Got it — since the interface didn’t expose the generated file as a downloadable link, I’ll give you the full Markdown content directly here so you can copy-paste into a file or I can recreate it again as a downloadable file if your UI supports it.

sequenceDiagram autonumber participant C as Client (dApp) participant S as API Server (/api) participant F as MultiChain<br/>x402 Facilitator (backend) participant RC as RouterContract<br/>(Base/Sepolia/Arb/Opt) participant D as DEX/Bridge<br/>(Uniswap/Mayan) participant L1 as Blockchain C->>S: 1. GET /api S-->>C: 2. 402 Payment Required<br/>(paymentRequirements: chains+tokens) C->>F: 3. POST /pay<br/>X-PAYMENT (signed payload) F->>F: 4. Verify signature + build RoutePlan<br/>(chain, tokenIn, tokenOut, amount, dest) F->>RC: 5. executeRoute(permit, route)<br/>(on chosen chain) RC->>D: 6. swap / bridge token as per route D->>L1: 7. On-chain txs (swap/bridge/transfer) L1-->>RC: 8. Tx confirmed (event with amountOut) RC-->>F: 9. Return txHash, amountOut F-->>S: 10. /settle success<br/>X-PAYMENT-RESPONSE S-->>C: 11. 200 OK + protected resource 

Deploy the same contract on:

• Base
• Sepolia
• Arbitrum
• Optimism

• Accept permit signature + routing params
• Pull tokens from user via permit
• Optionally swap tokens using DEX router
• Transfer to merchant payout address
• Emit event for backend confirmation

struct PermitData { address token; address owner; uint256 nonce; uint256 deadline; bytes sig; } struct RouteParams { bytes32 paymentId; address tokenIn; address tokenOut; uint256 amountIn; uint256 minAmountOut; address merchant; address dexRouter; bytes dexCalldata; }

function executeRoute(PermitData calldata permit, RouteParams calldata route) external onlyRelayer { // 1. Validate payment and routing info // 2. Pull funds from payer using permit // 3. If needed call Uniswap router using `dexCalldata` // 4. Transfer to merchant or trigger bridge contract call // 5. emit RouteExecuted(...) }

• Decode X-PAYMENT
• Verify signature with wallet signature typed data
• Validate supported chain & token
• Build RoutePlan
• Save PaymentRecord in memory DB
• Return { isValid: true }

• Fetch PaymentRecord
• Call router executeRoute()
• Wait for confirmation
• Return X-PAYMENT-RESPONSE

type ChainConfig = { chainId: number; rpcUrl: string; routerAddress: string; supportedTokens: TokenConfig[]; };

• Chain dropdown

• Token dropdown

• “Execute Payment”

• Logs:

  • PaymentID
  • Chosen chain & token
  • TX hash
  • Status timeline

We built a multi-chain x402 router that enables pay-any-chain, pay-any-token settlement with real-time access unlock for paid API resources.