Worked on BitGoJS, focusing on enhancing transaction authentication and multisig withdrawal security for EVM-based coin modules. Delivered a cross-module bug fix ensuring the isFirstSigner flag was correctly passed in 23 EVM modules, resolving ABI decoding and authentication issues. Expanded regression test coverage using TypeScript and unit testing to maintain round-trip integrity. In the following month, implemented end-to-end WebAuthn attestation support for multisig withdrawals by integrating AttestationPayload handling throughout the wallet transaction flow. Upgraded dependencies and codecs, aligning the SDK with upstream @bitgo/public-types, and improved serialization to preserve attestation data, reducing maintenance overhead and streamlining backend development workflows.