Hossain T.Hassan S.Bappy F.H.Yanhaona, Muhammad NurZaman T.S.Islam T.2026-09-082026-09-082025-01-01T. Hossain, S. Hassan, F. H. Bappy, M. N. Yanhaona, T. S. Zaman and T. Islam, "Bridging Immutability with Flexibility: A Scheme for Secure and Efficient Smart Contract Upgrades," 2025 IEEE International Conference on Blockchain and Cryptocurrency (ICBC), Pisa, Italy, 2025, pp. 1-5, doi: 10.1109/ICBC64466.2025.11114684.97983315413542-s2.0-105015368655https://hdl.handle.net/10361/29816The emergence of blockchain technology has revolutionized contract execution through the introduction of smart contracts. Ethereum, the leading blockchain platform, leverages smart contracts to power decentralized applications (DApps), enabling transparent and self-executing systems across various domains. While the immutability of smart contracts enhances security and trust, it also poses significant challenges for updates, defect resolution, and adaptation to changing requirements. Existing upgrade mechanisms are complex, resource-intensive, and costly in terms of gas consumption, often compromising security and limiting practical adoption. To address these challenges, we propose FlexiContracts+, a novel scheme for secure, in-place smart contract upgrades on Ethereum that preserves historical data without relying on multiple contracts or extensive pre-deployment planning. FlexiContracts+ enhances security, simplifies development, reduces engineering overhead, and supports adaptable, expandable smart contracts. Comprehensive testing demonstrates that FlexiContracts+ achieves a practical balance between immutability and flexibility, advancing the capabilities of smart contract systems.5 Pagesen-USScalabilitySmart contractsDecentralized applicationsRobustnessBlockchainsPlanningSecurityUsabilityTestingBlockchainEthereumSmart contractImmutabilityBlockchains (Databases).Smart contracts.Conference Proceeding10.1109/ICBC64466.2025.11114684