use-typescript-x402-core-avm

Install @x402-avm/core, @x402-avm/avm, and algosdk, then construct an x402Client and call registerExactAvmScheme with a ClientAvmSigner. The client's fetch method automatically handles 402 responses by signing payment transactions and retrying with the X-PAYMENT header.

Create an x402Facilitator and register the exact AVM scheme with a FacilitatorAvmSigner and supported networks. The signer must provide Algod client access, transaction simulation, group submission, and confirmation waiting; the facilitator then exposes verify and settle methods.

Yes, the ClientAvmSigner interface is compatible with @txnlab/use-wallet's signTransactions function. Wrap the wallet's activeAccount address and signTransactions method into a signer object and pass it to registerExactAvmScheme.

Fee abstraction is automatic when PaymentRequirements include a feePayer. The scheme creates a 2-transaction atomic group where the payment has zero fee and a fee payer self-payment covers both fees; the facilitator validates and signs the fee payer transaction before submission.

This error occurs when registerExactAvmScheme was not called on the client, server, or facilitator before use. Always register the AVM scheme immediately after constructing the x402 component, and ensure the network CAIP-2 identifier matches.

AVM_PRIVATE_KEY must be a Base64-encoded 64-byte key consisting of a 32-byte Ed25519 seed plus a 32-byte public key. Derive the address with algosdk.encodeAddress(secretKey.slice(32)); a wrong length produces an 'Invalid key length' error.