tools-only Smart Account Swap Integration Test Case
Build a swap integration that executes through an ERC-4337 smart account on Base.
Context
- TypeScript/Node.js backend service
- Need to swap USDC to ETH on Base (chain ID 8453)
- Using the Uniswap Trading API through an ERC-4337 smart account
- The smart account uses delegation for executing swaps
- After swap, ETH should be native ETH (not WETH)
Requirements
- Get swap calldata from Trading API (3-step flow)
- Wrap swap calldata in a delegation redemption execution
- Submit via bundler as a UserOperation
- Handle WETH unwrapping after swap (Base often returns WETH instead of native ETH)
- Implement rate limiting with exponential backoff for API calls
- Use legacy approval (direct to Universal Router) instead of Permit2
Constraints
- Must use viem for all blockchain interactions
- Must handle the Trading API 3-step flow correctly
- Must explain the approval target choice (legacy vs Permit2 for smart accounts)
- Must include WETH detection and unwrap logic for L2
- Must include retry logic with exponential backoff for 429 responses
- Should include error handling for bundler-specific errors
Expected Output
A working TypeScript implementation that demonstrates executing Uniswap swaps through an ERC-4337 smart account with delegation, including L2 WETH handling and rate limiting.