Backed by Index, Sequoia and Lux.
About the role
As a Research Engineer, you'll bridge research and production. You'll turn validated methods, benchmarks, and evaluation infrastructure from our research team into dependable, production-grade features. You’ll be responsible for the entire lifecycle of an AI feature—from building the underlying systems to customizing the models that make them run. Your work will involve both robust system design and the pragmatic application of advanced machine learning techniques, including model fine-tuning when necessary.
What they're looking for
- Experience: 3+ years of professional software engineering experience building and shipping AI/ML-powered products, with deep proficiency in Python and a proven track record of scalable, production-grade systems
- Post-training expertise: Familiarity with post-training techniques such as SFT and GRPO, plus hands-on experience with the systems and frameworks that run them at scale—distributed model training, VERL, and vLLM
- Practical AI skills: Hands-on experience with LLM APIs (e.g., OpenAI, Anthropic), RAG, agentic workflows, and the full ML project lifecycle
- Analytical and pragmatic: A data-driven approach to problem solving and strong intuition for when to build complex infrastructure versus ship a simple solution
- Product-focused: Driven by user impact and skilled at making smart technical trade-offs to deliver value quickly
- Ownership: You thrive on taking full responsibility for features, from initial concept through deployment and iteration
More about this role
Crosby is built on a simple conviction: a great legal system is the watermark of a great society — and the best legal work comes from combining human expertise with the right technology, not replacing one with the other.
Crosby is the first AI-native law firm, helping ambitious companies like Cursor, Ramp, and Cognition sign commercial contracts faster.
Legal work is both art and science, and we're mapping the frontier between the two — codifying what can be systematized, amplifying human judgment where it matters most. That's why the right way to bring AI into law isn't to sell software and walk away. It's to own the outcome together: higher-quality work, delivered faster. We build proprietary tools and human-in-the-loop workflows that change what's possible for corporate legal teams.
Crosby was founded by Ryan (Stanford Law, Cooley, startup GC) and John (Penn, first 15 engineers at Ramp). Help us transform one of society's most important industries.
As a Research Engineer, you'll bridge research and production. You'll turn validated methods, benchmarks, and evaluation infrastructure from our research team into dependable, production-grade features. You’ll be responsible for the...
Browse similar: AI jobs · AI startup jobs · Startup jobs