Documentation

x402 Facilitator

The facilitator verifies payment signatures and settles transactions on-chain.

What is a Facilitator?

In the x402 protocol, a facilitator is a trusted third-party service that bridges signed payment authorizations to on-chain settlement. The facilitator enables gasless payments — payers sign EIP-712 authorizations off-chain, and the facilitator submits the actual blockchain transaction.

The facilitator:

  1. Receives payment payloads from payees (servers)
  2. Verifies EIP-712 signatures against payment requirements
  3. Checks authorization validity (nonce, time bounds)
  4. Executes the on-chain transfer
  5. Returns settlement confirmation (tx hash, block number)

Primer Facilitator

Primer operates a public facilitator for Base networks:

endpoint
https://x402.primer.systems

Supported Networks

Network CAIP-2 ID Status
Base Mainnet eip155:8453 Supported
Base Sepolia eip155:84532 Supported
SKALE Base eip155:1187947933 Supported
SKALE Base Sepolia eip155:324705682 Supported
Default in SDK. The Primer facilitator is the default for Base networks — no configuration required.

API Endpoints

Endpoint Description
POST /verify Verify payment signature without settling
POST /settle Verify and execute payment on-chain
GET /supported List supported schemes and networks
GET /health Health check and configuration status
GET /contracts Get Prism contract addresses

Batch Settlement Endpoints

Endpoint Description
POST /batch/deposit Deposit funds into a payment channel
POST /batch/claim Claim funds from a payment channel
POST /batch/settle Settle claimed funds on-chain
POST /batch/refund Refund from channel (after withdraw delay)
GET /batch/contracts Get batch settlement contract addresses
GET /batch/channel/:id Get channel state by ID

Token Support

EIP-3009 Tokens (USDC, EURC)

Tokens implementing EIP-3009 support native gasless transfers via transferWithAuthorization. The facilitator calls this function directly on the token contract — no additional contracts required.

Standard ERC-20 via Prism

For tokens without EIP-3009 support, the Primer facilitator uses our Prism settlement contract. Prism enables gasless ERC-20 transfers through a signature-based flow:

  1. Payer approves Prism contract once (requires gas)
  2. Payer signs EIP-712 authorization for each payment
  3. Facilitator calls settleERC20() on Prism
  4. Prism transfers tokens from payer to payee

The facilitator auto-detects token type — if the token implements EIP-3009, it uses direct transfer; otherwise, it routes through Prism.

Payment Schemes

The Primer facilitator supports two x402 payment schemes:

  • exact — per-request settlement where the payer transfers a specific amount for each request
  • batch-settlement — payment channels where payers deposit to an escrow, servers claim in batches, and funds are settled periodically

Batch settlement is useful for high-frequency, low-value transactions where per-request gas costs would be prohibitive.

Primer Pay →