During November 2025, Mostrowski focused on stabilizing the IBM/vllm repository by addressing a critical bug in the test utilities. Using Python and leveraging strong testing skills, Mostrowski resolved a TypeError caused by improper hash function initialization, which had led to unreliable test execution and intermittent CI failures. The fix ensured that the hash function was correctly set up before use, eliminating a source of flaky tests and runtime errors. This targeted debugging improved the reliability of automated test runs and accelerated feedback cycles for code changes, contributing to more robust and predictable continuous integration workflows within the IBM/vllm project.