Worked on the quantumlib/Cirq repository to deliver protobuf-based serialization of circuit tags, enabling metadata tagging for calibration workflows and discounting semantics. Developed changes to the Circuit proto schema, introducing token_constant_index and tag_indices to support tagging metadata. Updated the CircuitSerializer to ensure accurate serialization and deserialization of custom tags such as CalibrationTag and DiscountTag, facilitating tagging-based workflows. Focused on maintaining forward- and backward-compatibility to improve automation and data fidelity across calibration and pricing pipelines. Utilized Python and Protocol Buffers, applying skills in API design and serialization to lay the groundwork for enhanced interoperability within quantum computing libraries.