Getting Started

Set up @cofhe/hardhat-plugin for local FHE contract development and testing

@cofhe/hardhat-plugin extends Hardhat with everything you need to build and test FHE-enabled contracts locally — mock contracts, a pre-configured CoFHE client, and test utilities.

What the plugin provides

• Mock contracts deployed automatically on every npx hardhat test / npx hardhat node run, simulating the full CoFHE coprocessor stack on the Hardhat network.
• hre.cofhe — a namespaced API for creating and connecting CoFHE clients with Hardhat signers.
• hre.cofhe.mocks — utilities for reading raw plaintext values and interacting with mock contracts directly in tests.
• Pre-configured networks — localcofhe, eth-sepolia, and arb-sepolia are injected automatically.

Installation

1. Install the package

   npm

   npm install @cofhe/hardhat-plugin @cofhe/sdk @cofhe/mock-contracts @fhenixprotocol/cofhe-contracts
   

   pnpm add @cofhe/hardhat-plugin @cofhe/sdk @cofhe/mock-contracts @fhenixprotocol/cofhe-contracts
   

   yarn add @cofhe/hardhat-plugin @cofhe/sdk @cofhe/mock-contracts @fhenixprotocol/cofhe-contracts
   
2. Import in your Hardhat config

   hardhat.config.ts

   import '@cofhe/hardhat-plugin';
   
   export default {
     solidity: '0.8.28',
   };
   

   That’s it. The plugin automatically deploys the mock contracts before every test run.

Configuration

The plugin adds an optional cofhe key to your Hardhat config:

hardhat.config.ts

import '@cofhe/hardhat-plugin';

export default {
  solidity: '0.8.28',
  cofhe: {
    logMocks: true,    // log FHE ops to the console (default: true)
    gasWarning: true,  // warn when mock gas usage is high (default: true)
  },
};

Pre-configured networks

The following networks are injected automatically. You can override any of them by defining the same key under networks in your config.

Network	URL	Chain ID
localcofhe	http://127.0.0.1:42069	—
eth-sepolia	Ethereum Sepolia public RPC	11155111
arb-sepolia	Arbitrum Sepolia public RPC	421614

For testnets, set PRIVATE_KEY (and optionally SEPOLIA_RPC_URL / ARBITRUM_SEPOLIA_RPC_URL) in your environment.

Auto-deployment

Mock contracts are deployed automatically before:

• npx hardhat test
• npx hardhat node

To skip auto-deployment (e.g., when running tests only against an external RPC):

COFHE_SKIP_MOCKS_DEPLOY=1 npx hardhat test

Next steps

• Client — create and connect a CoFHE client in tests.
• Mock Contracts — read plaintext values and interact with mock contracts.
• Logging — inspect FHE operations in test output.
• Testing — end-to-end test patterns.