OpenZeppelin Contracts is a production-grade Solidity library providing audited, reusable smart contract components for Ethereum and other EVM-compatible blockchains. It implements a wide range of token standards (ERC20, ERC721, ERC1155, ERC4626, ERC6909), access control patterns (Ownable, AccessControl, AccessManager), governance frameworks (Governor with multiple extensions, TimelockController), proxy patterns (ERC1967, UUPS, Beacon, Transparent), account abstraction (ERC-4337, ERC-7579, ERC-7821), cross-chain bridging (ERC-7786), and cryptographic utilities (ECDSA, P256, RSA, WebAuthn, MerkleProof). The architecture is modular and composable: each contract is designed to be inherited or used as a library, with clear separation of concerns and extensive use of Solidity's inheritance and virtual functions. Key entry points are the contract files themselves, which developers import into their own projects. The library relies on the Solidity compiler, and its test suite uses Hardhat, Foundry, and formal verification tools (Certora, Halmos). Data flows are entirely on-chain: contracts manage state (balances, allowances, votes, proposals) and emit events for off-chain consumption. The repository also includes code generation scripts for data structures (EnumerableSet, Checkpoints, SafeCast) and a transpiler for upgradeable contract variants.
This repository is the canonical reference implementation of ERC-4337 (Ethereum Account Abstraction) by the standard's authors. It provides a singleton EntryPoint contract that coordinates validation, execution, and gas accounting for UserOperations. The codebase includes abstract base contracts for accounts and paymasters, production-grade sample accounts (SimpleAccount, Simple7702Account), libraries for packed UserOperation hashing and EIP-7702 support, and extensive test and simulation infrastructure. It is deployed on Ethereum mainnet and supports paymasters, signature aggregators, counterfactual deployment via CREATE2, and EIP-7702 delegated code. The architecture is modular: core logic is separated into libraries (UserOperationLib, Helpers, Exec, Eip7702Support) and abstract contracts (BaseAccount, BasePaymaster, StakeManager, NonceManager) that can be reused in custom implementations. Gas optimization is a key focus, with patterns like transient storage, packed storage, and a custom nonReentrant guard. While the repo is tightly coupled to the EntryPoint's design, individual libraries and base contracts are reusable in any ERC-4337 integration.
Tempo is a custom Ethereum-compatible L1 blockchain built in Rust, offering a full node client with validator and follower modes. It diverges from standard Ethereum by introducing account abstraction (AA) as the default transaction type, 2D nonces, fee token mechanisms, and a novel consensus protocol using the Commonware framework with BLS threshold signatures and distributed key generation (DKG). The execution layer is based on revm (Rust EVM) with extensive use of hardfork-gated precompiled contracts (TIP20 tokens, stablecoin DEX, fee manager, storage credits, etc.), replacing many ERC standards. The architecture is actor-based, with separate crates for consensus, execution, payload building, transaction pool, and node orchestration. It includes a rich CLI, localnet dev environment, and extensive benchmarking and testing infrastructure. While primarily an application, it has strong research elements in consensus design, gas modeling, and economic experiments (e.g., fee AMM arb bot).