Worked on enhancing the MockCCIPRouter in the smartcontractkit/ccip and smartcontractkit/chainlink-evm repositories by introducing support for EVMExtraArgsV2 while maintaining backward compatibility with V1. Refactored Solidity smart contracts to handle both versions of extra arguments, updating internal logic to ensure seamless integration and reliable execution. Developed comprehensive unit and integration tests in JavaScript and Solidity to validate correct behavior for both valid and invalid inputs, reducing integration risk for downstream applications. This work expanded the CCIP protocol’s capabilities, enabling additional execution parameters and improving the developer experience through robust testing and careful attention to compatibility and protocol reliability.