SafeProxy
Users save deployment gas cost by deploying a SafeProxy contract instead of a deploying complete bytecode of Smart Account and associated contracts. The SafeProxy delegates all calls to a singleton contract, whose address is stored at slot(0) of the proxy contract. This means that the proxy contract itself is lightweight and inexpensive to deploy, while the actual logic is handled by the singleton contract.
For more information on how the proxy is deployed and the factors that determine the address of the proxy, see the SafeProxyFactory.