This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Senior Software Engineer - LIMS Modernization based in the United States. This senior engineering role sits at the center of a major modernization initiative for a mission-critical Laboratory Information Management System (LIMS). You will combine modern software engineering practices with deep analysis of a long-lived enterprise codebase and its business logic. The role gives you the opportunity to transform undocumented legacy knowledge into clear specifications, architecture, tests, and production-ready software. You will work closely with senior engineers, cloud and platform architects, infrastructure teams, and laboratory leadership. AI-assisted development will be a core part of the engineering workflow, alongside Spec-Driven Development, Test-Driven Development, and clean architecture. Your work will directly influence the future architecture, reliability, scalability, and maintainability of systems supporting laboratory operations. This is an opportunity to modernize a critical platform while building software that ultimately supports environmental protection and healthier communities.