> ## 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.

# Core concepts

> Understand resources, ownership, replacement, and lifecycle semantics.

## Three resources

* **Party**: a person or organisation represented by the source, including current source-owned contact details. A Receivable assigns each referenced Party's role as primary, joint, or guarantor.
* **Receivable**: one independently recoverable amount, responsible Parties, dates, and typed `credit_union.v1` loan context.
* **Payment observation**: immutable evidence of an externally received payment, refund, or reversal.

Create dependencies in that order. A missing parent returns `409 dependency_missing`; PayPathIQ does not auto-create or queue it.

Cases, workflow, communications, commitments, automation, and recovery policy remain PayPathIQ-owned projections. An Integration may update only its own source representation.

## Updates

`PUT` creates or replaces the complete source-owned representation. `PATCH` uses RFC 7396 JSON Merge Patch: omitted fields remain unchanged, `null` clears a nullable scalar, and an array replaces the whole source-owned collection. Payment observations are immutable and do not support `PATCH`.

This is the target contract. The current Party slice supports create, read, and identical retry only; a changed `PUT` for an existing Party returns `409 party_representation_conflict` until replacement ships.

The resource URL and normalized payload digest make identical retries safe. Under the target contract, a changed Party or Receivable payload becomes the next accepted source representation. A changed payload for an existing payment-observation ID returns `409 payment_observation_conflict`.

## Receivable authority

`recoverableAmount` is the sole recovery authority. `credit_union.v1` accepts EUR amounts with exactly two decimal places. Optional outstanding, arrears, instalment, and balance-breakdown amounts provide context and never expand the recoverable amount.

Pause, clear-pause, close, and reopen are explicit commands. They are not ordinary status patches, and they never resume PayPathIQ automation automatically.

## Safety assertions

Safety facts use a closed vocabulary and an explicit `active` or `cleared` state with `effectiveAt`. Omission never clears safety evidence. Unknown assertion types are rejected.