During January 2026, computermouth enhanced error handling in the fastly/js-compute-runtime repository by unifying Fastly API error mapping to KVStoreError, aligning the JavaScript SDK with the Rust SDK. This work involved developing a consistent mapping from FastlyStatus to KVStoreError, introducing new error cases, and providing more detailed, actionable error messages. Using C++ and leveraging expertise in API development and error handling, computermouth improved the reliability and clarity of error reporting for KVStore integrations. The contribution, co-authored with other developers, deepened cross-language consistency and enabled faster debugging, ultimately reducing support overhead and improving the developer experience for API consumers.