Zeno is a legal AI startup building a platform that helps lawyers research, review, and draft documents with real legal reasoning — not just text prediction. Our ambition isn’t just to “use LLMs in legal”, but to do research on what it means to represent, evaluate, and reason over law as a system .

We’re building technology that can retrieve statutes/case law precisely, apply legal tests step-by-step, and explain every answer transparently. Achieving that requires more than scaling models — it requires rigorous experimentation, strong evaluation methodology, and principled knowledge representations in a domain where ground truth is incomplete and correctness is non-negotiable.

We’re hiring a Senior/Staff Research Engineer to drive research at the intersection of LLM-heavy systems, knowledge representation, evaluation , and legal reasoning , contributing directly to both product quality and a deeper computational understanding of the legal system.

About The Role As a Research Engineer at Zeno, you work on core methodological problems at the intersection of LLM-heavy systems, knowledge representation, evaluation, and legal reasoning.

This is a research-driven role. You’ll tackle problems where:

• Ground truth is incomplete, noisy, or ambiguous
• “Correctness” is critical but hard to define
• Progress depends on rigorous experimentation

Your responsibility is to turn vague or ill-defined questions into measurable systems that improve over time, and to build the experimental infrastructure that makes that progress durable.

This role closely resembles Research Engineer or Applied Scientist roles at large tech companies or industrial research labs, with direct impact on a real, high-stakes product.

What You’ll Work On

• Build and maintain a reusable experimentation framework (reproducible runs, controlled comparisons, fast iteration loops)
• Design rigorous experiments: ablations, baselines, error taxonomies, uncertainty quantification
• Create evaluation datasets + benchmarks where no clean ground truth exists
• Prototype and validate computational models of law that formalize legal concepts, rules, and dependencies across jurisdictions.
• Adapt, combine, and when needed invent methods with meaningful compute
• Write internal research reports that turn ambiguous questions into measurable progress
• Collaborate closely with research scientists, ML engineers, and legal domain experts; hand off validated approaches for productionization

Who You Are

• A background in applied research, machine learning, data science, or a related quantitative field
• A PhD or strong MSc in biomedical engineering, physics, mathematics, or a related field
• Senior-level experience experience as a research engineer, machine learning engineer, or a similar role in industry research labs
• Strong experimental design skills and statistical reasoning
• Comfort working in domains with ambiguity, incomplete supervision, and high correctness requirements
• Strong Python skills for research code, experimentation, and analysis
• Ability to communicate findings clearly to engineering, product, and domain experts
• An independent, ownership-driven working style

Nice to have

• Experience in NLP, information retrieval, document understanding, or knowledge representation
• Experience with LLM systems beyond prompt-level work
• Familiarity with graph-based representations or structured knowledge systems
• Experience in legal, governmental, academic, or other high-complexity domains
• Publications or demonstrable applied research output

Why this role You’ll work with meaningful compute, highly protected research time, and a team that cares about rigor. Your work will directly shape how we define correctness in legal AI, and how law can be modeled as a coherent system that machines can navigate, reason over, and explain.

Join us on our mission to unify the legal systems of the world. We’re building the foundations of a more connected and intelligent legal ecosystem. You’ll work on systems that meaningfully improve how the law is applied across jurisdictions.

You’ll have ownership, autonomy, and the space to go deep on hard problems alongside a strong team of engineers and researchers. This is an environment for people who enjoy building from first principles, iterating quickly, and seeing their work move from concept to production.

If you’re motivated by purpose, intellectual challenge, and the opportunity to shape the future of law at a foundational level, we’d love to build this with you.

Why join us

• Work on a mission to unify the legal systems of the world and make law more accessible, consistent, and usable across jurisdictions.
• Build foundational systems at the intersection of research and engineering, with direct impact on how legal professionals apply the law.
• Join early and help shape the technical and intellectual foundations of a fast-growing company.
• Collaborate closely with a high-caliber team of engineers, researchers, and entrepreneurs who value depth, rigor, and clear thinking.
• Enjoy real ownership and autonomy, with the space to go deep on complex problems from first principles through production.
• Competitive compensation, strong upside as we grow, and an inspiring workplace in the heart of Rotterdam.