Architecture

Chainlink Local is a simulator that allows you to use Chainlink CCIP locally in Hardhat and Foundry. It is a set of smart contracts and scripts that aims to enable you to build, deploy and execute CCIP token transfers and arbitrary messages on a local Hardhat or Anvil (Foundry) node, both with and without forking.

User Contracts tested with Chainlink Local can be deployed to test networks without any modifications.

The simulator supports two modes:

• Local Simulator Mode: working with mock contracts on a locally running development blockchain node running on localhost
• Local Forked Mode: working with deployed Chainlink CCIP contracts using multiple forked networks

When working in local simulator mode, the simulator pre-deploys a set of smart contracts to a blank Hardhat/Anvil network EVM state and exposes their details with a call to the configuration() function. The simulator exposes two Router contracts named sourceRouter and destinationRouter to stay consistent with the mental model of routing cross-chain messages through two different Routers when using CCIP in production. However, in Chainlink Local, both are actually the same contract running on the local development blockchain node.

When working in local forked mode, Chainlink Local creates multiple locally running blockchain networks. You need an archive node that has historical network state in the pinned block from which you have forked for local development - see here and interact with the CCIP contract addresses for testnet.

Local forked mode includes the CCIP Local Simulator Fork, which exposes functionality to switch between forks and route messages to the destination blockchain. For Foundry, it uses a smart contract, and for Hardhat it uses a Typescript script.