Solidity Setup For existing projects, detect the framework by looking for hardhat.config.* (Hardhat) or foundry.toml (Foundry). For new projects, ask the user which framework they prefer. Hardhat Setup Initialize project (only if starting a new project) npx hardhat init

Hardhat v2

npx hardhat --init

Hardhat v3

Install OpenZeppelin Contracts: npm install @openzeppelin/contracts If using upgradeable contracts, also install the upgradeable variant: npm install @openzeppelin/contracts-upgradeable Foundry Setup Install Foundry curl -L https://foundry.paradigm.xyz | bash foundryup Initialize project (only if starting a new project) forge init my-project cd my-project Add OpenZeppelin Contracts: forge install OpenZeppelin/openzeppelin-contracts@v < VERSION

If using upgradeable contracts, also add the upgradeable variant: forge install OpenZeppelin/openzeppelin-contracts-upgradeable@v < VERSION

Look up the current version from https://github.com/OpenZeppelin/openzeppelin-contracts/releases . Pin to a release tag — without one, forge install pulls the default branch, which may be unstable. remappings.txt (if not using upgradeable contracts) @openzeppelin/contracts/=lib/openzeppelin-contracts/contracts/ remappings.txt (if using upgradeable contracts) @openzeppelin/contracts/=lib/openzeppelin-contracts-upgradeable/lib/openzeppelin-contracts/contracts/ @openzeppelin/contracts-upgradeable/=lib/openzeppelin-contracts-upgradeable/contracts/ Note The above remappings mean that both @openzeppelin/contracts/ (including proxy contracts) and @openzeppelin/contracts-upgradeable/ come from the openzeppelin-contracts-upgradeable submodule and its subdirectories, which includes its own transitive copy of openzeppelin-contracts of the same release version number. This format is needed for Etherscan verification to work. Particularly, any copies of openzeppelin-contracts that are installed separately are NOT used. Import Conventions Standard: @openzeppelin/contracts/token/ERC20/ERC20.sol Upgradeable: @openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol Use upgradeable variants only when deploying behind proxies; otherwise use standard contracts.