​

Polar billing platform integration

• Configure a cost-based meter in base currency units.
• Create the @ai-billing/polar destination.
• Map usage events to Polar customers.
• Sync user identity with externalId.

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Meter units

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Install dependencies

pnpm add @ai-billing/polar @polar-sh/sdk

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Configure environment variables

POLAR_ACCESS_TOKEN=****
POLAR_SERVER=sandbox # or production

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Create Polar billing destinations

import { createPolarDestination } from '@ai-billing/polar';

export function getBillingDestinations() {
  const polarAccessToken = process.env.POLAR_ACCESS_TOKEN;
  const polarServer = process.env.POLAR_SERVER as
    | 'sandbox'
    | 'production'
    | undefined;

  if (!polarAccessToken) return [];

  return [
    createPolarDestination({
      accessToken: polarAccessToken,
      server: polarServer ?? 'sandbox',
      eventName: 'llm_usage',
      externalCustomerIdKey: 'userId',
    }),
  ];
}

​

Sync Polar customers on signup

import { Polar } from '@polar-sh/sdk';

let _polar: Polar | null = null;

function getPolarClient(): Polar | null {
  if (_polar) return _polar;

  const accessToken = process.env.POLAR_ACCESS_TOKEN;
  if (!accessToken) return null;

  const server = (process.env.POLAR_SERVER ?? 'sandbox') as
    | 'sandbox'
    | 'production';

  _polar = new Polar({ accessToken, server });
  return _polar;
}

export async function createPolarCustomer(email: string, userId: string) {
  const polar = getPolarClient();
  if (!polar) return;

  try {
    await polar.customers.create({ email, externalId: userId });
  } catch (error) {
    console.error('[ai-billing] Failed to create Polar customer:', error);
  }
}

if (newUser) {
  await createPolarCustomer(validatedData.email, newUser.id);
}

​

Required tag contract

providerOptions: {
  'ai-billing-tags': {
    userId: session.user.id,
    modelId: chatModel,
    chatId: id,
  },
}

• userId in ai-billing-tags must match Polar externalId.
• Each user should have one Polar customer record.

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Verify polar metering

1. Register a new user and confirm a Polar customer exists with externalId = userId.
2. Trigger a model call and confirm an event named llm_usage appears.
3. Validate credits_consumed and cost_currency, plus the expected tag_* metadata and customer identity.
4. Confirm your environment uses the expected Polar server (sandbox or production).

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Common issues

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Events appear but don’t map to customers

• Confirm userId exists in ai-billing-tags.
• Confirm destination uses externalCustomerIdKey: 'userId'.
• Confirm customer creation uses externalId = userId.

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No events arrive in Polar

• Confirm POLAR_ACCESS_TOKEN is present at runtime.
• Confirm POLAR_SERVER matches the Polar workspace you are checking.
• Confirm framework routes call the billing-wrapped model helper.