cost during concurrent use.

USD to USDC: an illustrative calculation

The following figures are a worked example, not a model price. It assumes that this example quote explicitly converts USD to USDC at 1:1 and uses a token with six decimals. Production quotes must disclose their actual conversion and rounding policy.

The operator absorbs the sub-atomic remainder under the planned rounding policy. It is not saved as hidden debt or a future top-up. The project plan adds no model markup; any network fee is disclosed separately along with who pays it.

Chat pricing in USD

These are official USD rates only where the exact model is verified. Input, output, cached input, cache creation, and reasoning can have different definitions. Do not substitute a nearby model’s price for an unverified identifier.

Embedding and rerank pricing in USD

Use the hosted provider’s official billing unit. An open-weight model alone does not define a hosted API price. Batches include all submitted inputs; rerank includes the query and every candidate, regardless of top_n.

Media, realtime, and evaluation pricing in USD

Image count, video duration, speech characters, transcription duration, realtime sessions, and evaluation requests need separate units. A verified base rate does not establish a price for every size, quality, voice, or duration.

Price the selected output settings

Do not apply a generic multiplier across model families. Each modifier and any minimum must be confirmed against that exact model’s official pricing and frozen into the quote. Missing pricing means the paid route cannot be offered yet.

Inference and collection remain separate

Operation: quoted → authorized → dispatched → streaming / completed / failed / unknown
Collection: none → authorized → ready → settling → settled / zero_charge / unknown / failed

A successful stream does not prove collection settled. Read GET /api/v1/payments/{quote_id} for actual cost and a verified receipt. A collection retry must not rerun inference.

Pin the actual amount before settlement retry and preserve the same authorization and nonce. Verify chain, asset, allowed proxy, payer, merchant, amount, nonce, success, and the required block state. A transfer event alone is insufficient.

Unknown usage is never charged as the maximum

Missing final usage, an ambiguous dispatch, a consumed nonce without a bound transaction, or uncertain settlement enters reconciliation. Do not automatically debit the maximum, request a fresh signature, or rerun the model.

A known zero amount closes as zero_charge without a fabricated transaction. An allowance revoke or insufficient balance can cause collection_failed; the operator must bound outstanding liability and show the real state.

Calculator and production quotes

The calculator estimates USD cost from verified official rates where available. It does not create a live USDC quote, authorize payment, or imply that the selected model is connected.

The server produces live quote terms from the qualified model and enforceable limits. Rewards and campaigns can map to explicit per-request discounts or compensation under published policy, without creating a prepaid product balance.