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clawhub-x402-payments

Implements USDC x402 payments via PayAI (EIP-3009) and DHM x402 payments via EVVM native (signed pay). Use when adding x402 payment flows, PayAI Echo integration, EVVM pay() for DHM, agent-to-agent payments with Privy, or when the user asks how to do USDC/DHM x402 in the ClawHub/NHS EVVM app.

skill-install — Terminal

Install via CLI (Recommended)

clawhub install openclaw/skills/skills/arunnadarasa/digitalhealth
Or

ClawHub x402 Payments (USDC via PayAI + DHM via EVVM)

This skill documents the two x402 payment flows in the NHS EVVM / ClawHub app: USDC via PayAI Echo and DHM via EVVM native. Reference implementation lives in this repo.

Reference paths

FlowClient UIServer / config
USDC (PayAI)frontend/src/components/sections/USDCX402TestSection.tsxConfig: frontend/src/config/contracts.ts (X402_USDC_ECHO_URL, USDC_BASE_SEPOLIA)
DHM (EVVM)frontend/src/components/sections/X402TestSection.tsxserver/src/index.ts (GET 402, POST /payments/evvm/dhm)
EVVM signfrontend/src/lib/evvmSign.ts—

Chain: Base Sepolia (chainId 84532).

Flow 1: USDC x402 via PayAI Echo

PayAI returns 402 with an accepts array (not options). Client picks a USDC option, builds EIP-3009 TransferWithAuthorization, signs EIP-712, sends signature in PAYMENT-SIGNATURE header, retries the same URL; server returns 200 and may set PAYMENT-RESPONSE header with result (e.g. transaction hash).

Client steps

  1. Request resource
    GET <Echo URL> (e.g. https://x402.payai.network/api/base-sepolia/paid-content).

  2. Parse 402

    • Prefer PAYMENT-REQUIRED response header (base64-encoded JSON).
    • Fallback: response body may be JSON with accepts array.
    • Type: { x402Version?, error?, resource?, accepts: Array<{ scheme, network, amount, asset, payTo, maxTimeoutSeconds?, extra? }> }.

  3. Pick USDC option

    • From accepts, choose entry where asset matches USDC on Base Sepolia or extra.name === "USDC".
    • Use amount, asset, payTo, extra.name / extra.version for EIP-712.

  4. Build EIP-3009 authorization

    • Domain: name = extra?.name ?? "USDC", version = extra?.version ?? "2", chainId = 84532, verifyingContract = asset.
    • Type: TransferWithAuthorization: from, to, value, validAfter (0), validBefore (e.g. now + 300s), nonce (32 random bytes as hex).
    • Sign with signTypedData (EIP-712).

  5. Send payment and retry

    • Build payload: { x402Version: 2, scheme, network, accepted: { scheme, network, amount, asset, payTo, maxTimeoutSeconds, extra? }, payload: { signature, authorization: message }, extensions: {} }.
    • PAYMENT-SIGNATURE = base64(JSON.stringify(payload)).
    • Same URL: GET with header PAYMENT-SIGNATURE: <base64>.

  6. Read result

    • On 200: body is content. Optional PAYMENT-RESPONSE or X-PAYMENT-RESPONSE header (base64 JSON) may contain transaction (tx hash) etc.

Config

  • VITE_X402_USDC_ECHO_URL: PayAI Echo endpoint (default: https://x402.payai.network/api/base-sepolia/paid-content).
  • USDC on Base Sepolia: 0x036CbD53842c5426634e7929541eC2318f3dCF7e.

Flow 2: DHM x402 via EVVM native

Read Full Documentation on GitHub

Metadata

Author@arunnadarasa
Stars4473
Views1
Updated2026-05-01
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Add to Configuration

Paste this into your clawhub.json to enable this plugin.

{
  "plugins": {
    "official-arunnadarasa-digitalhealth": {
      "enabled": true,
      "auto_update": true
    }
  }
}
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