Getting Started - Fhenix Documentation

@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

Install the package

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

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)
    mocksDeployVerbosity: 'v',      // mock deployment log verbosity (default: 'v')
  },
};

mocksDeployVerbosity controls how much output the plugin prints while deploying the mock contracts at the start of each npx hardhat test / npx hardhat node run:

Value	Output
`''`	Silent — no deploy lines.
`'v'`	Single summary line per mock (default since `0.5.0`).
`'vv'`	Full per-contract deployment log, including each contract’s deployed address.

This is independent of logMocks, which controls runtime FHE-op logging (printed when your tests actually call FHE.*).

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.

​What the plugin provides

​Installation

​Configuration

​Pre-configured networks

​Auto-deployment

​Next steps