During August 2025, Marek contributed to the softwaremill/sttp-ai repository by developing a feature that exposed an optional usage field in chat completion streaming responses. He extended the backend data model to include detailed token counts for prompts, completions, and totals, enabling improved analytics and cost estimation for streaming chat usage. Marek implemented robust unit and integration tests to ensure accurate JSON parsing and reliable deserialization of usage data. His work focused on API integration and backend development using Scala and JSON, enhancing observability and maintaining streaming performance. The feature addressed the need for better usage tracking without introducing major bugs.