upgrade-solidity-contracts

| Pattern | Upgrade logic lives in | Best for |

| UUPS (UUPSUpgradeable) | Implementation contract (override authorizeUpgrade) | Most projects — lighter proxy, lower deploy gas | | Transparent | Separate ProxyAdmin contract | When admin/user call separation is critical — admin cannot accidentally call implementation functions |

| Beacon | Shared beacon contract | Multiple proxies sharing one implementation — upgrading the beacon atomically upgrades all proxies |

Upgrade Solidity smart contracts using OpenZeppelin proxy patterns. Use when users need to: (1) make contracts upgradeable with UUPS, Transparent, or Beacon proxies, (2) write initializers instead of constructors, (3) use the Hardhat or Foundry upgrades plugins, (4) understand storage layout rules and ERC-7201 namespaced storage, (5) validate upgrade safety, (6) manage proxy deployments and upgrades, or (7) understand upgrade restrictions between OpenZeppelin Contracts major versions. Source: openzeppelin/openzeppelin-skills.