005 · v3 Cumulative Payment Specification

005 is the normal fulfillment message of the 003 Final Payment Authorization. The transaction template, fees, sequence number, outputs, and signatures are uniquely determined by MultisigPool v4.0.0; go-bitfs only passes the authorization hash, the unsigned state transaction, and the independent Buyer signature.

All state transactions have exactly three funding outputs fixed as [Buyer, Seller, Arbiter]: output[0] is Buyer, output[1] is Seller with an absolute cumulative amount, and output[2] is Arbiter with a fixed amount of 0. The Buyer amount and fees are calculated by MultisigPool v4 and MUST NOT be copied or patched by the business layer.

005 CBOR

CumulativePaymentUpdateCBOR = deterministic CBOR([
  3,
  payment_authorization_hash,
  unsigned_state_tx_raw,
  buyer_transaction_signature
])

The unsigned transaction MUST have exactly one input and three funding outputs; the input unlockingScript MUST be empty and MUST NOT carry a single signature or the final dual-signed transaction. After verifying the Buyer's independent signature and the v4-compliant state, the Seller produces an independent Seller signature on the same unsigned transaction; the complete transaction is finally generated only via MergeArbitratedPoolBuyerSellerSignatures.

When submission fails, times out, or the txid/sequence number is inconsistent, the local accepted state MUST NOT advance; if the node has accepted the transaction but local persistence fails, the system MUST enter the external-state-uncertain state.

The 007 arbitration path does not depend on the Buyer signature from this 005 message. The arbitration path uses the same three-output rule, with signatures merged by Seller and Arbiter via MergeArbitratedPoolSellerArbiterSignatures.