> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cow.bleu.builders/llms.txt
> Use this file to discover all available pages before exploring further.

# Contract Verification

> Guide for verifying deployed Flash Loan Router contracts on block explorers

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

```bash theme={null}
forge script script/DeployAllContracts.s.sol:DeployAllContracts \
  --rpc-url $ETH_RPC_URL \
  --private-key $PRIVATE_KEY \
  --broadcast \
  --verify
```

<Note>
  Ensure the `ETHERSCAN_API_KEY` environment variable is set before using the `--verify` flag.
</Note>

## Manual Verification

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

### Prerequisites

<Steps>
  <Step title="Set environment variables">
    ```bash theme={null}
    export CHAIN_ID=1  # Target network chain ID
    export ETHERSCAN_API_KEY=your_api_key_here
    ```
  </Step>

  <Step title="Identify contract addresses">
    Find the deployed contract addresses in `networks.json` or from your deployment output.
  </Step>
</Steps>

### Verify FlashLoanRouter

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

```bash theme={null}
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)
```

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

### Verify AaveBorrower

The AaveBorrower is initialized with the FlashLoanRouter address.

```bash theme={null}
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.

```bash theme={null}
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

```bash theme={null}
cast abi-encode "constructor(type1,type2,...)" arg1 arg2 ...
```

### Examples

<CodeGroup>
  ```bash Single Address theme={null}
  # For contracts with single address parameter
  cast abi-encode "constructor(address)" 0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69
  ```

  ```bash Multiple Parameters theme={null}
  # For contracts with multiple parameters
  cast abi-encode "constructor(address,uint256,bool)" 0x... 1000000 true
  ```
</CodeGroup>

## 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`          |

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

## Verification Status

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

<AccordionGroup>
  <Accordion title="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.
  </Accordion>

  <Accordion title="Already Verified">
    ```
    Contract source code already verified
    ```

    The contract was previously verified. No action needed.
  </Accordion>

  <Accordion title="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.
  </Accordion>
</AccordionGroup>

## Troubleshooting

<AccordionGroup>
  <Accordion title="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.
  </Accordion>

  <Accordion title="Compiler version mismatch">
    The contracts are compiled with specific settings from `foundry.toml`:

    ```toml theme={null}
    solc = "0.8.28"
    evm_version = "cancun"
    optimizer = true
    optimizer_runs = 1000000
    ```

    Forge automatically uses these settings during verification.
  </Accordion>

  <Accordion title="Rate limiting">
    Block explorer APIs have rate limits. If you encounter rate limiting:

    1. Wait a few minutes before retrying
    2. Verify contracts sequentially, not in parallel
    3. Check your API key tier for rate limit details
  </Accordion>

  <Accordion title="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
  </Accordion>
</AccordionGroup>

## Verify Multiple Contracts

To verify all three contracts sequentially:

```bash theme={null}
#!/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!"
```

<Tip>
  Make the script executable with `chmod +x verify-all.sh` before running.
</Tip>

## Next Steps

<CardGroup cols={2}>
  <Card title="Deployment Guide" icon="rocket" href="/flash-loan-router/operations/deployment-guide">
    Learn how to deploy contracts to new networks
  </Card>

  <Card title="Supported Networks" icon="network-wired" href="/flash-loan-router/operations/networks">
    View verified contracts across all networks
  </Card>
</CardGroup>