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

# Changelog

> Dated changes to the PayPathIQ inbound API and its documentation.

Breaking changes are announced here before they take effect. See [Versioning and deprecation](/versioning-and-deprecation).

<Update label="2026-09-26" description="Sandbox handover">
  * Customer Contacts can now be updated. Send a stable `externalContactId` on each Contact; see [Updating Contacts](/concepts#updating-contacts).
  * When your Integration and PayPathIQ staff both change a Customer or Contact, the newest update wins; see [The latest update wins](/concepts#the-latest-update-wins).
  * Every problem `type` now links to an [error reference](/problems/validation_error) page.
  * Every `422 validation_error` now lists field problems in `errors`, with a JSON `pointer` and a [field error code](/errors-and-retries#field-error-codes).
  * Leaving a safety assertion type out of a supplied collection no longer clears it. Only `"state": "cleared"` clears an assertion.
  * The OpenAPI document now lists `409 receivable_state_conflict` for Receivable and Payment observation `PUT`, and `409 payment_policy_blocked` for Payment observation `PUT`. It no longer lists `pause_source_conflict` or a `409` for `close`, which the API never returned, or `500 internal_error`; unexpected failures return `503 projection_unavailable`.
  * Documented [rate limits](/errors-and-retries#rate-limits), [scopes](/authentication#scopes), and how to [get a sandbox key](/authentication#get-a-sandbox-key).
</Update>