> ## Documentation Index
> Fetch the complete documentation index at: https://developer.kalixo.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Kalixo event delivery

> Kalixo POSTs an `Event` to every enabled webhook endpoint subscribed to its
type. Verify the `Kalixo-Signature` header, answer with any 2xx within
10 seconds, then process asynchronously. Deliveries are retried with
exponential backoff for about 3 days. Deduplicate on `id`; ignore events
whose `data.object.version` is lower than what you already have.




## OpenAPI

````yaml /checkout/openapi.yaml webhook event
openapi: 3.1.0
info:
  title: Kalixo Checkout API
  version: '2026-10-01'
  summary: Payment orchestration API for Kalixo partners.
  description: >
    Kalixo Checkout lets partners collect payments from their shoppers through
    one

    provider-neutral API. Kalixo is merchant of record and handles payment

    processing, so partners never integrate a payment provider directly.


    - Amounts are integers in the currency's minor unit (EUR 49.99 = `4999`).

    - Server endpoints use a secret key (`kc_sk_test_...` or `kc_sk_live_...`).

    - Client endpoints are called by `Kalixo.js` with a publishable key and the
      checkout session's `client_secret`.
    - Every `POST` with a secret key requires an `Idempotency-Key` header.
  contact:
    name: Kalixo Checkout integrations
    email: integrations@kalixo.io
  license:
    name: Proprietary
    url: https://kalixo.io/legal
servers:
  - url: https://checkout.kalixo.io
    description: Live
  - url: https://sandbox.checkout.kalixo.io
    description: Sandbox (test keys only, connected to the provider test environment)
security:
  - secretKey: []
tags:
  - name: Checkout sessions
    description: >-
      Create a session with the amount to charge, then show it with Kalixo.js or
      the hosted checkout.
  - name: Payments
    description: Read payments and capture or cancel authorized payments.
  - name: Refunds
    description: Full and partial refunds of captured payments.
  - name: Payment links
    description: Kalixo-hosted payment links that survive provider switches.
  - name: Customers
    description: Customers and their stored payment methods for one-click checkout.
  - name: Disputes
    description: Chargebacks and information requests, plus evidence upload.
  - name: Events
    description: The event log behind webhooks.
  - name: Webhook endpoints
    description: Where Kalixo delivers signed events.
  - name: Reports
    description: CSV exports of transactions for reconciliation and partner invoicing.
  - name: Client
    description: Called by Kalixo.js and the hosted checkout. Not for partner servers.
paths: {}
components:
  securitySchemes:
    secretKey:
      type: http
      scheme: bearer
      description: Secret key, `kc_sk_test_...` or `kc_sk_live_...`. Server-side only.

````

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