starchild-ai-agent Cross-Chain Bridge
Single-command cross-chain token bridge for USDC/USDT across 6 EVM chains using Alchemy Account Abstraction (ERC-4337) with gas-sponsored transactions.
Supported Chains
- Arbitrum (chainId 42161)
- Base (chainId 8453)
- Ethereum (chainId 1)
- Optimism (chainId 10)
- Polygon (chainId 137)
- BSC (chainId 56)
Required Environment
ALCHEMY_API_KEY— Alchemy API key with Account Abstraction enabled
Usage
# Bridge 5 USDC from Arbitrum to Base
python3 bridge.py --amount 5 --token USDC --from arbitrum --to base
# Bridge 10 USDT from Base to Optimism
python3 bridge.py --amount 10 --token USDT --from base --to optimism
# List supported chains
python3 bridge.py --list-chains
How It Works
- Creates an Alchemy SmartAccount with LightSigner (gasless transactions)
- Approves the Across Protocol router to spend the token
- Executes the bridge via Across Protocol
- Waits for on-chain confirmation
- Reports the transaction hash
Key Features
- Gasless: No ETH needed — Alchemy sponsors gas via ERC-4337
- Single command: All chain IDs, contract addresses, and routing logic hardcoded
- Auto-approve: Token approval handled automatically
- 6 chains: Arbitrum, Base, Ethereum, Optimism, Polygon, BSC
- Cost: ~$0.035 per operation (0.3% bridge fee only)
Troubleshooting
- "ALCHEMY_API_KEY not set" — Export the key or add to workspace/.env
- "Insufficient token balance" — Check wallet balance on source chain
- "Bridge timeout" — Across bridge usually completes in 2-5 minutes