> ## 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.

# Deployment Guide

> Complete guide for deploying Flash Loan Router contracts to new and existing networks

This guide covers deploying the Flash Loan Router contracts to blockchain networks using Forge deployment scripts.

## Overview

The Flash Loan Router consists of three main contracts:

* **FlashLoanRouter**: Main entry point for flash loan settlements
* **AaveBorrower**: Adapter for Aave flash loans
* **ERC3156Borrower**: Adapter for ERC-3156 compliant lenders (e.g., Maker)

All contracts are deployed deterministically using `CREATE2` with the same addresses across all supported networks.

## Environment Setup

<Steps>
  <Step title="Create environment file">
    Copy the `.env.example` file to `.env` in the project root:

    ```bash theme={null}
    cp .env.example .env
    ```
  </Step>

  <Step title="Configure environment variables">
    Edit `.env` and set the required variables:

    ```bash theme={null}
    # Network configuration
    CHAIN_ID=1  # Target network chain ID
    ETH_RPC_URL=https://eth-mainnet.g.alchemy.com/v2/YOUR_API_KEY
    PRIVATE_KEY=0x...  # Deployer private key

    # Optional: For contract verification
    ETHERSCAN_API_KEY=your_etherscan_api_key

    # Optional: For single contract deployments
    # FLASHLOAN_ROUTER_ADDRESS=0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69
    ```
  </Step>

  <Step title="Load environment variables">
    Source the environment file before running deployment commands:

    ```bash theme={null}
    source .env
    ```
  </Step>
</Steps>

## Deploy All Contracts

For new network deployments, use the `DeployAllContracts` script to deploy all three contracts in a single transaction.

<Steps>
  <Step title="Dry-run the deployment">
    Test the deployment without broadcasting transactions:

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

    Review the output to ensure expected contract addresses and gas costs.
  </Step>

  <Step title="Broadcast deployment">
    Execute the actual deployment:

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

  <Step title="Deploy with verification">
    For Etherscan verification, add the `--verify` flag:

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

    <Note>
      Ensure `ETHERSCAN_API_KEY` is set in your `.env` file for verification to succeed.
    </Note>
  </Step>
</Steps>

## Deploy Single Contract

To deploy individual contracts on existing networks, use the single-deployment scripts.

### FlashLoanRouter

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

### AaveBorrower

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

### ERC3156Borrower

```bash theme={null}
forge script script/single-deployment/DeployERC3156Borrower.s.sol:DeployERC3156Borrower \
  --rpc-url $ETH_RPC_URL \
  --private-key $PRIVATE_KEY \
  --broadcast
```

## Update Deployment Records

After successful deployment, update the `networks.json` file to track contract addresses.

<Steps>
  <Step title="Generate networks.json">
    Run the generation script to update deployment records:

    ```bash theme={null}
    bash script/generate-networks-file.sh > networks.json
    ```

    This script reads broadcast files from `broadcast/` directory and generates the updated `networks.json`.
  </Step>

  <Step title="Manual updates (if needed)">
    For networks deployed outside of Forge scripts, manually update `broadcast/networks-manual.json` before regenerating.
  </Step>

  <Step title="Verify addresses">
    Check that `networks.json` contains the correct addresses for your deployed contracts:

    ```json theme={null}
    {
      "FlashLoanRouter": {
        "1": {
          "address": "0x9da8b48441583a2b93e2ef8213aad0ec0b392c69",
          "transactionHash": "0x..."
        }
      },
      "AaveBorrower": { ... },
      "ERC3156Borrower": { ... }
    }
    ```
  </Step>
</Steps>

## Deployment Architecture

The deployment process uses CREATE2 for deterministic addresses:

1. **FlashLoanRouter** is deployed first with the CoW Settlement contract address
2. **Borrower contracts** are deployed with the FlashLoanRouter address as constructor argument
3. All deployments use a fixed salt (`Constants.SALT`) for address determinism
4. If a contract already exists at the computed address, deployment is skipped

## Troubleshooting

<AccordionGroup>
  <Accordion title="CREATE2 collision error">
    This occurs when a contract already exists at the computed CREATE2 address. The deployment scripts automatically detect existing contracts and skip re-deployment.

    For single deployments requiring the FlashLoanRouter address, set the `FLASHLOAN_ROUTER_ADDRESS` environment variable.
  </Accordion>

  <Accordion title="Verification fails">
    Common causes:

    * Missing or invalid `ETHERSCAN_API_KEY`
    * Network not supported by Etherscan API
    * Constructor arguments mismatch

    See the [Contract Verification](/flash-loan-router/operations/verification) guide for manual verification steps.
  </Accordion>

  <Accordion title="Insufficient funds">
    Ensure the deployer account has sufficient native tokens (ETH, MATIC, etc.) for:

    * Contract deployment gas costs
    * Multiple contract deployments if using `DeployAllContracts`
  </Accordion>
</AccordionGroup>

## Next Steps

<CardGroup cols={2}>
  <Card title="Contract Verification" icon="shield-check" href="/flash-loan-router/operations/verification">
    Verify deployed contracts on block explorers
  </Card>

  <Card title="Supported Networks" icon="network-wired" href="/flash-loan-router/operations/networks">
    View all deployed contract addresses by network
  </Card>
</CardGroup>