Worked on the 0xPlaygrounds/rig repository to enhance the reliability of Chat Completions streaming by addressing a critical issue with cached input token population. Focused on backend development and API integration using Rust, the work ensured that usage metrics accurately reflected token counts by mapping cached tokens from streaming chunks to provider responses such as OpenAI and Baseten. Added automated testing to verify that tokens were correctly included in usage metrics, reducing billing risk and improving end-to-end token accounting. Maintained code quality through consistent formatting and cohesive changes, demonstrating a methodical approach to backend reliability and testing within the Rust ecosystem.