Evidence engine

The ProofRails engine is the processing layer behind the API and hosted application. It converts payment data into a consistent receipt and builds the evidence required to inspect that receipt later.

Pipeline

Stage	Engine action	Persisted result
Ingest	Validate the project, transaction reference and required payment fields.	Receipt with `pending` status.
Normalize	Store chain, transaction, parties, amount, asset, reference and optional resource hash.	Project-scoped receipt record.
Translate	Generate the applicable finance-readable files.	ISO 20022-style artifacts with individual hashes.
Package	Create receipt evidence and a canonical manifest.	`evidence.zip`.
Sign	Sign the manifest with Ed25519 and include the public key.	`manifest.sig` and `public_key.pem`.
Commit	Calculate the ZIP SHA-256 and submit it to EvidenceAnchor.	Bundle hash and anchor transaction.
Verify	Recompute files and compare the bundle hash with the onchain event.	Machine-readable verification result.

Receipt states

State	Meaning	Client action
`pending`	The receipt exists and background processing has started.	Poll the receipt or wait for an event.
`awaiting_anchor`	The bundle exists but the current hash has not been confirmed onchain.	Wait, or submit and confirm the anchor in tenant mode.
`anchored`	The current bundle hash matches a confirmed anchor transaction.	Treat the hosted receipt as complete.
`failed`	Processing or anchoring did not complete.	Inspect the error through your operational channel and retry only through a supported workflow.

Resource binding

A resource_hash binds delivered bytes to the receipt. In the hosted x402 flow, ProofRails hashes the protected JSON response body. For Receipt API integrations, the caller can provide a 0x-prefixed SHA-256 hash of a file or result.

This proves byte equality when the original resource is available for recomputation. It does not judge whether the resource was correct or useful.