Client

Create and connect a CofheClient inside a Hardhat 3 test

The plugin extends every Hardhat 3 connection with a cofhe namespace. There are three ways to create and connect a CofheClient from a test, in increasing order of control.

Batteries included (recommended)

cofhe.createClientWithBatteries(walletClient?) is the one-call setup. It:

1. Creates a CoFHE config with environment: 'hardhat'.
2. Creates a CofheClient.
3. Connects it using the wallet client you pass (or the first wallet client on the connection if you don’t).
4. Generates and signs a self permit so the client can immediately decrypt encrypted values.

import { describe, it } from 'node:test';
import { network } from 'hardhat';

describe('My FHE contract', async () => {
  const { viem, cofhe } = await network.connect();
  const [walletClient] = await viem.getWalletClients();

  it('decrypts a value', async () => {
    const client = await cofhe.createClientWithBatteries(walletClient);
    client.connected; // true
  });
});

Or call it with no arguments to use the first wallet client on the connection:

const client = await cofhe.createClientWithBatteries();

Because the self permit is created up-front, encrypt / decrypt / decryptForView / decryptForTx all work immediately without any additional setup.

Manual setup

For more control — custom config options, multiple signers, adjusting encryptDelay — set up the client step by step.

1. Create config

   const config = await cofhe.createConfig();
   // With overrides:
   const config = await cofhe.createConfig({ mocks: { encryptDelay: 0 } });
   

   cofhe.createConfig wraps createCofheConfig from @cofhe/sdk/node with two Hardhat-3-specific additions:

   • Sets environment: 'hardhat' automatically.
   • Defaults mocks.encryptDelay to 0 so tests run without artificial wait times.
2. Create the client

   const client = cofhe.createClient(config);
   

   The client is not connected yet — call client.connect(...) before using it.

3. Connect with the connection's wallet client

   const publicClient = await viem.getPublicClient();
   const [walletClient] = await viem.getWalletClients();
   
   await client.connect(publicClient, walletClient);
   

API summary

Method	Returns	Description
cofhe.createConfig(overrides?)	Promise<CofheConfig>	CoFHE config pre-wired for the Hardhat mock environment (environment: 'hardhat', mocks.encryptDelay: 0).
cofhe.createClient(config)	CofheClient	Unconnected client. Call client.connect(publicClient, walletClient) before use.
cofhe.createClientWithBatteries(walletClient?)	Promise<CofheClient>	Fully configured + connected + self-permit signed. Defaults to the first wallet client on the connection.

Using the client

Once connected, the client works identically to the standard SDK client. See:

• Encrypting Inputs
• Decrypt to View
• Decrypt to Transact
• Permits