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Documentation Index

Fetch the complete documentation index at: https://docs.nano-gpt.com/llms.txt

Use this file to discover all available pages before exploring further.

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Pay-As-You-Go Billing Override (API)

This override forces a request to be treated as paid (pay-as-you-go), even when the user has an active subscription and the model is subscription-included.

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What It Does

  • Forces a request to be treated as paid (pay-as-you-go).
  • Bypasses subscription coverage for that request.
  • Allows saved provider preferences to apply to subscription-included traffic.
  • Does not change which models support provider selection.

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When to Use It

Use billing_mode: "paygo" when:
  • A subscriber wants to force pay-as-you-go billing without selecting a provider in the request.
  • A subscriber wants saved provider preferences to apply to subscription-included traffic.
Explicit per-request provider selection already uses pay-as-you-go billing. If a subscriber sends X-Provider for a subscription-included model, the request is charged at the selected provider price and does not need X-Billing-Mode: paygo.

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Supported Inputs

Header
  • X-Billing-Mode: paygo (header name is case-insensitive)
  • x-billing-mode is also accepted
Body (all endpoints)
  • "billing_mode": "paygo"
  • Alias: "billingMode": "paygo"
Accepted values (case-insensitive)
  • paygo
  • pay-as-you-go
  • pay_as_you_go
  • paid
  • payg
Precedence: Body value wins if both body and header are present.

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API Examples

Example with explicit provider selection: 
POST /api/v1/chat/completions
X-Provider: deepinfra
Content-Type: application/json

{
  "model": "openai/gpt-oss-20b",
  "messages": [
    { "role": "user", "content": "Say hello in one sentence." }
  ]
}
Example forcing paygo without explicit provider selection: 
POST /api/v1/chat/completions
X-Billing-Mode: paygo
Content-Type: application/json

{
  "model": "openai/gpt-oss-20b",
  "messages": [
    { "role": "user", "content": "Say hello in one sentence." }
  ]
}
Responses: 
POST /api/v1/responses
X-Billing-Mode: paygo

{
  "model": "gpt-4o-mini",
  "input": "Hello"
}

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Provider Selection Notes

  • Provider selection only works for models that support it.
  • If a model does not support provider selection, X-Provider is ignored.
  • X-Provider explicitly selects a provider for the request.
  • Explicit provider selection is always pay-as-you-go and is charged at the selected provider’s price, including provider-selection markup.
  • For subscription users, sending X-Provider bypasses subscription coverage for that request. You do not need to also send X-Billing-Mode: paygo.
  • You cannot currently force a provider and have that same request count as subscription-included usage.

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Subscription and Limits Behavior

When billing_mode: "paygo" is set:
  • The request is not eligible for subscription coverage.
  • Subscription quota is not consumed.
  • Pay-as-you-go balance checks apply as normal.
If subscription.enablePaidModelsApi is false, the request is rejected (same as any other paid API request).

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FAQ

Does this affect which models are available? No. It only changes billing eligibility. Model availability is unchanged. Does it force a provider for non-selectable models? No. It only affects billing. Use X-Provider to explicitly select a provider for models that support provider selection. Can I combine this with BYOK? Yes. BYOK still works; paygo override only changes subscription eligibility.