x402 payments

x402 is an open payment protocol built on HTTP 402 status codes. When a Prudra-protected endpoint returns 402, it includes a PAYMENT-REQUIRED header containing the payment options in base64-encoded JSON. The agent decodes this header, signs an ERC-3009 authorization off-chain, and resubmits with the signature in the PAYMENT-SIGNATURE header. The agent’s wallet never sends a transaction directly. Prudra’s server receives the signed authorization, verifies it cryptographically, does the work, then settles on-chain. The agent pays with a signature — Prudra handles the blockchain interaction.

How the challenge works

The PAYMENT-REQUIRED header contains a base64-encoded array of payment options:

[
  {
    "scheme": "exact",
    "network": "base-mainnet",
    "maxAmountRequired": "10000",
    "resource": "https://your-api.com/analyse",
    "description": "Document analysis",
    "mimeType": "application/json",
    "payTo": "0x742d35Cc...",
    "maxTimeoutSeconds": 300,
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "extra": {
      "name": "USDC",
      "version": "2"
    }
  }
]

The agent selects an option matching its token preference (USDC), signs an ERC-3009 transferWithAuthorization off-chain, and returns it as the PAYMENT-SIGNATURE header (base64-encoded).

Settlement flow

Settlement happens after your handler responds. The agent doesn’t wait for on-chain confirmation — Prudra handles that asynchronously. The PAYMENT-RESPONSE header in the 200 response includes the txHash and a settlementPending flag.

When to use x402

Scenario	Recommendation
Agents using Base wallet	x402 or dual-protocol
Agents using USDC on Base	x402 or dual-protocol
Maximum compatibility	Dual-protocol (both x402 and MPP)
Session payments needed	Use MPP instead
Simple, one-off payments	x402

x402 does not support session payments. For multi-step workflows under one payment, use MPP or session payments.

Tokens and chains

x402 currently supports:

Token	Chain	Chain ID
USDC	Base	8453
USDC	Base Sepolia (testnet)	84532

How x402 works — ERC-3009 flow in depth
Add x402 to an endpoint — configure payMiddleware for x402
Test x402 payments — test without real funds
Handle the payment response — read the PAYMENT-RESPONSE header
Dual-protocol payments — use x402 and MPP together

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x402 payments

x402 payments

How the challenge works

Settlement flow

When to use x402

Tokens and chains

​x402 payments

​How the challenge works

​Settlement flow

​When to use x402

​Tokens and chains

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x402 payments

How the challenge works

Settlement flow

When to use x402

Tokens and chains

Related