Contract Verification

Contract verification allows users and developers to view and interact with your contract source code on block explorers like Etherscan.

Automatic Verification

The easiest way to verify contracts is during deployment by adding the --verify flag to your Forge script command.

During Deployment

forge script script/DeployAllContracts.s.sol:DeployAllContracts \
  --rpc-url $ETH_RPC_URL \
  --private-key $PRIVATE_KEY \
  --broadcast \
  --verify

Ensure the ETHERSCAN_API_KEY environment variable is set before using the --verify flag.

Manual Verification

If automatic verification fails or you need to verify an already deployed contract, use the forge verify-contract command.

Prerequisites

Set environment variables

export CHAIN_ID=1  # Target network chain ID
export ETHERSCAN_API_KEY=your_api_key_here

Identify contract addresses

Find the deployed contract addresses in networks.json or from your deployment output.

Verify FlashLoanRouter

The FlashLoanRouter is initialized with the CoW Settlement contract address (0x9008D19f58AAbD9eD0D60971565AA8510560ab41).

forge verify-contract \
  0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69 \
  src/FlashLoanRouter.sol:FlashLoanRouter \
  --chain-id $CHAIN_ID \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --constructor-args $(cast abi-encode "constructor(address)" 0x9008D19f58AAbD9eD0D60971565AA8510560ab41)

The constructor argument is the CoW Settlement contract address, which is consistent across all supported networks.

Verify AaveBorrower

The AaveBorrower is initialized with the FlashLoanRouter address.

forge verify-contract \
  0x7d9C4DeE56933151Bc5C909cfe09DEf0d315CB4A \
  src/AaveBorrower.sol:AaveBorrower \
  --chain-id $CHAIN_ID \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --constructor-args $(cast abi-encode "constructor(address)" 0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69)

Verify ERC3156Borrower

The ERC3156Borrower is also initialized with the FlashLoanRouter address.

forge verify-contract \
  0x47d71b4B3336AB2729436186C216955F3C27cD04 \
  src/ERC3156Borrower.sol:ERC3156Borrower \
  --chain-id $CHAIN_ID \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --constructor-args $(cast abi-encode "constructor(address)" 0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69)

Understanding Constructor Arguments

The cast abi-encode command encodes constructor arguments in the format expected by Etherscan.

Syntax

cast abi-encode "constructor(type1,type2,...)" arg1 arg2 ...

Examples

# For contracts with single address parameter
cast abi-encode "constructor(address)" 0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69

# For contracts with multiple parameters
cast abi-encode "constructor(address,uint256,bool)" 0x... 1000000 true

Network-Specific API Keys

Different networks require different API keys:

Network	Explorer	API Key Environment Variable
Ethereum	Etherscan	`ETHERSCAN_API_KEY`
Polygon	Polygonscan	`POLYGONSCAN_API_KEY`
Arbitrum	Arbiscan	`ARBISCAN_API_KEY`
Optimism	Optimistic Etherscan	`OPTIMISM_API_KEY`
Base	Basescan	`BASESCAN_API_KEY`
BSC	BscScan	`BSCSCAN_API_KEY`
Avalanche	Snowtrace	`SNOWTRACE_API_KEY`
Gnosis	Gnosisscan	`GNOSISSCAN_API_KEY`
Linea	Lineascan	`LINEASCAN_API_KEY`

Most explorers use the same API key infrastructure. Register at the respective explorer website to obtain your API key.

Verification Status

After running the verification command, you’ll see one of these outputs:

Success

Start verifying contract `0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69` deployed on mainnet
Submitting verification for [src/FlashLoanRouter.sol:FlashLoanRouter] "0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69".
Submitted contract for verification:
        Response: `OK`
        GUID: `abc123...`
        URL: https://etherscan.io/address/0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69
Contract verification status:
Response: `OK`
Details: `Pass - Verified`

The contract is successfully verified and visible on the explorer.

Already Verified

Contract source code already verified

The contract was previously verified. No action needed.

Failed

Error: Verification failed
Response: `NOTOK`
Details: `Error message here`

Common causes:

Incorrect constructor arguments
Wrong compiler version or settings
Invalid API key
Network issues

See troubleshooting section below.

Troubleshooting

Constructor argument mismatch

Ensure you’re using the correct addresses for constructor arguments:

FlashLoanRouter: Uses CoW Settlement address 0x9008D19f58AAbD9eD0D60971565AA8510560ab41
Borrower contracts: Use FlashLoanRouter address 0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69

Verify addresses in networks.json for the specific network.

Compiler version mismatch

The contracts are compiled with specific settings from foundry.toml:

solc = "0.8.28"
evm_version = "cancun"
optimizer = true
optimizer_runs = 1000000

Forge automatically uses these settings during verification.

Rate limiting

Block explorer APIs have rate limits. If you encounter rate limiting:

Wait a few minutes before retrying
Verify contracts sequentially, not in parallel
Check your API key tier for rate limit details

Invalid API key

Verify your API key is:

Correctly set in environment variables
Valid and not expired
For the correct network (e.g., mainnet vs testnet)
Has verification permissions enabled

Verify Multiple Contracts

To verify all three contracts sequentially:

#!/bin/bash

source .env

echo "Verifying FlashLoanRouter..."
forge verify-contract \
  0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69 \
  src/FlashLoanRouter.sol:FlashLoanRouter \
  --chain-id $CHAIN_ID \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --constructor-args $(cast abi-encode "constructor(address)" 0x9008D19f58AAbD9eD0D60971565AA8510560ab41)

echo "Verifying AaveBorrower..."
forge verify-contract \
  0x7d9C4DeE56933151Bc5C909cfe09DEf0d315CB4A \
  src/AaveBorrower.sol:AaveBorrower \
  --chain-id $CHAIN_ID \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --constructor-args $(cast abi-encode "constructor(address)" 0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69)

echo "Verifying ERC3156Borrower..."
forge verify-contract \
  0x47d71b4B3336AB2729436186C216955F3C27cD04 \
  src/ERC3156Borrower.sol:ERC3156Borrower \
  --chain-id $CHAIN_ID \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --constructor-args $(cast abi-encode "constructor(address)" 0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69)

echo "Verification complete!"

Make the script executable with chmod +x verify-all.sh before running.

Next Steps

Deployment Guide

Learn how to deploy contracts to new networks

Supported Networks

View verified contracts across all networks

Contracts

Hooks Trampoline

Composable CoW

Contracts SDK

Flash Loan Router

Automatic Verification

During Deployment

Manual Verification

Prerequisites

Verify FlashLoanRouter

Verify AaveBorrower

Verify ERC3156Borrower

Understanding Constructor Arguments

Syntax

Examples

Network-Specific API Keys

Verification Status

Troubleshooting

Verify Multiple Contracts

Next Steps

Deployment Guide

Supported Networks

​Automatic Verification

​During Deployment

​Manual Verification

​Prerequisites

​Verify FlashLoanRouter

​Verify AaveBorrower

​Verify ERC3156Borrower

​Understanding Constructor Arguments

​Syntax

​Examples

​Network-Specific API Keys

​Verification Status

​Troubleshooting

​Verify Multiple Contracts

​Next Steps

Deployment Guide

Supported Networks

Automatic Verification

During Deployment

Manual Verification

Prerequisites

Verify FlashLoanRouter

Verify AaveBorrower

Verify ERC3156Borrower

Understanding Constructor Arguments

Syntax

Examples

Network-Specific API Keys

Verification Status

Troubleshooting

Verify Multiple Contracts

Next Steps