@checkoutkit/core

Protocol types, Zod schemas, errors and constants for the Agentic Commerce Protocol. Every other CheckoutKit package builds on this one; you rarely install it directly.

pnpm add @checkoutkit/core

The schemas are generated from the upstream spec, not hand-transcribed. The JSON Schema and OpenAPI documents are vendored under spec/2026-04-17/ and compiled into Zod, so a spec bump is a regeneration and a diff review.

import { CheckoutSessionSchema, InvalidRequestError, SPEC_VERSIONS } from "@checkoutkit/core";

const session = CheckoutSessionSchema.parse(payload);

Two behaviours worth knowing:

• Unknown fields are preserved, not stripped. Upstream declares additionalProperties: false, but a newer peer's payload has to survive a round trip. Use strict(Schema) when you want the closed behaviour.
• Some enums are deliberately open. Where the spec says servers should accept unrecognized values, the schema does.

Errors serialise to the spec's Error envelope:

new InvalidRequestError({ code: "invalid_email", message: "...", param: "$.buyer.email" }).toBody();

CheckoutKit is an independent community implementation of the Agentic Commerce Protocol. It is not affiliated with, sponsored by, or endorsed by OpenAI or Stripe.

Part of CheckoutKit · Apache-2.0