Worked on the jeejeelee/vllm repository to address a critical bug in the structured output grammar reasoning token handling, focusing on backend stability and reliability. The solution involved implementing logic to trim reasoning tokens before grammar advancement and enforcing bitmask constraints when reasoning ended mid-window, directly reducing request failures. Comprehensive tests were added using pytest to validate boundary conditions across multiple backends, ensuring robust cross-backend behavior. The work was carried out in Python and emphasized structured-output and llm-inference skills, resulting in improved code quality and increased test coverage for complex boundary scenarios within the structured output pipeline, ultimately stabilizing deployments.