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Your autumn.config.ts file is the source of truth for your pricing. It exports features and plans using helper functions from the atmn package.
autumn.config.ts
import { feature, item, plan } from 'atmn';

export const messages = feature({ ... });
export const pro = plan({ ... });
Push changes with atmn push, or pull existing config with atmn pull.

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Features

Features define what can be gated, metered, or billed in your app.

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feature(config)

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id
string
required
Unique identifier used in API calls (check, track, etc).
​
name
string
required
Display name shown in the dashboard and billing UI.
​
type
enum
required
"boolean" | "metered" | "credit_system"
​
consumable
boolean
Required for metered features.
  • true — usage is consumed (messages, API calls, credits)
  • false — usage is ongoing (seats, storage, workspaces)
​
creditSchema
array
Required for credit_system features. Maps metered features to credit costs.Each entry: { meteredFeatureId: string, creditCost: number }

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Feature types

Boolean — simple on/off flag: 
export const sso = feature({
  id: 'sso',
  name: 'SSO Authentication',
  type: 'boolean',
});
Metered, consumable — used up and replenished (messages, API calls): 
export const messages = feature({
  id: 'messages',
  name: 'Messages',
  type: 'metered',
  consumable: true,
});
Metered, non-consumable — ongoing usage (seats, storage): 
export const seats = feature({
  id: 'seats',
  name: 'Seats',
  type: 'metered',
  consumable: false,
});
Credit system — maps multiple metered features to credit costs: 
export const basicModel = feature({
  id: 'basic_model',
  name: 'Basic Model',
  type: 'metered',
  consumable: true,
});

export const premiumModel = feature({
  id: 'premium_model',
  name: 'Premium Model',
  type: 'metered',
  consumable: true,
});

export const credits = feature({
  id: 'credits',
  name: 'AI Credits',
  type: 'credit_system',
  creditSchema: [
    { meteredFeatureId: basicModel.id, creditCost: 1 },
    { meteredFeatureId: premiumModel.id, creditCost: 5 },
  ],
});
If you set the price per credit to 1 cent, credits become monetary credits (eg, 5 credits = $0.05 per premium message).

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Plans

Plans combine features with pricing to create your subscription tiers, add-ons, and top-ups.

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plan(config)

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id
string
required
Unique identifier used in checkout and subscription APIs.
​
name
string
required
Display name shown in pricing tables and billing.
​
price
object
Base subscription price:
  • amount: number — price amount (eg, 20 for $20)
  • interval: string — "month" | "quarter" | "semi_annual" | "year" | "one_off"
​
items
array
Array of item() objects defining what’s included.
​
autoEnable
boolean
default:"false"
Automatically assign this plan to new customers. Typically used for free plans.
​
addOn
boolean
default:"false"
Allow this plan to be purchased alongside other plans (instead of replacing them).
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freeTrial
object
Free trial before billing starts:
  • durationLength: number — eg, 14
  • durationType: string — "day" | "month" | "year"
  • cardRequired: boolean — whether a card is needed to start the trial
​
group
string
Group related plans together. Plans in the same group replace each other on upgrade/downgrade.

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Plan items

Plan items define what each plan includes — usage limits, pricing, and billing behavior.

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item(config)

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featureId
string
required
The id of the feature to include.
​
included
number
Amount included for free. Omit for boolean features.
​
unlimited
boolean
Grant unlimited usage of this feature.
​
reset
object
How often the included amount resets:
  • interval: string — "hour" | "day" | "week" | "month" | "quarter" | "semi_annual" | "year"
  • intervalCount: number — defaults to 1
​
price
object
Pricing for usage beyond the included amount. See pricing patterns below.
​
proration
object
How to handle mid-cycle quantity changes:
  • onIncrease: "prorate" | "charge_immediately"
  • onDecrease: "prorate" | "refund_immediately" | "no_action"
​
rollover
object
Carry unused balance forward:
  • max: number — maximum rollover amount
  • expiryDurationType: "month" | "forever"
  • expiryDurationLength: number — ignored if type is "forever"

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Pricing patterns

The price object on a plan item supports different billing models: Usage-based — charge based on actual usage: 
item({
  featureId: seats.id,
  included: 5,
  price: {
    amount: 10,
    interval: 'month',
    billingMethod: 'usage_based',
    billingUnits: 1,
  },
})
Prepaid — customer buys a fixed quantity upfront: 
item({
  featureId: credits.id,
  price: {
    amount: 5,
    billingUnits: 100,
    billingMethod: 'prepaid',
  },
})
Tiered — price changes based on usage volume: 
item({
  featureId: apiCalls.id,
  price: {
    tiers: [
      { to: 1000, amount: 0.01 },
      { to: 10000, amount: 0.008 },
      { to: 'inf', amount: 0.005 },
    ],
    billingMethod: 'usage_based',
    interval: 'month',
  },
})

​
Price fields

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amount
number
Price per billingUnits. Mutually exclusive with tiers.
​
tiers
array
Tiered pricing. Each entry: { to: number | "inf", amount: number }. Mutually exclusive with amount.
​
billingMethod
enum
required
"usage_based" | "prepaid"
​
interval
enum
"week" | "month" | "quarter" | "semi_annual" | "year". Omit for one-time charges. Not needed if the plan item has a top-level reset.
​
billingUnits
number
default:"1"
Units per price. Eg, $5 per 100 credits = amount: 5, billingUnits: 100.
​
maxPurchase
number
Maximum quantity that can be purchased.

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Full example

A complete config with a free plan, a paid plan with a trial, and a credits top-up add-on:
autumn.config.ts
import { feature, item, plan } from 'atmn';

// Features
export const messages = feature({
  id: 'messages',
  name: 'Messages',
  type: 'metered',
  consumable: true,
});

export const seats = feature({
  id: 'seats',
  name: 'Seats',
  type: 'metered',
  consumable: false,
});

export const sso = feature({
  id: 'sso',
  name: 'SSO',
  type: 'boolean',
});

// Plans
export const free = plan({
  id: 'free',
  name: 'Free',
  autoEnable: true,
  items: [
    item({
      featureId: messages.id,
      included: 5,
      reset: { interval: 'month' },
    }),
    item({
      featureId: seats.id,
      included: 1,
    }),
  ],
});

export const pro = plan({
  id: 'pro',
  name: 'Pro',
  price: { amount: 20, interval: 'month' },
  freeTrial: {
    durationLength: 14,
    durationType: 'day',
    cardRequired: true,
  },
  items: [
    item({
      featureId: messages.id,
      included: 1000,
      reset: { interval: 'month' },
    }),
    item({
      featureId: seats.id,
      included: 5,
      price: {
        amount: 10,
        interval: 'month',
        billingMethod: 'usage_based',
        billingUnits: 1,
      },
    }),
    item({
      featureId: sso.id,
    }),
  ],
});

export const topUp = plan({
  id: 'top_up',
  name: 'Message Top-Up',
  addOn: true,
  items: [
    item({
      featureId: messages.id,
      price: {
        amount: 5,
        billingUnits: 100,
        billingMethod: 'prepaid',
      },
    }),
  ],
});