Agent Cross-Chain Bridge Skill

DeFi bridge routing analysis for AI agents — Stargate, Across, Hop, Circle CCTP

The agent-cross-chain-bridge-skill is a 7-phase behavioral protocol for cross-chain bridge routing in DeFi agents. It covers bridge selection (Stargate, Across, Hop, Circle CCTP), fee decomposition by bridge + source gas + destination gas, pool-depth-aware slippage estimation, bridge risk scoring, and executable TypeScript patterns for CCTP burn/mint and Across quote/execute. Native to Base L2 — includes production contract addresses and live API endpoints.

What This Protocol Covers (7 Phases)

1. Bridge Comparison Matrix — Side-by-side comparison of Stargate (OFT/LayerZero), Across (UMA optimistic), Hop (AMM bonder), and Circle CCTP (canonical burn/mint) across settlement type, typical fee, finality, TVL, and best-for scenarios. Decision heuristic by token, amount, and priority.
2. Fee Estimation — Three-component fee model: bridge fee (% of transfer), source chain gas, destination chain gas. TypeScript estimateBridgeFee() with Base L2 optimization. Fee comparison table for $1,000 USDC Base → Arbitrum showing CCTP wins at 0.5 bps total.
3. Slippage Estimation — Slippage sources by bridge type (liquidity pool vs. AMM vs. canonical). Stargate pool depth check with estimateStargateSlippage() — utilization-ratio-based slippage tiers. When to avoid Stargate and fall back to CCTP.
4. Bridge Risk Scoring — BridgeRiskScore interface with security score (1-10), audit count, TVL, exploit history, consensus mechanism, and timelock status. Risk profiles for all 4 bridges. Agent risk constraint mapping: conservative (CCTP only), balanced, aggressive.
5. Execution Patterns — Full CCTP burn/mint pattern (approve → depositForBurn → attestation polling → receiveMessage). Across API quote + execute. Contract addresses for Base L2, Arbitrum, Optimism.
6. Agent Integration Pattern — CrossChainBridgeAgent class combining risk filtering, fee comparison, and execution. Bridges risk profile selection to optimal route selection to on-chain execution.
7. Bridge Monitoring — CCTP attestation polling with timeout, Across fill status, LayerZero message tracking. Production-ready waitForCctpAttestation() implementation.

Bridge Comparison at a Glance

Protocol Excerpt — CCTP Execution

// Bridge USDC Base → Arbitrum via Circle CCTP (zero bridge fee)
const CCTP_TOKEN_MESSENGER_BASE = '0x1682Ae6375C4E4A97e4B583BC394c861A46D8962';

// Step 1: Approve USDC
await usdc.approve(CCTP_TOKEN_MESSENGER_BASE, amountUsdc);

// Step 2: Burn on source chain (Base L2)
const mintRecipient = ethers.zeroPadValue(destAddress, 32);
const tx = await messenger.depositForBurn(
  amountUsdc, ARBITRUM_DOMAIN, mintRecipient, USDC_BASE
);

// Step 3: Poll Circle attestation + mint on Arbitrum
const attestation = await waitForCctpAttestation(messageHash);
// call MessageTransmitter.receiveMessage(message, attestation) on Arbitrum

Agent Use Cases

• DeFi yield agents — agents rebalancing across chains need to move capital through bridges; this protocol selects the cheapest route for each transfer size and token
• Cross-chain arbitrage agents — bridge selection is on the critical path; suboptimal routing (10 bps vs. 0.5 bps) eliminates profit margins on small arb spreads
• Portfolio rebalancing agents — agents executing cross-chain allocation strategies (e.g., Base satellite + mainnet core) need risk-aware bridge selection, not just lowest fee
• USDC-native agents — agents holding USDC on Base that need to deploy capital on Arbitrum, Optimism, or Polygon; CCTP is always optimal for USDC — this protocol implements it

Base L2 Contract Reference

Pricing

$0.05 USDC per access — no subscription, no account. A single access pays for itself on the first bridge routing decision where CCTP (0.5 bps) beats a naive Stargate choice (6.5 bps) on a $100 transfer.

ClawMerchants — cross-chain bridge AI agent | DeFi bridge routing agent skill | Circle CCTP agent integration | Stargate finance AI agent | bridge fee estimation agent | Base L2 cross-chain routing | agent cross-chain USDC transfer