AnySpend Facilitator

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Overview

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Key Capabilities

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Multi-Token Payment Processing

• Stablecoins: USDC, DAI, USDT (on supported chains)
• Native tokens: ETH, SOL, BNB, MATIC
• Custom tokens: Any token with permit support, including project tokens like B3
• 19+ Networks: Support across EVM chains (Base, Ethereum, Arbitrum, etc.) and SVM (Solana)

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Cross-Chain Routing

• Same-chain payments: Direct token transfers with minimal overhead
• Cross-chain payments: Automatic bridging between networks (e.g., ETH → Base)
• Cross-VM payments: Experimental support for Solana ↔ EVM transfers
• Optimal routing: Smart route selection for best execution

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Automatic Token Conversion

• Buyer flexibility: Users pay with whatever token they hold
• Seller preference: Merchants receive their chosen settlement currency
• Best pricing: Routes through optimal DEX liquidity sources
• Slippage protection: Automatic safeguards against price impact

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Gasless Payments

• Facilitator covers all on-chain gas costs
• Users only sign EIP-712 messages
• No need to hold native tokens for gas
• Smooth user experience across all chains

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Standards Compliance

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x402 Protocol Compliant

• ✅ HTTP-native payments via 402 Payment Required status
• ✅ Standard headers (X-PAYMENT, X-PAYMENT-RESPONSE, X-PREFERRED-TOKEN)
• ✅ Exact payment scheme with recipient and amount verification
• ✅ Signature-based authorization (EIP-712, EIP-2612, EIP-3009)
• ✅ Cryptographic verification without trusted third parties

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Drop-in Replacement

• Client compatibility: Works with any x402-compliant client
• Server compatibility: Can be used with any x402 middleware
• No vendor lock-in: Standard HTTP APIs, switch facilitators anytime
• Interoperability: Integrates with Coinbase CDP x402, PayAI, and others

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Architecture

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Payment Flow

┌──────────────┐
│    Client    │  Signs payment authorization
│  (Any Token) │  preferredToken: DAI
└──────┬───────┘
       │
       │ X-PAYMENT header
       ▼
┌──────────────────────────┐
│   Resource Server        │
│   (Your API)             │
│                          │
│  AnySpend Middleware     │
│  • Intercepts request    │
│  • Gets quote            │
│  • Returns 402           │
└──────┬───────────────────┘
       │
       │ /verify, /settle
       ▼
┌──────────────────────────┐
│  AnySpend Facilitator    │
│  mainnet.anyspend.com    │
│                          │
│  • Validates signature   │
│  • Executes token swap   │
│  • Settles to seller     │
└──────┬───────────────────┘
       │
       │ On-chain txs
       ▼
┌──────────────────────────┐
│      Blockchain          │
│  • Receive payment       │
│  • Swap tokens (if needed) │
│  • Settle to merchant    │
└──────────────────────────┘

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Infrastructure Components

• RESTful HTTP API for payment verification and settlement
• WebSocket support for real-time payment status updates
• Rate limiting and DDoS protection
• 99.9% uptime SLA

• Aggregates liquidity from multiple DEXs
• Optimal routing for best execution prices
• Slippage protection and MEV resistance
• Cross-chain bridging integration

• Parallel transaction processing
• Automatic nonce management
• Failed transaction recovery
• Real-time settlement confirmation

• EIP-712 signature verification
• Replay attack prevention (nonce tracking)
• Deadline enforcement
• Smart contract audits

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API Endpoints

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POST /verify

• Fast validation (under 100ms)
• Check signature authenticity
• Verify deadline hasn’t expired
• No gas costs

{
  "x402Version": "0.2",
  "paymentHeader": "base64_encoded_payment",
  "paymentRequirements": {
    "scheme": "exact",
    "network": "base-mainnet",
    "amount": "1000000",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "recipient": "0xMerchantAddress..."
  }
}

{
  "valid": true
}

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POST /settle

• Execute payment authorization
• Swap tokens if needed (buyer token → seller token)
• Settle to resource server
• Return transaction hash for verification

{
  "x402Version": "0.2",
  "paymentHeader": "base64_encoded_payment",
  "paymentRequirements": { /* ... */ }
}

{
  "txHash": "0xabc123...",
  "network": "base-mainnet",
  "metadata": {
    "receiptTxHash": "0x...",
    "swapTxHash": "0x...",
    "settlementTxHash": "0x..."
  }
}

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POST /quote

• Calculate exact token amount for payment
• Get current exchange rate
• Estimate swap execution time

{
  "usdcAmount": "1000000",        // Target amount (1 USDC)
  "paymentToken": "0x50c5...",    // DAI address
  "network": "base-mainnet"
}

{
  "tokenAmount": "1000000000000000000",  // 1.0 DAI needed
  "exchangeRate": "1.0",
  "deadline": 1730000000,
  "route": {
    "srcToken": "0x50c5...",
    "dstToken": "0x8335...",
    "path": ["DAI", "USDC"]
  }
}

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GET /supported

{
  "schemes": [{
    "scheme": "exact",
    "networks": [
      "base",
      "ethereum",
      "arbitrum",
      "optimism",
      "polygon",
      "bsc",
      "avalanche",
      "solana"
    ]
  }]
}

​

Integration

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Server-Side (Express)

import { paymentMiddleware, facilitator } from '@b3dotfun/anyspend-x402';

const endpointConfig = {
  '/api/premium': {
    amount: '1.00',
    asset: 'USD'
  }
};

app.use(paymentMiddleware(
  '0xYourAddress...',
  endpointConfig,
  facilitator  // Pre-configured to mainnet.anyspend.com/x402
));

​

Server-Side (Custom)

import { X402Facilitator } from '@b3dotfun/anyspend-x402';

const facilitator = new X402Facilitator({
  url: 'https://mainnet.anyspend.com/x402',
  apiKey: process.env.ANYSPEND_API_KEY  // Optional
});

// Verify payment
const { valid } = await facilitator.verify(paymentHeader, requirements);

// Settle payment
const { txHash } = await facilitator.settle(paymentHeader, requirements);

​

Client-Side

import { X402Client } from 'anyspend-x402-client';

const client = new X402Client({
  walletClient,
  facilitatorUrl: 'https://mainnet.anyspend.com/x402'  // Optional, uses this by default
});

const response = await client.request('https://api.example.com/premium');

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Security

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Signature Verification

• USDC: EIP-3009 transferWithAuthorization
• Other tokens: EIP-2612 permit

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Replay Protection

• Each signature includes unique bytes32 nonce
• Nonce can only be used once per address
• No ordering dependencies

• Token contract maintains nonce counter
• Auto-increments on each permit execution
• Prevents out-of-order execution

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Deadline Enforcement

• Default: 5 minutes from signature time
• Prevents stale payment authorizations
• Automatic rejection of expired signatures

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No Private Key Access

• Users sign messages client-side
• Only signatures are transmitted
• Non-custodial architecture

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Performance

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Speed

• Verification: Under 100ms for signature validation
• Same-chain settlement: 2-10 seconds average
• Cross-chain settlement: 2-5 minutes (depends on bridging)
• Quote generation: Under 200ms

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Scalability

• Handles 1000+ concurrent payments
• Horizontal scaling for high throughput
• Parallel transaction processing
• Load balancing across multiple nodes

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Reliability

• 99.9% uptime guarantee
• Automatic failover and redundancy
• Failed transaction retry logic
• 24/7 monitoring and alerts

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Network Support

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EVM Mainnet Networks (12)

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EVM Testnets (5)

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SVM Networks (2)

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Why Choose AnySpend Facilitator?

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Getting Started

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Support

• Discord: discord.gg/b3dotfun
• GitHub: github.com/b3-fun/anyspend-x402
• Email: support@b3.fun
• Docs: docs.b3.fun