Principal Engineer, CoCounsel

Thomson Reuters; Frisco (TX); Hybrid; USD 130,000 - 160,000; Full time

Benefits offered by this job

Flexibility & work-life balance

Continuous learning opportunities

Mental health resources

Job summary

Thomson Reuters is seeking a Principal Software Engineer to set the technical direction for its AI-powered legal platform, CoCounsel. The role involves defining building patterns for MCP servers and working with large-scale data and AI systems.

The ideal candidate will have deep expertise in Python and experience in AI and large complex software projects. This position supports a hybrid work model, balancing in-office and remote work, and fosters a commitment to a diverse, inclusive work culture.

Qualifications

• Bachelor’s Degree in Computer Science, Computer Engineering, or equivalent experience.
• Demonstrated experience building with AI – LLMs, agents, and retrieval.
• Proven track record owning large, complex projects end-to-end.

Responsibilities

• Participate in shaping the company's AI platform and patterns.
• Work at real production scale with millions of documents.
• Lead initiatives across AI, product, and infrastructure.

Skills

Python expertise

AI and LLMs experience

Distributed systems knowledge

Identity and access management

Collaboration with cross-functional teams

Education

Bachelor’s Degree in Computer Science or related field

Tools

FastAPI

PostgreSQL

AWS

Job description

Principal Software Engineer – CoCounsel

CoCounsel is our most advanced AI offering to date – combining generative and agentic AI capabilities to help legal professionals move beyond prompting and start delegating. As a Principal Software Engineer, you will set the technical direction for the backend, AI orchestration, and identity systems that turn frontier models into reliable, secure, production‑grade workflows that attorneys, in‑house legal departments, and government agencies trust on real client matters every day.

About the role

This role sits at the heart of the CoCounsel Legal engineering organization, partnering closely with AI/ML engineers, researchers, product, and our identity and platform teams to deliver world‑class legal content and AI experiences at scale.

Responsibilities

• Participate in shaping the company's AI platform and patterns: define patterns for building MCP servers, designing agents, novel uses of LLMs, experimentation, and scalable infrastructure. 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, complex and ever‑changing law, privileged client data, and thousands of concurrent AI interactions from professionals doing time‑sensitive work. Consider implications to cloud costs, optimizations, etc.
• Small team, big surface area: join a tight group of senior engineers and researchers shipping quickly, with direct access to product leadership and customers. Think ownership of a startup with the runway of a public company.
• Technical leadership and cross‑functional influence: lead and/or design initiatives that cut across AI, product, identity, and infrastructure. Mentor staff and senior engineers, raising the bar on AI integration practices, system design, code quality, and security across the org. Be the expert in new model capabilities, collaborating closely with AI/ML engineers, researchers, designers, and PMs to translate industry improvements into reliable, user‑facing workflows that legal professionals trust. Help shape the team's roadmap, technical strategy, and engineering culture – from experimentation practices to testing, rollout, and postmortems. Define and lead the platform integration strategy across new and existing Thomson Reuters legal systems to deliver world‑class content and solutions for our customers.
• Identity, access, and trust: define how autonomous agents act on a user’s behalf safely: scoped delegation, least‑privilege service identities, secrets management, and consistent enforcement of entitlements across documents, matters, and content repositories. Partner with security, platform, and compliance teams on multi‑tenancy isolation, data residency, privilege protection, and audit trails. Consider the design and evolution of authentication and authorization across CoCounsel Legal – SSO/federation (SAML, OIDC, OAuth 2.0), token and session management, and fine‑grained, role‑ and attribute‑based access control (RBAC/ABAC).
• Scale, reliability, and performance: design for high‑throughput, low‑latency AI workloads: caching, queuing, rate‑limiting, model failover, and cost/performance trade‑offs. Work with large‑scale data – millions of documents, retrieval and search, vector stores, and indexing strategies tailored to legal use cases. Establish and refine SLOs, observability, and incident response for AI systems that must be correct, auditable, and trustworthy in professional legal workflows.

About You

• Bachelor’s Degree in Computer Science, Computer Engineering, a related field, or equivalent experience.
• Demonstrated experience building with AI – LLMs, agents, and retrieval – and a strong point of view on what “AI‑native” software should look like.
• Proven track record owning large, complex projects end‑to‑end: architecture, execution, rollout, and long‑term operation.
• Deep Python expertise and experience with production systems using frameworks like FastAPI (or similar), relational databases (PostgreSQL or equivalent), and a major cloud provider (AWS preferred).
• Strong background in distributed systems: data modeling, API contracts, observability, resilience patterns, and performance tuning under load.
• Hands‑on experience with identity and access management – designing or integrating authentication and authorization at scale (SSO, SAML, OIDC, OAuth 2.0, RBAC/ABAC, token/session management, or comparable IAM systems).
• Excellent communication skills and the ability to partner with product, design, security, and ML teams in a fast‑moving environment.

Preferred Skills & Experience

• Hands‑on experience designing and operating agentic systems in production – tool calling, MCP servers, multi‑step workflows, and orchestration around third‑party and in‑house LLMs, including prompt/response management, cost controls, and safety considerations.
• Experience with AI‑adjacent infrastructure: vector databases, embeddings, semantic search, or custom retrieval pipelines.
• Opinions and experience around automated testing, reliability, and release practices for systems with non‑deterministic model behavior.

Benefits

• Hybrid work model: flexible hybrid working environment (2‑3 days a week in the office) for office‑based roles.
• Flexibility & work‑life balance: policies allowing work from anywhere for up to 8 weeks per year.
• Career development and growth: continuous learning and skill development opportunities.
• Industry competitive benefits: flexible vacation, mental health days, Headspace app access, retirement savings, tuition reimbursement, employee incentive programs, and resources for mental, physical, and financial well‑being.
• Culture: commitment to inclusion, belonging, flexibility, and work‑life balance.
• Social impact: paid volunteer days and ESG initiative involvement.

Equal Employment Opportunity

Thomson Reuters is an Equal Employment Opportunity Employer providing a drug‑free workplace. We are committed to providing reasonable accommodations for individuals with disabilities, including veterans. If you reside in the United States and need an accommodation during the recruiting process, please contact our Human Resources Department.