Principal Software Engineer - AI Platform & Architecture (Saint Paul)

Thomson Reuters products power the professionals who are shaping the world. Our platforms drive legal, tax, accounting and audit products, including Cloud Audit Suite—a connected set of products spanning Engagement Manager, Guided Assurance, and Confirmation. As a Principal Software Engineer for Cloud Audit Suite, you will be the technical architect and hands-on design leader for our product platforms, integrating multiple products and technology stacks. You will also help drive our shift to an engineering-led, AI-native organization, one where AI writes much of the code and engineers stay in the loop to provide judgment, architecture, and direction where it matters most. About the role:Own the architecture, system design and AI strategy: You will be the principal engineer responsible for the architecture and system design of Cloud Audit Suite and new integrations to Confirmation and CoCounsel Audit via agents, APIs, MCP connections and shared components and repositories. Drive AI strategy for Cloud Audit Suite and help deliver the company's AI strategy. Set the technical direction for how we build MCP servers, design agents, find novel uses of LLMs, run experimentation, and stand up scalable solutions. Your decisions will influence multiple product lines, not just a single feature. Work at real production scale: Build and evolve systems that operate over millions of documents, structured and unstructured data, audit compliance rules, and thousands of concurrent AI interactions from accountants doing time‑sensitive work. Small teams, big surface area: Interact and lead across several teams of engineers, product, UX design and AI Labs partners to research, design and ship products quickly, with direct access to product leadership and customers. What you'll do:Technical leadership and cross‑functional influence Partner with the CoCounsel Audit Principal Engineer to determine the best ways to integrate Cloud Audit Suite (CAS) and CoCounsel Audi via MCP servers and tools, shared APIs, and agent-to-agent (A2A) integrations. Lead multi‑quarter initiatives that cut across product engineering, product, labs, UX design and infrastructure/operations teams. Mentor staff and senior engineers, raising the bar on system design, code quality, and AI-native engineering practices, including AI-assisted and AI-generated development with humans in the loop, across the org. Be the expert in new model capabilities and scalable AI integration strategies, collaborating closely with AI/ML engineers, researchers, designers, and PMs to translate industry improvements into reliable, user‑facing workflows that accountants trust. Help shape the team’s roadmap, technical strategy, and engineering culture – from experimentation practices to design, coding, testing, rollout, support and postmortems. Design and own AI‑first backend systems Own the end-to-end architecture and design of backend services (C#/.NET, Python, FastAPI, PostgreSQL, AWS, Vercel) that integrate and orchestrate across heterogeneous systems and technology stacks, powering generative AI agents, complex workflows and document‑centric experiences. Build and evolve AI orchestration: routing, tool calling, MCP servers, multi‑step workflows, safety and guardrails, and robust error handling around third‑party LLMs (OpenAI, Anthropic, and others). Scale, reliability, compliance and performance Design for high‑throughput, low‑latency AI workloads: caching, queuing, rate‑limiting, model failover, and cost/performance tradeoffs. Work with large‑scale data: millions of documents, retrieval and search, vector stores, and indexing strategies tailored to tax, account and audit use cases. Help establish and refine SLOs, observability, and incident response for AI systems that must be correct, auditable, and trustworthy in professional workflows. About You:You are a fit for the position of Principal Software Engineer if your background includes: Required Experience & Skills:Bachelors Degree in Computer Science, Computer Engineering, Related Field, or Equivalent Experience 8-10+ years of experience in full-stack application development, including hands-on architecture and design leadership for large-scale systems, building scalable web services and APIs. C#, .NET expertise and experience with production systems using frameworks like ASP.NET Core (or similar), relational databases (SQLServer, PostgreSQL or equivalent), and a major cloud provider (AWS preferred, Azure). Experience with Python in AI/ML system development, including model integration, data pipelines, or API-based orchestration Familiarity with actor model patterns and frameworks (Orleans, Akka, etc.) for resilient, message-driven distributed architectures Experience architecting and implementing accessible front-end solutions, including: JavaScript, Typescript, HTML, CSS; experience with modern JavaScript frameworks, e.g., Angular, React, etc.  Demonstrated experience and passion for AI systems and new engineering paradigms: LLMs, agents, retrieval, or similar – you care about what “AI‑native” software should look like and know what guardrails to put in place. Strong background in distributed systems and cross-system integration: data modeling, API contracts, integrating across heterogeneous services and technology stacks, observability, resilience patterns, and performance tuning under load. Proven track record owning large, complex projects end‑to‑end: architecture, execution, rollout, and long‑term support and maintenance. Excellent communication skills and the ability to partner with product, design, UX design and ML teams in a fast‑moving environment. Preferred Skills & ExperienceExperience designing and implementing CI/CD pipelines (i.e., GitHub Actions) Hands‑on experience integrating LLM APIs (e.g., OpenAI, Anthropic) into production applications, including prompt/response management, cost controls, and safety considerations. Experience with AI‑adjacent infrastructure: vector databases, embeddings, semantic search, or custom retrieval pipelines. Experience having direct interaction and communications with customers. Opinions and experience around automated testing, reliability, and release practices for systems with nondeterministic model behavior. Prior experience in domains where correctness, auditability, and compliance matter (fintech, tax, audit, legal, or similar), or strong interest in applying AI in those contexts.  #LI-TH1This posting is for proactive recruitment purposes and may be used to fill current openings or future vacancies within our organization.What’s in it For You?Hybrid Work Model: We’ve adopted a flexible hybrid working environment (2-3 days a week in the office depending on the role) for our office-based roles while delivering a seamless experience that is digitally and physically connected.Flexibility & Work-Life Balance: Flex My Way is a set of supportive workplace policies designed to help manage personal and professional responsibilities, whether caring for family, giving back to the community, or finding time to refresh and reset. This builds upon our flexible work arrangements, including work from anywhere for up to 8 weeks per year, empowering employees to achieve a better work-life balance.Career Development and Growth: By fostering a culture of continuous learning and skill development, we prepare our talent to tackle tomorrow’s challenges and deliver real-world solutions. Our Grow My Way programming and skills-first approach ensures you have the tools and knowledge to grow, lead, and thrive in an AI-enabled future.Industry Competitive Benefits: We offer comprehensive benefit plans to include flexible vacation, two company-wide Mental Health Days off, access to the Headspace app, retirement savings, tuition reimbursement, employee incentive programs, and resources for mental, physical, and financial wellbeing.Culture: Globally recognized, award-winning reputation for inclusion and belonging, flexibility, work-life balance, and more. We live by our values: Obsess over our Customers, Compete to Win, Challenge (Y)our Thinking, Act Fast / Learn Fast, and Stronger Together.Social Impact: Make an impact in your community with our Social Impact Institute. We offer employees two paid volunteer days off annually and opportunities to get involved with pro-bono consulting projects and Environmental, Social, and Governance (ESG) initiatives. Making a Real-World Impact: We are one of the few companies globally that helps its customers pursue justice, truth, and transparency. Together, with the professionals and institutions we serve, we help uphold the rule of law, turn the wheels of commerce, catch bad actors, report the facts, and provide trusted, unbiased information to people all over the world.Our use of AI within the recruitment process Thomson Reuters utilizes Artificial Intelligence (AI) to support parts of our global recruitment process. Unless you opt-out, our AI system will assess the information provided by you and compare it to the requirements listed for the role, and present the result to our recruitment personnel for further review. The AI system acts as a supporting tool, but there is always a human making the decision if you will be considered for the role.In the United States, Thomson Reuters offers a comprehensive benefits package to our employees. Our benefit package includes market competitive health, dental, vision, disability, and life insurance programs, as well as a competitive 401k plan with company match. In addition, Thomson Reuters offers market leading work life benefits with competitive vacation, sick and safe paid time off, paid holidays (including two company mental health days off), parental leave, sabbatical leave. These benefits meet or exceeds the requirements of paid time off in accordance with any applicable state or municipal laws. Finally, Thomson Reuters offers the following additional benefits: optional hospital, accident