Project Abstract Currently, smart contract wallets have three big problems: lack of customizability, vendor lock-in and duplication of engineering work. Most smart wallets that are being built today are opinionated in the sense that developers decide on the features of the wallet, which entails that the user’s feature preferences are effectively ignored. Secondly, most smart wallets lock users into using a specific interface, making it essentially impossible to switch between interfaces while retaining the same wallet contract. Finally, many teams in the space are building their own smart wallet implementation (either from scratch or based on ERC-4337), meaning that they are spending a large part of their time duplicating each other’s work to build core features such as simple access control or email recovery. Instead of re-implementing these same features, developers should be building new features such as novel ways of recovering an account, implementing banking-like features or using different cryptographic primitives for signature verification. Objectives The objective of this grant is to make rhinestone’s modular implementation of ERC-4337 production ready. On a very high level, this requires ensuring that the contracts are both secure and optimized. The contract standard will be open source using the GPL-3.0 license and our intention is to propose a new ERC for this open standard, should this be beneficial to the community. So far, the rhinestone team has built a working prototype of a modular implementation of ERC-4337 using diamond proxies (ERC-2535). This prototype placed us as winners of the infrastructure track at ETHDenver and won us 6 bounties from sponsors, including Scroll, zkSync and Coinbase.