Breaking fix: line_items shape now consistent across the SDK and API

Version: 1.0.105

We've resolved a spec drift in Calmony Pay where the SDK's line_items type did not match the shape required by the POST /v1/checkout/sessions REST endpoint. If you use the SDK to create checkout sessions, you will need to update your line_items usage.

---

What was the problem?

The SDK's CreateCheckoutSessionParams type defined line_items items with a flat structure:

// ❌ Old (incorrect) SDK shape
{
  price_id?: string;
  amount?: number;
  currency?: string;
  quantity?: number;
  description?: string;
}

At the same time, the REST API (POST /v1/checkout/sessions) required a Stripe-compatible nested structure:

// ✅ Required API shape
{
  price_data: {
    currency: string;
    unit_amount: number;
    product_data: {
      name: string;         // required
      description?: string; // optional
    };
  };
  quantity: number;
}

Because the SDK was not wrapping fields in price_data / product_data, every line_items entry sent to the API failed validation. Checkout sessions could not be created through the SDK.

---

What changed?

The SDK's CreateCheckoutSessionParams.line_items type has been updated to require the Stripe-style nested shape. The SDK will now serialise line_items correctly when calling the REST API.

The two affected files are:

• src/lib/calmony-pay/client.ts — SDK type definition and request serialisation
• src/app/api/v1/checkout/sessions/route.ts — REST API validation schema

---

Migrating your code

Update any call site that passes line_items to checkout.sessions.create().

Before (broken)

await pay.checkout.sessions.create({
  line_items: [
    {
      amount: 2500,
      currency: 'gbp',
      description: 'Pro Plan',
      quantity: 1,
    },
  ],
});

After (correct)

await pay.checkout.sessions.create({
  line_items: [
    {
      price_data: {
        currency: 'gbp',
        unit_amount: 2500, // in minor units, e.g. pence for GBP
        product_data: {
          name: 'Pro Plan',          // required
          description: 'Monthly subscription', // optional
        },
      },
      quantity: 1,
    },
  ],
});

---

Key field reference

Field	Type	Required	Notes
price_data	object	✅	Wrapper for pricing information
price_data.currency	string	✅	ISO 4217 currency code, e.g. gbp
price_data.unit_amount	number	✅	Amount in minor units (e.g. pence)
price_data.product_data	object	✅	Wrapper for product information
price_data.product_data.name	string	✅	Display name for the line item
price_data.product_data.description	string	❌	Optional description
quantity	number	✅	Number of units

---

Why the nested shape?

Calmony Pay's API is designed to be Stripe-compatible. The nested price_data / product_data shape mirrors the Stripe Checkout Sessions API, making it straightforward to migrate between Stripe and Calmony Pay, and to reuse existing Stripe integration code with minimal changes.