create-typescript-x402-facilitator

Install @x402-avm/core, @x402-avm/avm, algosdk, and express, then implement the FacilitatorAvmSigner interface and register it via registerExactAvmScheme from @x402-avm/avm/exact/facilitator. Expose /verify, /settle, and /supported endpoints through an Express server.

FacilitatorAvmSigner bridges the facilitator to Algorand with six methods: getAddresses, signTransaction, getAlgodClient, simulateTransactions, sendTransactions, and waitForConfirmation. It handles signing, simulation, submission, and confirmation of payment transaction groups.

Yes, register the facilitator with ALGORAND_MAINNET_CAIP2 instead of ALGORAND_TESTNET_CAIP2 when calling registerExactAvmScheme. Use the network constants from @x402-avm/avm rather than string literals.

Simulation fails when the group mixes signed and unsigned transactions without wrapping. Wrap unsigned transactions with new algosdk.SignedTransaction({ txn }) and set allowEmptySignatures: true in the SimulateRequest.

Bazaar is an optional extension that catalogs x402-protected resources. Resource servers declare discovery metadata with declareDiscoveryExtension, and facilitators extract it in onAfterSettle hooks using extractDiscoveryInfo to build a discovery API.

Common causes include insufficient ALGO in the facilitator address for fee-payer transactions, improperly concatenated signed bytes, or missing scheme registration. Concatenate signed transactions with Buffer.concat before sendRawTransaction and ensure registerExactAvmScheme was called.